GB2123891A

GB2123891A - Electromechanical release mechanism

Info

Publication number: GB2123891A
Application number: GB08318182A
Authority: GB
Inventors: Rae Keith Vallam; David Wing Kwon Wong
Original assignee: Guardall Ltd
Current assignee: Carrier Fire and Security UK Ltd
Priority date: 1982-07-09
Filing date: 1983-07-05
Publication date: 1984-02-08
Also published as: GB2123891B; GB8318182D0; ES523979A0; ES8405874A1; EP0099223A2; EP0099223A3

Abstract

A mechanism eg for holding open a fire door (A) against the action of a closing force (X) includes a pivoted latch bar (21) in a wall-mounted unit engaging a roller (27) attached via spring-biased arms (29) to the door. The bar (21) carries an armature (26) which is normally held in the latching position by an electromagnet (20). In the event of a fire the magnet (20) is de-energised to allow the latch bar (21) to pivot to an unlatching position (broken line) in which the roller (27) rolls down under the nose (24) of the bar under the action of the closing force (X),and allows the door to close. <IMAGE>

Description

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GB2 123 891 A

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SPECIFICATION

Electromechanical release mechanism

5 The present invention relates to an automatic release mechanism including electromagnetic means and adapted to hold a door or like member in a first position against the action of a force tending to move that member to a second position, when the electro-10 magnetic means are energised, and to release that memberformovementto its second position under the action of said force when the electromagnetic means are de-energised (hereinafter called "a mechanism of the kind stated").

15 Mechanisms of the kind stated are often provided in conjunction with fire doors eg in hospitals and other buildings so that a door can normally be held open by energisation of the electromagnetic means (against theforceofa conventional self-closer), to provide 20 unobstructed access through the respective doorway, but is released to close automatically by de-energisa-tion of the electromagnetic means in response to the detection of a fire. Such mechanisms are "fail-safe" in that they require a constant supply of electrical power 25 to keep the door in its open condition and if that power supply should fail for any reason the door will be released to move into its safety condition, ie closed. The devices hitherto available to provide this function do, however, have certain drawbacks. The conven-30 tional release mechanism comprises an electromagnet fixed in position adjacent to the door and arranged to cooperate with an armature plate mounted on the door, ie so that the electromagnet holds open the door by direct magnetic attraction. The electromagnet must 35 developaconstantattractiveforceonthedoorsuchas to exceed theforce applied by the self-closer and hence these known devices tend to consume undesir-* ably large amounts of power and are generally required to be mains-powered. Another consequence 40 of the high-power operation of known devices is that the magnet tends to become very hot after a continuous period of use and therefore often has to be located adjacent to the top edge of the door to avoid being inadvertently touched. Generally speaking, 45 however, this is not a desirable location from the point of view of wiring-in the device and for maintenance and testing purposes. The excessive heat generated by the device may also itself create a fire hazard.

It is therefore an aim of the invention to provide a 50 simple, compact, automatic release mechanism suitable forthe service described above but which is capable of operating at lower power levels than the known electromagnetictypes. Although primarily intended for use in connection with hinged or sliding 55 fire doors, release mechanisms according to the invention may also find application in the control of ordinary (non fire-protection) doors or other like members for different purposes. Also, while described herein in relation to a door which is normally 60 held open by the mechanism and released to close when the electromagnetic means are de-energised, mechanisms according to the invention may equally find application in relation to movable members -such as smoke ventilators - which are normally held 65 closed against the action of a self-opening device and are released to open upon de-energisation of the electromagnetic means.

The invention accordingly resides in a mechanism of the kind stated comprising a latching member 70 associated with the electromagnetic means and arranged normally to be held in a latching position by said electromagnetic means when the latterare energised and to released into an unlatching position when the electromagnetic means are de-energised; 75 and an engaging member biased adopt a predetermined position in which it is engageable with a portion of the latching member to hold the door or like member in its said first position againstthe action of said force when the latching member is in its said 80 latching position; the engaging member being arranged to move away from its said predetermined position against said bias underthe action of said force when the latching member moves to its unlatching position, thereby to disengage from the latching 85 member and releasethedoororlikememberfor movementto its second said position.

