WO2018172738A1

WO2018172738A1 - Round-counting device

Info

Publication number: WO2018172738A1
Application number: PCT/GB2018/050640
Authority: WO
Inventors: Michael Devine
Original assignee: Individual
Current assignee: Individual
Priority date: 2017-03-23
Filing date: 2018-03-13
Publication date: 2018-09-27
Anticipated expiration: 2019-09-23
Also published as: GB201704627D0; GB2560744A8; GB2560744A

Abstract

A round-counting device (100) for monitoring the number of ammunition rounds contained in a magazine of a firearm or paintball gun, the device comprising: a magnet for mounting on a magazine follower of the magazine; a plurality of reed switches (106) arranged in a spaced apart arrangement along a length of the device, wherein each of the reed switches is arranged to be activated by the magnet when the magazine follower is in a predetermined position within the magazine; wherein a signal output by an activated reed switch is indicative of the number of rounds in the magazine.

Description

Round-Counting Device

The present invention relates to a round-counting device for monitoring the number of ammunition rounds contained in a magazine of a firearm. The present invention also finds applications in paintball guns.

In the context of firearms, a magazine is a detachable device for storing and feeding ammunition rounds or cartridges to a repeating firearm. In operation, a magazine moves ammunition rounds stored in the magazine to a position where they can be loaded into the chamber of the firearm.

Figure 1 shows a typical magazine 1 for a firearm. In particular, Figure 1 shows a STANAG magazine which is a standardised magazine proposed by NATO to allow NATO members to easily share ammunition and magazines. The magazine 1 comprises a hollow shell 2 for storing ammunition rounds. The magazine 1 has an opening 4 at its upper end for receiving and storing ammunition rounds (not shown). When loaded with ammunition rounds, the open end of the magazine 1 can be inserted into a magazine well of a firearm, e.g. a rifle. When all the ammunition rounds have been discharged from the magazine, the magazine can be detached from the firearm and replaced with another loaded magazine.

Referring to Figure 2, this shows the magazine 1 of Figure 1 in disassembled form. The magazine 1 further comprises a magazine follower 8 and a spring 10. The magazine follower 8 is housed within the hollow shell 2 and contacts the ammunition rounds (not shown). The spring 10 is also housed within the hollow shell 2 and biases or urges the magazine follower 8 towards the opening 4. The magazine follower 8 and spring 10 are inserted into the hollow shell 2 via an opening (not shown) at a lower end of the magazine 1 which is closed by a base piece 6.

Ammunition rounds are loaded into the magazine 1 via opening 4. As rounds are loaded, the magazine follower 4 is depressed (moves downwards) and spring 10 is compressed until the magazine 1 is fully loaded. As rounds are discharged from the magazine 1, the spring 10 urges the magazine follower 8 and remaining rounds in the magazine 1 upwards towards opening 4 until all rounds have been discharged. The magazine follower therefore assumes a number of predetermined positions within the magazine, i.e. its linear position within the magazine changes, dependent upon the number of rounds contained in the magazine. A magazine for a paintball gun has essentially the same features and operates along the same principles as magazines for firearms, except in this case the ammunition rounds consist of paintballs. In a hostile situation, it is very useful to a soldier or law enforcement officer to know how many rounds remain in the magazine of their firearm because this informs them when they will need to change the magazine. Failure to have sufficient rounds in the magazine when entering a hostile situation may have potentially fatal consequences. Whilst it is not as critical for recreational gun users or paintball enthusiasts to know how many rounds of ammunition remain in the magazine of their weapons, it is still useful to have this information. Furthermore, knowing the number of rounds remaining in a magazine can have significant safety benefits because a user is informed to take more care if a firearm or paintball gun they assume responsibility for is known to be loaded.

The present invention was devised with the foregoing in mind.

