US 3866317 A
A reed switch is provided preferably with an envelope non-circular and in particular a flattened oval in cross section. Reed switch elements, each having a reed section, a sealing section and a lead section are sealed into the envelope along a part less than the total length of the sealing section, the unsealed part of the sealing section being in close engagement with the inner wall of the envelope. A method of making a reed switch is provided wherein reed switch elements each including a reed section, a sealing section and a lead section are inserted into a tube, preferably non-circular, the sealing section of the elements and the interior of the tube being so closely dimensioned as to permit them to locate the reed sections with respect to one another before and during a sealing process. In the preferred method, a multiplicity of pairs of switch elements are inserted in a glass tube of oval cross section, lengthwise of the tube, and sealed in place in a horizontal position, providing symmetrical sealed joints, and thereafter the tube offal between the switches is removed.
Description (OCR text may contain errors)
United States Patent Morrill, Jr.
1451 Feb. 18,1975
 REED SWITCHES AND PROCESS FOR Primary Examiner-Richard JJHerbst gMAKlNG THEM g I Assistant Examiner-James R. Duzan  Inventor: V ggwmgl Jr. a Attorney, Agent, or FzrmPolster and Polster  Assignee: Morex, Inc., St. Louis, l\1o v  ABSTRACT  Filed; Sept 26, 1973 A reed switch is provided preferably with an envelope non-circular and in particular a flattened oval in cross PP N05 400,796 section. Reed switch elements, each having a reed sec- Related Application Data tion, a sealing section and a lead section are sealed into the envelope along a part less than the total  gg g fgff zgol sept' 1972 length of the sealing section, the unsealed part of the 5' sealing section being in close engagement with the 1 inner wall of the envelope. A method of making a reed  US. Cl. 29/622 switch is provided wherein'reed switch elements each 1  Int. Cl. H01h 11/00 includin a reed section, a sealing section and a lead g  Field of Search....... 335/151. 152, 154; 29/622 section are inserted into a tube, preferably noncircular, the sealing section of the elements and the interior of the tube being so closely dimensioned as to  References Cited permit them tolocate the reed sections with respect to one another before and during a sealing process. In UNITED STATES PATENTS the preferred method, a multiplicity of pairs of switch 3,098,908 Heath elements are inserted in a glass tube of ova] cross sec- 31124570 3/1964 9 335/154 tion, lengthwise of the tube, and sealed in place in a 3,134,868 5/l964 Shme 335/154 horizontal Osition rovidin -S mmetrical Sealed 3,310,863 3/1967 Ellwood et 31.. 335/151 p p g y 3 388 463 6/1968 lnsley 335/151 101m and thereafter the tube offal between the 3,539,956 11/1970 Andersen et al... 335/154 swtches 3,599,129 8/1971 Arvay 335/l52 7 Claims, 7 Drawing Figures 5 l6 I9 1 /7 l6 Z 20 u 2 3. y! WHW a "1.! E I. q 15 i g PATENTED FEB 8 i975 SHEET 1 or 3 ATENIEU P5818196 V 3.866.317
SHEET 3 BF 3 FIG. 6.
REED SWITCHES AND PROCESS FOR MAKING THEM RELATED APPLICATION This application is a division of application Ser. No. 290,113, filed Sep. 18, 1972, now U.S. Pat. No. 3,794,944.
BACKGROUND OF THE INVENTION Normally, glass encapsulated reed switches are made by holding and positioning two metal reed members and a short length of glass tubing, in which the reed members fit loosely, in fixtures, vertically. The reed members of present day commercial reed switches are made up of a flat reed section and round uniformly sized sealing and electrode or lead sections, the sealing section being defined with respect to the lead section only by its being sealed to the glass tubing in the finished switch and being directly connected to the reed section. It can be seen that the flat reed sections, essentially elongatedly rectangular in plan, have six ways in which their relative positions and orientations must be controlled: three translational ways or degrees, lengthwise (amount of overlap), heightwise (amount of gap at the overlap), and lateral offset, and three rotational degrees which might be thought of as pitch, roll and yaw. Ordinarily, one of the reed members is sealed through one end of the glass tubing which fixes its position relative to the tube. The other reed member is located lengthwise for overlap, laid flat against the first to ensure against rotational disorientation (roll), then moved away from the fixed reed member a predetermined distance, to establish the desired gap, and then sealed through the other end of the glass tubing. The problems of yaw and pitch are resolved by making the reed members perfectly straight and chucking them in chucks the center lines of which, after the gapping movement, are parallel and lie in the same plane normal to the plane of the broad faces of the reed sections. The fixtures that are required to position and hold all three parts in a vertical position while the seals are made and the mechanisms necessary to insure their interaction with one another are very elaborate as those skilled in the art will recognize. The fixtures must have extremely accurate holding capabilities and the associated mechanisms must have extremely accurate positioning capabilities or the resulting switches will have large variations in operating characteristics. An example of a machine of the present commercial type is illustrated and described in Pityo US Pat. No. 3,537,276.
