GB2469110A

GB2469110A - Shutter status sensing switch

Info

Publication number: GB2469110A
Application number: GB0905763A
Authority: GB
Inventors: Alan Crossland; Graham Hickman
Original assignee: BA ELECTRONICS Ltd
Current assignee: BA ELECTRONICS Ltd
Priority date: 2009-04-03
Filing date: 2009-04-03
Publication date: 2010-10-06
Also published as: GB0905763D0

Abstract

A shutter, for example as used on a fire engine, consists of a number of laths 2, which are hingedly connected together and can be drawn across an opening and latched in the closed state by a latch member 4 which cooperates with a keeper 6. Within the keeper a sensor produces an electrically induced magnetic field that extends beyond the sensor so that the latch member is within the magnetic field when in the latched state. This causes eddy currents within the latch as it is made of, or covered at least in part with a conductive material, thereby producing an opposing magnetic field which changes the induction current. The change in the induction current is identified by a detector circuit which together with a control circuit registers the latch as present. In the absence of the latch the magnetic field is not opposed and therefore the induction current is unchanged and the detector circuit which together with a control circuit registers the latch member as absent. The control circuit may be used to operate a warning light or audible indicator. The latch may be connected to a light located in the space behind the shutter.

Description

I

Shutter Status Sensna Swftch This invention relates to roper shutters fitted to road vehides and s concerned in particular with a sensor that registers if such a rover shutter is opened or dosed by sensing the engagement of the latch mechanism by which such a shutter is latched dosed and switching an electrical circuit accordingly.

U.S. Patent Specification No. 5713621 discloses a system which uses a magnetically operated mechanical switch and requires a magnet to be fitted to the shutter latch to operate the switch and indicate whether the shutter is closed and that the latch is engaged. Other forms use mechanical switches that are operated by contact with the latch whilst it is engaged, these having moving parts which can be affected by movement of the latch during use of the vehide.

Both of these inventions use mechanica' switching which can be subject to fatigue and mechanical failure. UK Patent Specification No 2367409 discloses a similar system that uses an emitter and receiver to detect the presence of the latch whilst it is engaged by sending out a beam which is then reflected back by the latch and picked up by the receiver. This system requires the surface of the emitter and the receiver to be kept clean and dry as contamination and water can adverse'y affect the path of the beam.

An object of this invention is to provide a roller shutter with a atch sensing switch that has no moving parts that does not require the installation of a magnet on the shutter atch and is less affected by water or contamination or the movement of the latch due to vehicle motion.

According to this invention there is provided a roller shutter assembly comprising a structure which surrounds an opening, a roler shutter which comprises a plurality of laths hingedly connected together at their longitudinal edges and moveable across the opening in a direction substantially normal to those ongitudinal edges to open and close the opening, and a latch mechanism operable to retain the shutter in location in which t extends across the opening, the latch mechanism comprising at least one member mounted on the shutter and, for each atch member, at least one keeper which is mounted on the said structure and which has a portion with which the respective latch member co-operates to latch the shutter in the closed state, and a sensor which detects and registers the presence of the latch member, movement of the latch member beyond a distance away from the sensor causing the sensor to register the latch member's absence. The sensor is formed by an electrically induced magnetic field that extends beyond the end of the sensor and into the area occupied by the latch member when in the latched state. The latch member being made of, or covered at east in part with, a conductive material, by entering the sensor's magnetic field induces eddy currents within the conductive material that give rise to a second magnetic field which opposes the sensor's magnetic field. The sensor's magnetic field is induced by a highly stable tuned electric circuit and when the presence of the latch member opposes this magnetic field the result is a de-tuning of the circuit leading to reduced voltage amplitude, together with a voltage phase shift relative to the sensor's energising waveform. Both of these effects are detected, and are converted into a DC voltage whose magnitude is related to the proximity of the latch member, and is compared with a fixed threshold. When the voltage exceeds the threshold a control circuit registers the latch member present by making or breaking an electrical circuit for the duration of that presence. When the latch member is absent the magnetic field is not opposed and the highly tuned electric circuit is stable, then the control circuit registers the latch member absent by making or breaking an electrical circuit for the duration of that absence. A delay between the removal of the latch member from the sensor's magnetic field and the detection and the registration as absent stops false registration caused by vehicle motion induced latch member movement away from the sensor. Conveniently the sensor can be totally contained within a keeper which has no opening in way of the latch member and can be used, with or without the use of an electrical relay switch included within or outside of the keeper, to operate a warning light or other electrical or electrically controlled items.

Specific embodiments of this invention will now be described, by way of example only, and with reference to the accompanying drawings, of which:-Figure 1 is a fragmentary view n perspective showing the lower left hand corner of the shutter and the respective latch mechanism when the shutter is latched in its dosed position, the latch mechanism being viewed from outside the opening at a location displaced from the opening to the left of the opening; Figure 2 is a view similar to figure 1 Uustrating disengagement of the latch mechanism during initial opening of the shutter.