According to an aspect of the present invention, there is provided a round-counting device for monitoring the number of ammunition rounds contained in a magazine of a firearm or paintball gun, the device comprising: a magnet for mounting on a magazine follower of the magazine; a plurality of reed switches arranged in a spaced apart arrangement along a length of the device, wherein each of the reed switches is arranged to be activated by the magnet when the magazine follower is in a predetermined position within the magazine; wherein a signal output by an activated reed switch is indicative of the number of rounds in the magazine.

The predetermined position of the magazine follower relates to one of a series of predetermined or linear positions the magazine follower can assume along a length of the magazine dependent on the number of rounds contained in the magazine. The reed switches are arranged along a length of the device such that each read switch corresponds to one of the predetermined positions of the magazine follower and is activated by the magnet when the magazine follower is in that predetermined or corresponding position. An activated reed switches therefore detects and provides an output signal indicating the linear position of the magazine follower within the magazine, which linear position is indicative of the number of rounds contained in the magazine. A benefit of using reed switches as opposed to mechanical switches is that the switching contacts of reed switches are generally contained within a protective tube which shields the contacts from the ingress of dust, dirt or corrosion. Furthermore, no direct physical contact is required with the reed switch to activate the switch. The reed switch is activated by the magnetic field of the magnet and therefore the reed switch can be placed some distance from the magnet. It is also possible for there to be an intervening structure or material between the reed switch and magnet.

A further benefit of using reed switches is that they are passive devices, as opposed to active devices such as Hall Effect sensors. An electric current only passes through the reed switch when it is activated by the magnet, in contrast, in active devices electricity is required to control electron flow and therefore an active device such as a Hall Effect sensor is constantly consuming power, i.e. it has a quiescent current even when it is not actively detecting or switching. It is not possible to switch off an active device without losing its functionality. An active device is therefore less efficient and, in battery-powered applications, adversely affects battery life significantly. As reed switches only consume current when the switch is activated, battery life is significantly improved.

Another disadvantage of active devices is that they generally require extra components in order to achieve desirable results. For example, a Hall Effect sensor may require a bypass capacitor, reverse voltage protection, filtering circuitry and circuitry to inhibit DC transients in order to function satisfactorily, which components all consume power and further reduce battery life. A reed switch does not require such additional components, thereby further improving efficiency.

Optionally, the plurality of reed switches may be arranged in a ladder-type arrangement. In this arrangement, each rung of the ladder would have a reed switch and each rung would correspond to a predetermined position of the magazine follower within the magazine. This has been found to be a particularly efficient way of arranging the reed switches and reduces the number of connecting conductors required, i.e. only two conductor rails are required.

There may be one reed switch for each round to be counted. This allows the device to accurately determine the number of rounds to the nearest individual round. Optionally, a distance between each read switch may be equal to a diameter of an individual round. This also allows the device to accurately determine the number of rounds to the nearest individual round. The device may further comprise a weighting arrangement for differentially weighting the signal output from each of the reed switches, i.e. changing the voltage or current output by each of the reed switches by a different amount. Such an arrangement means that only a single output is required from the plurality of reed switches because the reed switch which has been activated can be identified by the weight that has been applied to its output signal. In the absence of a weighting arrangement, it would be necessary to have a separate output for each reed switch because the voltage or current output from each reed switch would be the same and with only one output it would be impossible to identify which reed switch has been activated. Furthermore, if all these separate outputs were to be processed by a microcontroller it would be necessary for the microcontroller to have as many inputs as reed switches, which for a large number of reed switches would increase the specification and cost of the microcontroller required. However, with a weighting arrangement only one input is required.

The weighting system may comprise a plurality of weighting elements such that each of the plurality of reed switches has a respective weighting element. Optionally, the plurality of weighting elements comprises a plurality of resistors such that each of the plurality of reed switches has a respective resistor and each resistor has a different resistance. Resistors are also passive devices and have been found to be particularly effective weighting elements.

The round-counting device may further comprise an additional resistor which forms a potential divider or voltage splitter with the plurality of resistors. By forming a potential divider, an analogue signal or voltage output can be obtained from between the additional resistor and the circuit containing the plurality of resistors.

