US3124670A

US3124670A - Reed switch having improved reed positioning means

Info

Publication number: US3124670A
Authority: US
Priority date: 1961-09-25
Publication date: 1964-03-10
Anticipated expiration: 1981-03-10
Also published as: GB1009997A; DE1188169B; NL283543A; BE622678A

Description

Ma rch 10, 1964 G. M. ROSE, JR 3,124,670

REED SWITCH HAVING IMPROVED REED POSITIONING MEANS Filed Sept. 25. 1961 IIIIIIIIIIIIIIL INVENTOR.

66 70 650x65 Aaszk 68 I I I lrramver United States Patent O 3,124,670 REED SWITCH HAVING IMPROVED REED PQSITIGNTNG MEANS George M. Rose, Jr., Mountain Lakes, N.J., assignor to Radio Corporation of America, a corporation of Delaware Filed Sept. 25, 1961, Ser. No. 140,603 Claims. (Cl. 20087) This invention relates to improved reed switches and to the method of making them.

Prior art reed switches comprise two relatively thin strips or reeds of magnetic metal, each strip being sealed near one end through an end of a short length of glass tubing which serves as an envelope. The inner ends of the reeds overlap slightly and are spaced a few thousandths of an inch apart. The overlapping ends of the reeds are brought into contact by applying a magnetic field thereto of suflicient strength to cause movement of the ends toward each other until they touch. The outer ends act as terminals of the switch. One manner of applying an actuating magnetic field to a reed switch is to surround the switch by a coil and to pass a current through the coil. At a certain value of current through the coil, the magnetic field will be great enough to cause the magnetic reeds to contact each other, closing a circuit to which the switch may be connected.

Such glass reed switches are usually made either by an automatic machine or by hand using supplementary jigs and fixtures. The major requirement is that the gap and the amount of overlap of the inner ends of the reeds be accurately controlled. This is important in that for a given magentic material and reed dimension, this gap and overlap determine the magnetic field required to operate the switch. It is important that this magnetic field be kept at a uniform value from switch to switch, especially because in use several reed switches are frequently enclosed by one large coil, and the individual switches must operate nearly in synchronism.

This requirement of controlled gap and overlap places a heavy burden on the machine or fixtures used to make the glass switch. Such machines or fixtures must be extremely accurate themselves in order to produce uniform glass switches. It is obvious that such machines or fixtures must provide accurately controlled motion in at least two and possibly three planes to make possible correct transverse alignment, overlap, and gap spacing.

A further problem in making glass reed switches arises from the fact that the mechanical forces needed to align the reeds can be applied only at the external ends of the reeds, well-removed from the seal regions. The seals are made at temperatures high enough to cause the reeds to lose much of their mechanical strength, so that the act of forcing the reeds in proper relative position can itself lead to reed distortion. Non-uniform cooling of the glass to metal seals can also give rise to internal glass stresses which tend to change the relative reed position on cooling to room temperature.

Another requirement is that the switch reeds or contacts be surrounded by a reducing atmosphere such as an atmosphere containing hydrogen in order to prevent the buildup of metal oxide films at the contacts. Such oxide films would interfere with switch action. However in switches mounted in glass envelopes, good metal to glass hermetic seals normally require the presence of an oxide layer on the metal member to be sealed to the glass. These two requirements tend to be mutually exclusive. At present, a careful adjustment of sealing temperature and the proportional amount of reducing element in the gas atmosphere is required to achieve good seals and freedom from oxide at the contact surfaces at the same time.

3,124,670 Patented Mar. 10, 1964 A pure hydrogen atmosphere would be most desirable but is virtually impossible in a switch employing a glass envelope.

A limitation suffered by the glass reed switch arises from the need to match the thermal expansion properties of the glass and reed metal used. It does not necessarily follow that the best reed material for glass sealing has at the same time the best magnetic properties. For optimum switch operation the reed metal should have high magnetic permeability coupled with a high value of saturation flux.

