US3828427A

US3828427A - Method for producing a glass-encapsulated reed-contact switch

Info

Publication number: US3828427A
Application number: US00389615A
Authority: US
Inventors: T Huttner
Original assignee: Bunker Ramo Corp
Current assignee: Amphenol Corp; Bunker Ramo Corp
Priority date: 1971-09-10
Filing date: 1973-08-20
Publication date: 1974-08-13
Anticipated expiration: 1991-08-13
Also published as: CH547009A; DD102006A5; DE2145463B2; BE788577A; DE2145463A1; FR2152828A1

Abstract

This disclosure relates to a method for producing reed switches whereby a first contact is embedded in one end of a glass tube, a second contact is positioned through the other end of the glass tube, the temperature of the other end is controlled to embed a portion of the second contact in viscous glass, a magnetic field is applied to both contacts during which time the second contact is moved with respect to the first contact until the reed switch is actuated, and finally, the other end of the glass tube is cooled to harden the viscous glass and hold the second contact.

Description

United States Patent 1191 Hiittner [4 Aug. 13, 1974 METHOD FOR PRODUCING A 3,281,664 10 1966 Campbell et a1 324/28 p TED A T 3,284,876 11/1966 Bultel 29/622 g zgig f SULA REE CONT C 3,537,276 11/1970 Pityo 29/622 X [75] Inventor: Theo Hiittner, Tegersee, Germany p i E i Ri h d fl b c k Assistant Examiner-V. A. Dipalma [73] Asslgnee 3: 2: 5 fi Corporation 0a Attorney, Agent, or Firm-W. Lohff; F. M. Arbuckle [22] Filed: Aug. 20, 1973 [57] ABSTRACT I 1 pp 389,615 This disclosure relates to a method for producing reed switches whereby a first contact is embedded in one 152 u.s.c1. 29/622, 29/203 R 65/155 end 0f a glass tube a seam! is Positimd 5 C 01 11 00 o 1/02 o 11/04 through the other 611C! 0f the glass tube, the tempera 58] Field of Search 29/622 R 200 P 203 D ture of the other end 15 controlled to embed a portion J 65/155 of the second contact in viscous glass, a magnetic field is applied to both contacts during which time the sec- [56] References Cited 0nd contact is moved with respect to the first contact until the reed switch is actuated, and finally, the other UNITED STATES PATENTS end of the glass tube is cooled to harden the viscous u and second 3,155,478 11/1964 0131166... 65/42 3,277,558 10/1966 Shaffer, J 29/622 x 5 Claims, 10 Drawing Figures PAIENIEnmm arm SHEET 2 OF 7 PAIENIEB m2: 31924 SHEET 7 BF 7 METHOD FOR PRODUCING A GLASS-ENCAPSULATED REED-CONTACT SWITCH This invention relates to a methodand apparatus for producing reed switches. More particularly, the field of art to which the invention relates concerns a method and apparatus in which a first contact paddle is embedded into a glass tube, a magnetic field corresponding to the operating field of the reed switch is applied to the glass tube, and a second contact paddle is moved relative to the first one. When the two paddles are a certain distance apart, the magnetic field causes the switch to actuate, whereupon the movement of the second contact paddle ceases and it is embedded into the glass tube. I

The contact paddles of reed switches are usually melted into a glass tube so that part of the paddle shaft protrudes to the outside. The rest of the paddle, including the contact area, remains inside the glass tube. In the open position, the contact areas of the two contact paddles are located a certain distance apart. When a magnetic field is applied to the reed switch, the field causes the paddle sections inside the glass tube to approach each other. In the production of reed switches, the distance between the paddles must be established with high accuracy so that the contact areas of the two paddles touch when a magnetic field of a predetermined strength is applied. In a magnetic field of a given strength, the force of attraction between the contact paddles is inversely proportional to the square of the distance between the paddles. High precision is required in the production of reed switches, since the distance between the paddles may be only several hundredths of a millimeter.