Optionally, the device may be configured to be mounted on or attached to a magazine. This allows the device to be retrofitted to existing magazines.

The round-counting device may further comprise a housing, the plurality of reed switches being arranged along a length of the housing, wherein the housing is configured to receive and hold a magazine. This arrangement also allows the device to be retrofitted to existing magazines.

Optionally, the housing may comprise a sleeve or shell. A sleeve or shell may conveniently be fitted around an existing magazine. The sleeve or shell may have an interior shaped to conform to the exterior of a magazine. This ensures a close fit with the magazine and inhibits the magazine from moving within the sleeve or shell.

Optionally, the interior may be shaped to conform to a STANAG magazine. This is a particularly common magazine as it is the standardised magazine proposed by NATO.

The round-counting device may further comprise a controller, the controller being configured to receive an input signal output by an activated reed switch and generate an output signal indicative of the number of rounds in the magazine. The controller may be a microcontroller which represents a cost-effective and versatile means of processing the required signals.

The round-counting device may further comprise a power source. This allows the device to be completely self-contained, i.e. there is no need to connect the device to an external power source.

Optionally, the round-counting device may further comprise a wireless communication device. This allows the device to communicate remotely with other devices such as a display mounted on a sight or helmet without the need for wires or other physical connectors, etc. It would also allow information regarding the number of rounds remaining in a magazine to be sent to a remote central command centre to allow such information to be monitored and warnings relating to low ammunition levels to be sent accordingly. The round-counting device may further comprise a display for displaying the number of rounds contained in the magazine. This allows information relating to the number of rounds remaining in a magazine to be displayed visually in a readily readable format.

According to another aspect of the present invention, there is provided a system comprising any one of the devices described above, the system further comprising a display for displaying the number of rounds contained in the magazine, wherein the device is configured to wirelessly communicate with the display.

The display may be integrated into a sight of a firearm or a user's helmet or eyewear. This has been found to be a particularly convenient location for displaying information relating to the number of rounds left in a magazine as in this location it is generally within a user's field of vision. According to yet another aspect of the present invention, there is provided a magazine comprising any one of the devices described above. According to yet another aspect of the present invention, there is provided a magazine for a firearm or a paintball gun, the magazine being configured to monitor the number of ammunition rounds contained in the magazine, the magazine comprising: a biasing element for urging rounds towards an open end of the magazine; and a force sensitive resistor connected to the biasing element so as to receive a compressive force from the biasing element when rounds are contained in the magazine; wherein a signal output by the force sensitive resistor is indicative of the number of rounds in the magazine.

A force sensitive resistor is a passive component that exhibits a decrease in resistance when a force applied to the resistor is increased. An advantage of using a force sensitive resistor is that it can directly monitor the compressive force in the magazine biasing element, which is generally a spring. Force sensitive resistors are typically formed as polymer thick film devices and consequently are very thin. They can therefore be incorporated into a magazine with minimal modification to the remainder of the magazine. The force sensitive resistor may be arranged between a base of the magazine and an end of the biasing element nearest the base. This has been found to be a particularly convenient location for receiving the compressive force from the spring. Due to the thin profile of the force sensitive resistor, no or minimal modification is required to the length of the spring. Optionally, the magazine may further comprise a controller, the controller being configured to receive an input signal output by the force sensitive resistor and generate an output signal indicative of the number of rounds in the magazine. The controller may be a microcontroller which represents a cost-effective and versatile means of processing the required signals. The magazine may further comprise a power source. This allows the device to be completely self-contained, i.e. there is no need to connect the device to an external power source.

The magazine may further comprise a wireless communication device. This allows the device to communicate remotely with other devices such as a display mounted on a sight or helmet without the need for wires or other physical connectors, etc. It would also allow information regarding the number of rounds remaining in a magazine to be sent to a remote central command centre to allow such information to be monitored and warnings relating to low ammunition levels to be sent accordingly.

Optionally, the magazine may further comprise a display for displaying the number of rounds contained in the magazine. This allows information relating to the number of rounds remaining in a magazine to be displayed visually in a readily readable format.

