Splash proof electromagnetic door holder

A splash proof electromagnetic door holder is sealed to prevent failures caused by exposure to moisture. The electromagnetic door holder comprises a ground box, a main housing attached to the ground box, and a coil assembly attached to the main housing. The coil assembly includes a bobbin containing a wire coil. A sealant, preferably epoxy, covers the face of the bobbin to prevent moisture from entering the coil assembly. A seal is incorporated between a coil passage in the main housing and the coil assembly. Seals are included between the main housing and the ground box. The resulting the electromagnetic door holder resists the entry of moisture into the electromagnetic door holder and thereby improves the reliability of the electromagnetic door holder.

BACKGROUND OF THE INVENTION

The present invention relates to splash proof electrical devices and in particular to splash proof electromagnetic door holders.

Electromagnetic door holders are commonly used in commercial buildings to release doors when, for example, fire alarms go off. A common type of electromagnetic door holder is a floor mounted electromagnetic door holder. A catch plate is mounted to the door, and swivelled to align the catch plate with the electromagnetic door holder. The electromagnetic door holder is attached to the floor to contact the catch plate when the door is fully open. The electromagnetic door holder is energized to hold the catch plate, and thereby hold the door in the open position. When electricity to the electromagnetic door holder is removed, the catch plate is released, and the door may close.

Unfortunately, such electromagnetic door holders generally reside in areas subjected to moisture. For example, water may be splashed on the electromagnetic door holder when the floor is mopped, and if the electromagnetic door holder is near an exit, rain water, or irrigation water, may reach the electromagnetic door holder. An electrical failure of the electromagnetic door holder may result from such exposure to moisture.

BRIEF SUMMARY OF THE INVENTION

The present invention addresses the above and other needs by providing a splash proof electromagnetic door holder which is sealed to prevent failures caused by exposure to moisture. The electromagnetic door holder comprises a ground box, a main housing attached to the ground box, and a coil assembly attached to the main housing. The coil assembly includes a bobbin containing a wire coil. A sealant, preferably epoxy, covers the face of the bobbin to prevent moisture from entering the coil assembly. A seal is incorporated between a coil passage in the main housing and the coil assembly. Seals are included between the main housing and the ground box. The resulting the electromagnetic door holder resists the entry of moisture into the electromagnetic door holder and thereby improves the reliability of the electromagnetic door holder.

In accordance with one aspect of the invention, there is provided a moisture resistant electromagnetic door holder comprising a ground box, a main housing attached to the ground box, and a sealed coil assembly attached to the main housing and having an exposed face. The main housing includes a coil passage and the coil assembly resides in the coil passage. A coil O-Ring resides between the main housing and the coil assembly to prevent moisture from entering the electromagnetic door holder through the coil passage.

In accordance with another aspect of the invention, there is provided a moisture resistant electromagnetic door holder comprising a ground box, a main housing attached to the ground box, and a sealed coil assembly attached to the main housing and having an exposed face. The coil assembly comprises a bobbin and a coil housing, and the bobbin resides in the coil housing. A sealing material resides over an otherwise exposed surface of the bobbin to prevent moisture from entering the coil assembly through the bobbin.

DETAILED DESCRIPTION OF THE INVENTION

A door10held open by an electromagnetic door holder12is shown inFIG. 1. The electromagnetic door holder12holds the door10open as long as power is provided to the electromagnetic door holder12. In the case of fire, or some other triggering event, power is removed, and the electromagnetic door holder12releases the door10to close in the doorway14. As can be seen, the electromagnetic door holder12resides on the floor and is thus exposed to floor cleaning liquids, and if the electromagnetic door holder12is near an exit, rain water, or irrigation water, may reach the electromagnetic door holder12.

A front perspective view of a splash proof electromagnetic door holder12according to the present invention is shown inFIG. 2A, and a rear perspective view of the splash proof electromagnetic door holder12is shown inFIG. 2B. The door holder12comprises a ground box16, ground box mounting holes22, a main housing18supporting coil assembly26(seeFIGS. 3A,3B,4) having a coil face19, and a ground box cover24with a plug20. The plug20may be removed to allow an electrical conduit to be attached to the ground box16, which electrical conduit is preferably a moisture proof electrical conduit.

