A FIRE DETECTOR

Abstract: A fire detector (l) having a body (2) detachably fastenable to a base (6) by complementary fastening means (6l,44) on body (2) and base (6), the body (2) comprising a hood part (4) and a cover part (3) detachably interengageable by complementary hook members (3l) and ledges (42) on the hood part (4) and cover part (3), locking members (62) are provided on the base (6) to maintain the hook members (3l) and ledges (42) in engagement when the body (2) is fastened to the base (6) by said fastening means (6l,44). In the embodiment described the hook members (3l) are on the free ends of the posts (32) mounted on the cover part (3), the ledges (42) are on the periphery of openings (43) through the hood part (4), and the locking members (62) enter the openings (43) when the body (2) is fastened to the base (6). Arcuate grooves (45) in the hood part (4) serve as lead-ins to the openings (43).

Description: The present invention relates to a fire detector and more particularly to the construction of the body and the base in a fire detector in which the body is comprised of a cover part and a hood part and which contains therein fire detecting means,the base being adapted to detachably fasten the body thereto. In general, a fire detector comprises a body in which are received fire detecting means to detect the appearance of a fire and electrical circuits to convert the output of the fire detecting means into electrical signals, etc. and a base which is adapted to be installed on a surface e.g. of a ceiling, in order to detachably fasten the body to said surface. In a known construction (see e.g. the document US-A-3767917), in order to facilitate the cleaning of the fire detecting means and the replacement of the elements of the electrical circuits, etc. during maintentance and inspection of the fire detector, the body comprises a cover part which is provided with claw members and a hood part which is provided with stepped portions to be engaged by the claw members. However, if the body thus comprising a cover part and a hood part is so constituted that they can be easily separated from each other during maintenance and inspection of the fire detector the cover part may be apt to easily come off from the hood part when fastening the body to the base due to the shock, vibrations, etc. to which the body may be possibly subjected, causing problems. Conversely, if the cover part and the hood part are so constituted that it is hard for the cover part to come off even when subjected to shock, vibration, etc. one or both of the cover and the hood parts may be easily damaged, or broken, etc. when it is attempted to disconnect them from each other at the time of maintenance, inspection, etc. of the fire detector, giving rise to other problems. The present invention provides a fire detector having a body detachably fastenable to a base by complementary fastening means on body and base, the body comprising a hood part and a cover part detachably interengageable by complementary hook members and ledges on the hood part and cover part, characterised in that locking members are provided on the base to maintain the hook members and ledges in engagement when the body is fastened to the base by said fastening means. Preferably the hook members are on the free ends of posts mounted on the cover part, the ledges are on the periphery of openings through the hood part,and the locking members enter the openings when the body is fastened to the base so maintaining the hook members and ledges in engagement. In a further preferred form arcuate grooves in the hood part lead to the openings, relative rotation of body and base being required in operation of the fastening means. Thus, in the fire detector in accordance with this preferred embodiment, since the hook members of the posts provided in the cover part are adapted to engage the ledges in the hood part, the connection of the cover part with and its release from the hood part can, on the one hand, be easily performed while on the other hand, once the cover and the hood parts have been fastened together to constitute the body and the so constituted body has been fastened to the base the locking members of the base fill in the gaps formed between the walls of the openings and the surfaces of the projecting posts. Therefore, the posts are prevented from coming out of the openings due to any possible shock, vibration, etc. to which they may be subjected. Further, the locking members on the base and the grooves in the hood part also serve as guides for the body when it is to be fastened to the base. Other objects and advantages of the present invention will become more apparent from the following description taken in connection with the accompanying drawings wherein are set forth by way of illustration and example certain embodiments of the present invention: Fig. l is a longitudinal cross-section view of one embodiment of a fire detector in accordance with the present invention; Fig. 2 is a top plan view of the hood part shown in Fig. l; Fig. 3 is a bottom plan view of the base shown in Fig. l; Fig. 4 is a partial view to illustrate the process of engagement between the slot formed in the hood part and the shifting member formed in the base shown in Figs. l and 3 on a larger scale; Fig. 5 is an enlarged view of a portion of Fig. l encircled by circle V; and Fig. 6 is an exploded view of Fig. 5. Now reference is made to Fig. l of the drawings wherein is shown an embodiment of the fire detector in accordance with the present invention at reference numeral l which comprises a body 2 comprising a cover part 3 and a hood part 4 and containing therein a printed board 53 on which are mounted fire detecting means 5l such as of the light-scattering type and electrical circuit elements such as a fire discriminating circuit or analogue/digital transducing circuit or the like, and a base 6 adapted to be secured by such as screws to the surface of a ceiling not shown and adapted to have the body 2 detachably fastened thereto when there is a relative rotation between them. The cover part 3 is provided on its upper surface with a number of vertically projecting posts 32 preferably at regular angular intervals, the upper ends of which are provided with a hook member 3l (See also Figs. 5 and 6), while in its lower portion with a number of air inlets 33 for leading smoke to the fire detecting means 5l. The hood part 4 is provided on its top wall 4l with openings 43 having a rectangular cross section in the same number and at the same positions as those of the projecting posts 32 on the cover part 3 (See also Figs. 5 and 6), each of the radially inward peripheral walls of the openings having a step-like engaging portion 42 at their upper edge portions to be engaged by the hook member 3l, respectively. Mounted below the under surface of the top wall 4l of the hood part 4 is the printed board 53 which mounts the fire detecting means 5l, electrical circuits elements 52, etc. and which is connected to blade fixtures 44 provided as engaging means on the upper surface of the top wall 4l through pin terminals not shown. When the posts 32 provided on the cover part 3 are inserted into the respective openings 43 formed in the hood part 4, respectively, the hook members 3l formed at the free ends of the posts 32 respectively engage the engaging portions 42 formed at the upper edges of the inner peripheral walls of the openings 43 formed in the hood part 4, respectively, whereby the cover part 3 and the hood part 4 are thus engaged together to form the body 2. The cover part 3 can be easily disconnected from the hood part 4 by using the fingers or a pointed object to move the free ends of the posts 32 to release the engagement between the hook members 3l and the engaging portions 42. In the upper surface of the top wall 4l of the hood part 4 concentric arcuate grooves 45 are provided in the same number as that of the openings 43, each in communication with the openings to form the respective gaps between the outer peripheral walls of the respective grooves 45 and the radially outer surfaces of the posts 32 when the hook members 3l of the posts 32 engage with the step-like engaging portions 42 formed in the top wall of the hood part 4 at the upper edge portions of the openings 43 of the hood part 4, respectively. See Fig. 5. As shown in Fig. 3 the base 6 is provided at its under surface with blade receiving fixtures 6l which act as engaging means in cooperation with the blade fixtures 44 to engage the hood part 4, and a corresponding number of locking members 62, each adapted to be received in the grooves 45 of the hood part 4, respectively, and adapted to reach and fill the respective gaps that are formed between the outer peripheral walls of the grooves 45 and the radially outer surfaces of the posts 32 when the blade fixtures 44 and the blade receiving fixtures 6l are engaged with each other as a result of the relative rotation between body 2 and the base 6. See Fig. 5. The base 6 is adapted to be preliminarily secured to the surface of a ceiling, etc. by such as screws (not shown) passed through the screw-holes 63, and the wires connected to an electrical source and signal wires (not shown) introduced through a bore 64 are connected to the blade receiving fixtures 6l. On assembly, as shown in Fig. 4, when the top wall 4l of the hood part 4 is urged upwards to abut against the lower edges of the locking members 62 and the body 2 is rotated relative to the base 6 the locking members 62 are respectively received within the grooves 45 until the blade fixtures 44 engage with the respective blade receiving fixtures 6l to stop the further rotation of the body 2. At this state, as shown in Figs.l and 5 the locking members 62 are respectively inserted into the respective gaps formed between the outer peripheral walls of the grooves 45 and radially outer surfaces of the posts 32. Therefore, as shown in Fig. 5, substantially all of the gaps are filled with the locking members 62 and the posts 32 are prevented from being moved due to shock, vibration, etc., to thereby securely engage the hook members 3l and the engaging portion 42. In this case, if the end walls of the grooves 45 and/or the side edges of the locking members 62 are so shaped that they have sloped surfaces converging downwards the moving of the locking members 62 into or out of the grooves 45 will be smoother. If the blade fixtures 44 and the blade receiving fixtures 6l have polarities or there are more than three sets of fixtures, then as shown in Figs. 2 and 3, the arcuate angles of the grooves 45 and the locking members 62 relative to the top wall 4l are not identical to each other and the grooves 45 and the locking members 62 can also serve as guides to surely and correctly engage the blade fixtures 44 with the blade receiving fixtures 6l. The opening 43 is not necessarily shaped so as to have a rectangular cross section, and the engaging portion 42 of the edge portion of the peripheral wall of the opening 43 may be embodied as e.g. a projection at the side edge of the peripheral wall of the opening 43. It is also possible that the grooves 45 are not provided with bottoms, but instead may be constituted as through-holes passing through the top wall 4l of the hood part 4. Thus, it will be appreciated that according to the present invention an improved fire detector is provided in which the cover part will not come off of the base as a result of shock or vibration when the body is fastened to the base and in which, at the time of maintenance, inspection, etc. of the detector the cover part and the hood part constituting the body can be easily detached from each other, the constitution thereof being extremely simple. It is to be understood that although certain forms of the present invention have been illustrated and described, it is not limited thereto except insofar as such limitations are included in the following claims.

