EP0800694B1

EP0800694B1 - Fire detector identification

Info

Publication number: EP0800694B1
Application number: EP96925845A
Authority: EP
Inventors: Stephen John Bayley
Original assignee: Thorn Security Ltd
Current assignee: Thorn Security Ltd
Priority date: 1995-07-27
Filing date: 1996-07-26
Publication date: 2000-05-24
Anticipated expiration: 2016-07-26
Also published as: GB9515391D0; DE69608538D1; EP0800694A1; WO1997005587A1

Description

The present invention relates to detectors for detecting abnormal conditions, principally smoke or fire, but has in addition application to detectors such as intruder detectors or detectors for noxious gas. In addition, the present invention relates to detectors for detecting or sensing desired parameters, for example in an air conditioning or environmental control system.

Fire or smoke detectors responsive to smoke fumes, temperature, radiation, etc. (herein referred to for convenience as "fire detectors") are typically ceiling mounted, and in industrial and commercial applications, form part of large arrays of detectors electrically coupled to a controller unit. The detectors are normally divided into zones for example on a floor by floor basis so that in the event of an alarm, the controller can determine which zone has sent an alarm signal. It is nowadays common in electronic alarm systems for each detector within each zone to be provided with an electronic switch representing the address of that detector, so that the controller can determine the specific detector or detectors from which the alarm originates.

Problems arise with such individually addressed fire detectors in initial installation and subsequent maintenance. Fire detectors are normally in two main parts, namely a base unit which is secured to a ceiling or other fixed surface and a detector unit which is releasably secured to the base unit and carries an appropriate sensor device. Since the base unit is fixed and the detector unit freely replaceable, it is the base unit which must carry the address. But the base unit is normally secured to the ceiling and wired to the alarm system by electricians who would not normally handle the delicate detector units. The detector units will normally be fitted in a subsequent operation by trained personnel during commissioning of the system.

Subsequent to installation of the base unit, an electrical continuity test is required through the system electrical wiring. This involves applying a high voltage ( e.g. about 500 volts ) to the base units, which can easily damage any delicate device mounted to the base units.

Since the detectors may be mounted on a ceiling which may be high above the ground, for example in an industrial environment, it is a common procedure to fit the detector unit to a base unit by placing the detector unit at the end of a long pole so that an installer, standing on the ground, may position the detector unit adjacent the base unit and then, by a clockwise movement , engage a bayonet fitting between the detector unit and the base unit so that the detector unit is secured onto the base unit.

As can be appreciated, the above considerations may result in excessive time spent on installation by personnel; however, the use of personnel is expensive and it is therefore desirable to minimise for each specific fire detector, the number of visits required, and the amount of time spent by personnel in the commissioning process.

A known type of fire detector is disclosed in EP-A-0362985. This discloses a base unit having an individual address encoded in the form of a plastic card which is inserted through a slot in the side of the base unit, and has a coded array of projections thereon for actuating electrical switches mounted in a sensor when the sensor is fitted to the base unit. Whilst this avoids the problems of a delicate electronic device mounted in the base unit, it nevertheless has disadvantages in that the card must be slid accurately into the slot in the base unit either as a subsequent operation, or in the initial installation, either by an electrician or trained personnel, and this may be a time consuming operation where high ceilings are involved, particularly since it is not possible to use a pole mechanism.

Having regard to the above, it is an object of the present invention to provide an improved fire detector.

In a first aspect, the present invention provides a detector , comprising:

a base unit for securing to a fixed surface, a detector unit containing means for detecting an abnormal condition or sensing a desired parameter, and means for releasably securing together the base unit and detector unit, and

address carrier means carrying an electrically encoded address of the base unit,

characterized in that the base unit includes address carrier latch means for fixedly securing the address carrier means, and the detector unit includes address retaining means for temporarily securing the address carrier means,
wherein the latch means and retaining means are so disposed and arranged that when the detector unit with the address carrier means held in the retaining means is secured to the base unit, the address carrier means becomes latched in the latch means and remains therein despite subsequent removal of the detector unit.

Thus, in accordance with the invention, the base unit can be installed without having any delicate electronic devices therein, and the address carrier means may subsequently be fitted into the base unit in a single act of mounting the detector unit to the base unit. Subsequent removal of the detector unit, e.g. for maintenance purposes, leaves the address carrier means mounted in the base unit.

