GB2141479A - Self-resetting door latch - Google Patents

Abstract

In a pet door having an open frame (11) and a top hung flap (12) therein, a latch mechanism (10) allows unobstructed outward opening movement of the flap (12) in direction B, but normally bars inward movement in the opposite direction A thanks to a raised catch (15). The catch is pivoted (at 29) and is held from below in its raised position by a collapsible strut formed by a toggle (17); the toggle is braced by a spring (35) against an abutment (36) which maintains the toggle in an uncollapsed state. When the flap (12) is required to open inwards, an actuator solenoid (19) is energised to thrust the toggle (17) overcentre, away from the abutment, to a collapsible state, whereupon the flap (12) can displace the catch (15) downwardly and swing open the toggle (17) being fully collapsed as the catch is displaced. The spring (35) automatically resets the catch (15) and returns the toggle (17) to its original position against the abutment (36). The catch (15) is mounted on a support cradle (16) (pivoted at 30) to enable the catch to move momentarily out of the way of the flap (12) as the latter swings back to its closed and latched position. <IMAGE>

Description

SPECIFICATION Self-resetting door latch This invention relates to a self-resetting door latch.

More particularly, the invention relates to a door latch for a door hinged to swing open in both directions about its hinge axis.

The latch to be described allows the door to be opened freely in one direction, but normally prevents opening in the opposite direction. On demand, however, the latch is disabled permitting opening of the door in the latter direction. The latch then resets itself for latching the door once again. The latch is temporarily displaceable as the door closes, to permit the door to pass the latch ,and then reengage the latch.

The latch is beneficial in any situation where free opening of a self-closing door is required in one direction, but unauthorised opening in the other direction is to be barred.

The latch has been devised primarily, but not exclusively, for pet doors having top-hung door flaps which close by swinging under gravity after opening in either direction.

According to the present invention, there is provided a latch mechanism for securing a doubleopening door against opening in one of its opposite opening directions, comprising a movable catch to engage and secure the door against open-ing in the said one direction in a normal operative position of the catch, a collapsible member to hold the catch in its normal position, and actuating means operable on demand to produce a collapsing of the collapsible member and thereby allow the catch to move out of its normal position to free the door for opening in the said one direction, the mechanism further including means to bias the said member to its noncollapsed state for resetting the catch to its normal operative position after operation of the actuating means.

In a preferred embodiment, the collapsible member is a toggle device maintained overcentred against an abutment by the biasing means, the device being overcentred away from the abutment to a state of collapse by a thrust exerted thereon by the actuating means.

Conveniently, operation of the actuating means places the toggle device in a state of partial collapse, and the device is collapsed fully when the catch is moved away from its normal position in response to an opening movement of the door in the said one direction.

The toggle device may have a pair of pivotallyinterconnected links, one of which is coupled to the catch and the other of which is adapted to be attached to a pivot mounting, and the biasing means is a spring tensioned between two attachment points on the links, said spring being stretched and further tensioned when the actuating means overcentres the device away from the abutment.

In a preferred embodiment, the catch is pivotally mounted, remote from the collapsible member, on a rockable support member which mounts said catch adjacent one end thereof, the support member being mounted to rock with the catch about an axis adjacent its other end and adjacent the collapsible member, the arrangement in use permitting the reset catch to be displaced by the moving door out of the path of movement of the door, as the door swings back to its closed position.

The invention comprehends a self-closing door such as a pet door fitted with the latch mechanism embodying the invention.

The latch mechanism is particularly useful for doors having clectronic or electomagnetic controls, when the actuating means may, most conveniently, be a solenoid operator.

The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 schematically illustrates part of a pet door fitted with a latch mechanism according to this invention, the mechanism being shown from one side in exploded illustration; Fig. 2 illustrates the mechanism as seen from above; Fig. 3 shows the mechanism, as seen from the front, in a latching position, Fig. 4 shows the mechanism, as seen from the side, in a door-releasing position; Fig. 5 shows the mechanism in the doorreleasing position, as seen from the front; Fig. 6 shows the mechanism from the side, deflected by the moving flap of the pet door; and Fig. 7 shows the mechanism from the side, in its latching position to prevent inward movement of the pet door flap.