The common practice, whereby the flexible reed portion of each metallic member is made by flattening round wire, results in a poor fit between the relatively large inside diameter of the loose fitting glass tubing and the relatively small outside diameter of the round wire at the seal area. During typical vertical sealing operations, this poor fit contributes to the formation of widely varying glass to metal joints at the upper and lower seals. These joints are often of poor quality resulting in a switch that can easily fail. At the same time, the present method of establishing the gap dictates that the wire at the seal area be small relative to theinside diameter of the glass tubing.
When flattened metal wires are sealed through the ends of relatively large loose fitting glass sleeves, in Order to make reed switches, poor coupling results between the external magnetic field and the internal metal reeds because the loose fitting glass sleeve prevents close proximity between the external field and the reeds. This in turn means that the external magnetic actuating field, whether produced by an electromagnet or a permanent magnet, must be excessively large, thus making the very desirable trend toward miniaturization of such components of electronic circuits as reed switches impractical.
Further, the presently used assembly fixtures are not only of such relatively large physical dimensions but also of such complexity that it is mechanically impractical to reduce their dimensions to a point at which they could successfully assemble and seal truly miniaturized reed switch parts. The sealing factor of such complex devices is such that holding and positioning of small parts to a few millionths of an inch is beyond practical mechanical consideration.
In addition, it is generally desirable to seal an inert gas atmosphere inside the glass reed switch body. This is commonly achieved by either flushing the reed assembly with inert gas while it is in the holding and positioning fixture'and before sealing, or surrounding the holding and positioning fixture with a gas tight jacket so that the ambient atmosphere can be removed from the unsealed reed assembly and replaced by inert gas before the seals are made.
A serious disadvantage results from this common method of assembly and introduction of inert gas. To avoid contamination of the inert gas atmosphere, infrared radiant heat energy is used to produce the glassmetal seals. Standard lead glass commonly used for electronic devices has a low infrared absorption characteristic and therefore when infrared radiant heat is used the glass requires a long time to heat to sealing temperatures. Accordngly, special glass compositions that are more infrared absorbent are used to make present-day commerical reed switches. These special glass compositions are several times more expensive than standard lead glass. The need to use special glass and for expensive infrared heat sources and the slow, one-at-a-time, assembly fixtures common today, make it practically impossible for reed switches to complete effectively with other low cost switching devices.
Because the common reed switch is made from a short length of glass tubing, open at both ends, contamination of the interior of the glass sleeve is a very real problem. Elaborate methods are required to clean the glass sleeves before assembly into the sealing fixture and further special clean room facilities are necessary to keep the assembly fixtures and all other parts from introducing foreign matter into the switch body. These additional precautions only contribute further to the high cost of making reed switches by the traditional methods and in effect limit the overall use of reed switches in the market place.
BRIEF SUMMARY OF THE INVENTION In accordance with this invention, generally stated, high precision hollow glass tubing is cut into lengths to accomodate the elements of a plurality and preferably a multiplicity of reed switches. The tubing is preferably non-circular in crosssection, and is formed to sufficiently closs dimensions to serve as a fixture for elements of the reed switches. The elements are shoved into the tubing to exactly predetermined positions lengthwise of the tubing. The individual switch members themselves have a reed section, a sealing section and an electrode or lead section. The reed section of each member has at least one face offset from the center line of the sealing section, whereby when two such members are positioned in the tube facing and slightly overlapping one another with one rotated 180 with respect to the other,-the facing ends of the reed sections are spaced by the amount of the offsets. While in the preferred embodiment, the offset of the reed section from the sealing section takes the form of a step, whereby the reed sections are parallel to one another throughout their length and parallel to the center line of the sealing sections, the reed sections can beoffset by introducing a controlled amount of pitch to the reed sections, so that'while the broad faces of the reed sections may lie in parallel planes, they are not necesarily parallel to the center lines of the sealing sections.
