GB2418007A

GB2418007A - Paintball gun control system

Info

Publication number: GB2418007A
Application number: GB0420018A
Authority: GB
Inventors: John Ronald Rice
Original assignee: NPF Ltd
Current assignee: NPF Ltd
Priority date: 2004-09-09
Filing date: 2004-09-09
Publication date: 2006-03-15
Also published as: GB0420018D0

Abstract

A paintball 10 gun includes a controller 26 arranged to control operation of the gun, and a sensor 44, 50 arranged to sense an aspect of the operation of the paintball gun 10, such as the arrival of a paintball in a certain position. The sensor comprises an emitter 44 arranged to emit light over a range of wavelengths including visible wavelengths, and a collector 50 arranged to collect light from the emitter and output a signal to the controller 26.

Description

r 2418007

PAINTBALL GUNS

The present invention relates to paintball guns, and in particular to sensing systems for paintball guns.

Paintball guns, sometimes referred to as markers, are typically pneumatically operated and fire paint filled capsules known as paintballs.

Such paintball guns can incorporate a detection system that detects either the presence of paintballs in the breech of the gun, or the operation of the firing mechanism, using an infra red light sensing system. These infra red devices are known within the paintball industry as "EYES" The use of through beam and reflective infra red devices is well known within the paintball industry and they consist of a near infrared emitter and phototransistor usually with a peak wavelength within the range of 620-960 nm. These phototransistors and infrared emitters are also usually matched pairs to ensure the wavelength peak values of the emitter and phototransistor are as close as possible to each other. It can be a problem with the use of these infrared systems that the emitters and collectors are prone to soiling by paint residue and dirt and it is essential that they are kept clean to ensure optimum performance. However, as the emitter is in the infrared spectrum this requires supporting test software incorporated into the control logic system that can indicate a problem via a display means.

It is also known to allow a predetermined time for the paintball to settle in the longitude bore of the gun after it has entered into that bore from the hopper on top of the gun, before firing the gun.

The present invention provides a paintball gun including a controller arranged to control operation of the gun, and a sensor arranged to sense an aspect of the operation of the paintball gun wherein the sensor d comprises an emitter arranged to emit light over a range of wavelengths including visible wavelengths, and a collector arranged to collect light from the emitter and output a signal to the controller.

The present invention further provides a hopper for a paintball gun having a sensor arranged to sense the movement of paintballs within or out of the hopper, wherein the sensor comprises an emitter arranged to emit light over a range of wavelengths including visible wavelengths, and a collector arranged to collect light from the emitter and output a signal. 10.. ..

Preferred embodiments of the present invention can provide an optical.

ball detection system that permits an element or step of a firing cycle by the detection or omission of a correctly positioned paintball within the .

gun by the occurrence of a signal condition between an emitter and photo:.

transistor. Also they can detect the position of the bolt that moves during....

a firing cycle with or without the paintball detection. The visible LED.

- optical detection system can also or alternatively be present within the loader/hopper paintball storage feeding device. This visible LED optical system can be a through beam device or a reflective device that uses the detection of the LED's irradiance or the omission of the LED irradiance by a signal condition between an emitter and photo transistor. A further aspect of this invention is the use a ball detection system that incorporates dynamic control that will compensate for the time taken for a paintball to settle into the longitude bore that the paintball is ejected from.

An aim of this invention is to use a visible wavelength for the emitter in the form of an LED that the infrared collector can detect within its spectral range of sensitivity and as it is visible light that the LED radiates the user can physically see if the LED is blocked or the collector is blocked by the illumination of the LED that are used for detection by a signal condition between an emitter and photo transistor. 1,

Another aspect of this "eye" paintball detection system is to use a dynamic control element in the firing command process.

This dynamic element can be used with eye detection systems that operate on the visible or non visible emitter that are used for detection by a signal condition between an emitter and photo transistor.

