GB2261702A - Latch mechanism - Google Patents

Abstract

A latch mechanism in the form of a panic bolt has a pivotal latch member (14) actuated by an operating handle (21) or a knob on a follower (16), such actuation also moving slides (17,18) with upper and lower shoots connected thereto. The latch member (14) has a keeper engaging part (32) and an operating lever (33) pivoted thereon, the lever (33) being engaged (at 43) by a lever assembly (22) on actuation of the handle (21) or knob, to retract the latch member. A locking member (45) pivotally mounted on the pivot axis (26) of the keeper engaging part (32) is too large to enter the keeper so that it remains retracted when the keeper engaging part is received in the keeper (fig 11), and carries a pin (47) which alters the path of movement of the operating lever (33) thereby preventing any attempt to force the keeper engaging part (32) from its keeper, in use. <IMAGE>

Description

LATCH MECHANISM This invention relates to a latch mechanism of the kind which comprises a housing, which is intended to be secured to one side of a hinged wing, such as an outwardly opening door, and which is provided with a latch member which is moveable relative to the housing so as to extend therefrom or be retracted therein, there being an operating member which is pivotally connected to the housing so as to project outwards therefrom and which can be actuated to retract the latch member. Such a mechanism is commonly referred to as a panic latch and is used on the interior sides of wings, such as doors, which are intended to be used as emergency exits from buildings.

Normally a wing carrying the latch mechanism on its inside surface is usually in its closed position, being received in its frame with the latch member held in its keeper at the frame. Opening of the wing by someone at the outside of the wing, if possible at all, is usually only by means of a handle which is normally kept locked. However unauthorised entry from outside is often attempted by someone trying to insert a tool or the like between the latch member and its keeper to produce sufficient thrust to cause retraction of the latch member, thereby allowing opening of the wing.

An object of the invention is to provide a latch mechanism in which the possibility of unauthorised retraction of a latch member out of its keeper is obviated or at least reduced.

According to the invention there is provided a latch mechanism of the kind specified wherein the latch member has a keeper engaging portion extendable from the housing to engage in a closed position of the wing, in use, with a keeper of a frame associated with said wing, and at at least one side of the keeper engaging portion there is a locking member which moves with the keeper engaging portion during at least part of both its normal retraction and extension upon movement of the operating member, the locking member and the keeper engaging portion both automatically retracting into or both being retractible into the housing when the wing is moved towards its closed position, in use, the locking member remaining retracted when the wing fully closes and the keeper engaging portion extends into its keeper, the locking member thereby preventing movement of the keeper engaging portion clear of its keeper unless there is movement of the operating member.

Preferably the latch member has an operating lever pivotally connected to it for transmitting actuation of said operating member to the keeper engaging portion to retract it, in use.

Desirably the operating lever engages with said locking member when the locking member remains retracted and said keeper engaging portion extends in the closed position of the wing, to prevent said movement of the keeper engaging portion clear of its keeper by the application of force to the latch member, in use, between the wing and its frame.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic side view of the interior of a latch mechanism of the invention, with the mechanism being intended to be part of panic bolt with upper and lower shoots as well as a central latch, an operating handle being shown; Figures 2 and 3 are respectively a side view and a front view of a locking member of the latch mechanism; Figure 4 to 6 are respectively a side view, a rear view and a top view of a keeper engaging portion of a latch member of the mechanism; Figure 7 and 8 are respectively a side view and a top view of an operating lever of the latch member of the mechanism; Figure 9 is a diagrammatic end view of the mechanism showing the latch member and locking member when in a door open position; Figure 10 is a view on arrow A of Figure 9;; Figure 11 and 12 correspond to Figures 9 and 10 in a door closed position; and Figure 13 is a fragmentary side view of part of the mechanism showing an anti-thrust arrangement for a bottom shoot of the panic bolt.