According to a conventional manufacturing method, a contact paddle is embedded in a glass tube, and the exact adjustment of a second contact paddle is made while a magnetic field of the same strength as the operating magnetic field is applied to the glass tube. The second contact paddle moves toward the first paddle, until the two contact paddles touch under the influence of the magnetic field. Closure of the contact is used to stop the motion of the second contact paddleLAdditional glass is then added around the second contact paddle which is then fixedly embedded into the glass tube. Such conventional methods are very convenient for automated production of reed contacts, because the second contact paddle itself determines its distance from the first contact paddle. However, as will be particularly detailed later, in the conventional manufacturing method, large differences between the magnetic field used to cause contact and the actual operating magnetic field occur, and cannot be eliminated.

According to another method of producing reed switches, two contact paddles are moved toward each other and are kept in a certain position by the application of a relatively strong magnetic field. The strength of the strong magnetic field greatly exceeds the actual operating magnetic field of the reed switch, and serves only as a substitute for the mechanical support of one contact paddle. The second contact paddle is supported by mechanical means. While thus supported, the two contact paddles are brought into precise engagement in the contact area by means of fingers embracing the paddles along their lateral edges. The glass tube is then pushed over the two contact paddles from the side of the magnetically supported paddle, and this paddle is melted into the glass tube. The strong magnetic field is turned off, since the first contact paddle is not supported by the glass tube, and the magnetic field would otherwise interfere with the adjustment of the contact paddles. The second contact paddle is then moved to a spaced relationship with respect to the first contact paddle by means of the mechanical support means. This motion must be performed with high precision and hence requires expensive equipment.

As further provided by certain prior art methods, both paddles can be moved relative to each other, further increasing the expense of the required mechanism.

Great differences in the response of reed switches produced according to such relatively expensive methods have still been observed.

An object of the present invention is to provide an improved method for fabricating reed switches at low cost. A further object of the present invention is to provide-a method for fabricating reed switches utilizing automatically controlled means for obtaining reed switches having a narrow response range that is held within low tolerance limits.

According to the present invention, one of the contact paddles is fixed in one end of a glass tube, while the other is moved relative to the first contact paddle while being embedded in a portion of the glass tube which is already melted and in a viscous state.

Both the distance between the two contact paddles and the distance between the contact area and the location at which the paddle is melted into the glass are of extreme importance for establishing close tolerance operating conditions. In order for the two contact paddles to move under the influence of the magnetic field, the shafts of the paddles located inside the glass tube must bend. The torsional moment which causes closure of the contacts is given by the product of the attractive force generated by the magnetic field acting upon the contact paddle times the length of the contact paddle section within the glass tube extending beyond the glass embedding point. Consequently, any variation in this length of the paddle section results in a variation in the response of the contact.

The large,-undesirable variations in the strength of the magnetic field required to actuate reed contacts produced according to the prior art are caused by variations in the length of the paddle section within the tube. In previous processes, the second paddle engaged the first paddle in a predetermined operating field while a torsion moment was effective. The torsion moment, in turn, depended upon the length of the contact paddle section extending beyond the paddle embedding point to the contact area. However, the length of the contact paddle which is later effective in the actual operation of the reed contact is smaller than the length effective during production of the reed switch. The exact position at which the paddle is embedded into the glass tube depends upon several factors which cannot be controlled in the prior art methods. Among these factors are: variations in the dimensions of the glass tubes (diameter and thickness of the tube walls); variations in the heating power required for the melting process (caused by the power gradually changing due to scaling and oxidation of the heater elments during the course of production); variations in the inert gas supplied; and differences between the thermal expansion Even when the second contact paddle is moved with high accuracy, the location at which the contact paddle section is embedded into the glass varies, resulting in contacts with a wide response range.

According to the method of the present invention, the point at which the second contact paddle is embedded into the molten glass is fixed before the adjustment of the second contact paddle, because the second contact paddle is surrounded by viscous glass during its motion. Only the paddle section protruding from the viscous melted glass into the interior of the glass tube is bent by the applied operating field. The motion of the contact is stopped when it reaches the precise distance at which it is actuated by the operating field. According to the method of the present invention, reed switches are thus produced with a well-defined response range.

All advantages of the prior art methods, particularly the adaptability for automatic production and the selfadjustment of the contact distance, are conserved in the method of this invention. The method of the invention is easy to apply, since only the heating for melting the glass or for cooling the glass need be controlled. Only those processes related to embedding of the second contact paddle must be precisely controlled, because the length of the first embedded contact paddle is the same during the self-adjustment of the second contact paddle as it is during the operation of the finished reed switch.