The eyes that are used to detect the presence or omission of a paintball need to have certain control parameters. This is due to the nature of a.. . .

paintball that can enter the longitude bore that the paintball is released.

from. When used with "paintball loaders" the loaders do not feed paintballs at a constant rate due to their mechanical feed mechanisms and .

variations between each model or variants within the same models can..

occur. Some examples of factors that can affect ball feed are; battery.... -

condition, motor resistance, how full the loader is. Also it is possible in. .

some instances to he able to out shoot the loader. Whilst the use of eyes can prevent totally out shooting a loader the draw rate of paintballs from the loader can be faster than the feed rate. This can cause paintballs to become spaced out in the stack. When this occurs as the paintball is fed into the chamber it can strike the chamber floor and bounce up. This can lead to problems occurring. Should further paintballs be directly behind the paintball to prevent the paintballs from bouncing the problem is reduced but this cannot be guaranteed and can apply excessive stress to the fragile paintballs generating breakages or drag loads onto the bolt.

Another problem is the eyes are not located absolutely on the floor of the chamber which means the paintball can have a travelling distance before the "eyes" can register a change in its signal condition. Even having eyes mounted onto the floor of the longitude bore does not address the problem but may improve the problem slightly. 1,

Also as a paintball bounces upwards, should the commencement of a the firing operation have occurred, due to the time lags of the physical bolt mechanisms eg: reaction time of the mechanical valves, electrically operated solenoids, electrically operated valves, static and dynamic friction forces, distance to travel, and speed, a paintball could then have generated the "eyes" to give a signal change condition before the mechanism can be stopped.

Therefore it is preferred to give the paintball a settling time. By being able to calculate the condition of the paintball it is possible to adjust this ball settling time dynamically to self compensate.

Paintballs when not forced, but falling under gravity, can also defy normal free fall conditions as the paintball can ricochet off the side walls of the loader, feed tube, ball retention devices or the bolt causing the paintball to take far longer than expected when free falling. Again this event can be detected and dynamic adjustments made to modify the firing sequence accordingly.

As the go command source occurs when the user pulls a trigger on the paintball marker, it has been found advantageous to use this command in a window of opportunity and the algorithm can run when the trigger is pulled, but should the condition be met after a period of time it may not be advantageous to progress the algorithm as this could result in a substantial delay from when the trigger is pulled to when the paintball is released which could present a safety hazard. But if this can be ignored because no hazard is deemed present, this delay can be permitted.

Another thing that may happen to the paintballs is that when forced "paintball loaders" are used they will project a paintball into the

J

longitude bore at a faster speed and this speed is reflected in its reaction when it hits the floor of the longitude bore in that it will bounce back faster. Again using dynamics it is possible to compensate for this. In our experimentation we also found it advantageous to use different algorithms for different loaders and should the user select another algorithm it still will use dynamic elements in each of the algorithms. Should two sets of emitters and detectors be used it is possible to use a single algorithm for any loader fitted.

Preferably the sensing means comprises two sensors, each arranged to detect one of the timing events. The additional sensor can be used as well as to monitor the feeding of paintballs and detect the presence of more than one paintball and to control the firing of the gun. For example, the known presence of an additional paintball is very beneficial as when a ball falls into the breech the presence of a paintball behind it will greatly reduce any ball bounce time as the paintball attempts to bounce back will be restricted by the paintball above it, and in this case the algorithm can compensate and reduce or eliminate the ball bounce time allowing the capability to be ready to receive a new fire command after the paintball in the longitudinal bore is ejected. Also in a situation of gaps between the paintball the algorithm can compensate or increase the ball bounce time as it will know by the omission of a paintball from been detected by the additional sensors within a timed opportunity that the probability that the paintball that has fallen into the longitudinal bore will bounce and it can increase the paintball settle time accordingly. This will also be cable of detecting a bouncing ball as should the first set of sensors 10 first detect the presence of a paintball by interruption of the sensor signal and then detect the absence of a paintball but the 2nd set then becomes interrupted is will assume a paintball is travailing upwards and again the ball settle time from the algorithm will interject and await the re-detection of the paintball by the first set of sensors and it may use verification by the second set of sensors and adjust the ball bounce time if applicable.

Preferred embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 is a sectional view through a paintball gun according to an embodiment of the invention; ..

Figure 2 is a cross section on line II of Figure 1 through the gun of. ë

Figure 1; -e Figure 3 shows a printed circuit board and power supply forming part of:. ..

the gun of Figure 1; * ë . . Figure 4 is a top view of part of the gun of Figure 1; Figure S is a graph showing the radiance and sensitivity of an emitter and collector of the gun of Figure 1, and a conventional emitter; Figure 5a is a schematic drawing of the gun of Figure 1 with a hopper according to a further embodiment of the invention connected to it; Figures 6a to 6p are partial sections through the gun of Figure 1 showing various states of operation; Figure 7 is a partial section through a paintball gun according to a second embodiment of the invention; and Figure 8 is a cross section through the gun of Figure 7.