The present invention is concerned with an antithrust arrangement at a latch bolt of a latch mechanism which may itself constitute a panic latch or may be incorporated into an arrangement having upper and lower shoots to form a panic bolt. With such an arrangement there would be a three point locking, namely at the upper and lower shoots and also at the centre latch bolt. Thus although the invention will largely be described in relation to a panic bolt, shown partly in Figure 1, it will be understood that the latch mechanism of the invention is equally applicable for use solely in the form of a panic latch.

The panic bolt shown in Figure 1 has a generally channel-shaped housing 10 with a base 11 and parallel sides 12, 13 respectively. It is intended that the housing would have a removable cover, with the base being secured by screws in a vertical orientation adjacent an edge of one side of a wing, for example a door, so that, in use, a latch member 14 can retract and extend from the housing, the door being hinged in an associated frame which has a conventional keeper arrangement, so that in a closed position of the door it is received in its frame and if the latch member is extended this engages into the keeper in the normal manner to retain the door closed.

Much of the structure of the panic bolt shown in Figure 1 is generally standard and does not form part of the present invention.

In particular the base has a circular opening 15 through which extends a cylindrical follower 16.

Moveable along the base of the housing 10 in opposite directions are a pair of slides 17, 18 respectively with overlapping ends. These slides can be activated from the outside of the door by means of said follower 16. The follower has a central spindle slot 19 for connection at the outside of the door to operating means such as a lever or knob handle. Normally a locking arrangement would be provided at the outside of the door in relation to said handle so as to prevent unauthorised entry from the outside of the door fitted with the panic bolt at its interior.

The follower 16 has slots in its internal part and these slots pick up pegs 20 fitted to the two slides 17, 18, so that as the follower is turned from its Figure 1 position, the slides move towards the centre of the unit.

At the inside of the door, the panic bolt has an operating handle 21. This is connected to a lever assembly 22 which comprises a pair of spaced parallel inter-connected plates 23 pivoted at an upper end on a shaft 24 extending between the sides 12, 13 of the housing. Shown in Figure 1 are two lever assemblies 22 at respective opposite sides of the latch member 14.

This is to make the mechanism unhanded, in that in use the operating handle 21 can be connected to the required one of the two lever assemblies to give right hand or left hand operation. Of course this provision for handing the mechanism on site is not essential and only one lever assembly 22 is strictly required.

One plate of a lever assembly 22 has an extension in the form of a hook 25 which, as will be explained, engages with part of the latch member 14 to retract it into the housing against the action of a biasing spring, not shown, which is contained on a pivot shaft 26 on which the latch member can turn to extend or retract out of or into the housing, as will be explained.

The lower end of the lever assembly 22 has studs 27 which engage the slides. As the handle 21 is pushed downwards, the levers of the assembly 22 push the slides towards the centre of the unit. The mechanism is returned to its original positions by means of two compression springs, one of which is shown in Figure 13 denoted by numeral 28. As will also further be explained in relation to Figure 13, the vertical shoots or tubes of the panic bolt, not shown, are connected to the slides by means of connectors 29, at least one of these connectors being adaptable to provide an anti-thrust arrangement in respect of the lower shoot. As shown in Figure 1, opposite end portions of the base are bent through 90" to provide location holes through which spigots 30 of the connectors 29 respectively pass. The upper and lower shoots are connected to said spigots and also themselves pass through the openings provided in said bent-up ends of the base.

Turning now to the construction of the latch member 14, this is carried on pivot shaft 26, which itself is supported by opposite, spaced portions 12a bent into the interior of the channel through 90 at edges of a generally rectangular opening 31 in the centre of side 12 of the housing. Instead of the portions 12a being integral with the channel, they can instead be formed on a separate latch mount which is screwed, in use, to the inner surface of side 12 of the housing to provide the portions 12a at the edges of the opening 31 as before.

