GB2364544A

GB2364544A - Variable force magnetic catch

Info

Publication number: GB2364544A
Application number: GB0016749A
Authority: GB
Inventors: Leslie William Hall
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-07-10
Filing date: 2000-07-10
Publication date: 2002-01-30
Also published as: GB0016749D0

Abstract

A magnetic catch is constructed so that its retentive force can be adjusted by the attachment of steel strips 107 between the pole pieces of magnet 102. For maximum force, eg to restrict a child's access, no strips 107 are used but the force can be progressively reduced by adding one or more strips 107.

Description

2364544 MAGNETIC LATCH The present invention relates to magnetic latches

for doors, drawers, or the like.

Magnetic latches consist of a first element which includes a permanent magnet in a housing which is adapted to be attached to a drawer or a door and a ferromagnetic strip which is adapted to be attached to the carcass of a housing for the drawer, or the jamb of a door, which the latch is to be used, or vice versa. Such latches are in common use, particularly in caravans.

A disadvantage of magnetic latches as used in caravans, is that they have to be sufficiently powerful to hold a door, or loaded drawer, shut against the impact loads generated while the caravan is in transit, which means that they can be too strong for elderly or very young people to use readily when the caravan has reached it's destination. On the other hand, sometimes it is desirable for a drawer or cupboard door to be difficult to open, for example to prevent a child gaining access to cutlery or powerful household chemicals.

It is an object of the present invention to provide an improved magnetic latch.

According to the present invention there is provided a magnetic latch as described above, wherein there is included a means for varying the effective magnetic flux produced by the magnet of the magnetic latch, thereby to vary the retentive force generated by the magnet. A simple means of varying the effective magnetic flux produced by the magnet latch is a series of strips of ferromagnetic material of different thicknesses which can be placed in contact with the poles of the magnetic latch.

Preferably, the metal strips are L - shaped, to facilitate their attachment to and removal from the poles of the magnet latch by a sliding action.

MAGNETIC LATCH The invention will now be described, by way of example, with reference to the accompanying drawing, which is a schematic view of a variable strength magnetic latch embodying the invention.

Referring to the drawing, a variable strength magnetic latch comprises a first component consisting of a housing 100, made of a non-magnetic material, which can be attached to the underside of a worktop or crossmember forming part of the carcass of a piece of furniture in which a drawer is housed, or to a jamb of a door, neither of which is shown in the drawing, by means of lugs 101. Mounted loosely in the housing 100 is a permanent magnet 102 which has pole pieces 103 which project slightly from the contact face 104 of the housing 100.

A second component of the latch is a steel plate 105 which is adapted to be attached to the inside of a drawer front or to a door, by means of two holes 106 in the plate 105.

Alternatively, the steel plate 105 also can be enclosed in a non-magnetic housing which includes lugs by means of which it can be attached to the inside of a drawer front or door, as before.

Also provided are a plurality of steel strips, only one of which, 107, is shown. These strips have a major portion 108 the dimensions of which are approximately the same as the area delineated by the pole pieces 103 of the magnet 102 and a minor portion 109 which projects at right angles to the major portion 108 of the steel strip 107 and provides a handle which facilitates the removal of the steel strip 107 from contact with the pole pieces 103 of the magnet 102 by a sliding action. The steel strips 107 are of varying thicknesses so as to enable the effective strength of the magnetic latch to be varied by placing one or another, or a combination, of the strips 107 in contact with the pole pieces 103 of the magnet 102.

Thus, when maximum latching force is required, as, for example, when a caravan is in transit, or a boat is at sea, no steel strip, or strips, 107 is used, but when the caravan or boat is at rest, one or more of the steel strips 107 is placed in contact with the pole pieces 103 of the magnet 102, to reduce the latching force to a desired level so as to make a drawer or door easy to open.

If it is desired to restrict a child's access to a cutlery drawer or a cupboard in which there are dangerous household chemicals, then again, the steel strip 107, or strips 107, can be removed and replaced when the child has gone to bed or is otherwise not present.

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Claims

1. A magnetic latch as hereinbefore described wherein there is included means for varying the effective magnetic flux produced by the magnet of the magnetic latch thereby to vary the retentive force generated by the magnet.

2. A magnetic latch according to claim 1 wherein the means for varying the effective magnetic flux produced by the said magnet comprises at least one ferromagnetic lamina adapted to fit between pole pieces associated with the said magnet thereby to vary the effective magnetic flux produced by the said magnet.

3. A magnetic latch according to claim 2 wherein the or each lamina is adapted to be removed from position on the pole pieces of the said magnet by a sliding action.

4. A magnetic latch substantially as hereinbefore described and with reference to the accompanying drawing.