MAGNETIC PROXIMITY SWITCH SYSTEM
The present application claims the benefit of Provisional U.S. patent application Ser. No. 60/016,309 (Jackson) filed May 8, 1996, which is hereby incorporated by reference. 5 Provisional U.S. patent application Ser. No. 60/028,491 (Jackson) filed Oct. 15, 1996, and Provisional U.S. patent application Ser. No. 60/030,988 (Jackson) filed Nov. 15, 1996, are hereby incorporated by reference.
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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a switch, and more particularly to a magnetically operated proximity switch ^ usable in, for example, a security system.
2. Discussion of the Related Art
While magnetic proximity switches are often confused with magnetic sensors, magnetic proximity switches represent a category of technology exclusive of magnetic sensors. 20 Conventional magnetic proximity switches comprise some combination of magnetic material, electrical contacts, and a mechanism to effect switching. At least one of the electrical contacts is attached to a coiled spring or leaf spring. A reed switch is one example of a conventional magnetic proximity 25 switch.
There are three basic types of reed switches: the dry reed, the mercury wetted reed, and the mercury wetted contact switching capsule. The magnetic behavior of all three reed switch types are similar, but the switches of the mercury type are restricted to certain mechanical orientations because they rely on gravity for successful operation. Mercury based switches also represent an environmental disposal hazard and are more expensive than the dry reed type.
FIG. 13 shows a perspective view of a conventional reed switch 100. The reed switch includes an electrically connecting lead wire 102 to which a flexible magnetically active electric contact member 104 is fixed, an electrically conducting lead wire 106 to which a nonmagnetically active 4Q rigid electrical contact member 108 is fixed, an optional lead wire 110 to which a magnetically active rigid electrical contact member 112 may be fixed. The system is enclosed in a hermetic glass envelope 114. In the absence of a magnetic field, the electrical contact 104 is in electrical contact with the non-magnetic electrical contact 108 as a result of a mechanical spring action created by the contact member 104. The lead and the electrical contacts 102, 104, 110, and 112 are composed of high permeability magnetic electrically conducting alloys such as Mu-Metal or the like for optimum 5Q performance. For proper operation of the switch, at least the electrical contact 108 must be non-magnetic so that no magnetic forces are developed therewith.
In the presence of a magnetic field, magnetic poles of opposite polarity are induced on the opposing sides of 55 magnetically active electrical contact members 104 and 112. The resulting magnetic attraction overcomes the opposing mechanical spring force so that the electrical contact 104 bends to make electrical contact with electrical contact 112, as shown in FIG. 13. When the magnetic field is removed, 60 the electrical contact returns to its original position electrical contact with electrical contact 108.
In selecting the materials, one desires materials with good electrical conductivity and magnetic properties which allow the activation of the switch. However, these two require- 65 ments conflict with each other. Magnetically active materials are not good conductors and good conductors are not
magnetically active. Reed switch manufacturers generally optimize these requirements by electroplating the electrical contact area with Rhodium or Ruthenium. However, this combination is particularly sensitive to electrical arcing. As a result, a hermetically sealed glass envelope filled with an inert glass is required to prevent corrosion of the electrical contacts. Even in a hermetic environment, maintaining consistent electrical contact pressure is difficult.
The necessity of the hermetic seal of the glass envelope results in numerous disadvantages. For example, reed switches are highly susceptible to damage. Also, any manipulation or jarring of the lead wires will destroy the seal joint. Further, if the reed switch is dropped, the glass envelope will likely be broken. Moreover, a hermetically sealed environment prevents manufacturing of a magnetic proximity switch having adjustable sensitivity or electrical contact pressure.
Additionally, reed switches suffer from problems in that their size cannot be easily miniaturized. If one attempts to reduce the size of the switch, either the actuation gap range would diminish or the false alarm rate would increase. Furthermore, reed switches suffer from wear and deterioration of the spring mechanisms, and mechanical complexity.