Claims: A fire detector (l) having a body (2) detachably fastenable to a base (6) by complementary fastening means (6l,44) on body (2) and base (6), the body (2) comprising a hood part (4) and a cover part (3) detachably interengageable by complementary hook members (3l) and ledges (42) on the hood part (4) and cover part (3), characterised in that locking members (62) are provided on the base (6) to maintain the hook members (3l) and ledges (42) in engagement when the body (2) is fastened to the base (6) by said fastening means (6l,44). A fire detector as claimed in claim l in which the hook members (3l) are on the free ends of the posts (32) mounted on the cover part (3), the ledges (42) are on the periphery of openings (43) through the hood part (4), and the locking members (62) enter the openings(43) when the body (2) is fastened to the base (6) so maintaining the hook members (3l) and ledges (42) in engagement. A fire detector as claimed in claim 2 in which arcuate grooves (45) in the hood part (4) lead to the openings (43), relative rotation of body (2) and base (6) being required on operation of the fastening means (6l,44). A fire detector as claimed in claim 3 in which end walls of the grooves (45) converge inwardly towards said opening (43). A fire detector as claimed in any preceding claim in which the locking members (62) are projections on the base (6). A fire detector as claimed in claim 5 in which circumferential walls of the projections converge towards the end remote from the base 6.

Inventors: IGARASHI, YOSHINORI NOHMI BOSAI KOGYO CO.LTD
Applicants: NOHMI BOSAI LTD.
Application year: 1987
Main classification: G08B17
IPC codes: G08B17