In an important class of use, reed switches are held closed by providing a permanently magnetized piece of magnetic material placed closely adjacent the reed switch. The surrounding, switch operating coil is so polarized as to oppose the field of this magnet so that current through the coil causes the reed switch to open. In such use, it would be desirable to have the envelope of the switch made of a permanent magnetic material. Glass, being non-magnetic obviously cannot be used to provide the desired permanent magnetic field.

A further class of reed switches comprises latching reed switches which stay closed, upon being closed by application to the reeds of a magnetic field, until a reverse magnetic field is applied to the reed switches. These latching reed switches include a magentizable piece of magnetic material of high retentivity. The current flowing in the surrounding, switch operating coil, causes the switch to close and the magnetic material to become magnetized, whereby upon cessation of flow of current in the coil, the reed switch is held closed by the field retained by the magnetic material. This switch may be opened by causing a current to flow in the coil of such polarity and of such value as to bring the retained magnetic field down to a value below that necessary to hold the reed switch closed. In such switches the envelope of the reed may be of high retentivity magnetic material.

It is therefore an object of this invention to provide an improved reed switch and an improved method of making reed switches.

It is an object of this invention to provide a reed switch construction and method of manufacture in which the elements may be accurately positioned at the temperature at which the completed switch will be used, using materials and structure which lend themselves to provide such accurate positioning in spite of normal manufacturing variations in reed enclosure and in reed material, and in which further processing and completion will not destroy the accurate positioning.

A further object of this invention is to provide an improved sealed reed switch structure which eliminates the problems of conventional sealed glass envelope reed switches.

It is another object of this invention to provide a reed switch in which an external holding field element is not required when normally closed switch operation or latching switch operation is called for.

The reed switch of this invention comprises a cylinder or tube of refractory insulating material such as forsterite having oppositely disposed parallel or longitudinal grooves in the inner wall thereof. The slots may extend the full length of the cylinder so that the cylinder can be readily formed by extrusion, for example. Ceramic materials are chosen for the envelopes because, after firing, these materials withstand brazing and processing temperatures without softening or substantial change in dimensions. The end surfaces may be metalized by any known process, preferably with molybdenum. Two similar reeds of a metal, such as 50-50% nickel-iron (commonly known as 52-alloy), each reed preferably having one or more wings and each reed having its inner end bent from the plane of the reed by a small angle of approximately 8. degrees are provided. These reeds are inserted, one at each end, into the ceramic cylinder so that the reed wing or wings engage the slots in the ceramic.

At insertion the reeds are oriented so that their bent ends face each other but extend outwardly in opposite directions from the plane of the reeds. The reeds are moved toward each other in the slots, the bent ends overlapping and approaching each other to. establish the working gap. The rather shallow angle of end bending pro? vides a ve-rnier action in gap adjustment. The overlap is less accurately controlled; however, more tolerance in overlap is permissible than in gap width. Final positioning may be achieved by moving the reeds toward each other while the assembly is submerged in a magnetic field of known strength, and while the reed terminals are connected to an external electrical indicating circuit. The reeds are moved toward each other until the combination of overlap and gap-spacing is such as to cause the gap suddenly to close under the influence of the magnetic field.

The envelope may then be hermetically sealed and simultaneously provided with a reducing atmosphere inside. This may be accomplished by placing a small cap of either metal or metalized ceramic over the external ends of the reeds and sliding these into contact with the previously metalized ends of the ceramic cylinder. A small ring of suitable brazing material such as silver solder may be provided, surrounding each end cap. This final assembly may then be placed in a furnace having a reducing gas atmosphere such as hydrogen. The temperature is raised until brazing occurs. A hermetic seal is thereby made at each end, and, since the sealing takes place in the furnace, the space inside the completed switch is provided with a reducing atmosphere.

In a preferred embodiment thereof, auxiliary spring members. are provided between the wings of the reeds and grooves in the tube.