Pet doors for which the latch of this invention was primarily devised are those which allow animals ready egress from the building, but which bar entry to unwanted animals such as strays, neighbours' pets and so on. Animals permitted entry are furnished with a collar bearing a key. The key actuates a control circuit responsible for enabling release of the latch, whereupon the animal can push the flap aside to enter the building. The control circuit and key form no part of the present invention and hence will not be described in detail. The circuit can involve electromagnetic sensing means responsive to a magnetic key. A more sophisticated circuit includes radio-frequency sensing means alert to specific radiated frequencies produced when a tuned circuit, constituting the key, is energised by an interrogating signal generated by the control circuit.Such a control circuit and key are disclosed in our pending G.B.

Patent Application No. 8211 861.

Use of the present latch mechanism is not confined to pet doors. The mechanism can, for instance, be used for access flaps to keycontrolled animal feeding stalls, in which the animals can only reach the food in their own allotted stalls. The mechanism is also suitable for latching appropriately self-closing doors or barriers, e.g. emergency exit doors or other exit doors of public buildings such as theatres.

Referring now to the drawings, a pet door embodying the preferred latch mechanism 10 comprises a door frame 11 and a top-hung door flap 1 2 capable of swinginq within the door opening 1 9. The door flap 1 2 can be swung in either direction about its top hinge (not shown) to allow a pet to pass through the door opening. However, the latch mechanism 10 normally prevents movement of the flap in one direction, A in Figs. 1, 4 and 7. When installed in a building, direction A will usually be the inward opening direction. Although inward opening is normally barred, the latch mechanism 10 does not hinder outward opening in direction B, so pets will have ready egress from the building.Upon a command signal generated by a control circuit (not shown), the latch mechanism 10 is disabled to the extent that a pet can push the door flap 1 2 from engagement with the mechanism 10 and enter the building.

The latch mechanism 10 comprises five components. They are: a pivotally movable catch 15, a support rocker or cradle 16, a collapsible strut 17, a biasing spring 1 8 and a latch disabling means 19.

The catch 1 5 comprises an arm 20 having an upstanding projection 21 at one end normally positioned to engage an edge (for instance the bottom edge) of the flap 1 2 and prevent inward opening movement. The upstanding projection 21 has a top or ramp surface 22 inclined to its door-engaging face, for a reason to be explained hereafter. There are three recesses traversing the underside of the aim 20. Beneath the upstanding projection 21, is recess 24; this is to receive the head 25 of the collapsible strut 1 7. At the opposite end of the arm 20 is recess 26, which is a cylindrical hollow having an inwardly-tapering entrance. Recess 24 has a similar form.Recess 26 permits the catch 15 to form a snap fit with a pivot pin portion of the cradle 1 6. Intermediate the recesses 25, 26 is a comparatively shallow recess to receive and retain the biasing spring 18.

The cradle 1 6 has two spaced-apart legs 28 interconnected at one end of the cradle by the pivot pin portion 29. The catch 1 5 is received between the legs 28, with its recess 26 pivotally engaged on pin portion 29. Oppositely-directed, aligned stub shafts 30 are provided on the legs 28, adjacent their free ends, remote from pivot pin portion 29. The stub shafts 30 engage in journals (not shown) suitably provided in the door frame 11. The cradle is therefore mounted to rock about an axis through the stub shafts 30, this axis being parallel to thc pin portion 29 on which the catch 1 5 pivots in the cradle. The stub shaft axis is closely adjacent the recess 24 seating the head 25 of the strut 1 7.

The collapsible strut 1 7 is an over-centring device or toggle linkage. As is conventional therefore, the toggle strut 1 7 has two links pivotallyinterconnected at axis 32. One link terminates in the head 25 which seats in the recess 24 of the catch 1 5. The other link is apertured at 33 for pivotal mounting to the door frame 11. The pivot axes at 32, 33 are mutually parallel. A tension spring 35 extend bctween attachment points therefor on the two links. The spring 35 urges the toggle strut 1 7 to over-centre against a fixed abutment 36 on the door frame 11. When the strut 1 7 is bearing upon the abutment 36, it is effectively rigid.The abutment 36 then prevents collapse of the strut 1 7. In this condition, the strut positively bars downward displacement of the catch 1 5 about the pivot pin portion 29 and consequential disengagement of upstanding portion 21 from the door flap edge. The strut 1 7 must be over-centred away from the abutment 36 before it can collapse and allow the latch mechanism 10 to yield to an inward opening movement of the door flap 1 2.