Preferably, the latching member comprises a pivo-tally-mounted bar providing a surface against which the engaging member abuts to hold the door or like 90 member in its first position and which is tilted relative to the engaging member when the bar pivots to its unlatching position so that, in use, the engaging member moves against said surface away from its predetermined position underthe action of said force. 95 The engaging member may itself comprise a roller carried between a pair of arms or by other cantilever means pivoted to a mounting memberforattachment to the door or like member, with spring means biasing the cantilever means to place the roller in said 100 predetermined position.

In a mechanism according to the invention the closing or equivalentforce on the door or like member is resisted through the latching member which in turn is held in its latching position by the electromagnetic 105 means; the mechanical advantage ofthe latching member can readily be chosen such as to require only a modest magnetic holding force to keep that member in its latching position, and hence the electromagnetic means can be operated at significantly reduced power 11 o levels as compared with the conventional form of device described above.

In use, mechanisms according to the invention may besetupwith eitherthe engaging memberorthe latching membermountedtothedoororthe like, 115 while the other of those members is fixed eg to an adjacent wall or other structure so as to achieve the specified engagement between the members when the door or the like is in its said first position.

These and otherfeatures ofthe present invention -120 will now be more particularly described, byway of example, with reference to the accompanying drawings, in which:

Figure 1 is a schematic plan view of atypical installation of a mechanism according to the invention

The drawings(s) originally filed was/were informal and the print here reproduced is taken from a later filed formal copy.

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GB 2 123 891 A

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to hold open a fire door;

Figure 2 is a side view, partly in section, of a first embodiment of a mechanism according to the invention, in its latched condition;

5 Figure3 is a viewsimilarto Figure 2 ofthe same mechanism in its releasing condition;

Figure 4 is an underneath plan view ofthe mechanism as shown in Figure 3; and

Figure 5 is a side view, partly in section, of a second 10 embodiment of a mechanism according to the invention, indicating both latched and releasing conditions.

Referring to Figure 1 there is shown a hinged fire dooriA in a corridor B. This door normally latched in an open position, as shown in full line, by a mechanism C, 15 so as to provide unrestricted passage th roug h the corridor. In the event of a fire, however, the door must close automatically to its broken line position shown in Figure 1-Tothis end thedoor is equipped witha conventional self-closer Dwhich applies a continuous 20 closingforcetothedoorinoppositiontothe mechanism C. As more fully described hereafter, the mechanism Cincludes an electromagnet which, while energised, holds the mechanism in a latching condition to keep the door open against the force ofthe 25 self-closer. If fire is detected, however, the energising currentto the electromagnet is cut off so that the mechanism releasesthedoortomoveto its closed position. The provision of a suitable self-closer D and of a suitable fire detection system for controlling the 30 supply ofelectrical powerto the electromagnet in the mechanism Care matters which will be apparent to those skilled in the art and need not befurther described herein.

In Figures 2-4 there is shown one example of a 35 mechanism according to the invention for use as the mechanism C. Amounting plate 1 is fixed over a recess E provided in the wall Fadjacent to the edge of the door>4(when open) at any suitable height, eg at skirting level. An electromagnet 2 is mounted within 40 the recess by means of a bracket 3 attached to the plate 1. Externally, the plate 1 supports a bracket 4 to which an L-shaped latch bar 5 is pivoted by a horizontal pin 6. The bar 5 extends through a slot 7 in the mounting plate 1 and at its inner end carries an armature plate 8 45 for cooperation with the core 2A ofthe electromagnet 2 and with the inner limb 3A ofthe bracket 3 (which provides a return path for magneticflux when the electromagnet is energised). With energising current supplied to the coil 2B ofthe electromagnet the plate 8 50 is normally held by the magnetto maintain the latch bar 5 in the generallly horizontal orientation illustrated in Figure 2.

Mounted to the door>4 is a channel-shaped bracket 9 to which a pair of paralled arms 10 are pivoted by a 55 horizontal pin 11. A roller 12 on a pin 13 is carried between the distal ends of the arms 10, and a torsion spring 14 biases the arms to adopt the generally horizontal orientation illustrated in Figure 2.