Referring to Figures 1 and 2, a paintball gun 10, comprises a main body 12, a barrel 14 extending from the front end of the body 12, a foregrip 16 extending downwards from the front end of the body 12, and a grip frame 18 extending downwards from the centre of the body 12. The grip frame 18 includes a trigger guard 20 and a grip 22 that houses a printed circuit board 24, having control electronics and a controller 26 on it and a battery 28, shown in more detail in Figure 3. A trigger 30 is pivotably mounted on the body, and a trigger sensor 32 provides an input to the controller 26 from which the controller can determine when the trigger 30 .

has been pulled and released. The body 18 has a longitudinal bore 33.. . formed in it that is aligned with the barrel 14. The front end of this bore 33 forms a breech 34 from which paintballs can be discharged into the . barrel 14. A paintball feed port 36 opens into the rear end of the breech 34 from above and a feed tube 38, which defines a feed chamber 39, . . extends upwards from the feed port 36. The feed tube is arranged for. . ë connection to a hopper that contains paintballs and is arranged to feed them into the breech 34 through the feed tube 38.

A bolt 40 is slidably located in the rear end of the longitudinal bore 33 and is movable between a retracted position, as shown in Figure 1, in which its front end is behind and completely clear of the feed port 36, and a forward position in which its front end is forward of the feed port 36 so that the bolt 40 covers the feed port.

The foregrip 16 has an air inlet 42 at its lower end which is supplied with high pressure air from a canister. A number of valves, which are conventional and electrically operated and will not be described in detail, control the flow of air from the inlet 42 to the back of the bolt 40 to control movement of the bolt 40 between its retracted and forward positions, and the flow of air through the bolt 40 to fire a paintball when the bolt is in its forward position.

A photo-emitter 44 is mounted on the body 18 on one side of the breech.

The emitter 44 is slightly above the very bottom 46 of the breech, and is arranged to emit a beam 48 of light horizontally across the breech, transversely to the longitudinal axis of the barrel 14. A collector, in the form of a phototransistor 50, is mounted in the body 18 on the opposite side of the breech, at the point towards which the light beam is emitted.

In this case the light beam is arranged to cross the breech at a distance from its bottom 46 which is about a quarter of the diameter of the longitudinal bore 33. The emitter 44 is controlled by the controller 26 which can turn the power to it on and off so that the emitter is switched between an emitting and a non-emitting state, and the beam 48 can be turned on and off. The collector 50 is arranged to produce a signal that varies with the amount of light it receives from the emitter 44, and that signal is input to the controller 26. This enables the controller to determine when the beam 48 is broken and when it is unbroken.

It will be noted that the emitter 44 and collector 50 are positioned so that the beam 48 can be broken by the bolt 40 when it is in its forward position, but not when it is in its retracted position, and so that the beam will be broken by a paintball as it falls into the breech.

Referring to Figure 5, the collector 50 is a silicone phototransistor which is sensitive to light at wavelengths between about 450 and about llOOnm, with a relatively good sensitivity between about 600 and about 1050nm and its peak at about 850nm. The emitter 44 is a visible super bright gallium aluminium arsenide light emitting diode (LED), with a wavelength range of 625 to 700nm and a peak radiance at about 675 rim This compares with a conventional GaAs emitter which has a peak wavelength in the range 900 to lOOOnm, also shown in Figure 5.

By replacing the GaAs emitter that in this example had a wave length range of 900 to 1000 nm, peak value of approximately 950 nm with a visible super bright Gallium Aluminium Arsenide light emitting diode LED with a wavelength range of 625 to 700 nm range, peak value 675nm and using a standard silicon phototransistor with a sensitivity wavelength range of 400 to 1000 nm it is still possible to detect the radiated light from the LED. Due to the LED no longer being matched to the A. . phototransistor it is possible to increase the LED's irradiance by..

increasing the current. It is preferred to ensure that the LED and the phototransistor are within the same wavelength band but as long as the band overlaps it will be able to be used.