A vehide such as a fire engine has an opening which provides access to a storage compartment. The opening is surrounded by a frame 1 (see figures 1 and 2) and is normaUy dosed by a roller shutter. The roller shutter comprises a plurality of elongate laths 2, which are hinged together along their longitudinal edges. The roUer shutter is urged towards the upper edge of the opening and the open position by means (not shown). The roller shutter is held in the closed position by at least one latch assembly 3 such as that which is described in British Patent No. 242850. The latch assembly 3 comprises at least one latch member 4 which is pivotally mounted on a respective mounting bracket 5 which is secured to the outer surface of the lath 2 of the roller shutter adjacent the respective end of that lath 2. The or each latch member 4 is in a vertical plane which also contains for the or each latch member 4 a respective keeper 6 which is fixed to the frame 1 alongside the opening. The keeper 6 projects outwardly from the frame 1 parallel to the edge of the opening. Its upper surface forms a ramp 7 which slopes downwardly and outwardly from the frame 1. The keeper 6 forms a bight 8 below the ramp 7. The horizontal depth of the bight 8 corresponds to the respective stop surface 9 of the latch member 4. The geometrical form of each latch member 4 is such that the stop surface 9 is located within the respective bight 8 (as shown in figure 1) whereby the shutter is latched against upward movement. Within at least one keeper 6 there is a sensor (not shown) which detects and registers the presence of the latch member 4, movement of the latch member 4 beyond a distance away from the sensor causing the sensor to register the latch member's 4 absence. The sensor is formed by an electrically induced magnetic field (not shown) that extends beyond the sensor and into the area occupied by the latch member 4 when in the latched state. The latch member 4 being made of, or covered at least in part with, a conductive material, by entering the sensor's magnetic field induces eddy currents (not shown) within the conductive material that give rise to a second magnetic field (not shown) which opposes the sensor's 4 magnetic field. The sensor's 4 magnetic field is induced by a highly stable tuned electric circuit (not shown) and when the presence of the latch member 4 and the second magnetic field opposes the sensor's magnetic field the result is a de-tuning of the circuit leading to reduced voltage amplitude, together with a voltage phase shift relative to the sensor's 4 energising waveform. Both of these effects are detected by a detector circuit (not shown), and are converted into a DC voltage whose magnitude is related to the proximity of the latch member 4, and this voltage is compared with a fixed threshold by a control circuit (not shown). When the voltage exceeds the threshold the control circuit registers the latch member 4 present. When the latch member 4 is absent the magnetic field is not opposed and the highly tuned electric circuit is stable, then the control circuit registers the latch member 4 absent. The control circuit s connected to an indicator light on the dashboard of vehicle (not shown) such that the said light is illuminated when the respective latch member 4 is registered as not being present thereby indicating that the shutter is either open or closed and not in the latched state.

An audible warning (not shown) controlled or generated by electrical means may be included together with or in place of the said warning light.

In certain embodiments, substantially as previously described and as shown in figures 1 to 2, where the control circuit is connected, either directly or by the use of an electrical relay switch (not shown) which may be contained within the respective keeper 6 or external to it, to at least one light within the storage compartment closed by the shutter. The control circuit is connected such that the said at least one light is illuminated when the respective latch member 4 is registered as being absent thereby illuminating the storage compartment when the shutter is opened. Electrically controlled items (not shown) may also be used in addition to or in place of the said at least one light.

Claims

CLAIMS1. A shutter assembly which comprises a structure which surrounds an opening, a shutter which comprises a plura'ity of laths hingedly connected together at their longitudinal edges and moveable across the opening in a direction substantiay normal to those ongitudinal edges to open and close the opening, and a latch mechanism operable to retain the shutter in a location in which it extends across the opening, the latch mechanism comprising at least one member mounted on the shutter and, for each latch member, at least one keeper which is mounted on the said structure and which has a portion with which the respective latch member co-operates to latch the shutter in the closed condition, and a sensor comprising an electricaly induced magnetic fied which extends beyond the sensor and is positioned such that when the latch member is engaged it is within the magnetic field, The latch member being made from or covered at least in part with an electrically conductive materia by entering the sensor's magnetic field induces eddy currents within the conductive material that give rise to a second magnetic field which opposes the sensor's magnetic field and this change in current is detected by a detector circuit which in conjunction with a control circuit then registers the presence of the latch member by making or breaking an electrical circuit for the duration of that presence, and the said position of the sensor also being such that when the latch member is not engaged with the keeper the induced magnetic field is not opposed and the detector and control circuit then registers the absence of the latch member by making or breaking an electrical circuit for the duration of that absence.
2. A shutter assembly according to claim 1, wherein the sensor's magnetic field is induced by a highly stable tuned electric circuit and when the presence of the latch member opposes said magnetic field the result is a de-tuning of the said circuit leading to reduced voltage amplitude, together with a voltage phase shift relative to the sensor's energising waveform.
3. A shutter assembly according to any one of claims I and 2, wherein the reduced voltage amptude, together with the voltage phase shift relative to the sensor's energising waveform are detected and converted into a DC voltage whose magnitude is related to the proximity of the latch member to the sensor, and is compared with a fixed thresho'd so that when the voltage exceeds the threshold the contro' circuit registers the latch member present.
4. A shutter assembly according to any one of claims 1 to 3, wherein a time delay is incorporated between the detector circuit detecting absence of the latch member and the control circuit making or breaking an &ectrical circuit.
5. A shutter assembly according to any one of daims I to 4, wherein the sensor is housed within a keeper.
6. A shutter assembly according to daim 5, in which more than one keeper containing a sensor is used.
7. A shutter assembly according to any one of daims I to 6, wherein the or each sensor is connected to an indicator light which is switched on by the detector when the or a latch member is not engaged.
8. A shutter assembly according to any one of claims I to7, wherein the or each sensor is connected to at least one light fitted in a position within the boundaries of the structure and behind the closed shutter said at least one light being switched on by the detector when the or a latch member is not engaged.
9. A shutter assembly according to any one of claims 7 or 8, wherein the switching of the at least one light is by the inclusion of an electrical relay switch.
10. A shutter assembly according to claim 9, wherein the relay switch and the sensor are both incorporated within a keeper.
11. A shutter assemb'y according to any one of cams 7 to 9, wherein an audio indicator or other e'ectronic item may be substituted for or be in addition to the at east one tight.
12. A shutter substantiay as described hereinbefore with reference to the accompanying drawings.