According to yet another aspect of the present invention, there is provided a round-counting device for monitoring the number of ammunition rounds contained in a magazine of a firearm or paintball gun, the device comprising: at least one sensor for detecting the presence of a round in the magazine, the device being configured to output a signal indicative of the number of rounds in the magazine.

One or more specific embodiments in accordance with aspects of the present invention will now be described, by way of example only, and with reference to the following drawings in which:

Figure 1 is a perspective view of a conventional magazine for a firearm. Figure 2 shows the magazine of Figure 1 in disassembled form.

Figure 3 is a schematic perspective and partial cutaway view of a device in accordance with an embodiment of the present invention viewed from a first end the device. Figure 4 is a schematic perspective and partial cutaway view of the device of Figure 3 viewed from a second end of the device.

Figure 5 is a schematic perspective and partial cutaway view of a device in accordance with another embodiment of the present invention.

Figure 6 is a circuit diagram for the devices of Figures 3, 4 and 5. Figure 7 is a perspective view of a sight for a firearm or paintball gun.

Figure 8 is a perspective view of a mask or visor which may be worn, for example, by a soldier or paintball enthusiast. Figure 9 is a schematic perspective and partial cutaway view of a magazine in accordance with another embodiment of the present invention.

Figure 10 is a circuit diagram for the device of Figure 9.

Referring to Figure 3, this shows a schematic perspective view of a round-counting device 100. The figure is schematic in that it shows a simplified illustration of the round-counting device 100, in which the location of various components is shown using circuit symbols rather than the actual shape of the component. Furthermore, the shape of the round- counting device 100 has been simplified, i.e. by showing a basic rectangular cross-section.

Round-counting device 100 comprises a hollow sleeve or shell 102 having a rectangular cross-section and comprising two wider sidewalls 103a and two narrower sidewalls 103b. The sleeve 102 is configured to receive or house a magazine (not shown), i.e. the sleeve 102 acts as a housing for the magazine. There is an opening 104 at a first end of the sleeve 102 through which a magazine can be inserted. The magazine is inserted base first, such that, when fully inserted, opening 4 of the magazine (see Figure 1) is located in the region of opening 104 of sleeve 102. Although Figure 3 shows sleeve 102 having a basic straight shape profile and rectangular cross-section, the skilled person will appreciate that the round-counting device 100 may have a more complex cross-section and shape profile dependent on the magazine it is configured to fit. Shaping sleeve 102 to conform to the magazine intended to receive ensures a tight fit and inhibits movement of the magazine relative to the device. Sufficient tolerances may be included to ensure easy insertion. In the case of significantly curved magazines, sleeve 102 may be openable such that the device may be fitted around a magazine.

A plurality of reed switches 106 is arranged along a length of one of the wider sidewalls 103a of sleeve 102. Each of the reed switches 106 is connected to a respective resistor R1, R2 ...RN to form a reed switch resistor pair. Each reed switch resistor pair is connected at either end to conductor rails 110. The reed switch resistor pairs and conductors rails 110 form a ladder-type arrangement in which the reed switch resistor pairs form the rungs of the ladder and are arranged in a spaced apart arrangement along the length of a side wail 103a.

Reed switches 106 are arranged so that they can be activated by a magnet (not shown) which is mounted on a magazine follower of the inserted magazine (see Figure 2, reference numeral 8), for example, in the cavity underlying the upper surface of the magazine follower. There is one reed switch 106 for each round to be detected. The reed switches 106 are spaced apart from each other by a diameter of a round. However, each reed switch is located a distance below the actual location of the round it is detecting because it is activated by the magnet mounted on the magazine follower, which is always located below the round. The reed switch resistor pairs and conductors rails 110 may be mounted either on the inside or outside of sleeve 102 or maybe embedded within one of sidewalls 103a for protection. Figure 4 shows a schematic perspective view of the round-counting device 100 of Figure 3 from a second end, i.e. an end of the device 100 opposite opening 104. Sleeve 102 is closed at its second end by a base unit 112. Base unit 112 is shown in a partial cutaway view and comprises a battery 114, a microcontroller 116 and a wireless communication chip 118. Battery 114 acts as a power source for the device and means that the device is completely self-contained, i.e. it does not require connection to external power source. Microcontroller 116 receives the output from the reed switch resistor pairs and outputs a signal indicative of the number of rounds remaining in the magazine to wireless application chip 118, which may communicate via any suitable wireless communication protocol, for example, Bluetooth™ or Wi-Fi. The output from device 100 may be communicated wirelessly to a display device (not shown) as discussed further below.