With the parts disposed as shown in Figure 2the 60 roller 12 engages behind the nose 15 ofthe latch bar 5 to hold the door A in its open position, against the force ofthe self-closer acting in the sense of arrow X. More particularly,the roller 12 engages theflat face 15A ofthe latch bar, which extends substantially 65 perpendicularlytothe direction of "pull" on the door.

at a point spaced slightly belowthe pivot pin 6. There is thus applied to the bar 5 a momenttending to pivot the latter in the anticlockwise sense about pin 6 (as viewed in the Figure). However, this moment is counteracted by the clockwise moment on the bar due to the attractive force ofthe electromagnet 2 acting on the armature plate 8. Furthermore, the moment arm of this magneticforce is many times the moment arm of the closing force acting through the roller 12 so that the force of attraction which the mag net 2 has to develop to hold the door open is only a fraction ofthe applied closing force. The corresponding power consumption ofthe electromagnet is therefore much lowerthan that which would be required to hold open the door by direct attraction of an armature plate fixed to the door. The magnet may thus be powered eg from a 24 d.c. supply such as is typically used to operate the detection and control equipment of an associated fire alarm system.

In the event of a fire, the energising current to the magnet coil 2B is cut off, allowing the latch bar 5 to pivot anticlockwise to the position shown in Figure 3. Thistilts the nose 15 ofthe bar so thattheface15Ais now inclined to the direction of"puII"Xapplied to the roller 12. The closing force accordingly now acts to roll the roller 12 down along the face 15A, pivoting the arms 10 against the bias of spring 14 to the position shown in Figure 3, whereupon the roller disengages from the latch bar and allows the doorto close.

If it is required to close the door at anytime without de-energising the magnet 2 this can be achieved in either of two ways. Firstly, the arms 10 can be depressed manually to clearthe bottom ofthe nose 15 and disengage from the latch barwithout disturbing the latter. Alternatively, if the door is pulled hard enough in the closing direction the attraction ofthe magnet 2forthe plate 8 can be overcome, allowing the latchbartobemovedtoitsreleasing positionof * Figure 3; reference numeral 16 indicates a "trimming" potentiometer in series with the magnet coil 2B by which the current through the coil and hence the intensity ofthe attractive force can be adjusted to determine the amount of "pull" required to override the mechanism in this way. Similarly, the mechanism can be set or reset into its latched condition from the door-closed condition either by placing the components by hand into their Figure 2 positions or simply by opening the door and pressing the roller 12 against the latch bar nose 15-this causes the rollerto roll down the arcuate surface 15B ofthe latch bar and then spring up behind the surface 15A, the same action serving to pivot the latch bar into its latching position if not already in that position.

Turning nowto Figure 5, this shows another automatic release mechanism functionally equivalent to the mechanism of Figures 2-4. In this case there is a two-part plastics casing 17/18 surface-mounted to the wall Fvia a backplate 19. Mounted within the casing is an electromagnet 20 and a straight latch bar 21 assembled in a plastics housing 22.The latch bar 21 is pivoted on a pin 23 and has a nose portion 24 extending outth rough a slot25atthe lower end ofthe housing 22. At its upper end the bar 21 carries an armature discc 26 for cooperation with the magnet 20, of which the core is indicated at 20A and the

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Claims

3 GB2 123 891 A 3 energising coil at 20B. The outer skirt portion 20C of the core 20A provides a return path for magneticflux when energised. With energising current supplied to the coil 20B the armature disc 26 is normally held by 5 the magnetto maintain the latch bar in the generally vertical orientation illustration in full line in Figure 5. For engaging with the latch bar 21 there is again a springbiased roller 27 mounted to the door A The roller is carried on stubs 28 at the ends of a pair 10 moulded plastics arms 29 which straddle a mounting body 30 and are pivoted thereto at 31. The arms 29 are biased to adopt the generally horizontal orientation illustrated in Figure 5 by means of leaf springs 32 moulded on to the arms engaging stops 33 on the 15 body30. With the parts disposed as shown in full line in Figure 5 the roller 27 engages the face 24A ofthe latch bar nose to hold the door open, against the force ofthe self-closer acting in the sense of arrow X, as in the case 20 ofthe Figures 2-4 embodiment. When the energising currrenttothe magnet coil 20B is cut off, the latch bar is allowed to pivot to the broken line position of Figu re 5 to tilt the face 24A relative to the rol ler 27. The roller accordingly rolls down the face 24A to the position 25 indicated in broken line and disengages from the latch barto permit closure ofthe door, again as in the case ofthe Figures 2-4 embodiment. Likewise, the mechanism can be manually disengaged, and re-set, as described aboveforthe previous embodiment. A 30 "trimming"potentiometerandtheterminalconnections for the power supply to the magnet 20 (not shown) are located in a compartment 34 in the casing part 18. The latch bar and magnet housing 22 is mounted in 35 the cylindrical "well" 17A ofthe casing part 17 in this embodimentthrough a circumferential series of intermeshing splines orteeth 35, which enable the housing 22 to be mounted in any one of a number of selected azimuthal orientations relative to the casing 40 17 and wall F. This is of advantage in aligning the latch bar 21 with the roller 27 in installations where the open door is inclined to the mounting surface forthe latch unit (ie, in the case of Figure 1, if the door/A opened at an angle to the wall surface F). Reference numeral 36 45 indicates a buffer pad carried bythebody30to cushion any impact of the dooragainst the latch unit. CLAIMS