When the paintball gun is in use and a hopper is connected to the feed.. . tube 38, the light from the emitter 44 will not be visible to a user in this embodiment. However, in order to check that the emitter is operating, the user can remove the hopper while the gun is switched on, and will be able to check that the emitter is working by looking down the feed tube 38.

Depending on the conditions, the user may be able to see the beam 48.

Alternatively, or in addition, he may be able to see the light from the emitter that is reflected off one or more parts of the gun, such as the sides of the breech.

In alternative embodiments the light from the emitter can be made visible to the user in other ways, such as by providing a transparent panel in the side of the breech. Also, rather than a through beam arrangement of sensor as described above, the sensor may be a reflective device. Indeed it may be any device that uses the detection of the LED's irradiance or the omission of the irradiance from the LED by a phototransistor. The spectral range used can also cover any wavelength of visible light emitted from an LED, for example the light can have any of a range of visible colours e.g. red, blue, white, green or orange. If more than one LED is used, then more than one wavelength of light can be used, either together with a single collector, or with separate collectors, one for each LED.

Other options are also possible once the use of this method is incorporated in that visual effects can be achieved by varying the intensity or the wavelength of the emitted light over time. For example the LED or LEDs can be cycled on and off at a controlled frequency to give a visually flashing light. Alternatively the use of a dual colour LED, or multiple LEDs together with timing control can be used to vary the colour of the emitted light with time. The use of such timed systems would require control software to ensure that the "flashes" or changes in colour could not give false triggers and the software would need to be able to distinguish between a correct detection or omission and a false signal.

However, as times of the controlled variations would be known to the controller, and controlled by it, they could be ignored as inputs to the detection system.

Referring to Figure 5a, a visible wavelength detection system can also be included in a hopper 60. This includes a visible emitter 62 and collector 64 located on opposite sides of the neck 66 of the hopper 60 and operating in the same way as those in the gun 10, so that the movement of paintballs out of the hopper 60 can be detected. The hopper detection system is connected to an agitator mechanism 67 which is arranged to agitate paintballs in the hopper 60 if the sensor 62, 64 ceases to detect a steady flow of paintballs through the neck 66 of the hopper. The sensor 62, 64 is also connected by a cable 68 to the controller 26 and battery 28 in the gun 10, onto which it is mounted, so that the controller 26 can use data from the hopper detection system when controlling the firing of the gun 10. In this case the controller 26 can be switched between different operating modes, one to use data from the hopper sensor 62, 64, and the other not to.

A user can check the operation of the hopper sensor 62, 64 by removing the cover 68 of the hopper and looking down into the neck 66 of the hopper while it is connected to the gun 10. If the 'eye' in the hopper is working, the user will be able to see the visible light beam either directly, or as reflected of the inside of the hopper 60. A.

The firing of the paintball gun 10 is controlled by the controller 26 on the.. . circuit board 24 on the basis of a number of detected events. As mentioned above, the controller 26 is arranged to detect when the trigger has been pulled. This triggers a fire demand which sets off a firing sequence. However, the fire demand does not always trigger firing of the.. ë

gun. Various other conditions have to be met before the gun will actually be fired, and the controller is arranged to issue a firing command signal, referred to as a go command, to initiate the actual firing of the gun.

At the start of the firing sequence, the bolt is retracted waiting for a paintball to enter the breech 34, as shown in Figure 6a. The arrival of a paintball, which defines a ball arrival time, is detected by a signal condition of the optical sensor, in this case a change in the output signal from the phototransistor 50 indicating breaking of the light beam 48 from the emitter 44. This signal condition can occur either before or after the firing demand, and is used in the control algorithm that controls firing of the gun. If the arrival of a paintball in the breech is not detected within a predetermined active time of the firing demand, then the algorithm resets and the firing demand is not acted on. A further firing demand is then required before the gun can be fired. t

Referring to Figure 6b, if a paintball 70 does break the optical beam 48, then if this is within the active time of a firing command, then it can be acted on, and a go command issued provided other conditions are met.

