US3348175A - Normally closed reed switch - Google Patents

Description

@ct. 17, 1967 A. J. WILKIS 3,348,175

NORMALLY CLOSED REED SWITCH Filed April 26, 1966 INVENTOR. ANTHONY J. WILKIS ATTY.

United States Patent 3,348,175 NURMALLY CLUSED REED SWlTCH Anthony J. Wilkis, Downers Grove, 11]., assignor to Automatic Electric Laboratories, Inc., Northlake, IlL, a corporation of Delaware 1 Filed Apr. 26, 1966, Ser. No. 545,386 3 Claims. (Cl. 335-154) This invention relates to sealed reed switches and more particularly to reed switches having a set of normally closed contacts.

Conventional break type reed switches usually are of basically make type design. That is, these switches comprise a pair of normally open reeds of magnetic material sealed into a glass capsule, but in addition, have a permanent magnet outside of the capsule for holding these normally open reeds in a normally closed position. Upon energization of a winding wound about the reed switch capsule, to produce a magnetic field, with polarity opposite to, and magnitude greater than, that of the permanent magnet, the reeds will be released from engagement.

U.S. Patent 2,922,856 discloses another example of a normally closed type reed switch device, which comprises two reeds, one of magentic material and the other of non-magnetic material, which extend into a sealed glass tube, one from each end thereof, and whose inner, contact ends are normally making contact with one another. Located inside the glass tube, near one end thereof, is an insulating member into which a magnetic element is mounted, in parallel, spaced relation to the non-magnetic reed. Upon operation of the switch, the inner contact end of the magnetic reed is drawn to the free end of the above magnetic element, thereby breaking contact between the inner, contact ends of the two reeds.

The construction of the above-mentioned reed switch requires, in addition to the usual mounting facilities for each of the two reeds, a separate mounting for the magnetic element and its associated insulating member.

Accordingly, it is an object of this invention to provide an improved break type reed switch device which does not require a magnet for biasing the switch in its normally closed position.

It is a further object of this invention to provide an improved break type reed switch of basically make type design which can be easily fabricated and economically produced.

The normally closed reed switch according to the principal feature of the present invention comprises a sealed envelope having two magnetic reeds extending thereinto,

one from each end of the envelope, in spaced relation to each other. One of the reeds has insulating means covering its inner end, and near this end there is attached a non-magnetic, metallic member whose free end normally contacts the inner end of the other magnetic reed. When the switch is energized, the two inner ends of the magnetic reeds are drawn together breaking the above-mentioned connection, but because of the presence of the insulating means, electrical contact is not made one with the other.

Other objects and features of this invention will become more apparent by reference to the following description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a side view of a preferred embodiment of a break type reed switch according to the invention in its unoperated condition, and

FIG. 2 is a side view of the reed switch of FIG. 1 in its operated condition.

Referring to FIG. 1, a preferred embodiment of the reed switch according to the invention comprises an envelope of insulating material, such as glass, into which two magnetic reeds 11 and 12 extend from opposite ends. An energizing winding 17, wound about envelope 10, is provided for actuating the switch.' The reeds overlap and are normally spaced from one another at their inner ends 14 and 16. Near the inner end 15 of one of reed 11 there is attached by welding, or other suitable means, a Z shaped, non-magnetic, metallic member or spring 13 which normally makes electrical and mechanical contact with the inner end 16 of the other magnetic reed 12. Reed 11 also has on its inner end 14 a coating of plastic insulating material, such as Teflon, to prevent electrical contact between the two magnetic reeds upon operation of the reed switch.

Upon energization of winding 17, the two inner ends 14 and 16 are drawn together as shown in FIG. 2, breaking the electrical and mechanical connection between metallic member 13 and the inner end of magnetic reed 12. As mentioned above, due to the coating of insulation on the inner end of reed 11, no electrical contact is made between the magnetic reeds when they are drawn together. It is to be noted that, instead of coating the entire inner end of reed 11, it would be possible to merely coat the confronting surfaces 1 8, 19 of one or both magnetic reeds 11 and 12. Also, insulating methods other than coating of the reed ends with plastic insulating material may be used. Also, actuation by magnetic means other than energizing winding 17 may be employed.