Where it is desired to provide a normally closed switch, the ceramic cylinder or tube may comprise a ferrite material which is in permanently. magnetized condition after the switch is. completed.

The invention is described in detail in connection with several figures in which:

FIG. 1 is a longitudinal section of a reed switch made in accordance with this invention;

FIG. 2 is a transverse section on line 2-4 of FIG. 1;

FIG. 3 is a partial longitudinal section of the reed switch turned 180 from the view of FIG. 1;

FIG. 4 is a partial longitudinal view showing a modified end enclosure of the reed switch;

FIG. 5 is a partial longitudinal section of a preferred form of reed switch made in accordance with this invention;

FIG. 6 is a section on line 6--6 of FIG. 5;

FIG. 7 is an enlarged perspective view of a spring holding member used in the reed switch of 'FIG. 5;

FIG. 8 is a perspective view of a preferred form of reed usable in the embodiments of FIGS. 1 and 5;

FIG. 9 is a diagrammatic illustration of a step in the method of positioning the reeds in the ceramic tubing comprising a part of the reed switch;

FIG. 10 is a partial longitud-nal view of a modified reed switch; and,

FIG. 11 is a section of 'FIG. 10 on line 11--11 thereof.

FIGS. 1-3 show one form of the reed switch of this invention comprising a relatively thin walled cylinder or tube 101 of ceramic material, Such as forsterite. It is 7 provided with two parallelslots or grooves 12 located oppositely to each other on the inside surface of the cylinder and along the length thereof. The sides of the grooves 12. are parallel and a side of one groove is in the same plane as a corresponding side of the other groove. The grooves areof the same height, the height being the distance between the two parallel walls of the groove. The slots or grooves 12 extend the full length of the cylinder so that the cylinder can be formed by a normal extrusion or isostatic process. The ends of the cylinder are metalized at 14 in a known manner with a suitable refractory metal such as molybdenum.

A pair of reeds 16 are provided, one reed 16 extending into the cylinder 10 from each end thereof. The reeds 16 are identical. They are made of a magnetic alloy, for example, about nickel and 50% iron, known as 52-alloy. The reeds are of uniform thickness and of a uniform width throughout most of their lengths. However, the reeds have oppositely directed wings 18 made integral therewith for fitting into the grooves 12 in the cylinder 10. The inner end of each reed 16 is bent out of the plane of the remainder of the reed at; a small angle such as 8 and for a short distance, for example, for from one to two times the width of the reed, as shown in FIG. 1 at 25). This angle of bend of the reed is important since the value of the magnetic field for closing the switch depends principally on the spacing and to a lesser extent on the overlap of the reeds. For example, the overlap may vary by plus or minus 2.0% from reed switch to reed switch while the spacing should be within plus or minus 5%. With a 7 to 9 degree angle, the ratio of change of spacing and of overlap, as the reeds are moved towards each other, is at an optimum value for quick, easy adjustment of the position of the reeds. If the angle of bend is greater, difiiculty is experienced in adjust-ing the gap. If the angle of bend is smaller, upon adjustment of the gap, the overlap may be excessive. It is important that the reed angles in a particular switch be alike.

A reed 16 extends into the cylinder 10 from each end thereof, the bent portions 20 being received within-the cylinder and with the wings 18 tightly fitting in the grooves 12. If necessary, the wings 18 are roughened or fluted or cambered, as indicated by the cross hatching in FIG. 3, to provide a tight fit between the wings 18 on the reeds 16 and the grooves 12 in the cylinder 10. The wings are long enough with respect to their width to insure that, after engagement of the wings, the main portions of the reeds lie in the same plane. The fit between wings and slots is of an interference sort, that is, the edge of the wing must yield a slight amount to permit entry of the wings in the slot. The ends of the reeds 16 which extend outside the cylinder and opposite the bent ends 20, protrude out of the cylinder lit to serve as electrical terminals of the reed switch.

