An electromagnetic lock

Abstract

An electromagnetic door lock is described including: a housing; an electromagnet core; the electromagnet core is formed from a ferrous metal and is mounted in the housing; at least one bobbin which is formed from metal or alloy; an arrangement of one or more wire coils is wound around the at least one bobbin and the at least one bobbin is mounted in association with the core; a removable cover formed from metal overlies the one or more wire coils; and the core includes exposed faces which extend through apertures in the cover to engage with an armature when the electromagnet is activated in use.

Description

[0001] AN ELECTROMAGNETIC LOCK

[0002] Technical Field

[0003] The present invention relates to electromagnetic locks and particularly relates to improvements in electromagnetic door locks which lessen their environmental impact.

[0004] Background to the Invention

[0005] Referring to figure 1, an electromagnetic lock, magnetic lock, or maglock is a locking device that consists of an electromagnet 100 and an armature plate 120.

[0006] The principle behind an electromagnetic door lock is the use of electromagnetism to lock a door when energised. The electromagnet 100 is usually affixed to a fixed part of a doorway in a building and the armature 120 is affixed to a door to control access through the door as part of a building access or security system. When energised, the electromagnet 100 attracts the armature 120 with a force large enough to prevent the door from being opened.

[0007] The electromagnet makes use of the fact that a current passing through one or more loops of wire produces a magnetic field. Typically the wire is wound onto a bobbin which is located around a ferromagnetic core 112 to form an electromagnet. The core is typically formed from welding together pieces of metal which make up the core. An epoxy potting compound is then poured around the core and bobbin to retain the bobbin in the lock and protect it from damage. After pouring and setting, the epoxy potting compound 114 forms a flat facing surface surrounding the core 112 and exposed regions of the core 112 stand just proud of the epoxy to magnetically mate with armature 20 in use.

[0008] The use of an epoxy potting compound 114 makes is impossible for the electromagnet 100 to be later dismantled for repair or recycling. In addition, during the production process the epoxy compound takes a significant amount of time to cure. The curing and welding processes also give off noxious fumes during the production process which have to be safely managed and ventilated away from the production area to protect the health and wellbeing of production workers. Even when ventilated away, these fumes nonetheless enter the atmosphere and may affect the local environment.

[0009] As well, if machining is carried out after the epoxy resin has cured then this causes epoxy dust and debris to be created which must be specially disposed of because it is a toxic substance.

[0010] There remains a need for improved electromagnetic door locks.

[0011] Summary of the Invention

[0012] In a first aspect the invention provides an electromagnetic door lock including: a housing; an electromagnet core; the electromagnet core is formed from a ferrous metal and is mounted in the housing; at least one bobbin which is formed from metal or alloy; an arrangement of one or more wire coils is wound around the at least one bobbin and the at least one bobbin is mounted in association with the core; a removable cover formed from metal overlies the one or more wire coils; and the core includes exposed faces which extend through apertures in the cover to engage with an armature when the electromagnet is activated in use.

[0013] The cover may be formed from a non-ferrous metal or alloy.

[0014] The cover may be formed from aluminium.

[0015] The electromagnet core may be formed as a solid block.

[0016] The electromagnet core may be formed by machining slots into a block of ferrous metal.

[0017] The electromagnet core may be formed by moulding. An electromagnetic door lock may further include a light emitting indicator which provides an indication of the locked or unlocked state of the lock and wherein the exposed region of the light emitting indicator is formed from thermo plastic rubber.

[0018] Brief Description of the Drawings

[0019] An embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0020] Figure 1 is a perspective view of a prior art electromagnetic door lock;

[0021] Figure 2 is a front view of an electromagnetic door lock;

[0022] Figure 3 is a cross-sectional view along the line D-D of figure 2;

[0023] Figure 4 is an exploded view of the electromagnetic door lock of figure 2; and

[0024] Figure 5 is a perspective view of the electromagnetic door lock of figure 2.

[0025] Detailed Description of the Preferred Embodiment

[0026] Referring to figures 2 to 5, an embodiment of the invention will be described in accordance with the following parts list:

[0027] Parts List:

[0028] 1 - Left ends

[0029] 2 - Cover plate

[0030] 3 - Bobbin and insulating material

[0031] 4 - Coil

[0032] 5 - Magnetic iron block core

[0033] 6 - Aluminium housing

[0034] 7 - Cover plate 8 - PCB

[0035] 9 - Right ends

[0036] 10 - Thermo plastic rubber LED casing

[0037] 11 - Spacer and securing bolts

[0038] 12 - Mounting plate

[0039] 13 - Fixing machine screw

[0040] 14 - Fixing machine screw

[0041] The cover plate 2 is formed from a metal and is preferably a non-ferrous metal such as aluminium. The bobbin 3 is formed from a metal such as stainless steel or aluminium.