The biasing spring 18 acts between the door frame, and the assembled catch 1 5 and cradle 16. It engages these assembled components 15, 1 6 at a location remote from the pivot axis through the stub shafts 30. The spring urges the pivot pin end of the cradle 1 6 upwardly about the said pivot axis, while affording the cradle an ability to pivot downwardly on its stub shafts 30. Yielding of the spring occurs when the door flap 12 is returning to its closed, Fig. 1, position after the latch 10 has released the flap and it has been opened inwardly. This will be described hereafter. The biasing spring could be a leaf spring or a compression spring. In the preferred embodiment, however, spring 18 is a spring wire in the shape of a hairpin having one leg braced against an abutment on the door frame and the other leg held in the shallow recess therefor in the underside of catch 15. The spring 1 8 is anchored to the door frame at the juncture between its legs.

The latch disabling means 1 9 is shown here as a solenoid-controlled actuator having a displaceable core 40. The core 40 is displaceable to over-centre the collapsible strut 17 away from the abutment 36. The core so functions while a command signal is received by the solenoid winding 41 from the control circuit (not shown). This command signal is generated while a "key" is sensed by the control circuit in the vicinity thereof. In acting to over-centre the strut 17, the core has to overcome the counter-acting force exerted by the strut spring 35 and accordingly the spring 35 must be quite weak. The core 40 engages an ear 42 on the strut 1 7 adjacent its central pivot point 32, when overcentring the strut.

The functioning of the latch mechanism 10 will be explained in more detail now.

It will be observed from Figs. 1 and 7 that an animal may-push the door flap 12- open from inside the building (in direction B) without difficulty. The catch 1 5 does not hinder such outward opening in any way because the door flap 1 2 swings away-from the catch upstanding portion 21. This portion 21 blocks inward opening movement of the flap 1 2 (in direction A), however, should an unwanted animal endeavour to enter the building. The flap 1 2 cannot be thrust past the catch 1 5 by any force, within practical limits, exerted thereon. This is because the strut 1 7 holds the catch in its normally raised position. At this time, the strut 1 7 is rigid, being braced against the abutment 36.The underneath support the strut 1 7 gives the catch is applied thereto at a point spaced from the pivot pin portion 29. Thus, the catch 1 5 is rendered incapable of swinging downwards by pivoting on the said portion 29. It is mechanically impossible for force exerted in direction A on catch portion 21 to pivot the assembled catch 1 5 and cradle 1 6 about the axis of shafts 30 so as to release the flap for inward opening movement.

Suppose now that a key-bearing animal wishing to enter the building approaches the door. The prescnce of the keyrwill lead to a command signal being fed to the solenoid 1 9.

The solenoid 1 9 will activate and displace the strut 1 7 from contact with the abutment 36, overcentring the strut. If the solenoid has a long enough throw, it may displace the strut 1 7 to the position shown in Fig. 5. In this case, the catch will drop about pivot pin portion 29 clear of the level 48 of the bottom edge of the door flap 12, so the flap is immediately freed for inward opening. Generally, however, the solenoid throw will not be so long, but nevertheless sufficient to displace .the strut 1 7 from the abutment and overcentre it. While overcentred, the strut will retain the catch 1 5 in a partly-raised position until the flap is pushed inwardly by the animal.When this happens, the flap 1 2 will displace the catch 1 5 about the pivot pin portion 29 and collapse the strut to the position shown in Fig. 5. As the strut 1 7 is collapsed, its spring 35 is stretched, as will be appreciated. Once the flap slips clear of the displaced catch, the spring 35 will relax and erect the strut, overcentring it against the abutment 36. The catch will be returned to its normal, raised position at the same time, i.e.

is reset.

Suppose now that an animal entering the building has just cleared the door. The flap 1 2 then swings back in direction B towards its closed position of its own accord. Towards the end of its swing, the flap edge encounter; the upstanding portion 21 of the raised catch 15.

For the latch mcchanism to lock the flap once more against entry of unwanted animals, the flap must pass the catch 1 5 to assume the catch-engaging position shown in Figs. 1 and 7. To make this possible, the catch is designed to be cammed downwardly away from the moving flap cdge. The camming action results from coaction of the ramped surface 22 with the moving flap 12, and rocking of the cradle 1 6. The catch is downwardly dlisplaceable due to the camming action, despite the strut 1 7 being erect and braced against the abutment 36. Fig. 6 shows the manner in which the catch is displaceable.