As preferred, the address carrier means is generally in the form of a slide member, preferably generally planar in form and retaining a circuit card or ceramic tile having a semiconductor device thereon and appropriate electrical contact points. Such arrangement is referred to herein as an address carrier assembly. The edges of the assembly are arranged to make sliding engagement in opposed grooves comprised in the address carrier latch means in the base unit. In addition, an upstanding resilient peg means formed in the address carrier latch means is arranged, when the carrier assembly slides in the grooves, to be moved against it resilient bias so that when the carrier assembly is moved to a desired final position the peg means moves under its resilient bias to engage an aperture in an inner region of the carrier assembly so as accurately to position the carrier assembly. At that position, the electrical contact points of the assembly engage contact strips within the detector unit.

As preferred, the base unit together with the latch means is formed as a one piece injection moulding so that the various elements of the latch means are formed integrally in the base unit. In particular the bias means merely comprises a finger formed from slots in the base unit with an upstanding peg formed thereon. Clearly as an alternative arrangement, the grooves and/or the peg assembly may be formed on the carrier assembly and arranged to engage counterpart features of ribs and apertures in the base unit. Once the carrier assembly is mounted in the peg means, it cannot be withdrawn during normal operation.

So far as concerns the address carrier retaining means of the detector unit, this comprises an arrangement for temporarily holding the carrier assembly in the detector unit but allows disengagement when the carrier means is engaged with the latch means of the base unit. As such, the retaining means while preventing movement must permit easy disengagement, and in one preferred form, upstanding pegs with enlarged heads are formed in the detector unit which engage in keyhole type slots in the carrier assembly so that the carrier assembly may be mounted on the pegs in the wider part of the keyhole slots and may then be moved so that a narrower portion of the keyhole slots engages the pegs in order to prevent subsequent vertical movement of the carrier assembly. During this movement to the narrower part of the keyhole slots, one end of the carrier assembly engages under bracket members on the detector unit, in order to locate the carrier assembly temporarily against movement.

Hence when the detector unit with the carrier assembly installed in the retaining means is mounted to the detector unit, rotating the detector unit onto the unit causes the free edge of the address carrier assembly to engage in said grooves of the latch means and when the detector is rotated through the predetermined arc of rotation the resilient peg means engages in the co-operating aperture of the carrier assembly to firmly engage the carrier assembly in the latch means. Subsequent counter rotation of the detector unit will disengage the retaining means, since the latch means now holds the carrier assembly firmly against rotation. Subsequent counter rotation of the detector unit will cause movement of the keyhole slots in the carrier assembly relative to the peg means in the detector unit so that in the position for disengagement of the detector unit from the base unit, the enlarged heads occupy the enlarged aperture position of the keyhole slots. In this position the detector unit may be removed from the base unit.

It is a further requirement of fire detectors that, with individually addressed base units, each detector unit should have a clearly visible label or flag which can be read by a person standing on the ground.

The arrangement disclosed in previously referred to EP-A-0362985 provides such an arrangement by a portion of the card carrying the encoded address remaining projecting from the base unit so as to be visible to an operator on the ground and having thereon a visual representation of the address. However such an arrangement is not desirable from the point of view of structural integrity of the interior of the base unit since the projecting end may be knocked and disturb the internal electrical connections.. In addition it is not possible to install such card remotely in a high ceiling, for example; the operator must install the card by hand.

In a second aspect, the present invention provides a detector , comprising:

a base unit for securing to a fixed surface, a detector unit containing means for detecting an abnormal condition or desired parameter, and means for releasably securing together the base unit and detector unit, and

label carrier means for affixing to the exterior of the base unit a visually readable label, indicating whether or not the detector unit is mounted to the base unit, characterized in that

the base unit includes a label carrier latch means for fixedly securing the label carrier means, and the detector unit includes a label carrier retaining means for temporarily securing the label carrier means,

wherein the latch means and retaining means are so disposed and arranged that when the detector unit with the label carrier means held in the retaining means is secured to the base unit, the label carrier means becomes latched in the latch means and remains therein despite subsequent removal of the detector unit.

Thus in accordance with this second aspect of the invention, the label carrier means may be installed on the periphery of the base unit when the detector unit is mounted on the base unit, in the same operation. This has advantages that personnel installing the base unit are not required to handle the label carrier, the label carrier is mounted to the base unit in a single operation with the mounting of the detector unit, and furthermore the structural integrity of the base unit is not disturbed; in particular an unintentional knock to the label carrier means will not disturb internal electrical connections.