These conditions include the expiry of a ball settle time that starts at the ball arrival time and lasts for a predetermined period, without the detection of a ball bounce. A ball bounce is detected by the beam 48 reaching the phototransistor 50, indicating that the ball has risen above the level of the beam 48. Provided these conditions are met, then the go command is issued. If a ball bounce is detected then a stop command is issued which indicates that the go command should not be issued at the.. . end of the ball settle time. ... ë

Referring to Figure 6c, at the end of the ball settle time it is assumed that the ball 70 has settled on the floor of the breech, and that it is therefore ready to be fired. The go command is therefore issued, which causes the.. .

bolt 40 to move forwards to the position shown in Figure 6d. In this forward position the front end of the bolt 40 has moved past the feed bore 36 preventing any other paintballs from moving into the breech, and the paintball 70 to be fired is moved forwards to the front end of the breech ready to be fired. When the paintball 70 has been fired, as shown in Figure be, the bolt starts to be retracted. However, while it still covers the feed bore 36, the next paintball 71 in the stack cannot enter the breech.

When the front end of the bolt 40 moves back past the eye, i.e. past the emitter 44 and collector 50, the beam 48 can again reach the collector, as shown in Figure 6f. This time is defined as a bolt retracted time, and starts a timing period. This timing period ends at the next ball arrival time, that is when the bolt 40 has been fully retracted and the next paintball 71 has fallen to a position where it breaks the beam 48 and the corresponding signal condition is detected, as shown in Figure fig. The length of this timing period is, also referred to as a ball drop time, indicative of how fast the paintball 71 is moving downwards, and is therefore used to determine the ball settle time that needs to be allowed before the go command is given.

If the ball 71 is moving quickly, then, if it is going to bounce, it will do this more quickly. Therefore the ball settling time can be made shorter if the ball drop time is short, but needs to be longer if the ball drop time is long. In this case the ball settling time is made proportional to the ball drop time, typically a quarter or a half of the ball drop time. At the end Of the ball settle time, it is again assumed that the next ball 71 has settled on the floor of the breech as shown in Figure 6h and is ready to be fired.

Again the go command can be given if a fire demand was given within a predetermined time before the ball arrival time, or before the bolt retracted time, or between the ball arrival time and the ball settle time.

Again, if the ball arrival is not detected within a predetermined active period of the firing demand, then the firing demand is not acted upon.

The above operation assumes that the paintballs 70, 71 are in a stack in the feed tube, and that therefore the ball arrival time will occur shortly after the bolt retracted time. However, in some cases the balls are not in a stack, but might be in freefall in the feed tube. This is shown in Figures 6i to 6p in which the condition of the gun 10 corresponds to that of Figures 6a to 6h. With the balls in this condition, it is very unlikely that a ball will arrive in the breach within a short time of the bolt retracted time. Therefore, if a ball arrival time does not occur within a predetermined period of the bolt retracted time, the algorithm of the controller 26 enters a different mode appropriate to freefalling balls. In this mode the speed of the falling balls cannot be estimated, and so the ball settle time is set to a default time. In this case the default time is relatively long. This is because the freefalling ball may not be truly falling, but may be bouncing off the sides of the feed tube and therefore falling very slowly. This would mean that it could bounce very slowly, and therefore the settle time needs to be set to be relatively long to ensure that the ball is not bouncing.

The manner in which the balls are fed into the feed tube from a hopper, and in particular the speed at which they are fed, and the force with which they are fed, can vary depending on whether the hopper is a simple gravity feed hopper, an agitated hopper, or a force feed hopper. This will lO affect the settle time that needs to be allowed for any given ball drop A. time. The gun 10 therefore has as user input that enables a user to set it,,, to one of a number of different modes. In each of the modes the ball settle time varies in a different way with the ball drop time. In this case there are four modes, and in each one the ball settle time is a different fraction of the ball drop time: one quarter, one half, three quarters and in..

the fourth mode, of equal time to the ball drop time. I. ë With the system of Figure 5a, the sensor 62, 62 in the hopper 60 can be used as well as that in the longitudinal bore of the gun 10, to monitor the feeding of paintballs and to control the firing of the gun. For example, the ball drop period can be defined as the time between detection that a ball has reached a predetermined position in the neck 66 of the hopper 60, and the ball arrival time in the breech. This would only work for freefalling balls, but could be used under certain circumstances. The ball settle time could therefore be made dependent on this longer ball drop time. For this to be possible, the height of the sensor in the hopper relative to the sensor in the breech 34 needs to be known exactly. This could be achieved by setting the controller to accommodate whichever particular design of hopper is being used.