Certain prior art discloses the possibility of moving the contact paddles in a paste-like melt. However, it does not disclose the concept of the present invention. It does not disclose at which stage of the production process the motion should be effected and what advantages are gained by that motion. The melted glass tube cannot influence the adjustment of the contact paddles. The distance between the contact paddles is adjusted by lateral shifting of one of the contact paddles. No magnetic field is applied, and hence, the contact paddles are not bent. One is thus led to the conclusion that the preliminary melting is accomplished while the paddle is shifted only to reduce the time required for production of the reed switch.

The two contact paddles can be demagnetized before the second contact paddle is moved according to this invention, in order to obtain precise adjustment of the paddles in the magnetic field corresponding to the actual operating magnetic field. The step of demagnetization eliminates any residual magnetism in the paddles which might cause misadjustment of the distance between the paddles. Demagnetization is particularly important to overcome the residual magnetism resulting from the exposure of the paddles to the very strong magnetic field used during preliminary adjustment of the contact paddles. Demagnetization can be accomplished by applying an alternating, gradually decreasing magnetic field to the contact paddles. In this manner, the magnetization of the contact paddles follows a series of hysteresis loops which continually decrease in size and finally vanish.

The method of the present invention eliminates the influence of undefined variables upon the adjustment of the distance between the contacts by demagnetizing the contact paddles and by melting the second contact paddle into the glass before adjustment of this distance.

The method of the present invention is executed using an apparatus comprising at least one electrically heated melting device and a contact paddle magetizing coil surrounding the glass tube of the reed switch. The apparatus is provided with an automatic switching unit for adjusting the heating current of the melting device and for exciting the coil-with appropriate alternating or direct current. The viscosity of the melted glass can be adjusted by the switching unit so that the second contact paddle can be moved in the melted glass, as provided by the invention.

The heater circuit for the melting device can be provided with a conventional rheostat for pre-adjustment of the heating current. An additional resistor which can be short circuited when necessary can be inserted between the rheostat and the heater element. This additional resistor reduces the heater current during the process of embedding the second contact paddle in order to lower the viscosity of the glass when the second contact paddle is being moved.

The automatic switching unit also controls the operation of the magnetizing coil. In one step, the coil produces a strong magnetic field around the glass tube in order to obtain preliminary adjustment of the position of the contact areas on the contact paddles. In a second step, the coil provides a continuously decreasing alternating field for the demagnetization of the contact paddles. In a final step, the coil provides a magnetic field equivalent to the operating magnetic field of the reed switch while the final adjustment of the distance between the contacts is being made.

Three sources of current are provided for producing the magnetic fields: l) A conventional D.C. source for generating the strong magnetic field, 2) an a.c. source (in series with a potentiometer) for providing the de magnetizing field, and 3) a constant current D.C. source for providing the magnetic field used during adjustment of the contact position.

A three-level switch connects the coil to one of these three sources. The strong D.C. source provides the strong magnetic field used to support one contact paddle during preliminary positioning. The a.c. source (including an adjustment potentiometer) generates the gradually decreasing, alternating magnetic field required for demagnetization. The constant current D.C. source provides the magnetic field used during the final distance adjustment and assures that the adjusting field corresponds exactly to the number of ampere turns of the operating magnetic field used in the actual operating of the reed switch.

Compared to known apparatus for fabricating reed switches, the apparatus of the present invention is characterized by a relatively small increase in the cost of the required equipment and yet produces reed switches which respond within a narrow operating range.

The method of the invention is described below with reference to the drawings which show two embodiments of equipment used in the production process according to the invention.

FIG. 1 shows a device for producing a reed switch in a first production step.

FIG. 2 shows the device in a second production step, drawn to a different scale.

FIG. 3 shows the device in still another production step.

FIG. 4 shows a portion of the device in still another production step.

FIG. 5 shows a circuit diagram of the windings used for melting.

FIG. 6 shows a section of another embodiment of the device, the section generally corresponding to that shown in FIG. 4.

FIG. 7 shows the device of FIG. 1 in another production step.