End closures are provided for the cylinder 10. The end enclosures shown in FIGS. 1-3 comprise cup-shaped metal caps 22, each having a slot 24 there-through through which the outer ends of the reeds 16 extend. If the com- 7 pleted reed switch, the caps 22 are brazed to the metalized end surfaces 14 of the cylinder 10 and to the reeds 16' at the contacting portions thereof, to form a vacuum tight sealed structure. The internal atmosphere of the reed switch may be argon, neon, helium or any inert gas. However, an atmosphere of or including hydrogen may preferably be provided in the manufacture of the reed switch.

If desired, a ceramic closure Z6 (FIG. 4) may be used to seal each end of the cylinder 10 instead of the metal cap 22 of FIG. 1. The ceramic cap 26 also has a metalized wall surface 28, and a slot 30 in cap 26 for receiving the reed is also metalized on its internal surface. The reed switch of FIG. 4 and that of FIGS. 1, 2 and 3 differ only in the end enclosure used.

In practice the interference fit between the wings and slots in the reed switch of FIGS. l-3 can be achieved only if the ceramic and reed parts are held to physical dimensions having tolerances somewhat closer than commercial tolerances. Such strict control of part dimensions requires undesirably costly procedures.

In another embodiment of the reed switch, two additional identical and easily fabricated spring members 48 (FIG. 7) are provided. Use of these spring members not only permits use of reeds and ceramics of commercial tolerances but also simplifies the problem of reed insertion, whereby reed switch costs are reduced. An embodiment of such a reed switch using spring members 48 is shown in FIGS. 5 and 6. In this embodiment, the cylinder 44 is similar to the cylinder of FIG. 1. However, the two parallel grooves 46 have a greater height dimension than the grooves 12 in the cylinder 10 of FIG. 1, in that room is provided in order to accommodate a spring member 48 surrounding each reed 50 at the winged portion 52 thereof. The reed 16 of the switch of FIG. 1 may be used in the switch of FIGS. 5 and 6, except that the roughening, fiuting or cambering of the wings is not necessary.

An improved reed 50 of FIG. 8 may be provided. Reed 50'differs from the reed of FiG. l in that a portion 54 of the reed is embossed at the bend of the reed, the embossed portion extending in the direction of the obtuse angle formed by the reed and its bent-out portion. The purpose of this embossed portion is to stiffen the bend between the main portion and the bent-up portion of reed 50 and to preserve the angle of the bend of the reed during heat treatments that are applied to the reed switch in the brazing process during the completion of the switch. This modified reed 50 shown in FIGS. 5, 6 and 8, may be used in the reed switches of FIG. 1 (and if one wing is omitted, the reed of FIGS. 5, 6- and 8 so modified may be used in the reed switch of FIGS. 10 and 11 to be described).

A reed switch spring member 43 is provided for holding each reed 50 in the grooves 46 of the cylinder 44. This spring member 4-8 is shown in FIGS. 5, 6 and 7. It comprises a piece of resilient sheet metal, for example, an alloy known as Inconel X, bent back upon itself. One portion 56 thereof is flat, and the other portion 58 thereof is bowed outwardly. The 'width of the member 48 is substantially equal to the width of the reed 50 at the wing portion 52 thereof. The member is cut away at the bend thereof to form a slot 60. The width of the slot 60 is sufiicient to receive the reed 50 between connecting portions 62 of the member but notthe Winged portion 52 thereof.

In the use of the member 48, the bent portion of the reed 50 is pushed through the slot 60 in the member 4 8. The reed 50 is then pushed further through the slot 66' until the wings 52 are received between the flat portion 56 and the bowed portion 58' of the member 48 and engage the bent portions 62 of the spring supporting member 48. Then the assembly of reed 5t) and member 43 is pushed into an end of the cylinder 44, an edge portion of an end of the flat portion 56 of the member 48 contacting one wall of the groove 46 while the opposite flat edge portion contacts the corresponding wall of the opposite groove 46. The narrow edges of the bowed portion 58 of the member 48 contact the corners of the grooves 46, as shown in FIG. 6.