Due to constraints imposed by the inherent structure of reed switches, incorporation of electrical contacts is compromised. Consequently, the life expectancy is extremely sensitive to operating conditions. Also, reed switches are sensitive to magnetic fields, thereby making them susceptible to extraneous fields generated by outside magnetic fields. This characteristic is further exasperated by the introduction of permanent biasing magnets used to polarize the reed switches for increased sensitivity. These problems cause unreliable performance, false alarms, or catastrophic failures, thereby resulting in increased costs and lack of trust in the corresponding security systems.
Because the read switch suffers from the above-noted limitations and disadvantages, an alternative design is needed.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a magnetic proximity switch system that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the invention is to eliminate the mechanical spring by suitable arrangement of magnetic materials such that the spring force is generated by magnetic fields.
Another object of the invention is to minimize arcing of the electrical contacts by use of magnetic fields.
Another object of the invention is to provide a switch achieving fast and reliable snap-action operation.
Another object of the invention is to provide a switch avoiding mechanical contact between, a switch actuator and a spring mechanism, and the electrical elements of the switch.
Another object of the invention is to provide a switch of sufficient simplicity that hermetic sealing of the electrical contacts is both practical and economical and, as a consequence of the hermetic seal, allowing greater flexibility in the choice of electrical contacts which also extends the life and reliability of the electrical contacts chosen.
Another object of the invention is to provide a switch that has adjustable sensitivity and adjustable contact pressure without mechanical contact with any of the electrical contact switching elements in an environment having a hermetic seal.
Another object of the invention is to provide a magnetic switch which is adapted for use in dusty, moist, explosive or combustible environments.
Another object of the invention is to provide a switch that, in at least one of its combinations, is substantially unidirec- 5 tional to a magnetic field.
Another object of the invention is to provide a switch that can be actuated by any magnetic material or exclusively a permanent magnet.
Another object of the invention is to provide a switch with 10 several possible combinations of magnetic materials and permanent magnets providing a variety of performance characteristics and ranges of economy.
Another object of the invention is to provide a switch that is bounceless.
Another object of the invention is to provide a switch that is a resettable latch.
Another object of the invention is to provide a switch that may be actuated through surfaces or at angles substantially 20 away from perpendicular to the axis of the switch while maintaining unidirectionality without substantial loss of sensitivity.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will 25 be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 30
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the magnetic proximity switch system includes a switch portion configured to connect and disconnect at least one electrical path, the switch portion having a 35 first magnetically active member moveable between a first position for connecting the at least one electrical path and a second position for disconnecting the at least one electrical path, and a second magnetically active member magnetically interacting with the first magnetically active member to 40 station the first magnetically active member to one of the first and second positions; and a magnetically active actuator movable relative to the switch portion between proximal and distal positions, wherein the actuator magnetically interacts with the first magnetically active member when in the 45 proximal position for setting the first magnetically active member to the other one of the first and second positions, and wherein at least one of the first and second magnetically active members comprises a magnet.