FIG. 8 is a circuit diagram of the coil of the melting device.

FIG. 9 is the demagnetization diagram.

FIG. shows a closed reed contact produced according to the method of the present invention.

The device shown in various production steps in the figures serves for producing a reed switch of the type shown in FIG. 10. The device comprises a glass tube 1 into which a first contact paddle 2 and a second contact paddle 3 are embedded by melting during execution of the method of the invention.

FIG. 1 shows the device in its initial position at the beginning of the process. The device comprises a supporting base 4 with a vertical guide column 5 attached to the supporting base, and an arm 7 which is rotatable around pivot 6. An embedding device (generally denoted by 8) is fixedly mounted on guide column 5. An upper paddle holder 9 and a lower paddle holder 10, both movable in the vertical direction, are also mounted on guide column 5. Two equal paddle supports 11 are mounted on arm 7 in mirror-image relationship. Each paddle support is provided with a support block 12 containing a groove 12a and with an adjustment block 13 carrying a stop 13a. Additionally, each paddle support 11 is provided with a clamp 14 which can be adjusted in the vertical direction by means of a spring-biased knob 15.

Between the two paddle supports 11, there is mounted an insertion device 16 for glass tubes at an offset portion of arm 7. The insertion device includes a spindle 17 parallel to arm 7 on holder 18 so that the distance and orientation of the spindle 17 relative to arm 7 can be modified by adjustment against a biasing spring. Arm 7 is provided with a guide groove 20 for parallel displacement. At the end opposite to the pivot, arm 7 ends in a handle 2l. Close to handle 21, a pin 22 is inserted in arm 7 and protrudes in a vertical direction from the side at which both paddle support 11 and spindle 17 are located. The direction of rotation of arm 7 from the position shown in FIG. 1 into some other position is indicated by arrow A at pivot 6. In FIG. 2, arm 7 is shown in its other limit position, i.e., the arm is then parallel to guidance column 5.

Embedding device 8, which is mounted at guide column 5 by means of a supporting member 23, consists of an electric paddlemagnetizing coil 24, a lower heater winding 25, and an upper heater winding 26. Paddle magnetizing coil 24 and the two

heater windings

25 and 26 are mounted on supporting member 23 in coaxial relationship so that all their axes are parallel to guide column 5. Arms of a holder 27 for the glass tubes are inserted between paddle magnetizing coil 24 and the two heater windings.

FIG. 5 shows the circuit diagram for

heater windings

25 and 26. These two heater windings can be switched on separately. Equal circuit elements are denoted by the same reference numerals in the circuit diagram of the two heater windings.

Heater windings

25 and 26 are connected to transformer 29 by means of leads 28. The heater current can be adjusted with variac 30. The circuit of lower heating winding 25 is provided with additional adjustment means. A switch 31 is inserted in the circuit of the primary winding of transformer 29. A resistor 32 is connected parallel to switch 31 so that this resistor becomes effective-in the primary circuit when switch 31 is opened.

FIG. 8 shows the circuitry for paddle magnetizing coil 24. Coil 24 is connected via leads 33 to a threelevel switch 34 whose three switch arms S1, S2, and S3 can be put into seven positions I to VII:

position I: no current through paddle-magnetizing coil 24; position II: paddle-magnetizing coil 24 is excited by direct current supplied from source 35; the very strong magnetic field (having a strength of several hundred ampere-turns) is generated for preliminary adjustment of the contact paddles; position III: no current through paddle-magnetizing coil 24;

position IV: switch arms S1 and S2 establish connections between paddle-magnetizing coil 24 and one end of potentiometer 36 and its slider 37, respectively. An a.c. motor 38 is connected to the secondary winding of transformer 39 by means of switch arm S3. The shaft of a.c. motor 38 is mechanically coupled to the shaft of potentiometer 36 and hence rotates slider 37. Consequently, a gradually decreasing a.c. voltage is applied to paddlemagnetizing coil 24 in order to produce a gradually decreasing magnetic field to demagnetize the paddles. The mechanical coupling between a.c. motor 38 and potentiometer 36 is such that once slider 37 has traveled its path, a cam mounted on the motor shaft switches a cam contact 40 to the right (as shown in FIG. 8) and hence switches off a.c. motor 38;