The round-counting device 100 has no physical connections to the magazine because the reed switches are activated by the magnetic field of the magnet mounted on the magazine follower. Furthermore, the round-counting device 100 has its own power source. Consequently, device 100 is completely interchangeable and can be used with other magazines of the same type or shape and size.

Referring to Figure 5, a round-counting device 200 according to another embodiment of the present invention is shown in which the device 200 has been integrated into a magazine 202. Device 200 comprises the same components and functions in the same way as device 100 of Figures 3 and 4.

Magazine 202 comprises a hollow shell 203 which is shown in partial cutaway view to reveal an internal magazine spring 207 disposed between a base of the magazine 202 and a magazine follower 208. The magazine spring 207 and magazine follower 208 urge ammunition rounds 209 towards opening 211 from where they can be loaded into the chamber of a firearm and discharged.

Reed switches 206 are arranged along a length of magazine shell 203 so as to be activated by a magnet 205 mounted on magazine follower 208. Each reed switch 206 has its own resistor R1, R2... RN to form a reed switch resistor pair. Each reed switch resistor pair is connected at either ends to conductor rails 210. The magazine 202 has a base unit 212 which houses a battery, microcontroller and wireless communication chip (not shown). The reed switches 206, resistors R1-RN and conductor rails 210 are arranged on the outside of magazine shell 203 as this avoids having to make the magazine 202 wider. However, the skilled person will appreciate that, if necessary, the magazine could be modified to make it wider in order to accommodate the components of the device 200 on the inside of the magazine. Figure 6 shows a circuit 300 for the devices 100 and 200 of Figures 3 and 4 respectively. Circuit 300 comprises a plurality of reed switches 306, each reed switch 306 having its own resistor R1, R2 ... RN to form a reed switch resistor pair. Each resistor R1-RN has a different resistance. The resistors constitute a weighting arrangement to differentially weight the signal output from each of the reed switches.

There is a reed switch resistor pair for each round in the magazine to be counted. The reed switch resistor pair of resistor R1 is arranged to be activated when there is one round in the magazine and is therefore located closest to the opening in the round-counting device 100 or opening in the magazine 202. The reed switch resistor pair of resistor R2 is arranged to be activated when there are two rounds in the magazine and so on. A STANAG magazine generally has 20 or 30 rounds. For simplicity, Figure 6 only shows reed switches 306 and associated resistors R1-RN. However, the skilled person will appreciate that the number of reed switch resistor pairs could be customised so as to correspond to the number of rounds to be counted. Each reed switch resistor pair is connected at either end to a respective conductor rail 310 in a ladder-type arrangement. An additional resistor R11 forms a potential divider with each of resistors R1-RN.

Circuit 300 further comprises a microcontroller 316 having an analogue input B1 which is connected to a connection point X between additional resistor R11 and resistors R1-RN. Analogue input B1 therefore reads or receives the voltage from point X in the circuit. A battery 314 acts as a power supply and supplies power to the microcontroller 316 and the conductor rails 310. When a reed switch 306 is activated by the magnet (not shown) current flows through the reed switch 306 and its respective resistor R1-RN. The potential from battery 314 is divided between the resistor R1-RN which has been activated and the additional resistor R11. As each resistor R1-RN has a different resistance, the voltage at point X read by analogue input B1 will differ depending on which read switch 306 has been activated. An analogue-to- digital converter (ADC) can be used to convert this analogue voltage into a value which can be processed by the microcontroller 316.