[0042] The iron block 5 is formed from a rectangular iron billet of soft iron which has been machined to form slots in the block to yield block 5 which has an “E” shaped cross sectional profile. The block 5 is formed by machining such as by milling or is fabricated by moulding or by joining pieces together using screw fasteners rather than welding iron pieces together to avoid generation of welding fumes. Once formed, the iron block 5 is 100% surface treated with an anti -corrosion treatment.

[0043] The LED casing 10 is L shaped of various dimension appearing on two viewable sides of the electromagnet and is made of thermo plastic elastomers or thermo plastic rubber which becomes hard when exposed to high temperatures and will not melt or bum.

[0044] The electromagnet is assembled according to the following method:

[0045] A. Assemble the housing case with left ends 1, right ends 9 with screws 13 and fit to mounting plate 12 with spacer 11 and securing bolt.

[0046] B. Wind electrical coil 4 around bobbin 3

[0047] C. Place the coil and bobbin assembly inside of block 5 to encircle the central arm of the “E” cross section. D. Secure the core assembly to the housing 6 with fixing screws 14.

[0048] E. Connect the coil to the PCB 8 and fit LED inside the thermos plastic rubber LED case 10.

[0049] F. Secure the cover plate 2 firmly on the core assembly with silicone glue.

[0050] G. Cover the PCB 8 with cover plate 7 and screws.

[0051] Referring to figure 5, the electromagnet 50 is shown fully assembled. The exposed ends of the “E” shaped profile of block 5 extend through slot shaped apertures in the cover plate 2 to stand just proud of the surface of the surrounding cover plate 2 to engage with an armature in use. The cover plate 2 protects the coil (not visible) and prevents any debris or other items from entering the electromagnet in use. Electromagnet 50 is used with a usual type of armature 120 such as that shown in figure 1.

[0052] The lock is predominantly formed from metal parts which have a low combustibility. In particular, the use of a metal bobbin enhances fire protection for the coil to improve the overall all fire rating performance of the electromagnet.

[0053] The electromagnet 50 is 100% flame resistant and so can be specified for use in locations which require use of fire rated locking devices.

[0054] The electromagnet 50 is able to be completely disassembled and repaired which was not possible in the prior art electromagnets due to the use of epoxy potting compound.

[0055] The electromagnet 50 is formed without welding processes and without curing epoxy resin which both produce harmful fumes. In addition, all parts are recyclable at the end of life of the product. The electromagnet 50 thus have a low environmental impact over the entire lifecycle of the product, from production to decommissioning. Any reference to prior art contained herein is not to be taken as an admission that the information is common general knowledge, unless otherwise indicated. Finally, it is to be appreciated that various alterations or additions may be made to the parts previously described without departing from the spirit or ambit of the present invention.

Claims

CLAIMS:

1. An electromagnetic door lock including: a housing; an electromagnet core; the electromagnet core is formed from a ferrous metal and is mounted in the housing; at least one bobbin which is formed from metal or alloy; an arrangement of one or more wire coils is wound around the at least one bobbin and the at least one bobbin is mounted in association with the core; a removable cover formed from metal overlies the one or more wire coils; and the core includes exposed faces which extend through apertures in the cover to engage with an armature when the electromagnet is activated in use.

2. An electromagnetic door lock according to claim 1 wherein the cover is formed from a non-ferrous metal or alloy.

3. An electromagnetic door lock according to claim 2 wherein the cover is formed from aluminium.

4. An electromagnetic door lock according to any preceding claim 1 wherein the electromagnet core is formed as a solid block.

5. An electromagnetic door lock according to claim 4 wherein the electromagnet core is formed by machining slots into a block of ferrous metal.

6. An electromagnetic door lock according to claim 4 wherein the electromagnet core is formed by moulding.

7. An electromagnetic door lock according to any preceding claim further including a light emitting indicator which provides an indication of the locked or unlocked state of the lock and wherein the exposed region of the light emitting indicator is formed from thermo plastic rubber.

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