TECHNICAL FIELD

The present invention relates to electronic position sensing systems and, in particular, to a position sensing system for a fire monitor, also commonly referred to as a fire fighting water cannon.

Although the present invention will be described herein with specific reference to position sensing systems for a fire monitor, it will be understood that the invention is not limited thereto and may be used for other applications and devices where the direction of aim needs to be determined, such as in video surveillance and camera monitoring systems.

BACKGROUND ART

The manufacture of fire monitors has conventionally used a number of different systems to determine the direction in which the fire monitor is aimed. Fire monitors with position sensors are used in a wide range of applications, such as in oil refineries, oil platforms, jetties, fire trucks and fire fighting tugs. Some of the systems used to determine the direction of aim include:

(a) potentiometers mounted on the drive shafts of the monitors,

(b) absolute encoders mounted on the drive motors or shafts of the monitors,

(c) relative encoders combined with a home position sensor, and

(d) motors with the ability to determine the number of rotations, such as stepper motors or brushless DC motors in combination with home position sensors.

Conventional fire monitors utilising the above systems suffer from a number of limitations. With the encoders and potentiometers, there are mechanical linkages that fail, and they are susceptible to water damage. With the relative encoders and rotation counting motors, a home position sensor is required, together with additional electronic components that make the system more complex.

Such systems are also quite expensive to implement.

In recent years, the electronics industry has developed sensors for acceleration (accelerometers) and magnetic field (magnetometers), and electronic gyroscopes for use in other fields.

It has been found by the present inventor that such sensors may be adapted or co-operatively configured for use in a position sensing system for a fire monitor.

DISCLOSURE OF INVENTION

It is an object of the present invention to utilise such a position sensing system to overcome, or at least substantially ameliorate, the aforementioned disadvantages and shortcomings of the fire monitors of the prior art.

According to one aspect of the invention, there is provided a position sensing system for a fire monitor, comprising:

(a) an accelerometer for determining the direction of tilt of the fire monitor relative to gravity and acceleration of the fire monitor in multiple axes due to motion,

(b) a magnetometer for determining the direction of the fire monitor in the horizontal plane relative to the earth's magnetic field,

(c) a microprocessor for receiving and processing information from the accelerometer and the magnetometer, and

(d) a waterproof housing assembly enclosing the accelerometer and magnetometer.

The position sensing system may further include a graphical display unit. The microprocessor may be enclosed in a separate waterproof housing assembly to that which encloses the accelerometer and magnetometer, either on a non-movable part or a movable part of the fire monitor, or on a platform separate to the fire monitor, which can be movable or non-movable.

According to another aspect of the invention, there is provided a fire monitor comprising:

(a) a nozzle through which fire fighting material is sprayed,

(b) a movable assembly for supporting the nozzle thereon,

(c) a first motor for controlling elevation of the nozzle support

assembly,

(d) a second motor for controlling rotation of the nozzle support

assembly, and

(e) the position sensing system described above mounted on the nozzle support assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic block diagram of a fire monitor position sensing system according to a preferred embodiment of the invention. Figure 2 is a perspective view of a fire monitor according to a preferred embodiment of the invention, to which is mounted the position sensing system of Figure 1.

Figure 3 is a front view of the fire monitor of Figure 2.

Figure 4 is a side view of the fire monitor of Figure 2 showing the range of elevational movement of the nozzle of the fire monitor. Figure 5 is a top view of the fire monitor of Figure 2 showing the range of rotational movement of the nozzle of the fire monitor. MODES FOR CARRYING OUT THE INVENTION

The fire monitor position sensing system 10 shown in Figure 1 comprises an elevation sensor 12, a rotation sensor 14, and a microprocessor unit 16 which transfers data between it and each of the sensors 12, 14. The sensors 12, 14 are structurally enclosed in a waterproof housing assembly which is mounted on a movable nozzle support assembly of a fire monitor 30 shown in Figures 2 to 5, to which the system 10 is operably connected. In this embodiment, the microprocessor unit 6 is enclosed in a separate waterproof housing assembly (not shown) which is not mounted on the movable nozzle support assembly.

The fire monitor 30 can be mounted in a fixed location, such as in a factory or industrial plant.

The system 10 optionally further includes a graphical display unit 18 to which processed data from the microprocessor unit 16 is transferred for display to a user of the system, the graphical display unit 18 being located remotely of the housing.

The display unit 18 can also serve as an input for instructions for controlling, via the microprocessor unit 16, the operation of the sensors 12, 14 and the movement of the nozzle support assembly of the fire monitor.

The system 10 also optionally further includes fixed reference sensors in the form of a second elevation sensor 22 and a second rotation sensor 24, which can be useful when a fire monitor is mounted on a moving platform, such as a fire truck, fire fighting boat, or other moving vehicle.

