GB2234071A

GB2234071A - Sensing device

Info

Publication number: GB2234071A
Application number: GB8916654A
Authority: GB
Inventors: Colin Arthur Mullins; Lawrence Edward Parsons
Original assignee: Wallop Defence Systems Ltd
Current assignee: EST Defence Company UK Ltd
Priority date: 1989-07-21
Filing date: 1989-07-21
Publication date: 1991-01-23
Also published as: GB8916654D0

Abstract

A device for sensing the presence/absence of ferro-magnetic material has a Hall-effect transducer 23 adjacent to a magnet 24 which is movable relative to the transducer. The magnet moves by attraction when ferro-magnetic material is brought adjacent the transducer and signals are produced accordingly. As shown the device detects the presence of a ferromagnetic casing of a rocket 10 (or ferromagnetic material thereon) in a rocket launcher. When the bottom edge 21 of the rocket casing is on a stop surface 20, the magnet 24 is attracted to produce a corresponding signal on cables 25. A secondary magnetic coil 12 on the rocket is then in its proper launch position around primary coil 13 on the launcher. <IMAGE>

Description

ENSING DEVCE This invention relates to sensing devices and in particular to devices for sensing the presence of ferro-magnetic material According to the present invention there is provided a device for sensing the presence of ferro-magnetic material in the vicinity of the device, said device comprising a Hall-effect transducer and a magnet located adjacent the transducer and adapted to move relative to the transducer when a ferro-magnetic material is moved reLative to the transducer to provide a signal indicative ot the presence or absence of the ferro-magnetic material adjacent the device.

Preferably, the magnet is disposed to move along a linear path toward and away from the transducer to provide signals particularly sensitive to the presence or absence of ferromagnetic material in the Line of said path.

Preferably, the transducer is screened to render it relatively insensitive to the presence of ferro-magnetic materiaL not disposed in the general direction of said path.

The device may comprise a housing of generally cylindrical shape within which is disposed the transducer and the magnet constrained to move aLong the axis of the cyLindricaL housing to provide signals particularly sensitive to the presence or absence of a ferro-magnetic material disposed adjacent the axis In a preferred appLication of the device it is disposed within a stop for a rocket in a rocket launcher and is adapted to sense the presence or absence of a rocket within the Launcher.

The invention wilL be described with reference to the accompanying drawing.

Referriny to the drawing, there is shown in sectionaL view the base of a rocket 10 disposed within a rocket launcher of which a base plate 11 is illustrated and to which is attached yuide rails (not shown) within which the rocket is aisposed and from which the rocket is fired and guided until the rocket Leaves the Launcher.

The rocket is of the inductively linked and fired type in which an inductive coil 12 on the rocket surrounds and is inductively tinked to a coil 13 mounted on the rocket launcher, the arrangement being such that a signal passed through the primary coil 13 wiLl fire the rocket 10 by view of the inductive linkage between the coils 12 and 13.

The coil 13 fixed to the Launcher is mounted on an ignition coil housing 14 which is fixed to the base pLate 11 by a threaded boss 15.

A stop 16 comprises an outer housing 17 mounted on a threaded stud 18 which is mounted on the base plate 11 The upper face 20 of the stop 16 provides a surface against which the lower edge 21 of the rocket casing 10 rests when the rocket is fully Loaded within the rocket launcher. In this Location, with the rocket resting against the surface 20, the secondary coil 12 is in full co-operation with the primary coil 13 to ensure that the full flux linkage is achieved between this inductively linked firing mechanism to ensure efficient ignition of the rocket.

The housing 17 of the stop 16 is formed of high nickel alloy (money K500-NA18) the main cylindrical casing being relatively thick and providing a screen ayainst the presence of ferromagnetic material outside the housing, save in the vicinity of the end face 20 where the thickness of the housing is reLativeLy thin.

Disposed within the housing 17 is an inner sleeve 2 of PTFE in the lower end of which is disposed a Hall-effect transducer 23 and in the upper end of which is mounted a rare earth magnet 24.

The rare earth magnet 24 is slideably disposed within the bore of the inner sleeve 22 such that it can move freely along the axis of the cylindrical sleeve both towards and away from the Hatt-effect transducer 23.