In another aspect, the proximity switch system includes a 50 switch portion, configured to connect and disconnect at least one electrical path, having a casing formed of a magnetically noninteracting material, at least one electrical contact disposed in the casing, a magnetically active armature member moveable along the casing between a first position and a 55 second position, the armature member contacting the electrical contact when in the first position to connect the at least one electrical path and the armature member being electrically isolated from the electric contact when in the second position to disconnect the at least one electrical path, and a 60 magnetically active biasing member disposed in the casing, wherein the biasing member magnetically interacts with the armature member to biasing the armature member in one of the first and second positions; and a magnetically active actuator movable with respect to the switch portion between 65 proximal and distal positions, wherein the actuator magnetically interacts with the armature member when in the
proximal position to move the armature to the other one of the first and second positions, and wherein at least one of the armature member and the biasing member include a magnet.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. In the drawings:
FIG. 1 is a schematic view of a single pole single throw magnetic switch in repulsion mode according to this an embodiment of the present invention;
FIG. 2 is a schematic view of a single pole single throw magnetic switch with three permanent magnets in attraction mode according to another embodiment of the present invention;
FIG. 3 is a schematic view of a single pole double throw magnetic switch with three permanent magnets in attraction mode according to another embodiment of the present invention;
FIG. 4 is a schematic view of a double pole double throw magnetic switch with three permanent magnets in attraction mode according another embodiment of the present invention;
FIG. 5 is a schematic view of a double pole double throw magnetic switch with one permanent magnet in attraction mode according to another embodiment of the present invention;
FIG. 6 is a schematic view of a double pole double throw magnetic switch with two permanent magnets in attraction mode according to another embodiment of the present invention;
FIG. 7 is as schematic view of another double pole double throw magnetic switch with two permanent magnets in attraction mode according to another embodiment of the present invention;
FIG. 8 is a schematic view of another single pole double throw magnetic switch with two permanent magnets in attraction mode and an electro-magnet according to another embodiment of the present invention;
FIG. 9 is a schematic view of another single pole double throw magnetic switch with pole pieces according to another embodiment of the present invention;
FIG. 10 is a schematic view of another single pole double throw magnetic switch operated as a resettable latch;
FIG. 11 is a schematic view of two single pole double throw magnetic switches operated in tandem;
FIGS. 12A and 12B are schematic views showing a means for adjusting air flow around the armature; and
FIG. 13 is schematic view of a reed switch according to a conventional proximity switch.
DESCRIPTION OF THE PREFERRED
EMBODIMENTS
Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.
The magnetic proximity switch system according to the present invention comprises three main elements which are
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magnetically active and at least one of which is a magnet. The spring member is fixed in a predisposed position within the switch. The contact armature is limitedly movable within a switch casing. The contact armature may include electrical contacts or may itself be an electrical contact. The spring 5 member biases the contact armature at one position via a magnetic interaction. The actuator, which is external to the switch, causes the contact armature to move to a second position when the actuator is proximate to the contact armature and overcomes the influence of the spring member. 10 The movement of the contact armature from one position to the other causes electrical connections to be formed and unformed. Preferably, the contact armature may be constrained to travel along the axis of a tubular cavity within the switch casing having a cross-sectional of any shape. The 15 contact member may move by sliding, be guided by linear bearings, or any other suitable means. One or both ends of travel may be constrained by electrical contacts fixed in predetermined locations to the spring magnet to make the switch single throw or double throw. The number of elec- 20 trical poles is defined by the desired construction of the electrical contacts.
With the proximity switch system according to the present invention, the inherent presence of magnetic fields at the position of the electrical contacts tends to quench arcing. 25 The magnetic proximity switch is inherently unidirectional, and, depending upon the particular combination of magnetic materials and permanent magnets, may be polarized. If the particular combination of magnetic materials are chosen and arranged such that the magnetic forces result in attraction, as 30 opposed to repulsion, snap-action results. The sensitivity of any particular preferred embodiment of the switch, the maximum distance between the closest end of travel of the contact armature to the actuator and the actuator at which switching action commences, may be adjusted by changing 35 the distance between the spring magnet and the end of travel of the contact armature closest to the spring magnet. Any preferred embodiment can be easily hermetically sealed to provide corrosion free electrical contacts and explosion proof switching. The motion of the contact armature from 40 one end of travel to the other, which is constrained to travel along the axis of a tube of any cross-sectional shape, may be critically or over damped. The armature acts as a piston, by controlling the air flow within the tube to provide a bounceless switch. Pole pieces may be attached to the switch and 45 to the actuator magnets which changes the angle of directionality away from the axis of the switch such that the switch may be oriented at angles to the actuator without substantial loss of sensitivity. This arrangement may be constructed such that the switch becomes a resettable latch. 50 Two or more switches may be constructed in tandem whereby the actuation of one switch results in the actuation of the others.