These fixed reference sensors 22, 24 are structurally enclosed in a second waterproof housing assembly which is mounted either on a part of the fire monitor that does not move with the nozzle support assembly, or on the movable platform, so that movement relative to the reference sensor can be calculated. This enables the movement of the platform to be compensated for.

Data is transferred between each of the fixed reference sensors 22, 24 and the microprocessor unit 16.

The output data of all the sensors is processed by the microprocessor unit 16, which may be part of an interactive computer, to determine the position of the fire monitor relative to the moving platform.

In a preferred embodiment, the or each elevation sensor is an

accelerometer, and the or each rotation sensor is a magnetometer.

The accelerometer, which can measure the acceleration of an object, including its acceleration due to gravity, is so mounted on the fire monitor as to readily measure the direction of its tilt relative to gravity and the values of its acceleration in multiple axes due to motion. Therefore, the accelerometer is able to readily measure the direction of the fire monitor in the vertical plane and its relative motion in other planes.

The magnetometer, which can measure the earth's magnetic field and so act as an electronic compass, is so mounted on the fire monitor as to readily measure the direction of the fire monitor in the horizontal plane relative to the earth's magnetic field.

The combination of an accelerometer with a magnetometer can provide a two or three axes position sensing system.

In an alternative aspect, the accelerometer is combined with a home position sensor in the horizontal plane so as to measure the fire monitor's relative motion in the horizontal plane, as well as providing a two axes position sensing system.

In another alternative aspect, the position sensing system includes an electronic gyroscope which, when combined with a home position sensor or with an accelerometer and/or a magnetometer, can provide a two or three axes position sensing system for the fire monitor.

Various combinations of such sensors that may be useful for a fire monitor position sensing system would be apparent to persons skilled in the art in light of this description of the present invention. For instance, an elevation sensor may be provided by a combination of a home position sensor and an electronic gyroscope, and a rotation sensor may be provided by a combination of a home position sensor and an accelerometer, or by a combination of a home position sensor and an electronic gyroscope.

The fire monitor 30 shown in Figures 2 to 5 has, as described above, a movable nozzle support assembly 32 on which is mounted a waterproof housing assembly 34 enclosing an elevation sensor 12 and a rotation sensor 14 of a position sensing system 10 operably connected to the fire monitor 30. The sensors 12, 14 may ideally be potted for waterproofing before insertion into a structurally protective outer enclosure. A microprocessor unit 16 of the system 10 is enclosed in a separate waterproof housing assembly mounted on a non-movable part of the fire monitor 30 or on a platform separate to the fire monitor 30. In some embodiments, the microprocessor unit may be enclosed in a separate waterproof housing assembly mounted on a movable part of the fire monitor.

Fire fighting material can be sprayed through a nozzle 36 supported on the assembly 32 of the fire monitor 30. There is a first motor 38 for controlling elevation of the nozzle support assembly 32 (and hence the elevational movement and direction of the nozzle 36) and a second motor 40 for controlling rotation of the nozzle support assembly 32 (and hence the rotational movement and direction of the nozzle 36). The motors 38, 40 thus allow movement of the nozzle support assembly 32 with its attached nozzle 36 in two axes, and so the sensors 12, 14 of position sensing system 10 which is mounted on the movable assembly 32 are also movable therewith in the same two axes.

The range of elevational movement of the nozzle 36 (about a horizontal axis 41) is shown by numeral 42 in Figure 4, and the range of rotational movement of the nozzle 36 (about a vertical axis 43) is shown by numeral 44 in Figure 5.

The fire monitor 30 also has, optionally, a nozzle spray pattern adjustment motor 46 mounted on the nozzle 36 and, optionally, a radio system located within an enclosure 48 for operating the fire monitor 30 by radio remote control.

The accuracy of the direction of aim of a fire monitor employing the position sensing system of the present invention is in the order of (an industry accepted) plus or minus one degree (+/- 2°), although even greater accuracy is possible with refinements of the present invention.

It is another advantage of the present invention that an accelerometer, magnetometer and electronic gyroscope can be used individually or in combination to produce a fire monitor position sensing system that has no mechanical linkages (and so has improved structural and functional reliability), does not require a home position sensor, and can be readily enclosed in a waterproof housing. Similarly, the cost of manufacture, operation, maintenance and repair of such systems may be relatively low.

It will be apparent to persons skilled in the art that various modifications may be made in details of design and construction of the position sensing system and of the fire monitor employing the position sensing system described above without departing from the scope or ambit of the present invention. INDUSTRIAL APPLICABILITY

The fire monitor position sensing system of the present invention has industrial applicability in the field of fire fighting.