The latch mount also provides in its portions 12a respective aligned holes to carry pivot shaft 26 and latch member 14 pivotted thereon. Accordingly the latch parts can be assembled as a separate assembly operation on the latch mount, which is then screwed in position on the housing. Assembly is thus facilitated and springing can be less complex. The latch member 14 can extend and retract through this opening 31 which is, for a reason to be explained, wider than the latch member 14.

The latch member is basically formed in two parts, namely a keeper engaging portion 32 and an operating lever 33. The portion 32 is shown in Figures 4 to 6 and has a generally leading flat surface part 34 terminating in an edge 35 which forms the junction with a curved trailing surface part 36. Extending rearwardly from the flat surface part 34 remote from the edge 35 is a generally hook-shaped part 37 having a flat under-surface 38 which joins a flat surface 39 which itself extends to part 36. The part 37 is bifurcated and the pivot shaft 26 passes through the arms formed by said bifurcation approximately at the junction of the surface part 34 with the hook-shaped part 37, as shown in Figure 6.The interior of the portion 32 is provided with a recess extending inwardly from surface 39, this recess 40 being shown best in Figure 4 as defining a location for a pivot 41 on which the operating lever 33 is carried.

As shown in Figure 8, the lever 33 is generally of T-shape in plan, being pivoted at 42 at the free end of its longer stem-part. Thus when connected to the keeper engaging portion 32, the stem extends through the recess 40, as for example shown in Figures 9 and 11 with a laterally extending, platform 43 of the T-shape being generally disposed beneath the hook-shaped part 37.

However, the platform 43 of the lever 33 extends both laterally and forwardly beyond the end of this part 37.

A short coil spring 44 is arranged between a plug (not shown) held between the bifurcated arms of part 37 and the stem of the lever 33, this spring 44 being relatively weak and serving to bias the lever downwardly from the under-surface 38 of the portion 32. Generally, as will be described, these two portions 32 and 33 of the latch member 14 swing together when the latch is retracted or extended by means of the operating handle 21, even though the lever 33 is pivotally connected to the part 32. The swinging movement of this latch member 14 provides the outer edge of the platform 43 with a part-circular arc which is just clear of the inside surface of the side 13 of the housing.

The latch member 14 has associated with it an anti-thrust arrangement in the form of a locking member 45 shown in Figures 2 and 3. This locking member 45 is in the form of a pair of spaced, parallel, interconnected plates 46 of generally triangular shape. The plates are pivoted at respective upper corners on the pivot shaft 26, the plates 46 being disposed at opposite upper and lower sides respectively of the latch member 14, and in particular the portion 32 thereof. Not only are the plates pivoted on the same axis as the portion 32, but they generally follow its shape in regard to the parts 34 and 36, as shown in Figure 9. However, as can be seen from Figure 9, the plates 46 extend further downwardly and inwardly beyond the part 36 and at this lower corner the plates 36 are interconnected by a shaft 47, shown best in Figure 3.Normally this shaft 47 lies behind the surface 39 and engages an arcuate lower surface part 48 of operating lever 33 of similar curvature to that of surface part 36. The shaft 47 is shown spaced from part 48 in Figures 9 and 10 for clarity. The shaft 47 thus carries the downwardly biased lever 33.

The aforementioned spring, not shown, which is carried on the pivot shaft 26 is arranged to bias both the portion 32 and the locking member 45 to their extended position shown in Figure 9 in normal use, with the operating handle forced outward of the housing by the springs 28. In this position the under-surface of the lateral platform of the lever 33 is disposed slightly above the hook 25 on one plate 23 of the lever assembly 22, so that if the operating handle is depressed, this hook acts on the platform of lever 33 causing it to move slightly upwardly to contact the hook-shaped part 37 of keeper engaging portion 32, with the result that the portion 32, moves together with the operating lever 33 about its pivot so as to retract the latch member 14, and as this occurs the surface 39 of the portion 32 engages the shaft 47 and thus pulls the locking member 45 rearwardly with it, so that in the retracted state, with incidently the upper and lower panic shoots retracted, the latch member 14 and also the locking member 45 are completely received in the housing. Means are provided, preferably at the end of one of the shoots for locking the arrangement in this position. If the handle is released the latch member 14 and locking member 45 are returned to their extended position by means of the spring on the shaft 26.