The structure of the proximity switch system according to the present invention will now be described in detail with 55 reference to FIGS. 1 through 12.
Referring to FIG. 1, a sectional view of a switch actuated by a permanent magnet actuator 4 in the open circuit state according to the present invention is shown which includes a switch casing or tube 5 made of any electrically conducting 60 non-magnetic material, for example, copper. A spring magnet 1, made from any permanent magnet material, is fixed to the tube 5. An electrical contact 3, made of any suitable contact material that is non-magnetic, is attached to an electrical insulator 6, the electrical insulator being fixed to 65 the tube 5. An electrically conducting wire 8 is electrically fastened to the tube 5. Another electrically conducting wire
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7 is electrically fastened to the electrical contact 3. The contact armature 2, made from any conducting permanent magnet material, is in electrical contact with the tube 5.
When the actuator magnet 4 is sufficiently removed from the proximity of the contact armature 2, the contact armature 2 is repelled by the opposing forces between the spring magnet 1 and the contact armature 2 due to the predisposition of their like poles as shown and forced to make electrical contact with the electrical contact 3 resulting in a closed circuit. The actuator 4, when sufficiently proximate to the contact armature 2, over powers, by repulsion, the influence of the spring magnet 1 on the contact armature 2 causing it to travel away from the electrical contact 3, due to the predisposition of the like poles, resulting in an open circuit as shown. The predetermined distance between the spring magnet 1 and the contact armature 2 in combination with the magnetic properties of the spring magnet 1, the contact armature 2, and the actuator 4, sets the maximum actuation distance between the contact armature 2 and the actuator 4.
Referring to FIG. 2, a sectional view of another switch actuated by a permanent magnet actuator 4 in the closed circuit state according to the present invention is shown which includes a switch casing or tube 5 made of any electrically conducting non-magnetic material for example copper. A spring magnet 1, made from any permanent magnet material, is fixed to the tube 5. An electrical contact 3, made of any suitable contact material that is nonmagnetic, is attached to an electrical insulator 6, the electrical insulator being fixed to the tube 5. An electrically conducting wire 8 is electrically fastened to the tube 5. Another electrically conducting wire 7 is electrically fastened to the electrical contact 3. The contact armature 2, made from any conducting permanent magnet material, is in electrical contact with the tube 5. A spacer 9, made of any non-magnetic material, interposed between the spring magnet 1 and the contact armature 2, is fixed to the tube 5.
When the actuator magnet 4 is sufficiently removed from the proximity of the contact armature 2, the contact armature 2 is attracted to the spring magnet 1 by the forces between the spring magnet 1 and the contact armature 2 due to the predisposition of their opposite poles, as shown, and constrained by the spacer 9, which is fixed to the spring magnet 1, such that the contact armature 2 may not travel closer to the spring magnet 1 than the predetermined thickness of the spacer 9. The distance between the spring magnet 1 and the contact armature 2, as predetermined by the thickness of the spacer 9 in combination with the magnetic properties of the spring magnet 1, the contact armature 2, and the actuator 4, sets the maximum actuation distance between the contact armature 2 and the actuator 4. The actuator 4, when sufficiently proximate to the contact armature 2, over powers, by attraction, the influence of the spring magnet 1 on the contact armature 2 causing it to travel toward and make electrical contact with the electrical contact 3, by snap action, due to the predisposition of the opposite poles, resulting in a closed circuit as shown.
Referring to FIG. 3, a sectional view of another switch actuated by a permanent magnet actuator 4 according to the present invention is shown which includes a switch casing or tube 5 made of any electrically conducting non-magnetic material for example copper. A spring magnet 1, made from any permanent magnet material, is fixed to the tube 5. An electrical contact 3, made of any suitable contact material that is non-magnetic, is attached to an electrical insulator 6, the electrical insulator being fixed to the tube 5. Another electrical contact 11, also made of any suitable contact
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