A perspective view of a sealed coil assembly26according to the present invention is shown inFIG. 3. The coil assemble26comprises a circuit housing34, a coil insulator30, and a coil housing28, having a base portion (or flange)28a.

A side view of the coil assembly26according to the present invention is shown inFIG. 3Aand a top view of the coil assembly26is shown inFIG. 3B. The coil assembly26includes three electrical terminals36for connecting a power source to the coil assembly26. The coil assembly preferably receives a power signal between 12 and 24 Volts Direct Current (VDC) or between 24 and 120 Volts Alternating Current (VAC) to energize the coil. Four coil screw passages38are provided in the base portion28afor attaching the coil assembly26to the main housing18(FIG. 2A). A coil insulator30resides between the coil housing28and a circuit housing34. The three electrical terminals36preferably reside on the exterior of the circuit housing34.

A cross-sectional view of the coil assembly taken along line4—4ofFIG. 3Bis shown inFIG. 4. The coil face19comprises a coil seal40residing over a bobbin44, and a core face42aof a core42. The seal40resists the entry of moisture into the coil assembly26, and preferably prevents the entry of moisture into the coil assembly26. The seal40is preferably an epoxy seal. A Printed Circuit (PC) board46resides in the circuit housing34.

The main housing18and the coil assembly26are shown prior to assembly inFIG. 5A. The main housing18includes coil posts48for attachment of the coil assembly26to the main housing18using coil screws50.

The main housing18and the coil assembly26are shown after assembly inFIG. 5B. A cross-sectional view of the assembled main housing18and the coil assembly26taken along line6—6ofFIG. 5Bis shown inFIG. 6. The coil assembly26resides in a coil passage49(seeFIG. 7). A moisture seal comprising an coil O-Ring52resides between the coil assembly26and the coil passage49, thereby resisting the entry of moisture into the door holder12, and preferably preventing the entry of moisture into the door holder12.

A top view of the main housing18attached to a ground box16is shown inFIG. 6A, and an end view of the main housing18attached to the ground box16is shown inFIG. 6B. A cross-sectional view showing the main housing18attached to a housing mating surface53of the ground box16, taken along line7–7ofFIG. 6B, is shown inFIG. 7. The main housing18is attached to the ground box16by main housing screws54, and the ground box cover24is attached to the ground box16by cover screws62. A second plug20aresides in a bottom surface of the ground box, which plug20amay be removed to allow electrical conduit to be attached to the ground box16.

A moisture proof housing seal is provided between the main housing18to the housing mating surface53to resisting the entry of moisture into the door holder12, and preferably preventing the entry of moisture into the door holder12. The moisture proof housing seal comprises a main housing O-Ring56running proximal to an outer edge of the main housing18and housing screw O-Rings58residing around the main housing screws54.

A cover moisture seal resides between the ground box cover24and the ground box16to resisting the entry of moisture into the door holder12, and preferably preventing the entry of moisture into the door holder12. The cover moisture seal comprises a cover O-Ring60residing between a cover mating surface59of the ground box16and the ground box cover24.

A front view of the ground box16showing the housing mating surface53(seeFIG. 7) of the ground box16is shown inFIG. 8A. A main housing O-Ring groove64in the housing mating surface53is provided to position the main housing O-Ring56, wherein the main housing O-Ring56partially resides in the main housing O-Ring groove64. Housing screw O-Ring grooves66in the housing mating surface53are provided to position the housing screw O-Rings58, wherein the housing screw O-Rings58partially reside in the housing screw O-Ring grooves66.

A rear view of the ground box16showing the cover mating surface59(seeFIG. 7) of the ground box16is shown inFIG. 8B. Cover screw passages72are provided for the cover screws62(seeFIG. 7). A cover O-Ring groove68in the cover mating surface59is provided to position the cover O-Ring60, wherein the cover O-Ring60partially resides in the main cover O-Ring groove68.

A double door holder12ais shown unassembledFIG. 9Aand assembled inFIG. 9B. A link plate74resides between the ground boxes16. The cover screws62attach each ground box16to the link plate74, and the cover O-Rings60provide seals between each ground box16and the link plate74.