As is usual with doors to which panic latches or panic bolts are fitted, the door is normally held closed with its latch engaging in a corresponding-keeper in the door frame. Clearly the door can be closed and the latch engaged in its keeper in either of two ways, namely either by merely slamming the door without operating the handle 21 or alternatively the handle on the exterior of the door, or by operating either of these handles to retract the latch bolt, followed by a closing of the door and then a release of either handle to release the latch bolt into its keeper. In either event once the latch bolt has been extended into its keeper there is, with normal panic bolts, the possibility of someone trying to gain unauthorised entry at the door by inserting an implement or a piece of plastic or the like between the door and the frame to try to force the latch bolt out of its keeper. As mentioned above, the present invention provides the locking member 45 as an anti-thrust device to counter such an attempt at unauthorised entry.

It is intended that this panic bolt is used with an associated keeper at the door frame which is of a size to match the keeper engaging portion 32 but which is too small also to admit into it the locking member 45. In other words, the opening defined by the keeper is larger than the width of the portion 32 alone but is smaller than the width of the portion 32 together with the plates 46 at its upper and lower sides.

Accordingly if the door were merely to be forced shut without retracting the portion 32 and locking member 45, these two components would initially be forced inwardly into the housing against their biasing spring by them both engaging with the outside of the keeper.

However once the door has reached its fully closed position the keeper engaging portion 32 would be able to spring out into engagement with the keeper, whereas the locking member 45 would be prevented from doing so by its plates 46 engaging respective outer parts of the keeper frame. Similarly if the inner or outer handle at the door were to be operated to cause retraction of the portion 32 and locking member 45 the door could be closed, but thereafter once the handle was released, again only the portion 32 would be able to enter the keeper, with the locking member 45 held in its retracted position in the housing.

The consequences of this holding in of the locking member 45 can be explained with reference to Figures 9 to 12.

In Figures 9 and 10, the door is regarded as being open and it can be seen that in this position the latch member 14 and the locking member 45 can be moved inwards and outwards of the housing essentially as a single unit, with the rear edge of the platform of the lever 33 describing an arc which just clears the inner surface of the side 13 as previously mentioned. The shaft 47 of the locking member 45 remains in contact with the surface 48 of the lever 33.

However once the locking member 45 has been retracted into the housing its shaft 47 moves to the position shown in Figures 11 and 12. With the latch member 14 also in its retracted position the relative engagement positions of the shaft 47 and under-surface 48 would remain as with Figure 9. However, if the locking member 45 remains retracted whilst the latch member 14 is allowed to extend out of the housing, the lever 33 now assumes a different position relative ço the shaft 47.

As can be seen best from Figure 7, the lever 33 is stepped in its lower surface to provide a shoulder 49 leading to a flat under-surface 50. From Figures 9 and 11 it will be appreciated that once the portion 32 and associated operating lever 33 extend with the locking member 45 still being retracted, the shoulder 49 passes down over the shaft 47, and the spring 44 is of sufficient strength to effect this as a 'snap' action.

The lever 33 is now in its lowered position, but still supported by the shaft 47, over which the flat surface 50 runs. Accordingly when the portion 32 and lever 33 are fully extended, as shown in Figure 11, the shaft 47 is engaged with the under-surface 50 at a position some way beyond the downwardly extending shoulder surface 49. In fact the spacing from the shoulder would be greater than that schematically shown in Figure 11.

The position now reached is effectively a dead latch position in that apart from a small degree of initial rearward movement, the portion 32 and lever 33 are prevented from retracting, i.e. from disengaging from the keeper. This is because any such inward force on the latch portion 32 produces a resultant horizontal or generally horizontal movement of the lever 33 by way of the flat surface 50 running over the shaft 47, only a small amount of this horizontal movement being possible before the outer edge of the platform engages against the inner surface of side 13, with the portion 32 not clear of its keeper.