As preferred, the label carrier retaining means are such that the label carrier is held temporarily in the retaining means. For example the label carrier may be formed to clip over a peripheral wall of the detector unit.. When the detector unit is mounted to the base unit and rotated, a latch means comprising a projecting finger member of the label carrier engages in a slot in the base unit. Rotation of the detector unit through the predetermined arc of rotation causes a resiliently mounted latch in the base unit to engage a hooked end of the finger member such that the label carrier is firmly held in the label latch means. Subsequent counter rotation of the detector unit for removal of the detector unit will cause disengagement of the clip fitting of the label carrier to the detector unit and the label carrier will be held firmly engaged in the latch means.

In accordance with a further preferred embodiment of the invention, it has been appreciated that further improvements may be made in creating efficiency of installation. This further preferred embodiment of the invention is based on the recognition that although it is conventional practice within the security industry to provide fire detectors in two parts as a base unit and a detector unit, which detector unit is secured to the base unit by placing the detector unit to the base unit and rotating the detector unit clockwise to cause electrical and mechanical interconnection of the two parts, it is nevertheless possible to envisage a further interengaged position of the detector unit and the base unit in an inoperative or parked position of the detector unit.

The advantage of such an arrangement is that the detector unit may be mounted to the base unit in a parked position wherein the detector unit is not electrically connected to the alarm wiring. As a subsequent operation, electrical continuity tests may be carried out on the alarm installation, and when everything is satisfactory, the detector unit may be rotated from the parked inoperative position to the fully operative position. This may be done with a long pole mechanism which is commonly used in the art. Thus substantial improvements in efficiency of use of operators time may be achieved.

In a further preferred embodiment, the present invention provides a detector comprising:

a base unit for securing to a fixed surface, a detector unit containing means for detecting an abnormal condition or sensing a desired parameter, and means for releasably securing together the base unit and detector unit by placing the units together and rotating the detector unit through a first arc of rotation to a position in which the detector is operative,

and the releasable securing means including a stop means which is arranged such that normally only rotation in the direction of the first arc is permitted but which can be disabled manually to permit rotation of the detector unit in a counter direction through a second arc of rotation to a parked position in which the detector unit is inoperative while the detector unit remains secured to the base unit.

In accordance with this further preferred embodiment of the invention, substantial savings in personnel's time can be achieved. After the base unit is installed, the detector unit is affixed to the base unit in the parked position. Electrical continuity tests and any other inspections required may then be carried out. As a subsequent operation, the detector unit may be moved from the parked position to the operative position. Since this movement will be a movement in the normal direction of movement common throughout the industry for fitting a detector unit to the base unit, there is no necessity to instruct a field operator in a different fitting procedure from that with which he is acquainted, with consequent dangers of mistakes etc.

In accordance with the preferred form of the invention, when the detector unit engages the base unit prior to its rotation for releasable securing, a stop means, preferably comprising a flexible latch member engages a cooperating stop member on the detector unit and base unit, so that normally the detector unit may only be rotated in a position for securing. A manually operable plunger member projecting to the exterior of the base unit may be provided for engaging the flexible latch member such as to disengage the latch member from the stop member and permitting rotation of the detector unit in a direction counter to that required for normal fitting ( alternatively, a tool such as a small screwdriver may be employed for such disengagement ). Rotation of the head in this counter direction permits movement to a parked position in order to secure the detector unit in position on the base unit but in a parked position.

It will be understood that the first and second aspect of the invention may be advantageously employed with this third aspect of the invention, wherein the locking onto the base unit of the address carrier assembly and the label carrier occur when the detector unit is moved to the operative position from the parked position.

Brief Description of the Drawings

A preferred embodiment of the invention will now be described with reference to the accompanying drawings wherein:-

Figure 1 is a three dimensional side view of a fire detector according to the invention;

Figure 2 is a counterpart view to that of Figure 1 but with a detector unit spaced from a base unit of the detector;

Figure 3 is a three dimensional view showing constructional details of the interior of the base unit;

Figure 4 is a view similar to that of Figure 3 but with an address carrier assembly mounted in the base unit;

Figure 5 is a three dimensional view of the detector unit showing constructional details of the upper side of the detector unit and with an address carrier assembly for mounting in the detector unit;

Figure 6 is a plan view of the lower side of the address carrier assembly;