Table 1 below shows the ADC readings obtained from a 10-bit ADC (1024 possible values) of microcontroller 316 for different values of resistors for R1-RN for a 20 round magazine, i.e. N = 20.

Table 1

The number of different resistance values attainable is limited by the number of standard resistor values available. Therefore, to generate a sufficient number of different resistance values it is necessary to add an extra resistor in series to generate a different resistance for a certain reed switch resistor pair. This is shown in Table 1 above where a resistor has been added in a second column under Resistor Values. As can be seen from Table 1 , the resistor values used generate a range of clearly distinguishable ADC readings, which allows the microcontroller 316 to clearly distinguish which reed switch has been activated. The ADC reading can be processed by embedded software or firmware within microcontroller 316 to determine the number of rounds contained in the magazine.

Referring again to Figure 6, when a round is loaded into a magazine, the reed switch 306 connected to resistor R1 will be activated. This will generate a unique ADC reading within microcontroller 316, allowing the microcontroller 316 to determine that there is one round loaded in the magazine. As further rounds are loaded into the magazine, successive reed switches 306 will be activated, i.e. the reed switches 306 connected to resistors R2-RN. For example, when there are 10 rounds in the magazine the reed switch connected to resistor R10 will be activated, which in turn will generate its own unique ADC reading and allow the microcontroller 316 to determine that there are 10 rounds loaded in the magazine. Similarly, as rounds are discharged by the firearm or paintball gun successive reed switches in a direction from RN back to R1 will be activated, allowing the microcontroller 316 to determine how many rounds left in the magazine as rounds are being discharged.

A benefit of using the weighting arrangement provided by resistors R1-RN is that it is only necessary to have one output from the plurality of reed switch resistor pairs, i.e. the output read at point X in the circuit by analogue input 81, as opposed to an output for each reed switch resistor pair. This single output can then be processed by the microcontroller 316 and the reed switch which has been activated identified by the weighting of the input signal, i.e. the voltage read from point X in Figure 6. Accordingly, a lower specification microcontroller can be used having fewer inputs and outputs.

By identifying which reed switch has been activated, microcontroller 316 can determine how many rounds remain in the magazine. This information can be output from microcontroller 316, for example, to a wireless communication device or display (not shown) to present the information to a user. Referring to Figure 7, this shows a perspective view of a sight 400 for a firearm or paintball gun. in particular, Figure 7 shows a holographic sight having a viewing window 450 through which a user can view a target. The site has internal optics (not shown) configured to project a holographic image of a reticle 458 within the viewing window 450. The sight is also configured to project a number 460 indicating the number of rounds remaining with the magazine of their firearm or paintball gun. This means that a user can be informed of the number of rounds remaining within the magazine without having to look away from a target viewed through the sight 400. The sight 400 has a battery 452 for powering the sight 400, a wireless communication chip 454 for receiving data relating to the number of rounds remaining within the magazine and a microcontroller 456 for controlling operation of the sight 400.

Figure 8 shows a perspective view of a mask or visor 500 which may be worn by a soldier or paintball enthusiast. The mask 500 has a lens or viewing window 550. A display 560, such as a small organic light emitting diode (OLED) screen, is provided for displaying the number of rounds remaining in the magazine. The display 560 is mounted on the mask 500 at a point below and outside a user's focus sightline and in their peripheral vision. This arrangement allows a user to quickly glance at the display 560 to be informed of the number of rounds remaining in the magazine. The skilled person will appreciate that such a display could similarly be mounted on a user's helmet.