position V: no current through paddle-magnetizing coil 24, switch arm S3 supplies current via cam contact 40 to a.c. motor 38 which continues to run until cam contact 40 returns into its initial position (switch position a) shown in FIG. 8 and, hence, disconnects the motor. When this occurs, slider 37 is returned into its initial position;

position VI: coil 24 is connected (by means of S1 and S2) to an adjustable constant-current source 41 which produces a magnetic field in paddlemagnetizing coil 24 for final adjustment of paddle 3, the field having a strength equivalent to the ampere-tum figure of the operating magnetic field of the reed switch; and

position VII: no current through paddle-magnetizing coil 24.

The upper paddle holder 9 is provided with a carriage 42 which can move along guide column 5. Carriage 42 carries a paddle-clamping device 43 with two arms which are kept in crosswise relationship by rivet 44 and can rotate. The figures display a tongue-like clamp 43a on the two arms of paddle-clamping device 43 and an actuating end 43b of the other arm. Each end of the actuating arms of paddle-clamping devices 43 is provided with a pole plate 45. A paddle-clamping coil 46 is mounted on carriage 42 between the two pole plates of paddle-clamping device 43.

Lower paddle holder 10 comprises a carriage 47 which can be adjusted in vertical direction along guide column and which consists of a carriage base 47a and a support 47b for the clamping device, the support being rotatable around axis 48. The rotation of paddleclamping support 47b is limited by the diameter of an opening 49 surrounding the shaft of carriage base 47a. Paddle-clamping coils 46 are mounted at support 47b for the lower paddle holder and on carriage 42 for the upper paddle holder 9. Paddle-clamping device 43 is constructed in the same way for both the upper and lower paddle holders, and, hence, the same reference numerals are used.

Carriage base 470 is provided with an arm 50 protruding perpendicular to guide column 5. Arm 50 carries a motor (not shown) for cam wheel 52 and an armmoving electromagnet 53. Arm-moving electromagnet 53 includes a coil 53a'and an armature 53b connected to the upper portion of an arm 54 which extends perpendicular to support 47b of the paddle-clamping device. A bevelled portion 55 forms the bottom section of arm 54. Arm 54 rests on cam wheel 52 in its rest position, i.e., when arm-moving electromagnet 53 is not excited.

The process of producing reed switches according to the invention takes place in the following sequence, when the above-described device is used. The device is first in the initial position shown in FIG. 1, i.e., arm 7 is in the horizontal position. The upper paddle holder 9 and the lower paddle holder 10 are spaced from embedding device 8. The components of the reed switch to be assembled, i.e., glass tube 1 and the two contact paddles 2 and 3 are set in a preadjustment position on arm 7.v Glass tube 1 is placed on spindle 17 which is slightly lifted, along with its holder 18, in order to facilitate insertion of the glass tube. After that, holder 18 is lowered into the position shown in FIG. 1. The two contact paddles 2 and 3 are transferred into a predetermined position by means of support block 12 and adjustment block 13. Contact paddle 2 is located in the paddle support close to the handle, and contact paddle 3, in the paddle holder far from the handle.

In the configuration shown in the figures, contact area 211 of the first contact paddle is on the left side and appears turned upward, whereas contact area 3a of the second contact paddle is on the right side and appears turned downward. In order to insert the contact pad dles, clamps 14 are lifted by means of knob 15 and rotated out of their position by the knob (as indicated by the broken lines at the right paddle support 11). When returned into their initial positions, clamps 14 keep the contact paddles in the pre-adjustment positions.

Arm 7 is rotated, by means of handle 21, in the direction of the arrow, until the position shown in FIG. 2 has been reached. Arm 7 is fixed in this position by means which are not shown in the figure. In the last phase of the lifting operation, pin 22 closes a switch 56 which leads to the excitation of paddle-clamping coils 46 at paddle holders 9 and 10 (the corresponding circuitry is not shown). Consequently, pole plates 45 are attracted and paddle-clamping devices 43 close. When this occurs, paddle-clamping devices 43 embrace contact paddles 2 and 3 which were supplied by arm 7 in certain positions. The circuitry for paddle-clamping coils 46 is such that the paddle-clamping devices close even when switch 56 is opened in a later stage of the process. After that, knobs- 15 are actuated to open clamps 14 and, consequently, the contact paddles are held only by paddle-clamping-devices 43.