Preferably, the sealing section is dimensioned to fit closely enough within the tubing to establish the desired lateral spacing of the free ends of the reed sections, and the sealing section is sufficiently long relative to the zone of heating during the sealing process so that the parts of the sealing section which extend beyond the softening zone at any moment and bear against the unsoftened area of the tube serve to maintain the alignment and spacing of the reeds during the sealing process. All of the seals are made, and the tubing is then cut to define each individual switch assembly. The offal between switches, previously housing the lead sections, is discarded.
The sealing can be done in a horizontal position, and the great length of the tubing, and the fact that no elaborate'individual fixtures are needed to hold'the separate switch elements during the sealing process make it easy to avoid contamination even without the use of a clean room."
The resulting finished reed switch is symmetrical, un-
like the conventional vertically sealed type, and preferably the reed sections bear lightly against a straight, undistorted inner wall of the reed section of the envelope where they are most sensitive to an external magnetic field. The bearing of the reed section against the inner wall not only increases the sensitivity, but serves to damp vibration of the reed, known in the art as bounce.
The sealing joints are also superior to those known heretofore because the fit between the sealing sections and the glass tubing is so close that it requires that less glass be melted to obtain a seal, and the softened glass cannot sag into undesirable configurations.
As one skilled in the art will recognize, the method of this invention permits the commercial manufacture of reed switches smaller than any known heretofore, and accordingly makes possible miniaturization of circuits involving reed switches.
One of the objects of this invention is to provide a method of making reed switches which is faster, sim- Other objects will become apparent to those skilled.
in the art in light of the following description and accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWING In the drawing, FIG. I is a view in perspective, much enlarged, of a single reed switch assembly, illustrating the cooperation between the sealing section of a reed element and the tubing of which the envelope is made;
FIG. 2 is a view in perspective, also much enlarged, of a section of non-circular glass tubing;
FIG. 3 is a view in perspective showing two sets of pairs of reed switch elements located inside a long noncircular glass tube;
FIG. 4 is a somewhat schematic view in perspective showing metal reedvswitch elements in the process of being heat sealed in the glass tube;
FIG. 5 is a somewhat schematic view in perspective illustrating the removal of offal glass tubing and showing finished reed switch assemblies;
FIG. 6 is a view in side elevation showing a multiplicity of reed switch elevation showing a multiplicity of reed switch elements sealed within a single envelope to form a unitary assembly of series-connected reed switches; and
FIG. 7 is a view in side elevation of still antoher embodiment of reed switch assembly corresponding to the assembly shown in FIG. 6, in that successive lead sections are connected in series.
DETAILED DESCRIPTION Referring now to the drawings for one illustrative embodiment of reed switch of this invention and process of making it, reference numeral 1 indicates a completed switch, made up of an envelope '2, and reed switch elements 3 and 4.
In the embodiment shown, reed switch elements 3 and 4 are identical, and include a reed section I0, a sealing section 11 and an electrode or lead section 12. The reed sections 10.are offset from the longitudinal center of the sealing section 11, and one of the elements 3 and 4 is rotated and translated with respect to the other in each reed-switch so that the reed sections 10 face one another and are spaced heightwise by the sum of their offsets when the sealing sections of the two elements are aligned longitudinally. The ends of the reed sections of the elements 3 and 4 overlap slighly, in a way conventional to reed switches. In the preferred embodiment, in which the elements 3 and 4 are inserted into a non-circular tube 13, the sealing section 11 is sized to fit closely within the non-circular tube, and is of a length to ensure against misalignment in five of the six degrees of freedom which must be controlled, leaving only the lengthwise (overlap) position to be determined and controlled. Thus, the sealing section, cooperating with the inner wall of the envelope itself, is also the locating and positioning means in five of the six degrees of freedom.
