The subject disclosure relates to electronic relays and switches, and more particularly to bistable reed switch relays.
Various bistable reed switch relays have been constructed in the past.
Illustrative relay embodiments contemplate a relay comprising a reed switch positioned within an actuation or drive coil and a permanent magnet for biasing or holding the reed switch contact closed where the permanent magnet is positioned outside of and spaced apart from the actuation or drive coil and in contact with an input or output lead of the reed switch.
In a first illustrative embodiment, a relay is provided comprising a housing having a central portion wherein first and second reed switches are positioned. An electrically conductive coil is wrapped around the central portion of the housing. First and second input leads of the respective first and second reed switches enter the housing at a first end thereof and are connected to supply respective input signals to the first and second reed switches. In the first illustrative embodiment, each of the first and second input leads comprises a material which transfers magnetic energy.
Further according the first illustrative embodiment, first and second permanent magnets are mounted at the first end of the housing so as to directly contact a respective one of the first and second reed switch input leads at a point prior to those leads entering the housing. The first and second permanent magnets each have a strength selected to hold a respective reed switch relay contact of each of the first and second reed switches closed after supply of drive current to the electrically conductive coil has initially caused those respective relay contacts to close.
Other embodiments may comprise a similar structure wherein only a single reed relay switch and a single permanent magnet are employed or may comprise a similar structure wherein more than two reed relay switches are employed. Embodiments may be constructed wherein the output leads of the reed switches exit at an opposite end of the housing or at the same end as the input leads. Various embodiments are configured to operate as bistable reed switch relays. While illustrative embodiments described below place a permanent magnet or magnets in direct contact with the reed switch input lead or leads, other embodiments may be configured where the permanent magnet(s) directly contact the reed switch output lead or leads.
The illustrative embodiments further contemplate a method of making a relay comprising positioning a reed switch in a housing with an input lead and an output of the reed switch extending outside of the housing; wrapping an actuating coil around the housing; positioning a permanent magnet outside the housing, spaced apart from the actuating coil, and directly mechanically contacting one of the input or output leads of the reed switch and, prior to the step of positioning the permanent magnet outside the housing and in contact with a reed switch lead, selecting the strength of the permanent magnet to hold a contact of the reed switch closed after that contact has been initially closed.
The first and second un-insulated bare iron input leads 19, 21 enter through the first end 23 of the housing 13 and provide respective input signals to the respective reed switches 15, 17. Respective output leads 25, 26 comprise respective output terminals of the reed switches 15, 17 and exit at a second or opposite end 24 of the housing 13. In an illustrative embodiment, the leads 19, 21 may be 0.020 inches in diameter, but of course may have other dimensions in other embodiments.
The housing 13 has a first flange 29 at its first end 23, a second flange 31 at its second end 24, and a central barrel or bobbin 33 located between the flanges 29, 31. The barrel 33 encloses the reed switches 15, 17 and has a conductive coil 47 wrapped around it between the flanges 29, 31, which, in one embodiment, may be formed of insulated copper wire. When supplied with drive current, the conductive coil 47 either opens or closes respective contacts 75, 77 (
As seen in
In illustrative embodiments, the input leads 19, 21 must be iron, iron alloy or other magnetic material in order to transfer the magnetic energy required to hold the contacts 75, 77 of the reed switches 15, 17 closed, after a drive pulse to the coil 47 has initially closed them. In some embodiments, increasing the iron concentration in the leads 19, 21 over conventional iron reed switch leads may be employed to enhance performance.
In an alternate embodiment, the conductors 19, 21 could be insulated as opposed to bare uninsulated conductors, but such a construction would typically require larger permanent magnets to achieve the same magnetic strength at the reed switch contacts 75, 77. In an illustrative embodiment, the housing 13 may be a single piece molded part, and the flanges 29, 31 serve to hold the permanent magnets 41, 43 and coil wires in place in the housing 13.
In one illustrative embodiment, the permanent magnets 41, 43 are cubes of quite small dimensions, for example, 0.0625 inch on a side. The permanent magnets 41, 43 may have other shapes and dimensions in other embodiments. The positioning of two small permanent magnets in a dual reed switch embodiment enables wrapping a magnetic shield, e.g. 49, around the relay coils, further reducing any de-magnetization effect that the relay coil 47 might have on the permanent magnets 41, 43. The cross-section of
In assembly of one embodiment according to
In operation of the bistable relay 11, the coil 47 first pulses in one direction, creating a magnetic field which closes the reed switch contacts 75, 77. The permanent magnets 41, 43 supply a magnetic field sufficient to keep the reed switch contacts 75, 77 closed while the reed switch coil 47 is off. To open the relay contacts 75, 77, a reverse pulse is applied to the coil 47, temporarily interrupting the permanent magnet magnetic field and allowing the contacts 75, 77 to open.
Various embodiments constructed according to the teachings above can exhibit various advantages. For example, locating a bias magnet, e.g. 41 outside the strong field of the actuation coil 47 and situated directly touching an iron lead, e.g. 19, of a reed switch significantly reduces or eliminates demagnetization of the permanent magnet by the strong coil magnetic field. It is also possible to use a much weaker permanent magnet, allowing closer relay placements. In some applications, the strength of the permanent magnet need only be one-half to one-tenth the power required when permanent magnets are placed inside the actuation coil windings. Additionally, the size of the relay may be much smaller than various existing designs, and the cost may be one fourth that of typical twin circuit bistable reed relays.
Illustrative dimensions in inches for one illustrative embodiment of a relay according to
Alternate embodiments may be constructed according the principles disclosed above—for example, an embodiment which employs a single reed switch as opposed to two or more than two. Thus, illustrative embodiments may comprise at least one reed switch. As discussed in connection with
In one embodiment, the tube 202 may be formed of tin-plated steel but may constructed of other suitable magnetic material in other embodiments, for example, such as mu metal. In the embodiment of
As a result of the construction shown in
In various embodiments, the shield structure of
From the foregoing, those skilled in the art will appreciate that various adaptations and modifications of the just described illustrative embodiments can be configured without departing from the scope and spirit of the invention. Therefore, it is to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described herein.
This application claims the benefit of and priority to U.S. Provisional Patent Application No. 62/296,079, filed Feb. 17, 2016, and entitled, “Bistable Relay,” the contents of which is incorporated herein by this reference in its entirety.
Number | Date | Country | |
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62296079 | Feb 2016 | US |