GB2286420A

GB2286420A - An anti-tamper panic latch mechanism for a door

Info

Publication number: GB2286420A
Application number: GB9402033A
Authority: GB
Inventors: Roger Smith
Original assignee: FRED DUNCOMBE Ltd
Current assignee: FRED DUNCOMBE Ltd
Priority date: 1994-02-03
Filing date: 1994-02-03
Publication date: 1995-08-16
Anticipated expiration: 2014-02-03
Also published as: GB9402033D0; GB2286420B

Abstract

A panic latch mechanism comprises latch bolts 26, 28 which are prevented from being forced, eg by a thief, in a vertically opposed direction from their locked position by a pivotly mounted paw 56 which engages, by virtue of spring 60, flange 58 on transfer member 34. In operation handle 18 rotates lever 64 which moves the pawl 56 out of engagement and raises lower latching member 32 connected to bolt 28. The motion of member 32 is imparted to upper latching member 30, via pins 42, 44 and transfer member 34, so as to free bolt 26. On release of the handle 18 springs 52, 60 return the mechanism to its locked position. An outside access mechanism, eg a barrel lock, may directly actuate member 34 (see fig 5 - 8). <IMAGE>

Description

EMERGENCY DOOR LATCH MECHANISM This invention relates to latch mechanisms for emergency doors, particularly mechanisms of the kind having movable vertical bolts, one engaging a door frame above a door and the other engaging the floor below. Such mechanisms are often termed panic bolts, and the bolts are withdrawn from their sockets by a lever or bar readily operable from the interior of the building. Operation of the latch mechanism from the outside is not usually possible, though in certain circumstances an external access device may be provided; such external devices are usually operated by a key or the like. Emergency doors having panic bolt latch mechanisms are found in most public buildings.

As noted above panic bolt latch mechanisms are not usually operable from the outside, and thus are often considered secure. However they do have the disadvantage that both bolts may be freed by directly moving one of the bolts, for example by pushing a spade under the emergency door and urging the lower bolt upwards. This is a consequence of the reversible nature of known mechanisms, but it does render public buildings vulnerable to a determined thief.

GB-A-1511738 proposes a panic bolt arrangement in which movement of the lower bolt (but not the upper bolt) causes the mechanism to jam by means of a wedging action.

Whilst this arrangement offers some advantage it is not effective against movement of the upper bolt, which is often easily accessible through a soft wood door frame. Moreover the wedging action requires upward movement of the lower bolt which may itself reduce the effectiveness with which the lower bolt engages the ground socket.

According to the invention there is provided a latch mechanism for a door, the latch mechanism comprising: a body; first and second latching members movable in the body in opposite directions; transfer means pivotable in the body and engaged with said latching members so that arcuate movement of the transfer means is imparted to each latching member as translation in unison in said opposite directions; an actuator operable to move said transfer means arcuately; and releasable locking means to lock said transfer means against arcuate motion, said locking means being released on movement of said actuator.

Thus arcuate movement of the transfer means ensures linear movement of the latching members to engage and disengage locking bolts.

Preferably said actuator engages one of said latching members.

In a preferred embodiment said transfer means is an elongate arm pivoted at its mid point and having first and second radially extending slots diametrically opposed, the first slot engaging an upstanding post of the first latching member, and the second slot engaging an upstanding post of the second latching member. This arrangement allows arcuate motion of the transfer means to impart linear motion to the latching members for movement in unison.

The latching members may comprise generally planar overlapping members slidable in said body and having end slots adapted to accommodate said transfer means. The outer ends of said latching members may have upstanding flanges for attachment by any convenient means to rod like bolts.

In the preferred embodiment the body comprises a generally rectangular box from the short ends of which extend said latching members or bolts forming integral parts thereof; rod like bolts may be journalled in corresponding apertures of the body and may be co-axial.

The actuator preferably comprises an arm pivotable on the front face of the body and having a lever engageable with one of said latching members. The arm may have a socket at the outer end thereof for engagement in use with a generally horizontal operating bar, the other end of which is engaged in a slave unit of the latch mechanism. The actuator lever engages in the preferred embodiment in an aperture in one of said latching members such that arcuate movement of the actuator directly moves one latching member in translation, and thus the other latching member by virtue of arcuate movement of the transfer means.