The relative dimensions of the thickness of wings 52, the height of the slot 46 and the thickness of the metal comprising the spring member 48 are such that, were it not for the bowed or roof-like deformation of the one part 58 of the member 48, the member 48, having the reed therein would readily slide into the slot 46 with one or two mils clearance. However, the roof-like deforma tion of one part 58 of the spring member 48 more than takes up this clearance. On insertion thereof in the groove 46, therefore, the edges of groove 46, press on bowed portion 58 and tend to flatten it. The bowed portion 58 resiliently resists this flattening pressure and therefore, spring pressure is exerted on both sides of the reed wings 52, and for substantially their whole length, in such a way as to force the reed wings against the fiat section of the spring and it in. turn against the opposite side of the ceramic slot. Since each reed 5t) and its respective spring member 43 extends into the same slot 43 from opposite ends thereof, both reeds are thereby referred to the same surface of the slot 46. The member 48 being of spring metal holds the reed 5t firmly but adjustably in the grooves 46 in the cylinder 44. The use of spring members 48 not only makes for more positive reed location but also permits the use of reed wings and ceramic slots having dimensional tolerances which are readily achievable with conventional ceramic and metal working technology. The end caps 22 used with the reed switch of FIGS. 5 and 6 do not differ from that described in connection with FIGS. l3. The end cap of FIG. 4 may be used with the reed switch of FIGS. 5 and 6 if desired.

The enclosure of any herein described reed switch may comprise a magnetic ferrite ceramic material where particular advantages, as explained below, will arise. This known material may have a magnetic field induced there in by applying a magnetic field thereto. If a high retentivity ferrite material is used, the induced magnetic field remains after the applied field is removed. This known material is an insulator which responds well to ceramic processingthat is, it can be extruded into the form of a tube having grooves in the inner sunface thereof. After the extruded form is baked, a strong, dimensionally stable tube having grooves therein results which is suitable for use as enclosures for reed switches of the type described above. Use of such magnetic material provides the fur ther properties to the magnetic switch that a normally closed switch may be provided and that upon closing a reed switch by applying a magnetic field thereto, the reed switch will stay closed until another magnetic field is applied in a direction so as to de-miagnetize the enclosure.

The reeds of any reed switch herein described are adjusted to their final position at room temperature and before the end caps are brazed into position. The method of adjusting the reed switch is illustrated in FIG. 9.

In FIG. 9, the outwardly extending terminals 16 of a capless reed switch, such as any one thereof described herein, is connected in series with a source of electricity 64, a meter 66, and, if desired, a current limiting resistor 68. A coil 70, surrounding the cylinder 10' of the capless reed switch, is connected in series with a source of current 72 and, if desired, a current limiting resistor 74, to apply a magnetic field of selected strength to the reeds in the interior of the cylinder 10. The reeds are pushed towards each other, until the meter 66 indicates that a circuit has been made. At this point of adjustment, the reeds are so spaced and have such an overlap that the reed switch will close whenever a magnetic field of the same value is applied to the reed switch. This method of positioning the reeds of the reed switch provides reed switches which close at the same value of magnetic field even though there be differences in material of the reeds or in the size and shape of the tube and of the reeds. This technique of adjusting reed position makes it possible to produce any number of reed switches having substantially the same operating characteristics.

After adjustment of the position of the reeds, the next step in the manufacture of the reed switch takes place. End caps, together with a suitable brazing material, are positioned over the outwardly extending portions of the reeds, until the lips of the caps contact the metalized ends of the cylinder. The end caps are brazed in any suitable atmosphere, preferably in a hydrogen furnace, to the ends of the cylinder and to the reeds. Due to the strength and dimensional stability of the material of the cylinder, and due to the fact that no force is applied to the parts comprising the reed switch during the step of brazing, the completed switch closes at substantially the same magnetic field which closed it before brazing. Also, where a neutral or reducing atmosphere is used in the furnace, oxidation of the parts of the reed is prevented. When reducing atmospheres are used in the brazing furnace, any organic material present in the switch enclosure will be destroyed. Such material in a switch enclosure is known to be deleterious to useful life of a switch. Upon completion of the brazing an attenuated atmosphere will be present within the cylinder. Or, if desired, the completion of the sealing may take place in inert gas whereby attenuated inert gas remains in the envelope of the completed switch. Where it is desired to have higher or lower gas pressure in the switch enclosure, the furnace gas pressure is adjusted accordingly.