1. An automatic release mechanism including electromagnetic means and adapted to hold a door or 50 like member in a first position against the action of a force tending to move that memberto a second position, when the electromagnetic means are energised, and to release that member for movement to its second position underthe action of said force when 55 the electromagnetic means are de-energised, comprising: a latcing member associated with the electromagnetic means and arranged normally to be held in a latching position by said electromagnetic means when the latter are energised and to be released into 60 an unlatching position when the electromagnetic means are de-energised; and an engaging member biased to adopt a predetermined position in which it is engageable with a portion ofthe latching memberto hold the door or like member in its said first position 65 againsttheactionofsaidforce when the latching member is in its latching position; the engaging member being arranged to move away from its said predetermined position against said bias underthe action of said force when the latching member moves to its unlatching position, thereby to disengagefrom the latching member and release the door or like memberfor movementto its second said position.

2. A mechanism according to claim 1 wherein the latching membercomprises a pivotally-mounted bar providing a surface against which the engaging member abuts to hold the door or like member in its first position and which is tilted relative to the engaging member when the bar pivots to its unlatching position so that, in use, the engaging member moves against said surface away from its predetermined position underthe action of said force.

3. A mechanism according to claim 2 wherein said surface is provided at one end ofthe bar; the bar carries at its other end an armature for cooperation with the electromagnetic means; and the pivot point ofthe bar is closer to said surface than to said armature.

4. A mechanism according to claim 3 wherein the bar is generally L-shaped with the longer limb thereof carrying the armature and the shorter limb thereof providing said surface; in use, the longer limb being disposed generally horizontallly when in the latching position, with the shorter limb depending therefrom.

5. A mechanism according to claim 3 wherein the bar is generally straight and pivoted intermediate its ends with the longer portion thereof carrying the armature and the shorter portion thereof providing said surface; in use, the bar being disposed generally vertically when in the latching position, with the shorter portion lowermost.

6. A mechanism according to any preceding claim wherein the engaging membercomprisesa roller carried by cantilever means pivoted to a mounting memberfor attachmentto the door or like member, with spring means biasing the cantilever means to place the roller in said predetermined position.

7. A mechanism according to any preceding claim wherein the latching member is configured such that, in use, with the engaging member in its said predetermined position andthedoororlike member in its second position, movement ofthe door or like member into its first position causes the engaging memberto strike a surface ofthe latching member so as to be deflected thereby around the latching member and then re-engage with the latching member underthe action of said bias in the position to hold thedoororlike memberin its first position.

8. A mechanism according to claim 7 wherein, in use, if the latching member is in its unlatcing position theaforesaid striking ofthe latching member by the engaging member causes the latching memberto move to its latching position.

9. A mechanism according to any preceding claim wherein the electromagnetic means and latching member are embodied in a unit for location in a casing adapted to be mounted in juxtaposition to a door or like member, and said unit and casing are configured to permittheirinterrengagementin a plurality of discrete relative azimuthal orientations.

10. An automatic release mechanism substantially

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GB 2 123 891 A

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as hereinbefore described with reference to Figures 2-4 or Figure 5 ofthe accompanying drawings

Printed for Her Majesty's Stationery Office by TheTweeddale Press Ltd., Berwick-upon-Tweed, 1984.

Published atthe Patent Office, 25 Southampton Buildings, London WC2A1 AY, from which copies may be obtained.