The mechanism may include resilient means to bias the latching members apart, and said resilient means preferably comprises a coiled compression spring acting directly between respective abutments of the latching members.

In a preferred embodiment the locking means is pivotably mounted for movement from a locked to an unlocked condition, and may comprise a pawl pivotably attached to one of the latching members, and having a free end adapted to engage said transfer means.

Preferably the pawl engages said transfer means to one side of line connecting the pivot axis of said transfer means and the pivot axis of said pawl. In the preferred embodiment the pawl abuts said transfer means to prevent arcuate movement of said transfer means in the bolt disengaging direction. Preferably the mechanism includes resilient return means to bias the locking means to the locked condition, said return means may for example comprise a helical tension spring anchored at one end on the pawl and at the other end on said body or on one of said latching members.

In the preferred embodiment, said actuator lever is adapted to engage said pawl, initial movement of said lever moving said pawl arcuately away from said transfer means to a disengaged condition. Preferably the pawl is biased into engagement with said actuator, this arrangement ensuring that initial actuator movement is transmitted to said pawl without lost motion.

Preferably, the pawl is also movable on direct pivotable movement of the transfer means. Sufficient lost motion may be provided within the system to allow the pawl to be moved to a disengaged condition by the transfer member before movement of the latching members. This allows operation of the latch mechanism by external means for pivoting the transfer means.

In the preferred embodiment the actuator lever is adapted to engage a latching member after a predetermined initial travel, the predetermined travel being sufficient to permit disengagement of said locking means.

External access devices for attachment to the outside of doors have also been developed for latch mechanisms.

Hitherto such devices have been bulky, expensive to manufacture and liable to jam in adverse conditions, such as damp or cold weather, and particularly after long periods of non-use.

According to a second aspect of the invention, there is provided an external access device having a body, a handle arcuately movable with respect to the body about a pivot axis, drive means coaxial with the pivot axis of the handle and extending from the body on the opposite side to said handle, and disengageable engagement means between the handle and the drive means to selectively engage the said handle and spindle for arcuate movement in unison.

Preferably the engagement means is key operated, and in a preferred embodiment it is operated by a barrel lock.

Preferably the engagement means is connected for arcuate movement with the handle, and is movable with respect to the handle to selectively engage'the drive means.

In a preferred embodiment the engagement means is a plunger movable radially with respect to the pivot axis of the handle, and the drive spindle includes receiving means into which the plunger is movable for engaging the drive spindle and the handle for arcuate movement in unison.

In a preferred embodiment, the drive spindle has a drive plate includes an aperture for engagement with the plunger. The plunger may be movable radially outwardly to engage the drive spindle.

Other features of the invention will be apparent from the following description of a preferred embodiment of the invention describea with reference to the accompanying drawings in which: Fig. 1 is a front elevation of the latch mechanism, having fragmentary views of the upper and lower bolts and push bar; Fig..2 is an elevation from the right hand side of Fig. 1 as viewed; Fig. 3 is a rear elevation of the latch mechanism, from which a back plate has been removed and; Fig. 4 is a cross section along the line 4-4 of Fig.

3.

Fig. 5 is a front elevation of an external access mechanism; Fig. 6 is a cross section along line 6-6 of Fig. 5; Fig. 7 is a cross section along line 7-7 of Fig. 6 showing the slot surround and the plunger in a disengaged condition; Fig. 8 is a cross section similar to Fig. 8 but where the plunger is in an engaged condition.

The emergency door latch mechanism 10 consists of a rectangular, die cast body 12 having a front face, upstanding side walls and an open back. The back is closed by a removable cover 13 secured to the back by any suitable method, such as by set screws (not shown). The external side of the front face has a pair of cast symmetrical bosses 20,22 between which an aperture opens to the interior of the body.

An actuator 16 extends through the aperture and is pivotably mounted between the bosses 20,22 about an axis substantially parallel to the short side walls of the body 12. The outer portion of the actuator 16 comprises a generally rectangular die cast handle 18, and the inner portion is an integral lever 64 of a substantially square cross section. As illustrated in Fig. 4 the lever 64 is substantially perpendicular to the front face of the body 12 when the handle 18 extends downwardly at an angle of about 450.