Referring to Figures 7 and 8 in a second embodiment of the invention a paintball gun includes all of the features of the first embodiment, which are indicated by the same reference numerals preceded by a 1, but further includes a second visible wavelength optical sensor in the feed chamber 139 above the first sensor. This second upper optical sensor includes an emitter 151 and collector 153 which are identical to the first emitter 152 and collector 154, and located above them in the sides of the feed tube 138 so that the light beam from the emitter 152 to the collector 154 passes across the feed tube directly above the beam 148 from the lower sensor.

They are arranged at a height above the bottom of the breech that is just I'. , greater than the diameter of a paintball, so that when a paintball is resting, ., on the bottom of the breech, the beam 155 will reach the collector 153.

The additional sensor is also connected to the controller in the grip frame ' so that it can be used in the control algorithm for firing the gun. 2 With this embodiment, the two eyes can be used to measure the speed of a.. ^ paintball falling into the breech, by measuring the ball drop time between the paintball breaking the upper beam 155 and the same paintball breaking the lower beam 148. The settling time can then be varied depending on this ball drop time in the same way as described above. The advantage of having two sensors is that the speed of the paintball can be estimated more accurately.

The upper sensor 151, 153 can also be used to detect, when one paintball has fallen into the breech, whether there is a further paintball above it or not. In order to do this, the controller 26 is arranged to measure theperiod between the time when the first paintball falls below the upper beam 155, and the time when that beam is broken again by the next paintball. This gives a measure of the distance between the two paintballs.

If the further paintball follows the first one within a predetermined time, then this can be taken as an indication that the second ball is close enough to prevent bouncing of the first ball. In this case the settling time can be either reduced or omitted altogether. If the second ball is in contact with the first, then the upper sensor will not detect a space between the two balls at all. However, this can be detected because the distance between the two beams is greater than the diameter of the paintball. Therefore if the lower beam is broken before the upper beam is made, i.e. reaches the upper collector 153, then this indicates that two paintballs are in contact, and therefore close enough to prevent bouncing of the first paintball. If a gap of more than a predetermined time is detected between the two paintballs, then this indicates that the first one is more likely to bounce, ë and the settling time can be increased. .' .: ë The two sensors can also be used to improve the accuracy of detection of a bouncing paintball. If the lower sensor 144, 150 detect the presence of a paintball by the interruption of its beam 148, and then the absence of a.. .

paintball by the re-making of the beam, and then the upper sensor 151, . 153 detects the presence of a paintball by interruption of the upper beam 155, this indicated that the paintball has moved upwards. The controller is then arranged to wait for the ball to fall below the upper beam 155, and to break the lower beam 148 again, before the ball is assumed to be again in the bottom of the breach. The settling time can then be restarted.

In the system of Figures 7 and 8, if the lower sensor is not working, for example because either the emitter or the collector has become covered with dirt or paint, then the upper sensor alone can be used to determine the speed of the paintball. This can be done by using the breaking of the beam 155 as an indication of when the bottom of the paintball reaches the beam, and the re-making of the beam as an indication that the top of the same paintball reaches the level of the beam. Since the diameter of the paintball is known reasonably accurately, this can be used as a measure the speed of the paintball, and the settling time can be controlled accordingly. Similarly, if the upper sensor is not working, then lower sensor can be used to control the firing in the same way as that of the first embodiment. The controller 26 is therefore arranged to detect when one of the sensors is not working, by monitoring the signals from the two sensors. If, for example, one of the sensors detects its beam being broken and re-made a predetermined number of times without the other sensor producing any change of signal, then the controller can infer that the second sensor is not operating, and switch to a mode in which only the other sensor is used. ë . - -e.. ë- . ...

Claims

1. A paintball gun including a controller arranged to control operation of the gun, and a sensor arranged to sense an aspect of the operation of the paintball gun wherein the sensor comprises an emitter arranged to emit light over a range of wavelengths including visible wavelengths, and a collector arranged to collect light from the emitter and output a signal to the controller.

2. A paintball gun according to claim 1 wherein the emitter is positioned such that the light it emits is visible to a user from the exterior of the gun. .

ace:

3. A paintball gun according to claim 2 wherein the light travailing.....

directly from the emitter to the collector is visible to a user from the..