Figure 7 is a three dimensional view of a label carrier for mounting to the outside of the fire detector;

Figures 8 is a view similar to Figure 5 of the upper side of the detector unit with the label carrier mounted on the detector unit;

Figures 9 and 10 are fragmentary three dimensional views of the side of a base unit, Figure 9 showing the label carrier in a position before mounting on the base unit, and Figure 10 showing the label carrier mounted on the base unit;

Figure 11 is a plan view of the lower side of the base unit with a manually operable plunger for insertion in an aperture in the side of the base unit;

Figure 12 is a fragmentary enlarged view corresponding to that of Figure 11 showing the plunger mounted in the aperture in the side of the base unit; and

Figure 13 is a fragmentary three dimensional view of the base unit corresponding to Figure 12.

Description of the Preferred Embodiment

In simple terms a fire detector consists of a base unit, which is used to terminate field wiring and a detector unit which contains electronics and sensing elements, which is plugged into the base unit to become part of the system.

The base unit in an addressable system holds its unique address, so that the detection of a fire can be pinpointed. The base unit in a conventional system is known as part of a zone and does not hold a unique address.

Installation and commissioning is time consuming and a large cost element of the overall cost. The following features of the present invention are aimed at speeding up installation and reducing cost:

1. The enabling of a detector unit to be fitted to and held in a base unit in a parked position without making electrical contact to the field wiring.

2. Access to a such parked position is made by distorting or moving a portion of the base unit to allow the detector unit to rotate to this position.

3. This can be done by hand or remotely via a pole and special tool from the ground.

4. The normal fitting of a detector unit is by plugging in perpendicular to the ceiling and rotating clockwise to a stop. The fitting of a detector unit into the temporary park position is achieved by plugging in as before and rotating anticlockwise to a stop.

5. To allow the base unit address, which is held on a carrier, to be fitted on a detector unit at ground level and transferred to the base unit at ceiling level when the detector unit is fitted in the normal way.

6. To allow a label, which is held on a carrier and gives a visual indication of the address, to be fitted on a detector unit at ground level and transferred to the base unit when the detector unit is fitted in the normal way. The label is visible from the floor with the detector unit fitted.

7. The address and label carriers are transferred onto the base unit by the use of distorting plastic latches.

8. Subsequent removal or fitting of detector units will not disturb the address and label carrier previously fitted to a base unit.

Advantages

1. The visits to the ceiling by commissioning personnel are reduced.

2. Loop wiring can be tested with the detector unit fitted in the temporary park position.

3. The base unit address can be set at floor level.

4. The base unit when being installed on the ceiling does not contain the address hardware and therefore it can not be damaged.

Referring now to the drawings and Figures 1 and 2 in particular, a smoke detector 2 is shown (referred to herein for convenience as a fire detector) in an orientation suitable for mounting to a ceiling surface 4. In accordance with the normal convention in the industry, the upper side of the detector is that nearest the ceiling whereas the lower side is that furthest from the ceiling and nearest the ground; this is the convention used in the present specification. The detector comprises an upper base unit 6 for securing to the ceiling and a lower detector unit 8 containing a smoke sensor arrangement which is releasably engageable with the base unit by engaging the detector unit in the base unit 6 and then rotating the detector unit in a clockwise direction by about 17° in order to engage a bayonet fitting. A means (not shown) for locking together the base unit and detector unit is provided and may be unlocked by a tool insertable through an aperture 9.

Details of the bayonet fitting are shown in Figure 3, 4, 7 and 8. In Figures 3 and 4 the lower side of the base unit has around its periphery 10 four slots 12 (only two of which can be seen) to define a bayonet connection arrangement, the

slots having extensions

13, 14 extending in opposite directions. The slots 12 are arranged to receive relatively small elongate strips 16 (see Figure 5) mounted on an inner rim 18 of the upper surface of the detector unit. The detector unit has an outer rim 20 for forming a flush surface with the base unit when mounted thereon.

Referring now to Figure 3, 4, 5 and 6 detailed features of construction are shown for enabling mounting of an address carrier assembly 30. Address carrier 30 is formed as a one piece plastic injection moulding in the form of a slide having the outline of an arc of circle with arcuate side edges 31 and has at one side as shown a rectangular aperture 32 forming part of a latch means, in its central portion two keyhole slots 34 forming part of a retaining means and on its other side two recesses 36 forming part of the retaining means. There is mounted an EEPROM device ( not shown ) electrically coupled to a ceramic tile or printed circuit card 38, which circuit card 38 is mounted within a mating recess 39 within carrier 30. Although not shown the EEPROM device is housed in a further recess 41 within recess 39 (Figure 5). Circuit card 30 has a row of electrical contacts 42 for engaging a counterpart row of electrical contact spring pressings 44 disposed on the detector unit, shown schematically.

