Magnetic safety latch

A magnetic latch for a gate has first and second units for mounting on a gate and a gate post respectively. The first unit has a displaceable latch element displaceably mounted in a support in a housing and biased to a retracted position, and a second unit with a complementary engagement structure with which a latching portion of the latch element is adapted to engage when the magnetic latch is in a latching position and the latch element is displaced to a projecting position. A magnetic attracting arrangement is provided to cause the latch element to move to the projecting position and engage in the engagement structure when the magnetic latch is in the latching position, and then the engagement structure prevents movement of the door or gate away from the closed position. A retraction element is provided in the first unit for displacing the support and increasing the bias on the latch element to exceed the force of the magnetic attracting arrangement, whereby the latch element moves towards the retracted position and the gate may be moved from the closed position.

The present invention relates to magnetic safety latches and a typical installation is as a safety latch for a gate arranged so that young children cannot reach and operate the latch to pass through the gate, but an older person being able to reach and operate the latch and open the gate. A very important application is to swimming pools where hinged gates must be opened outwardly and the latch mechanism must either be so high that a young child could not reach it and operate it, or must be so mounted that equally a young child could not reach the mechanism to open it.

Similarly, playgrounds for young children may need a gate arranged in the opposite fashion so that a young child could not operate the latch to go out of the playground unsupervised.

The present assignees are the proprietors of Australian Patent No 649,664 and equivalent U.S. Pat. No. 5,362,116 which discloses two models of magnetic safety latch for swimming pool gates. In both cases, an important characterising feature of these latches is that there is no mechanical inter-engagement and in particular no mechanical resistance required when the gate moves to its closed position, for example under the influence of spring hinges. Thus, the prospect of mechanical resistance of mechanical latches preventing the gate reaching the fully closed position and latching occurring is obviated.

For particular applications, new and useful alternatives to known arrangements would provide further consumer choice.

The present invention is directed to providing such consumer choices and may be implemented in embodiments which are economic, convenient to manufacture and install yet are robust, have longevity and provide a high degree of safety.

In one aspect, the present invention provides a magnetic latch for securing a door or gate in a closed position, the latch having a first unit with a displaceable latch element displaceably mounted in a support in a housing and biased to a retracted position, a second unit with a complementary engagement structure with which a latching portion of the latch element is adapted to engage when the magnetic latch is in a latching position and the latch element is displaced to a projecting position, a magnetic attracting arrangement provided in the latch element and the second unit to cause the latch element to move to the projecting position and engage in the engagement structure when the magnetic latch is in the latching position, and then the engagement structure preventing movement of the door or gate away from the closed position, and a retraction element in the first unit for displacing the support and increasing the bias on the latch element to exceed the force of the magnetic attracting arrangement, whereby the latch element moves towards the retracted position and the gate may be moved from the closed position.

The magnet attracting arrangement could be solid or tubular or a combination of solid and tubular portions.

It follows that embodiments made be described as providing for the displaceable latch element to float within quite wide limits.

An important market requirement that is increasing is for the provision of a key locking arrangement for a magnetic latch. The present invention lends itself to such an option as a key actuated lock can be mounted on the first unit or the second unit and can be arranged to lock in position the retraction element and typically the support for the displaceable element; the displaceable element can be slideable within the support under the influence of the spring biasing.

When it is chosen to provide a lock on the first unit, the lock can be mounted on the housing or in the retraction element.

The magnetic attracting arrangement can operate so that freedom of motion exists with the lock actuated into the locked position, yet retraction of the latch element to open the latch is not possible.

Embodiments of the invention can be especially beneficial in being compact and visually attractive, especially when installed in such installations as swimming pools, which frequently now have glass surrounds and glass gates. Such installations need a robust and reliable latch mechanism yet one that can be embodied with appropriate aesthetics.

Another important safety feature, especially with magnetic latches which may be locked, is that when the gate is open the owner may choose to key lock the latch and then remove the key. Embodiments of the present invention lend themselves to safety by virtue of the design ensuring that if locking is effected with the gate open, then irrespective of whether manual intervention causes the displaceable latch element to be projected or retracted, it can still float. Consequently, when released, the displaceable latch element moves under its biasing to a retracted position so that when the gate is released and it reaches the closed position, there will be no impediment to the magnetic forces again establishing latching.

In one embodiment, the first unit has a housing having a base adapted to be secured, for example by screws, to a gate. The retraction element and support may be integrated into a single structure through which the displaceable latch element passes, the latch element being an elongate structure, slideable within the support and the biasing can be in the form of a compression spring acting between an internal shoulder of the support and end portion of the latch element remote from the free end of the latch element which is adapted to engage in latching engagement in the engagement structure of the second unit.

The latch element could be solid, tubular or a combination of solid and tubular portions.