...CLME: exterior of the gun. .... A. .e

4. A paintball gun according to claim 2 or claim 3 wherein the emitter A: is arranged to emit light such that it is visible to a user from the exterior of the gun after reflection.

5. A paintball gun according to any of claims 1 to 4 wherein the emitter is positioned such that the light it emits is visible to a user through a paintball feed port of the gun.

6. A paintball gun according to any foregoing claim wherein the controller is arranged to control the emitter so that the light it emits varies over time.

7. A paintball gun according to claim 6 wherein the controller is arranged to control the emitter so that the intensity of the emitted light varies over time.

8. A paintball gun according to claim 6 or claim 7 wherein the controller is arranged to control the emitter so that the wavelength of the emitted light varies over time.

9. A control system for a paintball gun, the system comprising sensing means arranged to measure a time interval between two timing events relating to the movement of a paintball into a firing position, and control means arranged to issue a fire command to fire the gun at a time that depends on the length of the time interval. .. :....

:

10. A control system according to claim 9 wherein control means is .

arranged to issue the fire command after a delay from a firing initiation.

. :...CLME: event. .... :. .

11. A control system according to claim 10 wherein the firing initiation . ë::

event is one of the timing events. .

12. A control system according to claim 10 wherein the firing initiation event is not one of the timing events.

13. A control system according to any of claims 10 to 12 wherein the delay is arranged to depend on the interval.

14. A control system according to claim 13 wherein the delay is arranged to increase if the interval increases.

15. A control system according to claim 14 wherein the delay is arranged to be proportional to the interval.

16. A control system according to any of claims 9 to 15 which has a plurality of settings arranged to provide different relationships between the interval and the timing of the firing command.

17. A control system according to claim 16 further comprising a user input arranged to enable a user to select one of the settings.

18. A control system according to any of claims 9 to 17 wherein one of the timing events is an event that allows movement of the paintball past a predetermined position. .

19. A control system according to claim 18 wherein said one of the timing events is the detection of a bolt of the gun in a predetermined position. . A.

20. A control system according to any of claims 9 to 19 wherein one of the timing events is the detection of the paintball reaching a predetermined position.

21. A control system according to claim 20 wherein both of the timing events are the detection of the paintball reaching respective predetermined positions.

22. A control system according to any of claims 9 to 21 wherein the sensing means comprises a first sensor arranged to detect one of the timing events and a second sensor arranged to detect the other of the timing events.

23. A control system according to any of claims 9 to 22 wherein the sensing means includes a sensor located in a breech of the gun such that it 4.

can detect arrival of a paintball in the breech, and movement of a bolt of the gun in the breech.

24. A control system according to any of claims 9 to 23 wherein the sensing means includes a sensor located in a feed tube of the gun.

25. A control system according to any of claims 9 to 24 including a single sensor arranged to detect both timing events.

26. A control system according to any of claims 9 to 25 wherein the issue of the firing command is modified if a predetermined condition is not met.

27. A control system according to claim 26 wherein the predetermined condition is the arrival of the paintball in a predetermined position within a maximum ball arrival period.

28. A control system according to claim 27 when dependent on claim wherein the maximum ball arrival period is a fixed proportion of the delay.

29. A control system according to claim 28 wherein the maximum ball arrival period is equal to the delay.

30. A control system according to any of claims 26 to 29 wherein, if the condition is not met, the timing of the firing command is modified.

31. A control system according to any of claims 9 to 30 wherein the sensing means is arranged to measure the distance between two paintballs.

32. A control system according to claim 31 wherein the sensing means is arranged to detect when the two paintballs are less than a predetermined distance apart.

33. A control system according to claim 31 or claim 32 when dependent on claim 10 wherein the control means is arranged to control the delay depending on the distance between the two paintballs.

34. A control system according to claim 22 wherein the control means is arranged to detect when one of the sensors is not operating correctly, and to switch to a mode in which it bases its control on signals from the other sensor.

35. A paintball gun including a control system according to any. ., . :.

foregoing claim. ::::.

36. A control system for a paintball gun substantially as hereinbefore as; described with reference to any one or more of the accompanying drawings.

37. A paintball gun substantially as hereinbefore described with reference to any one or more of the accompanying drawings.