The sealing section 11 of each of the elements 3 and 4 is bonded in a glass-to-metal bond through a part but less than the full longitudinal reach of thesealing sec tion.
The reed switch elements 3 and 4 are in some respects conventional in that they are made of any of a number of well known alloys that are both ferromagnetic and have a coefficient of expansion comparable with the glass of the tubing, typically lead glass. The reed section 10 is generally plated as in conventional reed switches, and the sealing section is selectively oxidized to ensure proper bonding, in the conventional way.
In other respects, the reed switch elements 3 and 4 are peculiar to the switch of this invention. As has been indicated, the sealing section is made to very close dimensional accuracy not only in length but in width and thickness, so as to fit closely within a tube 13.
The tube 13, from which one or preferably a plurality of switch envelopes is produced, has a bore 14, which is also made to extremely close tolerances and dimensioned closely to receive the sealing sections of the switch elements.
The bore of the tubing 13 is preferably non-circular in cross section and generally symmetrically oval. The term oval" is used broadly to embrace non-circular shapes of a generally elliptical or flattened elliptical type such as is exemplified by the shape of the tube 13 and its bore I4 in the illustrative embodiment shown.
In the preferred embodiment of method of this invention, reed switch elements are pushed into a tube 13 of a length sufficient to accommodate a plurality and preferably a multiplicity of sets of pairs of elements 3 and 4. In FIG. 3, for convenience of illustration, two sets are illustrated, but as many as eighty or more may be inserted by means of push rods, the travel of which is precisely determinable. The travel of the push rods determines the amount of overlap of the reed sections the fit of the sealing sections 11 and the amount of offset of the reed sections from the sealing sections deter-' mines the heightwise spacing of the ends of the reed sections.
Preferably, reed elements are inserted simultaneously in a multiplicity of tubes. The tube 13 is either loaded while on or is loaded and then placed on a support 25, as shown particularly in FIG. 4. The loaded tube I3 may be flushed with inert gas and one end sealed initially or a stream of inert gas may be directed through the bore 14, from one end 15, and a first seal made by softening the glass of the tube 13 by flames 17 at the sealing section 11 of the element closest to the end through which the inert gas-is being introduced. The area of the tube heated by the flames 17 is narrower than the length of the sealing section 11. Because the sealing section 11 is in such close contact with the inner wall of the tube 13, a seal between the sealing section 11 and the glass tube is accomplished quickly and easily. If a stream of gas was introduced during the first switch sealing step, the introduction of the inert gas can now be cut off. In either case, successive seals are made, sequentially in the direction of the open end of the tube, by flames l8, l9 and 20, respectively from burners identified by the same reference numerals. Burners for flames 17 are omitted for clarity. Flames I8, 19 and 20 are shown in phantom lines to indicate that they are ignited or applied to the sealing areas between them sequentially. It can be seen that because the seals are made with the tubing and switches in a horizontal position, the seals can be identical and the both because no different treatment must be accorded the two ends in the process, as distinguished from the conventional method, and because the close fit of the sealing section permits the sealing to be accomplished with a minimum of distortion.
The sealed assemblies are now annealed and cooled, and thereafter offal sections 21 are removed, as by nicking and bending, leaving discrete finished reed switches l as indicated in FIG. 5.
In the illustrative embodiment shown, the support 25 is a series of bands 16 forming part of a conveyor. The bands 16 are spaced to permit flame from a burner beneath the bands to supply flames 17, 18, I9 and 20 from below to balance flames from above, as indicated in FIG. 4.
As has been indicated, since the sealing areas 26 pro duced by the flames l7, l8, l9 and 20 are narrow compared with the length of the sealing sections 11 of the elements, the sealing sections continue to serve their locating function during the sealing process. It is apparent that once the sealing has been accomplished and the seal cooled sufficiently to maintain the relative positions of the elements, any additional area of the sealing section or of the lead section, for that matter, can be sealed in or bonded to tubing without affecting the critical position of the reed sections.
It can be seen that since flame or hot gas can be used as the glass softening means, the tubing can be made of a standard lead or flint glass as distinguished from the special colored glasses commonly utilized in present machines in which infrared energy is used to produce the glass-metal seals.