For connection to field wiring, the base unit 6 has four terminals 202 spaced around its periphery ( Figure 11), and a further inwardly positioned terminal 203. Each terminal 202 has a strip extension 204 with a leaf spring arrangement for firmly gripping contact blades 206 mounted on detector unit 8 when it is moved to the operative position. Contact blades 206 are coupled to electronic circuits within the detector unit.

Referring to Figure 3, it may be seen there are

opposed grooves

50, 52 for receiving the arcuate edges 31 of carrier assembly 30. In addition, a latch member 54 is provided in the base unit wherein a U shaped slot 56 defines a finger 58 with an upstanding latch projection 60 at its free end. This latch projection is adapted to fit within aperture 32 of carrier assembly 30, as may be seen in Figure 4.

Grooves

50, 52 and latch 54, together with the arcuate edges 31 of assembly 30 and rectangular aperture 32, constitute an address carrier latching means.

Referring to Figures 5 and 8, the upper side of detector unit 8 has two upstanding projections 70 with enlarged rectangular heads 72. These rectangular heads are dimensioned to engage within the widened portions 74 of keyhole slots 34 whereas the lower portions 76 of projections 70 are dimensioned to engage within a narrower part 78 of keyhole slots 34. Further narrower parts 79 of the key hole slots are also provided.

In addition two locating projections 80 upstand from the upper surface of detector unit 8, together with brackets 82 which extend laterally, their free ends having on the underside (not shown) pips for engaging in recesses 36 of assembly 30. In an alternative arrangement, the pips and recesses 36 are omitted.

Projections

70, 80, 82 of the detector unit together with

apertures

34, 36 of the carrier assembly together constitute an address carrier retaining means for mounting the carrier assembly to the detector unit. .

It is appropriate to now describe the mounting of the detector unit to the base unit, together with transference of the address carrier assembly. As a first step, a skilled operator will place the carrier assembly 30 onto the retaining means (31-82) of the detector unit as shown in Figure 5 by positioning the widened aperture portion 74 of the keyhole slots 34 over the widened head portions 72 of projections 70. The carrier assembly is then rotated through an arc of a circle so that the lower portions 76 of projections 70 engage in the narrower keyhole slot portions 78 of keyhole slots 34 while the right hand edge of assembly 30 moves under brackets 82 so that the pips thereon engage in recesses 36 and contacts 42 engage the spring contact pressings 44 . In this position, carrier assembly 30 is temporarily retained within the detector unit and will remain there despite movement of the detector unit and accidental knocks etc. to the base unit. However, the carrier assembly is not firmly latched in this position.

Referring now to Figures 3 and 4, when the detector unit is engaged in the base unit and is rotated in a clockwise direction by 17° for engaging the projections 16 into slot extensions 13 of the bayonet fittings , the arcuate edges 31 of carrier assembly 30 will engage within

grooves

50, 52 of base unit 6 in order to locate the carrier assembly within the base unit. Rotation of the detector unit to the working position will cause latch projection 60 to engage within rectangular aperture 32. This is the position shown in Figure 4. In this position, the carrier assembly is fully engaged in the base unit, and subsequent anti-clockwise rotation of the detector unit will disengage the carrier assembly from the detector unit since as described above, it is merely retained by the retaining force of pips engaging apertures 36 and/or the electrical spring contact pressings. In the latched position as shown in figure 4, the electrical contacts 42 on circuit card 40 will engage with electrical contact pressings 44 on the detector unit in order to provide a secure electrical connection of the encoded address EEPROM to the alarm system.

Referring now to Figure 5 and 7 to 10, a label carrier 90 is shown for affixing to the periphery of the smoke detector. The label carrier has a flat label portion 92 for receiving a visually readable label (not shown). This label portion 92 is connected via a bracket member 94 to an arcuate finger member 96 which includes a notch 98 at one free end, and vertically extending strips 100, two of which have pips ( domed protrusions ) 102. In Figure 5, a portion 104 of rim 20, of reduced height, has two dimples 106. As shown in Figure 8, label carrier 90 fits within portion 104, with bracket 94 and strips 100 clipping over rim portion 104 and pips 102 engaging in dimples 106, thereby to provide a label carrier retaining means.