Cabliny 25 connected to the HalL-effect transducer 23 by an interface circuit housed within a casing 26 connects the Hall- effect transducer to appropriate circuitry to provide signals dependent upon the position of the magnet 24 relative to the Hall- effect transducer 23.

In use, the rocket launcher will be disposed with its Launching rails elevated to provide the most appropriate firing eLevation for a rocket and the stop 16 will be elevated in line with the launcher rails In this position the rare earth magnet 24 will be disposed at the lower end of the bore of sleeve 22 closely adjacent the end face of the transducer 23.

When a rocket 10 is loaded into the barrel of the rocket launcher it will slide down the rails of the launcher until the end face 21 of the rocket engages the end face 20 of the stop 16, in thte location shown in the drawing.

The presence of the ferro-magnetic material forming the casing of the rocket 10 will attract the magnet 24 to the upper end of the stop 16 until the magnet 24 is disposed against the end face 20 of the stop 16, i.e. in the broken line position snow in the drawing.

The movement of the magnet 24 away from the end face of transcucer 23 will generate a signal passing through cables 25 to instrumentation (not shown) which wiLl signal the presence of the rocket 10.

Upon firing the rocket 10 by the inductive ignition system 12, 13 the absence of the ferro-magnetic casing of the rocket adjacent the end face 20 will cause the magnet 24 to fall away from the end face 20 toward the transducer 23 thereby causing a signal to pass through the cabling 25 to the instrumentation signaling the absence of a rocket from the rocket Launcher.

With the present invention there is provided an extremely sensitive but accurate sensing device for sensing the presence or absence of a rocket within a rocket launcher. It wiLl be appreciated that the same arrangement can be used to detect the presence or absence of any ferro-magnetic material By the present design the device is particularly sensitive to material adjacent the end face of the device 16 and relatively insensitive to any ferro-magnetic material disposed around the outer casino other than adjacent the end face . The device can be eqall applied to other situations other td rocket launcher.

A particular attraction of the present design is that the device is housed within a rocket stop which operates to control the location of the rocket and ensure an efficient co-operation between the fixed inductive coil 13 and the coil 12 on the rocket, thereby ensuring efficient operation of the ignition system.

By housing the transducer 23 and magnet 24 within a completely sealed housing 17, the apparatus is particularly suitable for use in relatively hostile environments, e.g. rocket Launchers on board ships, which can be exposed to weather and in particuLar water which can affect the operation of such devices if not adequately protected.

The device can of course be used with other rocket launchers. It need not be used with rocket launchers which use inductively linked coiLs for the purposes of ignition and need not be used with launchers utilising a guide rail system. The device may be used as the stop of any rocket launcher or, indeed, in any other device in which a sensitive transducer is needed to sense the presence of ferro-magnetic material.

In the particular application the device need not sense the casing of the rocket but could sense a ferro-magnetic device attached to the rocket. Such an arrangement would be particularly suitable if the rocket were not made of ferro-magnetic material.

Claims

1. A device for sensing the presence of ferromagnetic material in the vicinity of the device, said device comprising a Hall-effect transducer and a magnet located adjacent the transducer and adapted to move relative to the transducer when a ferro-magnetic material is moved relative to the transducer to provide a signal indicative of the presence or absence of the ferro-magnetic material adjacent the device.

2. A device as claimed in claim 1 wherein the magnet is disposed to move along a linear path toward and away from the transducer to provide signals particularly sensitive to the presence or absence of ferro-magnetic material in the line of said path.

3. A device as claimed in claim 2 wherein the transducer is screened te render it relatively insensitive to the presence of ferro-magnetic material not disposed in the general direction of said path.

4. A device as claimed in claim 3 comprising a housing of generally cylindrical shape within which is disposed said transducer and said magnet is constrained to move along the axis of said cylindrical housing and provide signals particularly sensitive to the presence or absence of a ferro-magnetic material disposed adjacent the axis.

5. A device as claimed in any preceding claim disposed within a stop for a rocket within a rocket launcher and adapted to sense the presence or absence of a rocket within the launcher.

6. A device substantia-lly as hereinbefore described with reference to and as illustrated in the accompanying drawing.