The handle 18 includes at its outer end a socket to receive an operating bar 24 which extends horizontally in use to a slave unit (not shown) having a similar body and a pivoting handle. The operating bar 24 may be of any suitable section and material. Within the body the lever 64 passes through an aperture 62 in a lower latching member 32, such that arcuate movement of the actuator handle 18 results in up and down movement of the lower latching member 32.

The member 32 is connected to a lower latch bolt 28 of circular cross section which passes through a close fitting aperture 29 in the lower side wall of the body. A similar upper latch bolt 26 passes through a corresponding aperture 27 in the upper side wall of the body, and is connected to an upper latching member 30, the latching members 30,32 sliding over each other in the direction of movement of the bolts 26,28.

The latching members 30,32 are generally planar and have respective upstanding end flanges 46,47 to which the latch bolts are connected, for example by welding.

The latch bolts 26,28 are provided with connection means (not shown) at their ends distal from the body, the connection means being for connection to bolt extensions (not shown) adapted to the particular size of the door to which the device is to be affixed in use. The latch bolts 26,28 are coaxial, and the extensions can be of any suitable type and material attachable to the latch bolts by any suitable method (such as by screw threads or roll pins).

The latching members 30,32 each have an overlapping central slot 31,33 at their inner ends through which passes a transfer member 34 journalled in the interior of the front face of the body. The transfer member 34 has opposite symmetrical transfer arms 36, which extend substantially across the interior of the body. The transfer arms 36 have fork ends 38,40 having a common axis, each fork end engaging a short post 42,44 upstanding from a respective latching member 30,32, and the posts being parallel to the pivot axis of the transfer member 34; linear motion of one of said latching members thus causes arcuate movement of the transfer member 34, and consequent linear motion of the other latching member in the opposite direction.

The upper latching member 30 passes between the lower latching member 32 and the interior of the front face of the body 12 as illustrated, and the lower latching member is cut away to allow relative inward movement of the upper latching member 30, which would otherwise be prevented by contact between the post 42 of the upper latching member and the lower latching member.

Upper latching member 30 includes an upstanding flange 50 on the same side as pivot pin 42 and parallel thereto; the flange may be attached by welding or formed in any other convenient manner. A guide post 48 extends between the flange 46 and flange 50 substantially parallel to the axis of the bolts 26,28; the post is fixed to flange 46 and journalled in flange 50. A coiled compression spring 52 surrounds the guide post 48 and urges the flanges 46,50 and thus the latching members 30,32 apart. The guide rod 48 does not extend the full internal length of the body, as this would prevent disengaging movement of the lower latching member 32.

In Fig. 3, parts of the guide post 48 and the coiled compression spring 52 have been omitted for clarity of the overall arrangement. Similarly, in Fig. 4, the coiled compression spring has been shown in fragmentary form.

Extending from the lower latching member 32, parallel to the pivot axis of the transfer arm 34 and to one side of slot 62, is a pivot pin 54. Pivotably mounted on this pivot pin 54 is a generally triangular pawl 56 which has attached between itself and the lower latching member 32 a helical tension spring 60 anchored to the lower latching member on opposite side of slot 62. The spring 60 biases the pawl 56 anticlockwise. The pawl 56 is pivoted about one of its corners with an apex 70 uppermost.

As illustrated the apex 70 of the locking member abuts a flange 58 of the transfer member 34 the flange 58 upstanding and being perpendicular to the axis of the slots 38,40. The abutment of the apex 70 against the flange 58 prevents sliding movement of the latching members 30,32 in the manner described below, but the pawl 56 may be pivoted out of engagement with the transfer member 34.

The third corner 72 of the pawl 56 abuts the lever 64, and by means of the spring 60 the lever 64 is urged away from contact with the lower latching member 32 at the end 74 of the slot 62 nearest the transfer arm 34. In this way, a clearance gap 66 is formed between the end 74 of the slot 62 and the lever 64.