Thus in effect the fact that the lever 33 is biased down onto engagement with the shaft 47 alters the path of movement of this lever, so that during attempted retraction, after slight initial movement, further inwards pressure on the portion 32 is resisted by the engagement of the platform edge against the rear side 13 of the housing, providing a positive resistance force.

Accordingly by the simple provision of the anti-thrust locking member 45, any attempt to force the latch bolt into its housing by inserting a tool or the like between the door and its frame at the keeper, will be foiled.

Operation of the handle 21 or a handle at the opposite side of the door will cause the hook 25 to lift the platform 43 as previously described thereby shooting the bolts and withdrawing the portion 32 together with its lever 33, the lifting of the platform 43 moving the lever 33 clear of the shaft 47 to allow this retraction of the latch member 14 now to take place.

Figure 13 shows part of the latch mechanism of Figure 1, where the right hand spigot 30 would be connected to the lower shoot of the latch bolt. This connector 29 at the end of its associated slide, has an upstanding, laterally offset projection 51 thereon. As mentioned previously, the lever assembly for moving the slides comprises a pair of spaced plates 23. One of these is shown in Figure 13 and it can be seen that at its lower portion it is provided with a notch or cut-out 52 which is arranged to receive a leading part of the projection 51 if the lower bolt is lifted slightly.

Accordingly normal operation of a handle at either side of the door will cause the lever assemblies to move the slides in the normal way and there is no initial movement of the slide 18 relative to the shown lever 23 prior to normal movement of the slide. However if an attempt were to be made from outside of the door to lift the lower shoot out of its keeper there is sufficient lost-motion between the slide 18 and its connector 29 to allow initial lifting of the shoot to move the projection 51 into engagement in the notch 52 in the plate 23. This small amount of movement is insufficient to allow the shoot to be lifted out of its keeper, but once this initial movement has been made further lifting is impossible since upwards force on the shoot is resisted by the plates 23. Thus this provides an effective antithrust device in relation to the bottom shoot.This device could of course be used on both upper and lower shoots or on the upper shoot alone, though normally it would be the lower shoot, as described to which it would be applicable.

As mentioned earlier in the description, the latch mechanism in the invention is applicable to both panic latches and also panic bolts. With a panic bolt having three-point locking as described, there can be conventional top and bottom shoots with a top trip unit being provided automatically to release the shoots when the door is closed. Alternatively the shoots could connect to pullman type latches at the top and bottom of the door, with the top unit having an automatically release trigger. A further alternative application of the invention would be merely to a panic latch to operate mortice locks and latches, a further alternative being the use of a push pad to replace a cross arm and end box as used with a conventional panic latch.

Claims (16)

1. A latch mechanism of the kind specified, wherein the latch member has a keeper engaging portion extendable from the housing to engage in a closed position of the wing, in use, with a keeper of a frame associated with said wing, and at at least one side of the keeper engaging portion there is a locking member which moves with the keeper engaging portion during at least part of both its normal retraction and extension upon movement of the operating member, the locking member and the keeper engaging portion both automatically retracting into or both being retractible into the housing when the wing is moved towards its closed position, in use, the locking member remaining retracted when the wing fully closes and the keeper engaging portion extends into its keeper, the locking member thereby preventing movement of the keeper engaging portion clear of its keeper unless there is movement of the operating member.

2. A latch mechanism as claimed in Claim 1, wherein the latch member has an operating lever pivotally connected to it for transmitting actuation of said operating member to the keeper engaging portion to retract it, in use.

3. A latch mechanism as claimed in Claim 2, wherein when the locking member moves with the keeper engaging portion it engages a first surface of the operating lever, whilst when the locking member remains retracted and said keeper engaging portion extends in the closed position of the wing, the locking member engages a second surface of the operating lever to prevent said movement of the keeper engaging portion clear of its keeper by the application of force to the latch member, in use, between the wing and its frame.