The following example is given merely by way of illustration and not by way of limitation.
Kimble glass Type KGI2 or Corning type 0120 lead glass of initially round crosssection is formed on a metal mandrelby Well known vacuum forming methods so'that the resulting glass will have very closely controlled dimensions. Oval tubing with an internal cross section of 0.0202 0.0001 inch for the minor axis and 0.0510 i 0.0002 inch for the major axis and a wall thickness of 0.012 t 0.001 inch is selected from the vacuum formed stock.
Metal reed members with a minor axis of 00200 i 0.000l inch and a major axis of 0.0500 i 0.0005 inch in the sealing area and a reed length of 0. I88 inch, seal length of 0. l 88 inch and electrode length of 0.300 inch are made from any of a number of glass sealing alloys such as Westinghouse 52, Driver-Harris 152, or Carpenter Technology 52 by well known stamping and coining methods.
A 12 inch length of vacuum formed glass tubing is se lected and one end is flared by heating with a gas torch and forming the tubing in a fixture while hot so that after cooling the metal reeds can be easily inserted into the flared end of the tubing without causing chipping of the glass or scoring of the metal reed member.
Sixteen reed members are inserted in the flared end of the tubing one at a time while a stream of inert gas is flushed through the glass tubing and each reed member is positioned by a round push rod of the proper dimensions to fit easily in the minor axis of the glass tube and of sucha length as to properly position the reed members so that eight switches are developed in accordance with my previous explanation. Each reed member has a slight bend between the sealing section and the outer end of the electrode portion so that as it is pushed into the tube a slight frictional engagement develops between the glass and reed thereby preventing any change 'of position lengthwise during subsequent handling. The reeds of each pair of reeds overlap each other at the contact ends a total of 0.006 inch in the plane parallel to the flat portion of the reeds and the gap between reeds is 0.002 inch in a plane 90 to the flat portion of the reeds.
After the reeds have been inserted and positioned and while inert gas is flushed through the tube, the end opposite to the flare is sealed by a gas torch and the assembly of glass and fixed reed members is ready for sealing.
The assembly is put in a sealing fixture as previously outlined and seals are made progressively, starting at the sealed end opposite the flare and progressing one at a time toward the open flared end by a plurality of very small hydrogen and oxygen fires 0.010 inch in diameter located in a vertical plane around the seal areas. Inert gas is continuously flooded around the open end of the glass tube so that air cannot get into the assembly during sealing. As each seal is made a small amount of inert gas which was previously flushed into the tubing will be expelled toward the open end due to expansion of the trapped inert gas from heating at the joint. This small flow of gas will pass between the major axis of the reed members and the inner glass wall. Continuous flooding of the open end of the tube with inert gas assures that no air will be drawn into the tubing.
The glass temperature at the sealing area is 1,775 F. during the sealing operation and the time for each seal is seconds. By allowing the assembly to cool at a controlled rate after sealing, a complete annealing of the joints is accomplished.
After annealing, the assembly is cut by scoring and cracking the glass at proper intervals of 0.600 and 0.900 inch to produce finished switches with an overall length of 1.346 inches and a glass length of 0.600 inch.
Numerous variations in the construction of the reed switch of this invention and in the method of making it will of course occur to those skilled in the art in the light of the foregoing disclosure. Merely by way of example, while push rods have been described as the lengthwise positioning means, the switch elements may be moved to their proper positions by other means, such as magnets. If, for an and gate application, for instance, series connected switches are desired, lead sections of two or more successive switches can be made integral and the switches kept in a common unitary envelope. FIGS. 6 and 7 illustrate two illustrative embodiments of such series-connected switch assemblies. Other conveying means, different from the bands illustrated, can be used, such, for example, as wires or plates, and different heating means can be used for the sealing process, as long as the area of heating is closely controlled. In FIG. 4, the burner heads for the sealing steps are indicated as being aligned and simply actuated serially, but in practice the burner heads may be spaced laterally as well as stepped lengthwise and the tubes moved under successive, constantly burning flames. While the oval tubing described is preferred, other non-circular sections can be used. Even circular tubing may be employed with some of the steps of this invention to provide methods of production and switches which are superior to those now known, though inferior to the preferred embodiments of this invention. When round tubing is used, some means must be provided for controlling the roll of the switch elements relative to one another, such, for example, as the maintenance of a magnetic field during the positioning and sealing steps.