Preferably, the invention is implemented using a magnet mounted within the second unit, the latching element being a metal pin having magnetic properties, e.g. a suitable grade of steel. Alternatively, the magnet may be in the latching element and the second unit can comprise ferromagnetic material.

A further option is for both the second unit and the latching element to have permanent magnets of polarity arranged to attract the parts when in or near the latching position.

An especially important embodiment of the invention is one incorporating a key-operated lock mounted on the facia of the housing of the first unit or mounted in the retraction element and selectively engageable with the support and the associated retraction element whereby the retraction element can be locked against movement yet the latch element remains slideably mounted within the support and subject to its biasing.

The magnetic latch of the drawings comprises a latching unit10and a receiving unit12adapted respectively to be mounted on a structure such as a gate and a gate post with suitable fixing screws.FIGS. 1 and 2show provision for fixing screws to pass through horizontally elongated slots14in the latching unit10and vertically elongated slots16in the receiving unit12whereby the units respectively, before final tightening of the screws, can be adjusted for true alignment respectively horizontally and vertically. In use, press-in cover elements will be provided for closing the apertures leading to the slots14and16.

As can most clearly be discerned fromFIG. 3, the latching unit10comprises a housing18with a base plate20and displaceably mounting therein, for movement along a horizontal axis, an elongate actuator22comprising a retraction element, such as a retraction knob24, and at the forward end a support barrel26in which a latching pin28is slidingly mounted for limited independent movement relative to the actuator22. As best shown inFIG. 1A, on its rear surface the support barrel26has an axially extending element, such as an integral spline23, extending outwardly and guided to a corresponding complementary element or slot23ain, the housing10to prevent rotation of the support barrel. Support for the latching pin is provided at the forward support barrel26and also within an enlarged bore30of the knob in which a cap32, fitted to the end of the latching pin28, can slide. A helical compression spring34is mounted over the rear end portion of the latching pin28, the forward end of the spring being seated on a shoulder36defining an end of the support barrel26and the rear end of the spring being seated on a shoulder of the cap32.

The housing18in its forward middle portion has a sub-housing for accommodating a key-operated lock38.FIG. 3shows the lock in the locked condition in which its locking tongue40projects to be located behind a shoulder formed on the barrel26. Thus in the locked position the pressure on the knob30to move the actuator to a retracted position is resisted by a lock tongue40. In the configuration shown inFIG. 3, the latching pin28(conveniently of a suitable grade of ferromagnetic steel) is magnetically attracted into latching engagement of the second unit12and thus the associated gate cannot be opened. The latch unit12comprises a main body portion having a central cavity for accommodating a high coercivity permanent magnet42which is located in a weather-sealed cavity by engagement of a back plate44. As can best be seen fromFIG. 1, the housing12has an oval shaped latching cavity46which permits a degree of vertical misalignment between the enlarged head of the latching pin28and the receiving cavity yet latching will still occur. For example, a gate or gate post may drop slightly and this can be accommodated with the design.

In the embodiment atFIG. 3, the cap32is fitted to a circular cross-section spigot portion29of the latching pin28and the cap, of two parts, is fitted firmly to the spigot. The cap32has a base portion32A fitted over the spigot and providing an annular cavity and a curved cap32B is provided with a projecting lip which fits into the annular cavity to complete the installation.

Regarding the configuration shown inFIG. 3, it will be appreciated that the latching pin28is free to float relative to the other components of the latch unit10. Therefore, if for example due to thermal contraction at night the distance between the first and second unit increases, under the magnetic attraction the latching pin28can move relative to the latching unit10and the actuator22to maintain the head27of the latching pin firmly engaged in the cavity46and maintain the latching engagement as shown inFIG. 3.

WhereasFIGS. 2 and 3show a closed and locked configuration,FIGS. 4 and 5shows the configuration when the lock is unlocked and the latch is closed. When the lock38is unlocked, tongue40is rotated to be displaced away from an annular shoulder27of the support barrel26. The knob24can then be pulled to the right to the configuration shown inFIGS. 6 and 7. This action causes the spring34to a fully compressed and an enlarged tip32of the latching pin28abuts the end face31of the housing18. During retraction, the support barrel26of the actuator22has been slidingly supported on an aperture defined in the right hand side wall of the housing18and is further supported by engagement around the periphery of the latching pin28while the opposite end of the latching pin28has been slidingly supported in a corresponding aperture in the left hand side wall of the housing nearer the second unit. It will be appreciated that the initial movement of the actuator22to the right (as shown in the drawing) initially increases the load on and compression of the helical spring34until the force applied to the latching pin28exceeds the magnetic attraction occurring in the position shown inFIG. 3. However, an interior shoulder39in the mid-portion of the actuator22will ultimately engage the interior of the cap32A to displace the latching pin28to the retracted position ofFIG. 7.