4. A latch mechanism as claimed in Claim 3, wherein normal retraction of the keeper engaging portion, when the locking member moves with it, causes part of said operating lever to describe an unobstructed arc of movement, whereas once said locking member is in its retracted state with the keeper engaging portion extended into its keeper, said attempted movement of the keeper engaging portion by the application of said force results in said part of said operating lever describing a path of movement which is obstructed, thereby preventing said attempted movement releasing said keeper engaging portion from its keeper.

5. A latch mechanism as claimed in Claim 4, having a housing, and wherein said operating lever has a platform, an extremity of said platform describing said unobstructed arc of movement, when the keeper engaging portion and locking member retract together, and said obstructed path when said attempted movement of the keeper engaging portion occurs with the locking member in its retracted state, said obstruction being engagement of said extremity of the platform with said housing.

6. A latch mechanism as claimed in Claim 4 or Claim 5, wherein said operating lever has a shoulder between said first and second surfaces thereof, relative movement of an abutment of said locking member past said shoulder occurring when said locking member remains retracted and the keeper engaging portion extends, in use, said subsequent attempted movement of the keeper engaging portion causing movement of said operating lever to be guided by engagement of its second surface with the locking member with the result that the movement of said operating lever part is altered from said unobstructed arc, when the locking member engages said first surface, to said obstructed path.

7. A latch mechanism as claimed in Claim 5, wherein actuation of said operating member to retract the keeper engaging portion of the latch member is via a lever assembly acting on said platform of the operating lever to move the platform against the keeper engaging portion of the latch means, which is pivoted at an opening in the housing.

8. A latch mechanism as claimed in Claim 1, having a housing, and wherein said keeper engaging portion and said locking lever are pivotally mounted on a common axis and are extendable and retractable through an opening in said housing, being biased so as normally to be extended from the housing.

9. A latch mechanism as claimed in Claim 8, wherein normal extension and retraction of the keeper engaging portion and said locking lever is effected by actuation of a lever assembly, which is itself connected via a slide with further means for alternatively carrying out said normal extension and retraction disposed, in use, at the opposite side of the wing from the latch mechanism.

10. A latch mechanism as claimed in Claim 9, wherein a pair of said lever assemblies are provided at respective opposite sides of the latch means and are connected to a pair of said slides respectively, the slides being connected to said further means.

11. A latch mechanism as claimed in Claim 10, wherein the further means is a arcuately movable follower for connection to an operating knob or handle.

12. A latch mechanism as claimed in Claim 10 or Claim 11, wherein the slides have respective extensions in the form of locking rods extending in opposite directions out of the housing and being movable into and out of engagement with respective keepers, in use.

13. A latch mechanism as claimed in Claim 12, wherein the slides are biased apart and are connected to said locking rods by respective connectors, a lever assembly connected to one slide and the connector associated with said one slide having a notch and complementary projection respectively or vice versa, and there being sufficient lost motion between said slide and its associated connector so that any attempt, in use, to force the locking rod of said one slide from its keeper results in said lost motion being taken up and said projection engaging in said notch thereby to prevent further movement of said locking rod from its keeper.

14. A latch mechanism as claimed in any one of Claims 10 to 13, wherein the lever assemblies are identical so that, in use, said operating member is engaged with one of the lever assemblies, but is removable therefrom for alternative engagement with the other of the lever assemblies to alter the handing of the mechanism.

15. A latch mechanism and keeper combination comprising a latch mechanism as claimed in Claim 1, wherein the keeper is intended to be disposed, in use, at said frame associated with said wing, and is sized so that in the closed position of the wing the keeper engaging portion of the latch means is biased into it, whereas the locking member is too large to be received into it and remains retracted.

16. A latch mechanism substantially as hereinbefore described, with reference to, and as shown in the accompanying drawings.