As shown, the strut 1 7 prevents displacement of catch 1 5 about pivot pin portion 29.

Instead, thc catch 1 5 is momentarilly displaced jointly with the cradle 1 6 by the flap.

The assembled catch and cradle rock downwardly thanks to the pivotal attachment of the cradle 1 6 to the door frame through its stub shafts 30. This displacement is against the bias of spring 1 8. Thus, when the flap has encountered, displaced and passed the catch 15, the spring 1 8 will thrust the catch and cradle assembly upwardly about the stub shaft axils. The catch 1 5 is thereby raised and returned once again to its normal position, when it will prevent inward opening of the flap until such time as the solenoid is activated.

The latch mechanism 10 described above has a very positive action. Before the solenoid 1 9 is activated, the flap 1 2 is entirely secure, no inward force exerted thereon being effcctive to override the catch 1 5. No significant force is needed to displace the flap past the catch after activation of the solenoid. The mechanical arrangemcnt is such that release of the catch 15, for inward flap movement, can be brought about by low strength solenoids. Even if the flap were somehow thrust hard against the catch before the solenoid is activated, this will not perturb operation of the latch mechanism in any way. In particular, the ease of overcentring the strut 1 7 is not changed for the worse. The spring-biased strut 1 7 resets the catch automatically once the flap 21 has passed the catch. Indeed, resetting occurs should a key-bearing animal approach within range of the control circuit but decide against entering the building and then move out of range.

In principle, the catch 1 5 could possess two upstanding portions suitably spaced apart to receive the flap therebetween. With such an arrangement, the latch mechanism 10 will be able to lock the door against opening in either direction in the absence of the proper key.

Claims (11)

1. A latch mechanism for securing a doub leopening door against opening in one of its opposite opening directions, comprisling a movable catch to engage and secure the door against opening in the said one direction in a normal operative position of the catch, a collapsible member to hold the catch in its normal positlion, and actuating means operable on demand to produce a collapsing of the collapsible member and thereby allow the catch to move out of its normal position to free the door for opening in the said one direction, the mechanism further including means to bias the said member to its noncollapsed state for resetting the catch to its normal operative position after operation of the actuating means.

2. A mechanism according to claim 1, wherein the catch ils pivotally movable into and out of its normal operative position and the collapsible member is a strut which engages the catch at a point remote from the pivot axis of the catch.

3. A mechanism according to claim 1 or claim 2, wherein the collapsible member is a toggle device 1 maintained overcentred against an abutment by the biasing means, the device being overcentred away from the abutment to a state of collapse by a thrust exerted thereon by the actuating means.

4. A mechanism according to claim 3, wherein the toggle device has a pair of pivotally-interconnected links, one of which is coupled to the catch and the other of which is adapted to be attached to a pivot mounting, and the biasing means is a spring tensioned between two attachment points on the links, said spring being stretched and further tensioned when the actuating means overcentres the device away from the abutment.

5. A mechanism according to claim 3 or claim 4, wherein operation of the actuating means places the toggle device in a state of partial collapse, and the device is collapsed fully when the catch is moved away from its normal position in response to an opening movement of the door in the said one direction.

6. A mechanism according to any of claims 1 to 5, wherein the actuating means is a solenoid actuator.

7. A mechanism according to any of claims 1 to 5, wherein the catch is pivotally mounted, remote from the collapsible mem- ber, on a rockable support member which mounts said catch adjacent one end thereof, the support member being mounted to rock with the catch about an axis adjacent its other end and adjacent the collapsible member the arrangement in use permitting the reset catch to be displaced by the moving door out of the path of movement of the door, as the door swings back to its closed position.

8. A mechanism according to claim 7, further including spring means biasing the catch and support member in a direction opposite that in which the reset catch is displaced by the moving door.

9. A latch mechanism substantially as herein described with reference to and as shown in the accompanying drawings.

10. A door fitted with a latch mechanism according to any one of the preceding claims.

11. A door according to claim 10, having means to return the door to its closed position after opening in at least the said one direction.

1 2. A door for the passage of an animal into and out of a building, said door being fitted with a latch mechanism according to any of claims 1 to 9, and said door being top hung in its door frame so as to return under gravity to its closed position after opening in either direction.