A modified reed switch is shown in FIGS. and ll. The cylinder 32 of FIGS. 10 and 11 differs from the cylinder it) in FIGS. 14' only in that three straight

parallel grooves

34, 36 and 33, which may be triangular, are provided in the inner surface of the cylinder 32'. These

grooves

34, 36 and 38 may be 120 apart about the inner surface of the cylinder 32. The reed 40 used in the reed switch of FIGS. 10 and 11 differs from the reed 16 in FIGS. 14 in that the reed 44) comprises only one wing 42 along one edge only of the reed 40, the other edge being,

straight. A small rectangular piece of spring sheet metal 41 is provided for holding the reed 40 in cylinder 32. This piece of sheet metal 41 may be brazed to the reed 40 perpendicular to the reed and opposite the wing 42. This piece of spring metal 41 is of such size that it fits into the cylinder 32 with the ends of the spring 41 fitting into adjacent grooves 36 and 33. The reed 40 is pushed into the cylinder 32 with its wing 42 in the third groove 34 and with the spring 41, which is brazed to the reed, in the other two grooves. When properly fitted into the tube, the spring 41 is bowed out a little by the pressure on it of the reed 40, as shown in FIG. 11. The degree of bowing depends on the relative width of the reed and of its wing to the internal size of the tube and the depth of the grooves therein. The wing 42 need not be roughened since wing 42 does not fill groove 34. Thereby a reed.

switch is produced in which the reed is held tightly in the tubing evenv through manufacturing dimensional variations are present in the reed and in the enclosure.

While a metal cap 22 is shown in FIG. 10, a ceramic closure member 26 such as that shown in FIG. 4 may be used with the reed switch of FIGS. 10 and 11. The

position of the reeds of FIGS. 10 and. 11 may be adjusted in the same manner as the reeds of the other herein described reed switches. The cylinder 32 of FIGS. 10 and ll may may be a ferrite, if desired, and reeds each having an embossed portion as shown in FIG. 8, may be used in the modification 1 of FIGS. 10 and 11, one wing being omitted.

' While the reeds used in the reed switches of this invention are preferably of uniform width (except at the wings thereof) and thickness, the width of the reeds may decrease gradually along the length thereof or they may be grooved laterally, between the wings and the bent-up portion thereof, to control the location of the fiexure due to the application of the magnetic field thereto.

The reed. switch construction described herein includes several novel features, some of which are as follows:

The slotted ceramic cylinder, being completely rigid at all temperatures involved in. assembly provides inherent jigging or alignment for the metal reeds. This is impossible in the glass construction where the ends of the glass tube must of necessity be heated to plasticity to make the reed seals.

At assembly, once the reed wings have engaged the slots in the ceramic cylinder, the reeds need only to be pushed linearly toward each other. Their position in the other two geometric planes is automatically set. Even the line of advance is controlled by the slots in the ceramic. The assembly machine or fixture is thereby greatly simplified over that required for glass switch assembly.

The bent ends of the reeds, in addition to making possible the linear advance described, enable simultaneous adjustment of reed overlap and gap spacing both of which contribute to switch sensitivity. In fact the bent end, linear traverse features serve to reduce a number of potenmagnetic field until the gap between them suddenly closes because of this field. The main performance specification for reed switches is the value of magnetic field to" give contact closure. This method permits easy, accuratecontrol of this value. The closure of the gap at correct reed position during assembly can be used to complete an external electrical circuit which would immediately stop the reed-advance mechanism of an assembly machine as by inserting a relay in circuit with the reeds. Thus, each switch sub-assembly may automatically control itself. This latter self-control feature is virtually impossible with glass switches because the reeds, at glass sealing temperature, depart substantially in their magnetic properties from their room temperature values. It is likely that at sealing temperatures the metal will be above its Curie point where magnetic properties vanish.