The abutment between the apex 70 of the pawl 56 and the flange 58 of the transfer member 34 is situated to the left of an imaginary line drawn between the respective pivoting axes of the transfer member 34 and the pawl 56, as illustrated in Fig. 3. The pawl 56 is shaped so that it may be moved arcuately, in a clockwise direction in Fig. 3, without interfering with any part of the transfer member 34, to a position where the transfer member 34 may pivot freely without obstruction, thus permitting linear movement of the latching members 30,32. However, the spring 60 which urges the pawl 56 into the locking position, exerts sufficient force to maintain the pawl 56 in the locking position despite the torque applied by the weight of the actuator 16 through the lever 64.

In operation, the actuator 16 is pushed downward by forcing the handle 18 through arcuate motion in an anticlockwise direction (Fig. 2), the lever 64 moving through the clearance gap 66, and in doing so, moving the pawl 56 arcuately, so that the apex 70 is moved away from abutment with the flange 58 to a position where it does not interfere with the mechanism. Further movement of the lever 64 imparts translation of the lower latching member 32 upwards (Fig. 3), and resultant motion of the transfer member 34 and the upper latching member 30, thus moving any bolt extensions inwardly to release a door. On release of the handle 18, the two springs 52,60 act to return the mechanism to the locked position as shown in Fig. 3.

An attempt to actuate the system by applying force to either of the latch bolts 26,28, or the associated bolt extensions, without use of the actuator 16, will not result in movement of the said latch bolts 26,28 as the pawl 56 will prevent upward movement of the lower latching member 32.

Direct arcuate movement of the transfer member 34 (for example by means of an access device located on the other side of the door) causes the flange 58 to move the pawl 56 to a disengaging condition, thus allowing sliding of the latching members 30,32. The forks 38,40 include sufficient clearance to allow the pawl 56 to move fully to a disengaging condition before the posts 42,44 of the latching members 30,32 are engaged by the transfer member 34.

An outside access mechanism 100 comprises a rectangular die cast body 110 having a front face and four side faces, and having an open rear, the rear being covered by a backplate 111. In its front face is journalled a circular die cast handle 112, whose pivoting axis is perpendicular to the plane of the front face of the body 110. Mounted axially in the handle 112 is a barrel lock 114 of known type, having a keyhole 116 in the exposed front face of the handle 112.The other end portion 118 of the barrel lock 114 is pivotable with the barrel on application of a key (not shown) to the lock, and this portion 118 includes a narrow post 120 coaxial with the handle 112, engaged with which is a generally cylindrical operating member 122 having protruding from its face distal from the barrel lock 114, an operating arm 124 parallel to the pivoting axis of the handle, and offset so that pivotal movement of the barrel of the lock 114 will cause the operating arm 124 to trace out an arc.

A plunger 126 is engaged to slide in one direction, perpendicular to the axis of rotation of the handle 112, in a slot 128 in a circular surround 129 the end of the handle in the interior of the body, and engaged with this plunger 126 is the operating arm 124, so that arcuate motion of the operating arm 124 causes lateral motion of the plunger 126.

To avoid backlash or other unwanted motion, a helical compression spring 130 is provided between respective abutments 132,134 of the plunger 126 and the slot 128.

A drive plate 136 is provided which has an annular extension 138 to surround the plunger 126 and the slot surround 129. An aperture 140 is included in the annular extension for passage of the plunger 126. The drive plate 136 is connected to a drive spindle 142 which is coaxial with the handle 112, and passes through the backplate 111 to pass through a door (not shown), and thus the drive plate 136 pivots coaxially with the handle 112.

In use the outside access device 100 has two states.

In the first state, the plunger 126 does not protrude into the aperture 140 of the annular extension 138 of the drive plate 136. In this case, pivoting of the handle does not impart arcuate motion of the drive plate 136 and drive spindle 142, as the plunger 126 does not engage in the aperture 140. In the second state, the plunger 126 protrudes into the aperture 140 and so any arcuate motion of the handle 112 is transmitted directly to the drive spindle 142.

The mechanism is moved from the first state to the second state or vice versa by arcuate movement of the barrel of the barrel lock 114. This causes the plunger 126 to move in or out of the aperture 140 as required.