Thus, the normally closed reed switch according to the invention requires no external permanent biasing magnet, and yet has a structure generally similar to that of a conventional make type reed switch, requiring, like the make type switch, only two mounting facilities, one for each of the two magnetic reeds. Therefore, the normally closed reed switch of the present invention is relatively simple to construct and economical to produce.

Due to the fact that no biasing magnet is used to hold the reed switch of the invention normally closed, there is no danger, as there is with a break type switch biased by a permanent magnet, that the field of the magnet will cause false operations of make type contact switches that may be used along with the break type switch. Also, the reeds of the above-mentioned break type switches which rely on permanent magnet biasing tend to stick due to remanent magnetism unless special measures are taken to prevent this. In contrast, the present construction eliminates the danger of sticking upon energization by virtue of spring 13 being of non-magnetic material, and upon release by virtue of the fact that the inner ends of magnetic reeds 11 and 12 are separated by insulating material. By the same token, the thickness of the insulating layer may be used to control the release time of the reed switch if desired.

It will be obvious to those skilled in the art that changes and modifications may be made without departing from this invention in its broadest aspects and therefore the aim in the appended claims is to cover all such changes and modifications as are within the true spirit and scope of this invention.

What is claimed is:

1. A reed switch comprising:

a sealed envelope of insulating material having first and second magnetic reeds extending thereinto with one surface of their respective inner ends facing each other in an overlapping, normally spaced relation;

insulating means on said surface of the overlapping inner end of at least one of said reeds;

a non-magnetic, metallic member secured to said first reed near said inner end thereof, and bent to extend in spaced parallel relationship to said insulating means to normally make both mechanical and electrical contact with the surface of the overlapping inner end of said second reed opposite said one surface; and magnetic actuating means arranged outside said envelope and operative upon actuation to cause the inner ends of said first and second reeds to be attracted towards one another to thereby break contact between said metallic member and the inner end of said second reed. 2. A reed switch as claimed in claim 1 wherein said reeds extend into said sealed envelope from the opposite ends thereof, and wherein said non-magnetic, metallic member is substantially Z-shaped and is welded to said first reed.

References Cited UNITED STATES PATENTS 1/1960 Karrer 335154 8/1964 Ohki et al. 335-154 X 1 BERNARD A. GILHEANY, Primary Examiner.

R. N. ENVALL, ]R., Assistant Examiner.

Claims (1)

1. A REED SWITCH COMPRISING: A SEALED ENVELOPE OF INSULATING MATERIAL HAVING FIRST AND SECOND MAGNETIC REEDS EXTENDING THEREINTO WITH ONE SURFACE OF THEIR RESPECTIVE INNER ENDS FACING EACH OTHER IN AN OVERLAPPING, NORMALLY SPACED RELATION; INSULATING MEANS ON SAID SURFACE OF THE OVERLAPPING INNER END OF AT LEAST ONE OF SAID REEDS; A NON-MAGNETIC, METALLIC MEMBER SECURED TO SAID FIRST REED NEAR SAID INNER END THEREOF, AND BENT TO EXTEND IN SPACED PARALLEL RELATIONSHIP TO SAID INSULATING MEANS TO NORMALLY TAKE BOTH MECHANICAL AND ELECTRICAL CONTACT WITH THE SURFACE OF THE OVERLAPPING INNER END OF SAID SECOND REED OPPOSITE SAID ONE SURFACE; AND MAGNETIC ACTUATING MEANS ARRANGED OUTSIDE SAID ENVELOPE AND OPERATIVE UPON ACTUATION TO CAUSE THE INNER ENDS OF SAID FIRST AND SECOND REEDS TO BE ATTRACTED TOWARDS ONE ANOTHER TO THEREBY BREAK CONTACT BETWEEN SAID METALLIC MEMBER AND THE INNER END OF SAID SECOND REED.

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