Referring now to Figures 9 and 10, a label carrier latch means for coupling the label carrier to the base unit is shown. This latch means comprises a wall portion 110 integral with the base unit and defining through slot 111 for receiving the free end of finger 96. Notch 98 of finger portion 96 is arranged to engage a latch member 116 of the base unit. Latch member 116 comprises a plastic finger 118 formed between two slots 120 having an upstanding projection free end 122 for resilient engagement into notch 98.

In operation it will be understood that at the same time as address carrier assembly 30 is mounted to the detector unit, the label carrier 90 will at the same time be mounted to the exterior rim of the detector unit in a temporary retained position shown in Figure 8. The label carrier is secured in this position against movement of the detector unit and accidental knocks etc., but is not fixedly held in this position. When the detector unit is engaged with the base unit and before clockwise rotation, the label carrier will have the position shown in Figure 9 relative to the latch member 116. Upon clockwise rotation to the position shown in Figure 10, the finger 96 of the label carrier engages within slot 111 and, when the detector unit is rotated to its working position, the latch head 116 engages within notch 98 to firmly lock the label carrier to the base unit. Subsequent anti-clockwise rotation of the detector unit will cause the latch mechanism 96-122 to disengage pips and

dimples

102, 106 as the label carrier is disengaged from the retaining means and firmly held in the latch means. Thus the detector unit may be subsequently removed from the base unit leaving the label carrier attached in position to the base unit.

Referring now to Figure 11 to 13, this shows further constructional details of the smoke detector for achieving a park position of the detector unit 8 on the base unit 6. The base unit and detector unit have a park stop mechanism comprising a latch finger 140 formed in the base unit between two slots 142 and having a free end in the form of a hook portion 144, together with a guide portion 146 extending from part way along the length of finger 140. Hook 144 is arranged to engage a stop member 150 ( Figures 5,8 ) extending from the inner rim 18 of detector unit 6. A recess 152 is positioned immediately adjacent stop member 150.

A plunger member 160 is mounted in a slot 162 in the side wall of the base unit and comprises a manually operable portion 164 which projects from the base unit and an inner head portion 166 which extends into the slot and is held within the slot by resilient barbs 168. The inner end of the plunger is adapted to abut against finger 140 as shown in Figure 12. Guide portion 146 serves to guide the plunger to the abutting position.

Thus in use, the detector unit is engaged in the base unit and rotated so that the bayonet fittings are located. The rib projections 16 in the detector unit engage within slots 12. Clockwise movement of the detector unit causes projections 16 to engage within slot extensions 13 in which the detector unit is in the fully operative position; in this position, terminals 202 are connected to blades 206 for powering the detector unit. If however it is desired to move the detector unit to the parked position, then an anticlockwise movement is necessary to engage in extensions 14 of the slots. Normally, rotation in the anticlockwise direction is prevented by stop projection 150 on the inner rim of the detector unit engaging against hook portion 144. In order to permit movement to the parked position, it is necessary to displace plunger 164 by pushing the free end inwardly. This may be done by means of a suitable tool member at the end of a pole member used by the installer for mounting the detector unit. With the plunger member 160 fully pushed in through slot 162, its end 166 engages against hook portion 144 in order to move the hook portion 144 inwardly against the resilient bias of finger 140. This movement disengages hook 144 from projection 150, and permits anticlockwise movement of the detector unit so that projection 150 moves past hook 144 to a parked position in which hook 144 engages within recess 152. In this position, projection 16 of the bayonet connection are fully engaged in slot extensions 14, and projections 70 are positioned in keyhole slot parts 79 on the address carrier.

In the parked position, contact blades 206 are disengaged from terminals 202 so that the detector unit and the address carrier are electrically isolated; thus there are no electrical connections made between the detector unit and the base unit and electrical continuity tests may be carried out.

When it is desired to make the detector fully operative, it is necessary to rotate the detector unit in a clockwise direction from the parked position to the fully operative position. This may be done simply by engaging the detector unit with a pole mechanism and making a clockwise rotational movement. The projection 150 and hook 144 have mutually sloping surfaces 180 which will lift the hook 144 in order to permit movement therepast and continued clockwise rotation moves the detector unit into the operative position, as has been fully described above.