The drive spindle 142 may typically be engaged with the transfer member 36 of an internal latch mechanism.

Claims

CLAIMS:

1. A latch mechanism for a door, the latch mechanism comprising a body, first and second latching members movable in the body in opposite directions, transfer means pivotable in the body and engaged with said latching members so that arcuate movement of the transfer means is imparted to each latching member as translation in unison in said opposite directions, an actuator operable to move said transfer means arcuately, and releasable locking means to lock said transfer means against arcuate motion, said locking means being released on movement of said actuator.

2. The latch mechanism of claim 1 wherein the actuator engages one of said latching members.

3. The latch mechanism of claim 1 or claim 2 wherein said transfer means is an elongate arm pivoted at its mid point and having first and second radially extending slots diametrically opposed, the first slot engaging an upstanding post of the first latching member, and the second slot engaging an upstanding post of the second latching member.

4. The latch mechanism of any preceding claim wherein the latching members comprise generally planar overlapping members slidable in said body and having end slots adapted to accommodate said transfer means.

5. The latch mechanism of any preceding claim wherein the outer ends of said latching members have upstanding flanges for attachment by any convenient means to rod like bolts.

6. the latch mechanism of any preceding claim wherein the body comprises a generally rectangular box from the short ends of which extend said latching members or bolts forming integral parts thereof.

7. The latch mechanism of claim 6 wherein rod like bolts are journalled in corresponding apertures of the body.

8. The latch mechanism of claim 7 wherein the bolts are co-axial.

9. The latch mechanism of any one of claims 6-8 wherein the actuator comprises an arm pivotable on the front face of the body and having a lever engageable with one of said latching members.

10. The latch mechanism of claim 9 wherein the arm has a socket at the outer end thereof for engagement in use with a generally horizontal operating bar, the other end of which is engaged in a slave unit of the latch mechanism.

11. The latch mechanism of claim 10 wherein the actuator lever engages in an aperture in one of said latching members such that arcuate movement of the actuator directly moves one latching member in translation, and thus the other latching member by virtue of arcuate movement of the transfer means.

12. The latch mechanism of any preceding claim wherein the mechanism includes resilient means to bias the latching members apart.

13. The latch mechanism of claim 12 wherein said resilient means comprises a coiled compression spring acting directly between respective abutments of the latching members.

14. The latch mechanism of any preceding claim wherein the locking means is pivotably mounted for movement from a locked to an unlocked condition.

15. The latch mechanism of claim 14 wherein the mechanism includes resilient return means to bias the locking means to the locked condition.

16. The latch mechanism of claim 15 wherein said return means comprises a helical tension spring anchored at one end on the locking means and at the other end on said body or on one of said latching members.

17. The latch mechanism of any one of claims 14-16 wherein the locking means comprises a pawl pivotably attached to one of the latching members, and having a free end adapted to engage said transfer means.

18. The latch mechanism of claim 15 wherein the pawl engages said transfer means to one side of line connecting the pivot axis of said transfer means and the pivot axis of said pawl.

19. The latch mechanism of claim 16 wherein the pawl abuts said transfer means to prevent arcuate movement of said transfer means in the bolt disengaging direction.

20. The latch mechanism of any one of claims 17-19 when appendant to any one of claims 9-11 wherein said actuator lever is adapted to engage said locking means, initial movement of said lever moving said locking means arcuately away from said transfer means to a disengaged condition.

21. The latch mechanism of claim 20 wherein the locking means is biased into engagement with said actuator, this arrangement ensuring that initial actuator movement is transmitted to said locking means without lost motion.

22. The latch mechanism of claim 20 or claim 21 wherein the actuator lever is adapted to engage a latching member after a predetermined initial travel, the predetermined travel being sufficient to permit disengagement of said locking means.

23. The latch mechanism of any one of claims 17-22 wherein the locking means is also movable on direct pivotable movement of the transfer means.

24. The latch mechanism of claim 23 wherein sufficient lost motion is provided within the system to allow the locking means to be moved to a disengaged condition by the transfer member before movement of the latching members.

25. The latch mechanism substantially as described herewith with reference to the drawings.