Referring to Figure 9, there is shown a magazine 600 in accordance with another embodiment of the present invention. The magazine 600 has been adapted to monitor the number of ammunition rounds contained therein and comprises a hollow shell 603 which is shown in partial cutaway view to reveal an internal magazine spring 607 and a magazine follower 608. The magazine spring 607 acts as a biasing element and together with magazine follower 608 urge ammunition rounds 209 towards opening 611 from where they can be loaded into the chamber of a firearm and discharged. A force sensitive resistor 606 is disposed between a base 610 of magazine 600 and magazine spring 607. As rounds 609 are loaded into the magazine, magazine spring 607 is compressed. The compressive force from magazine spring 607 is received by the force sensitive resistor 606. As the compressive force in the magazine spring 607 increases, the resistance of force sensitive resistor 606 decreases. Similarly, as rounds 609 are discharged from the magazine the compressive force in the magazine spring 607 decreases and the resistance of force sensitive resistor 606 increases. The force sensitive resistor 606 can therefore directly monitor the compressive force in the magazine spring 607, which provide an indication of the number of rounds in the magazine.

The magazine 600 has a base unit 612 which houses a battery 614, microcontroller (not shown) and a wireless communication chip 616.

Referring to Figure 10, this shows a circuit 700 for use in magazine 600 of Figure 9. Circuit 700 comprises a force sensitive resistor 706 and an additional resistor R711, which forms a potential divider with force sensitive resistor 706. Force sensitive resistor 706 can be disposed between a base 610 of magazine 600 and magazine spring 607. Circuit 700 further comprises a microcontroller 716 having an analogue input B1 which is connected to a connection point Y between additional resistor R711 and force sensitive resistor 706. Analogue input B1 of microcontroller 716 therefore reads or receives the voltage from point Y in the circuit. A battery 714 acts as a power supply and supplies power to the microcontroller 716 and a voltage across the potential divider formed by additional resistor R711 and force sensitive resistor 706.

When a round is loaded into magazine 600, magazine spring 607 is compressed which in turn compresses force sensitive resistor 706, thereby decreasing the resistance of force sensitive resistor 706. Similarly, when a round is discharged from magazine 600, the compressive force in magazine spring 607 is reduced and the resistance of force sensitive resistor 706 increases. Therefore, with each successive round which is loaded into or discharged from magazine 600, the resistance in force sensitive resistor 706 changes and consequently the voltage at point Y read by analogue input B1 will change dependent on the number of rounds in magazine 600. The resistance of the force sensitive resistor 706 and the voltage at point y is therefore an indicator of the number of rounds contained in the magazine.

Similar to the circuit of Figure 6 above, an analogue-to-digital converter (ADC) can be used to convert the analogue voltage read from point Y in the circuit 700 into a value which can be processed by the microcontroller 716. The ADC reading can be processed by embedded software or firmware within microcontroller 716 to determine the number of rounds contained in the magazine. This information can be output from microcontroller 716, for example, to a wireless communication device or display (not shown) to present the information to a user.

Various modifications will be apparent to those skilled in the art. For example, the round- counting device or magazine can be modified so that reed switches are arranged on both sides of the device or magazine, i.e. along both of the wider sidewalls of the device or magazine. In such an arrangement, the reed switches on one side of the magazine could be configured to be activated for each odd numbered round in the magazine whilst the reed switches on the other side of the magazine could be configured to be activated for each even numbered round in the magazine. In which case, the spacing between the reed switches would be equal to substantially twice the diameter of a round.

In embodiments of the device which employ a sleeve or shell to receive a magazine, it may be necessary to modify the magazine well of a firearm or paintball gun to receive a wider magazine incorporating the sleeve or shell. Alternatively, the sleeve or shell may stop short of the top of the magazine so as to not affect the width of the part of magazine which is inserted into the magazine well. In which case, the device would not count down to the last round, as this would be within the magazine well of the firearm or paintball gun. Instead, the device would count down to the last 2 or 3 rounds. However, this would still provide sufficient warning to a user as to when they are about to run out of ammunition.

Instead of the display being located remotely from the device, it could be mounted on the device or magazine. The display could be a 7 segment LED or LCD or OLED screen. AH references made herein to orientation (e.g. up, down, upper, lower, top, bottom, upwards and downwards) are made for the purposes of describing relative spatial arrangements of the features of the device, and are not intended to be limiting in any sense. The skilled person will appreciate that references made to orientation or direction herein are with respect to the orientation shown in the figures or a firearm or paintball gun in normal use.