Referring now toFIGS. 8 and 9, the position is shown when a gate has been opened and the latch unit10is remote from the magnetic unit12and the knob24released. The lock is not locked. The knob24has been released so it re-establishes the same position in the housing as inFIG. 3. The helical spring, however, extends to urge the latching pin28to its fully retracted position as shown. Therefore, if the gate is released and closes, for example under the action of spring hinges, when the latching unit10is in juxtaposition with the magnetic unit12for latching, the latching pin28is free to be attracted under magnetic influence to the configuration shown inFIG. 3with the compression spring partly compressed and thus magnetic latching will occur with the lock in the unlocked configuration.

FIGS. 10 and 11, however, show the configuration when the latch (and gate) are in the open position and the lock is locked, yet the latching pin is free. Therefore when the gate is released and moves to a latching position, the latching pin is free to move to the position shown inFIGS. 2 and 3.

In the event the user perversely seeks to lock the lock when the latching unit is in the configuration shown inFIGS. 6 and 7, when the actuator22is released it moves towards the position ofFIGS. 2 and 3but cannot fully move to that position because of interference of the leading shoulder27with the tongue40of the lock38. Thus, the actuator22is a little to the right of the configuration shown inFIG. 3yet, when a gate is closed, safety occurs because the latching pin28is free to move under the influence of the magnetic force to achieve latching. The latching unit is not locked but has safely achieved magnetic latching.

Referring now to the second embodiment ofFIGS. 12-22, like parts have been given like reference numerals and where a component is equivalent, the reference numeral is 100 greater; for example the lock38ofFIG. 1becomes lock138inFIG. 12.

The primary difference in the second embodiment is that the lock138is axially engaged within the end portion of the actuating knob124rather than being mounted in the housing and extending transversely of the product. To achieve this, the detailed form of the housing118and the internal structure differs in detail as will now be described particularly with reference toFIG. 14showing the product when the latch is closed and the lock has been engaged. Thus the latching pin28is magnetically attracted towards the high coercivity magnet42in the second unit12but the latching pin is shorter than the first embodiment yet its right hand end is identical with a closure cap32mounted to the spigot portion29of the pin, with the helical compression spring34located between, at the left hand end, the inner end wall of a tubular actuator122and at the right hand end the inner end wall of the cap32. Unlike the first embodiment, when the spring34is partially extended in the closed and locked position ofFIG. 3, in this case the compression spring34is substantially compressed. It will be noted that the peripheral portion of the shoulder of the cap32engages against a shoulder139in the intermediate portion of the actuator, the shoulder most clearly being seen in for exampleFIG. 20.

The actuator122is a slideable barrel supported within the housing118at its forward end particularly by support legs121extending inwardly from the closure plate120on the rear face. The actuator122is further supported at its right hand end by being a sliding fit within a tubular extension119of the housing which extends into an annular cavity defined between the outer wall of a cylindrical extension123and the profiled knob124which is adapted to be manually gripped for displacement purposes. The actuator122has a integrally formed spline125extending from its forward mid-position for engaging in a complementing slot in the housing10to prevent rotation of the actuator122. The lock138is secured conventionally within the cylindrical extension123. The lock138has a lock tongue140which, by comparingFIGS. 14 and 16, can be seen to be such that the tongue when moved to the locking position moves laterally through an aperture125in the side wall of the cylindrical extension123and an aligned aperture127in the adjacent extension119of the housing.

Thus in the configuration ofFIG. 14the lock tongue140projects through the actuator122and housing extension119thereby preventing manual displacement of the actuating knob124. However, the latching pin128is free to float so that the close juxtaposition of the tip33of the latching pin towards the magnet is maintained despite thermal expansion or contraction or other movement of the gate and gate post which the product is fitted.

When the lock is unlocked as shown inFIG. 16, then manual pressure may be applied to the knob124to displace the actuator and interconnected latching pin to the right relative to the housing to adopt the position shown inFIG. 18.

When the associated gate has been opened and the knob124released, but the lock is retained in unlocked condition, then the configuration ofFIG. 20is achieved. A leading end shoulder of the knob comes into abutment with a corresponding shoulder151on the rear of the housing118. In this configuration the spring34is substantially extended and urges the end cap32away from the shoulder139within the actuator122. Consequently if the gate is released and moved to a closed position then when the latching pin128comes into appropriate juxtaposition with the second unit12, then the configuration shown in FIG.14is readopted and the spring34substantially compressed due to the magnetic attraction forces.

In the event that in the open and free position the lock138is locked, then the configuration ofFIG. 22arises. The tongue140is projected through the aligned apertures125and127to lock the knob124relative to the housing118so that if the gate is released and moves to the latching position, the latching pin128is free to be a magnetically attracted into the position shown inFIG. 16with compression of the spring arising. Thus automatically there is safely established the locked arrangement ofFIG. 14.