Other configurations of the reed switch elements may be used. The reed section of one of the elements making up the switch can be made shorter than the other moving the contact area toward one end of the envelope. The one reed element can be shortened even to the extent of serving essentially asa fixed contact at one end of the envelope. Two reed elements with short reed sections stepped in opposite directions can be insulated from one another and inserted at one end with a long reed section positioned between them to form a double throw switch. In addition to the forming of the sealing section to conform to the configuration of the inner surface of tubes made in shapes different from the shape illustrated, the lead or electrode section can be positioned symmetrically with respect to the sealing section, for example, and can be made of any desired cross-sectional shape, as long as it does not interfere with the insertion of the reed elements into the tube. An advantage of the configuration of the reed elements of the preferred embodiment is that a very slight bending of the lead section in a direction toward the contiguous surface of the tubing provides the frictional engagement desired to ensure against unwanted lengthwise displacement of the positioned reed elements before and during the sealing process.
These variations are merely illustrative.
Having thus described the invention, what is claimed and desired to-be secured by Letters Patent is:
l. A method of forming a reed switch comprising forming a non-circular, non-magnetic tube, inserting into said tube and positioning in lengthwise spaced positions a plurality of sets of pairs of reed switch elements, each of said elements including a reed section, a sealing section engaging the inner wall of said tube, and a lead section, the reed elements of each set being in facing and partly overlapping position, and thereafter sealing the reed elements of each set within said tube along at least a part of said sealing section.
2. The method of claim 1 wherein the reed section of each of said elements is offset laterally from the sealing section, facing reed sections being offset in opposite directions with respect to one another, and the sealing section of each element is closely dimensioned with respect to the inside dimensions of the tube closely to engage the wall of said tube, and sealing section serving as the sole locating element to determine and control at least five or six degrees of freedom of the reed elements of each pair of elements when said elements are inserted into said tube.
3. The method of claim 2 wherein the sealing section of each element is ofa length with respect to the sealing area to project beyond the sealing area during initial sealing whereby said sealing section maintains its locating function during the sealing step.
4. A method of forming a reed switch comprising forming a non-circular, non-magnetic tube, inserting into said tube and positioning in lengthwise spaced positions a plurality of sets of pairs of reed switch elements, each of said elements including a reed section, a sealing section engaging the inner wall of said tube, and a lead section, the reed elements of each set being in facing and partly overlapping position, sealing the reed elements of each set within said tube along at least a part of said sealing section, and thereafter removing tube parts between successive sealed sets to produce separate reed switches.
5. The method of claim 4 wherein the tube is formed of glass.
6. The method of claim 5 wherein the last step is accomplished by scoring the tube and subsequently bending said tube.
7. A method of forming a reed switch comprising forming a non-circular, non-magnetic tube, forming a reed switch element having a reed section, a lead section and a sealing section intermediate said reed and lead sections, said sealing section being dimensioned with respect to the interior configuration of said tube to engage the inside wall of said tube through a substantial length, inserting said switch elements into said tube,
causing said sealing section to bear upon said inner wall to serve as the sole locating element to determine and to control at least five of six degrees of freedom of the reed element, and thereafter sealing said elements in said tube intermediate the ends of said sealing section but through less than the full length of the sealing section of said element, whereby the engagement of the sealing section with the inside wall of said tube in the areas of the sealing section and tube beyond the area in which the tube and sealing section are sealed serves during the sealing step to maintain said element in its predetermined position.
UNITED STATES PATENT OFFICE CERTIFICATE OF CGRREC'HON Patent No. 3 866 317 Dated February 975 Inventor(s) Vaughan Morrill Jr.
It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:
Column 2, line 12, delete "complete" and insert compete and Column 4, lines 19-20, after "switch" delete "elevation showing a multiplicity of reed switch"; line 46, delete slighly" and insert slightly Signed and sealed this 6th day of May 1975.
C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks FORM PO-lOSO (IO-S9) USCOMM-DC 80376-P69 w u.s. GOVERNMENT PRINTING ornc: 1909 o-ass-su,