In an alternative arrangement, plunger member 160 may be omitted, and hook member 140 may simply be engaged through slot 162 with the end of a small screwdriver to release the stop mechanism.

Claims

A detector (2), comprising:

a base unit (6) for securing to a fixed surface (4), a detector unit (8) containing means for detecting an abnormal condition or sensing a desired parameter, and means for releasably securing together the base unit and detector unit, and

address carrier means (30) carrying an electrically encoded address of the base unit, characterized in that

the base unit includes an address carrier latch means (50, 52, 60) for fixedly securing the address carrier means, and the detector unit includes an address carrier retaining means (70, 80, 82) for temporarily securing the address carrier means,

wherein the latch means and retaining means are so disposed and arranged that when the detector unit with the address carrier means held in the retaining means is secured to the base unit, the address carrier means becomes latched in the latch means and remains therein despite subsequent removal of the detector unit.
A detector according to claim 1, wherein said releasable securing means is such as to act when the detector unit engages the base unit and a rotation of the detector unit is made through a predetermined arc of rotation,
and wherein the latch means is disposed at the lower face of the base unit and the retaining means is disposed at the upper face of the detector unit so that said rotation of the detector unit moves the address carrier means into engagement with the latch means.
A detector according to claim 1 or 2, wherein the address carrier means is in the form of a slide, and includes a circuit card (38) or ceramic tile on which a device is mounted containing said electrically encoded address.
A detector according to any preceding claim, wherein the address carrier means is in the form of a slide, and wherein the latch means has groove means (50, 52) for receiving opposed edge regions (31) of the address carrier means.
A detector according to any preceding claim, wherein the address carrier latch means comprises an interengageable aperture (32) and resiliently biased latch member (54) disposed on the address carrier means and base unit, respectively.
A detector according to any preceding claim wherein the address carrier retaining means comprises interengaging keyhole slots (34) and upstanding peg members (70) disposed on the address carrier means and detector unit, respectively the keyhole slots having a widened portion (74) and a narrowed portion (78), and the upstanding peg members having enlarged end portions (72) adapted to be received in the widened slot portions, and the narrow slot portions (78) being adapted to engage with shank portions (76) of the upstanding peg members.
A detector according to any preceding claim wherein the retaining means includes locating bracket members (80, 82) for positioning over an edge portion (31) of the address carrier means.
A detector as claimed in any preceding claim, including:

label carrier means (90) for affixing to the exterior of the base unit a label visually readable and indicating whether or not the detector unit is mounted to the base unit,

the base unit including a label carrier latch means (110, 111, 116, 118, 120, 122) for fixedly securing the label carrier means, and the detector unit including a label carrier retaining means (104, 106) for temporarily securing the label carrier means,

wherein the latch means and retaining means are so disposed and arranged that when the detector unit with the label carrier means held in the retaining means is secured to the base unit, the label carrier means becomes latched in the latch means and remains therein despite subsequent removal of the detector unit.
A detector according to claim 8, wherein the releasable securing means is such as to act when the detector unit engages the base unit and a rotation of the detector unit is made through a predetermined arc of rotation,
and wherein the label carrier latch means is disposed at a lower part of the base unit and the label carrier retaining means is disposed at an upper part of the detector unit so that said rotation of the detector unit moves the label carrier means into engagement with the latch means.
A detector according to claim 8 or 9 wherein the label carrier means includes a generally flat member (92) for receiving a label having at one edge a clip assembly adapted to interengage with a rim edge portion (104) of the detector unit, to form said label carrier retaining means.
A detector according to claim 8, 9 or 10, wherein said label carrier latch means comprises a slotted member (111) disposed on the base unit to receive an elongate finger portion (96) of the label carrier means, and the base unit including a resiliently mounted latch member (116) for interengaging a recess (98) in said elongate finger portion to form said label carrier latch means.
A detector according to any preceding claim,
wherein said releasable securing means arts by placing the base unit and the detector unit together and rotating the detector unit through a first arc of rotation to a position in which the detector is operative,
and the releasable securing means includes a stop means (144, 150) which is arranged such that normally only rotation in the direction of the first arc is permitted but which can be disabled manually to permit rotation of the detector unit in a counter direction through a second arc of rotation to a parked position in which the detector unit is inoperative while the detector unit remains secured to the base unit.
A detector according to claim 12, wherein said releasable securing means comprises a bayonet fitting (12-14,16) wherein the detector unit and the base unit include interengaging projection members (16) and recesses (12-14), respectively, wherein the recesses extend in two opposing directions to permit the bayonet fitting to be established by rotation in a clockwise direction or in an anticlockwise direction.
A detector according to claim 12 or 13, wherein the stop means includes an interengageable projection member (150) and hook member (144) disposed on the base unit and detector unit, respectively so as normally to prevent rotation of the detector unit through said second arc of rotation.
A detector according to claim 14, wherein the stop means is accessible from the exterior of the detector for engaging said hook member for movement of the hook member to a position out of engagement with said stop member whereby the detector unit can be rotated to the park position.
A detector according to claim 15, including a manually operable member (164) secured in the base unit for said engaging of the hook member.
A detector according to any of claims 14 to 16 including a recess means (152) adjacent the projection member into which the hook member engages for retaining the detector in the parked position.
A detector according to any of claims 14 to 17 wherein the hook member and projection member have mutually cooperating surfaces for permitting disengagement when the detector unit is rotated from the parked position towards the operative position.
A detector (2), comprising:

a base unit (6) for securing to a fixed surface (4), a detector unit (8) containing means for detecting an abnormal condition or a desired parameter, and means for releasably securing together the base unit and detector unit, and

label carrier means (90) for affixing to the exterior of the base unit a label visually readable and indicating whether or not the detector unit is mounted to the base unit, characterized in that

the base unit includes a label carrier latch means (110, 111, 116, 118, 120, 122) for fixedly securing the label carrier means, and the detector unit includes a label carrier retaining means (104, 106) for temporarily securing the label carrier means,

wherein the latch means and retaining means are so disposed and arranged that when the detector unit with the label carrier means held in the retaining means is secured to the base unit, the label carrier means becomes latched in the latch means and remains therein despite subsequent removal of the detector unit.
A detector according to claim 19, wherein the releasable securing means is such as to act when the detector unit engages the base unit and a rotation of the detector unit is made through a predetermined arc of rotation,
and wherein the label carrier latch means is disposed at a lower part of the base unit and the label carrier retaining means is disposed at an upper part of the detector unit so that said rotation of the detector unit moves the label carrier means into engagement with the label carrier latch means.
A detector according to claim 19 or 20 wherein the label carrier means includes a generally flat member (92) for receiving a label and having at one edge a bracket assembly adapted to interengage with a rim portion (104) of the detector unit to form said label carrier retaining means.
A detector according to claim 21, wherein said label carrier latch means comprises a slotted member (111) disposed on the base unit to receive an elongate finger portion (96) of the label carrier means, and the base unit including a resiliently mounted latch member (116) for engaging a recess (98) in said elongate finger portion to form said label carrier latch means.
A detector according to any of claims 19 to 22,
wherein said releasable securing means acts by placing the base unit and the detector unit together and rotating the detector unit through a first arc of rotation to a position in which the detector is operative,
and the releasable securing means includes a stop means (144, 150) which is arranged such that normally only rotation in the direction of the first arc is permitted but which can be disabled manually to permit rotation of the detector unit in a counter direction through a second arc of rotation to a parked position in which the detector unit is inoperative while the detector unit remains secured to the base unit.
A detector according to claim 23, wherein said releasable securing means comprises a bayonet fitting (12-14,16) wherein the detector unit and the base unit include interengaging projection members (16) and recesses (12-14), respectively, wherein the recesses extend in two opposing directions to permit the bayonet fitting to be established by rotation in a clockwise direction or in an anticlockwise direction.
A detector according to claim 23 or 24, wherein the stop means includes an interengageable projection member (150) and hook member (144) disposed on the base unit and detector unit, respectively so as normally to prevent rotation of the detector unit through said second arc of rotation.
A detector according to claim 25, wherein the stop means is accessible from the exterior of the detector for engaging said hook member for movement of the hook member to a position out of engagement with said stop member whereby the detector unit can be rotated to the park position.
A detector according to claim 26, including a manually operable member (116) secured in the base unit for said engaging of the hook member.
A detector according to any of claims 25 to 27 including a recess means (152) adjacent the projection member into which the hook member engages for retaining the detector in the parked position.
A detector according to any of claims 25 to 28 wherein the hook member and projection member have mutually cooperating surfaces for permitting disengagement when the detector unit is rotated from the parked position towards the operative position.