Complete hermetic sealing at high temperture in hydrogen provides optimum life performance in a reed switch because it not only inhibits or delays for a very' long time the build-up of oxide or nitride films on the contact surfaces, but also serves to remove, by burning, any organic material in the switch enclosure. Such organic material (even in almost trace amounts) is known to decrease the operating life of reed switches.

This method of enclosing also permits the use of a very wide range of gas pressures if desired, simply by controlling the gas pressure in the brazing furnace. Reducing atmospheres are preferable. However, if inert gas (argon, ne on, helium, etc.) filling is desirable, it can be provided for in the design of the brazing furnace. Vacuum sealing can also be accommodated. v

The nickel-iron alloy known as 52-alloy appears to have acceptable magnetic properties. However, if better magnetic alloys become available, they can be readily accommodated in this construction because their thermal expansion properties play no appreciable part in the switch construction, contrary to the case of the'glass switch. The only requirement for such new alloys is that they can stand the processing temperatures.

Other features of great interest are possible with this new construction. By substituting a'permanently mag-- netized ferrite ceramic material for the forsterite ceramic, a normally closed switch may be produced. That is, uponpassing a current through the surrounding coil of a value to bring the magnetic field down substantially to zero, the reed switch, which was closed by the permanent magnet, will be opened. However, upon cessation of the flow of current, the field of the permanent magnet will close the reed switch. Furthermore, by substituting a highretentivity ferrite ceramic material for the forsterite ceramic, a latching relay or switch can be produced. In such a. switch the surrounding coil can be made to pro duce a. longitudinal magnetic field in the ferrite cylinder; The field from this cylinder couples to the reeds inside the cylinder producing flux at the reed gap causing contact closure on removal of the coil field. The contacts will remain closed until a reverse magnetic field is applied to the ferrite cylinder as by sending a current in the opposite direction through the operating coil, of sufficiently high value substantially to demagnetize the ferrite enclosure but not of high enough value to remagnetize the ferrite enclosure in the opposite direction. Such ferrite ceramic materials having these different magnetic properties are known.

Thus, it is possible with basically only a material change to make either a normally open reed switch, a normally closed reed switch, or a latching reed switch. This latter is of great importance in applications such as computer and telephone switching networks.

What is claimed is:

1. An hermetically sealed reed switch comprising a ceramic tubular envelope member having a pair of longitudinal internal grooves in the Wall at each end thereof, and a pair of reeds having wing portions, said wing portions being held snugly within said grooves for accurately positioning the reeds with respect to one another within said envelope member.

2. An hermetically sealed reed switch comprising a ceramic tubular envelope member having a pair of longitudinal internal grooves in the wall at each end thereof, a pair of reeds having wing portions, said wing portions being held snugly Within said grooves for accurately positioning the reeds With respect to one another within said envelope member, and cap members hermetically sealed to opposite ends of said envelope member for closing said envelope member, said reeds passing through said cap members and being hermetically sealed thereto.

3. A reed switch comprising a closure tube having a pair of longitudinal internal grooves in the wall at each end thereof, a pair of reeds having wing portions, said wing portions being held snugly within said grooves for accurately positioning the reeds within said tube, and end portions of each of said reeds overlapping within said tube, the inner ends of each of said reeds being bent in opposite directions at an angle of from 7 to about 9 degrees with respect to the axis of said tube.