Claims

Claims 1. A round-counting device for monitoring the number of ammunition rounds contained in a magazine of a firearm or paintball gun, the device comprising:

a magnet for mounting on a magazine follower of the magazine; a plurality of reed switches arranged in a spaced apart arrangement along a length of the device, wherein each of the reed switches is arranged to be activated by the magnet when the magazine follower is in a predetermined position within the magazine;

wherein a signal output by an activated reed switch is indicative of the number of rounds in the magazine.

2. A round-counting device according to claim 1, wherein the plurality of reed switches are arranged in a ladder-type arrangement.

3. A round-counting device according to claim 1 or 2, wherein there is one reed switch for each round to be counted.

4. A round-counting device according to claim 3, wherein a distance between each read switch is equal to a diameter of an individual round.

5. A round-counting device according to any one of the preceding claims, the device further comprising a weighting arrangement for differentially weighting the signal output from each of the reed switches.

6. A round-counting device according to claim 5, wherein the weighting arrangement comprises a plurality of weighting elements such that each of the plurality of reed switches has a respective weighting element.

7. A round-counting device according to claim 6, wherein the plurality of weighting elements comprises a plurality of resistors such that each of the plurality of reed switches has a respective resistor and each resistor has a different resistance.

8. A round-counting device according to any one of claims 5 to 7, further comprising an additional resistor which forms a potential divider with the plurality of resistors.

9. A round-counting device according to any one of the preceding claims, wherein the device is configured to be mounted on or attached to a magazine.

10. A round-counting device according to any one of claims 1 to 8, further comprising a housing, the plurality of reed switches being arranged along a length of the housing, wherein the housing is configured to receive and hold a magazine.

11. A round-counting device according to claim 10, wherein the housing comprises a sleeve or shell.

12. A round-counting device according to claim 11, wherein the sleeve or shell has an interior shaped to conform to the exterior of a magazine.

13. A round-counting device according to claim 12, wherein the interior is shaped to conform to a STANAG magazine.

14. A round-counting device according to any one of the preceding claims, further comprising a controller, the controller being configured to receive an input signal output by an activated reed switch and generate an output signal indicative of the number of rounds in the magazine.

15. A round-counting device according to any one of the preceding claims, further comprising a power source.

16. A round-counting device according to any one of the preceding claims, further comprising a wireless communication device.

17. A round-counting device according to any one of the preceding claims, further comprising a display for displaying the number of rounds contained in the magazine.

18. A system comprising the device of any one of claims 1 to 17, the system further comprising a display for displaying the number of rounds contained in the magazine, wherein the device is configured to wirelessly communicate with the display.

19. A system according to claim 18, wherein the display is integrated into a sight of a firearm or a user's helmet or eyewear.

20. A magazine comprising the round-counting device of any one of claims 1 to 17.

21. A magazine for a firearm or a paintball gun, the magazine being configured to monitor the number of ammunition rounds contained in the magazine, the magazine comprising:

a biasing element for urging rounds towards an open end of the magazine; and

a force sensitive resistor connected to the biasing element so as to receive a compressive force from the biasing element when rounds are contained in the magazine;

wherein a signal output by the force sensitive resistor is indicative of the number of rounds in the magazine.

22. A magazine according to claim 21, wherein the force sensitive resistor is arranged between a base of the magazine and an end of the biasing element nearest the base.

23. A magazine according to claim 21 or 22, further comprising a controller, the controller being configured to receive an input signal output by the force sensitive resistor and generate an output signal indicative of the number of rounds in the magazine.

24. A magazine according to any one of claims 21 to 23, further comprising a power source.

25. A magazine according to any one of claims 21 to 24, further comprising a wireless communication device.

26. A magazine according to any one of claims 21 to 25, further comprising a display for displaying the number of rounds contained in the magazine.