4. A reed switch comprising a tubular envelope having a pair of longitudinal internal grooves in the inner wall at each end thereof, a pair of reeds extending into said tube from opposite ends of said tube, portions of each of said reeds being received within said grooves, and a reed holding spring member extending across each end of said tube, said spring member being tensioned and pressing said reeds firmly against wall portions of said grooves for accurately positioning the reeds within said tube with respect to one another.

5. A reed switch comprising a tubular envelope having a pair of longitudinal internal grooves in the inner wall at each end thereof, a pair of reeds extending into said tube from opposite ends of said tube, portions of each of said reeds being received Within said grooves, and a reed holding spring member extending across each end of said tube, said spring member being tensioned and pressing said reeds firmly against wall portions of said grooves for accurately positioning the reeds within said tube, said reeds extending into overlapping relation within said tube, and the inner ends of each of said reeds being oppositely bent at an angle from about 7 to about 9 degrees with respect to the axis of said tube.

6. An hermetically sealed reed switch comprising a ceramic tubular envelope member having a pair of longitudinal internal grooves in the inner wall at each end thereof, cap members hermetically sealed to opposite ends of said envelope member for closing said envelope member, a pair of reeds extending into said tube from opposite ends of said tubular member, said reeds extending through said cap members and being hermetically sealed thereto, portions of each of said reeds being received within said grooves, and a reed holding spring member extending across each end of said tubular memher, said spring member being tensioned and pressing said reeds firmly against wall portions of said grooves for accurately positioning the reeds within said tubular member, said reeds extending into overlapping relation within said tubular member, and inner ends of each of said reeds being oppositely bent at an angle from about 7 to 9 with respect to the axis of said tubular member.

7. A reed switch including a tubular envelope, the inner wall of said envelope having a pair of parallel grooves extending along said envelope and on opposite sides thereof, one side of each of said grooves lying in a common plane, an elongated reed element of conducting material supported at each end of said envelope from said grooves, spring means press fitting each of said reeds against said one side of each of said grooves and holding the inner ends of said reeds in accurate position with respect to each other, the other ends of said reeds extending outside said envelope and providing terminals, and said reeds being sealed vacuum tight to said envelope adjacent to said other ends.

8. A reed switch including a tubular envelope, the inner wall of said envelope having a pair of parallel grooves extending along said envelope and on opposite sides thereof, one side of each of said grooves lying in a common plane, an elongated reed element of conducting material supported at each end of said envelope from said grooves, spring means press fitting each of said reeds against said one side of each of said grooves, the inner ends of said reeds being at an angle to the rest of said reeds and in overlapping relation, the other ends of said reeds extending outside said envelope and providing terminals, and said reeds being sealed vacuum tight to said enveiope adjacent to said other ends.

9. A reed switch comprising a refractory non-conductive tube having a plurality of longitudinal internal grooves in the wall thereof, a reed holding member extending across said tube, the edges of said member extending into said grooves, said member comprising resilient sheet metal bent over on itself, the material at the bend being cut away to provide a slot in said member, and a reed extending into said tube and through said slot.

10. A reed switch comprising a non-conductive tube having a plurality of internal grooves in the wall thereof, a reed holding member in said tube, said member comprising resilient sheet metal bent over on itself to provide a bend, material at the bend being removed to provide a slot in said member, said sheet metal being flat in one part and bowed in another part, said parts being separated by said bend, edges of said parts extending into said grooves, and a reed extending into said tube through said slot.

References Cited in the file of this patent UNITED STATES PATENTS 2,406,021 Little Aug. 20, 1946 2,535,400 Ellwood Dec. 26, 1950 2,547,003 Hastings Apr. 3, 1951 2,648,167 Ellwood Aug. 11, 1953 2,922,855 Ducati Jan. 26, 1960 2,965,739 Alexandersson Dec. 20, 1960 3,025,371 Medal Mar. 13, 1962 3,032,628 Ellwood May 1, 1962 3,067,304 Bergstrasser et a1 Dec. 4, 1962 FOREIGN PATENTS 501,249 Italy Nov. 23, 1954 1,074,124 Germany Jan. 28, 1960