Holder 18 for glass tube 1 is shifted upward in the direction of arrow C, until holder 27 for the glass tube carries the same, whereupon holder 18 is moved downward. Arm 7 is then moved back into its initial position (opposite to direction A of rotation) and may receive new contact paddles and another glass tube while the actual production process continues. FIG. 3 shows a part of the device important for the further process which continues from that stage. The ensuing stages of the process are determined by electric signals.

The upper paddle holder 9 is moved downward, along with carriage 42, along guide column 5 (arrow D). The motion can be effected by electrical or pneumatic drive means. During this motion, first contact paddle 2 enters into the upper opening of glass tube 1. This condition is shown in FIG. 4. The process control sends a current through upper heater winding 26 which begins to glow. The current can be adjusted by means of variac 30. The upper end of glass tube 1 becomes soft and shrinks onto upper contact paddle 2. After switching off the current, heater winding 26 and glass tube 1 become cool embedding contact paddle 2 in the glass tube 1.

An inert gas can be supplied via nozzle 57 (FIG. 4) to a reed switch to be filled in conventional fashion with an inert gas. Before upper contact paddle 2 has been embedded, the gas which flows in direction of arrows E and F flows through glass tube 1 and is switched off only after the lower end of the glass tube has been closed.

In the following step of the process, the lower paddle holder 10 is moved upward along guide column 5, until the lower paddle 3 extends from below intothe glass tube. This pre-adjustment positions contact paddle 3 a certain distance in the horizontal direction from the upper contact paddle 2 which had been previously embedded.

For the purpose of obtaining a precise adjustment of the two contact areas, arm-moving electromagnet 53 is excited so that arm 54 is attracted and hence, support 47b for the paddle-clamping device is moved with respect to carriage base 47a. Contact area 3a of lower contact paddle 3 engages in this position contact area 2a of the upper contact paddle 2. After that, three-level switch 34 of FIG. 8 is moved into position II so that a relatively strong magnetic field is generated in paddlemagnetizing coil 24. By interrupting the current through paddle-clamping coil 46 for a short time, clamp 43a releases the lower contact paddle 3 for a short time so that the position of the two contact areas can be mechanically pre-adjusted to obtain optimum engagement over the contact areas under the influence of the magnetic field. After that, paddle-clamping coil 46 closes paddle-clamping device 43, and three-level switch 34 is moved into position III in which the current through paddle-magnetizing coil 24 in interrupted. Since arm-moving electromagnet 53 continues to keep support 47b for the clamping device in the new position, contact areas 2a and 3a of the two contact paddles remain in engagement at that time.

In the ensuing step of the process, the two contact paddles are demagnetized in order to eliminate any residual magnetization. To do this, the two contact paddles, whose contact areas are still in engagement, are exposed to a gradually decreasing magnetic field. This field is generated by paddle-magnetizing coil 24 when three-level switch 34 has been put into position IV.

Switch arm S3 connects a.c. motor 38 to the secondary winding of transformer 39. The shaft of a.c. motor 38 rotates via a reduction gear, and slider 37 of potentiometer 36 moves over the resistance winding of the potentiometer. Thus, a gradually decreasing a.c. voltage is applied to paddle-magnetizing coil 24 through arms S1 and S2 of the three-level switch 34 so that a gradually decreasing alternating magnetic field is generated. The magnetization in the contact paddles situated in the alternating magnetic field passes through a hysteresis loop as shown in FIG. 9. The coordinate denoted by J.W. in FIG. 9 represents the field strength, and the coordinate denoted by B, represents the magnetic induction. The effective alternating current at the beginning of the demagnetization process corresponds to the dc. current applied to the coil for the purpose of preliminary adjustment of the contact areas. The size of the hysteresis loop decreases gradually, and the loop ends finally at the coordinate origin when the potentiometer voltage vanishes. In this position of the potentiometer slider, a cam mounted on the shaft of a.c. motor 38 actuates cam contact 40 and shifts the same from the position a" shown in FIG. 8 to position b shownby broken lines. Thus, the a.c. motor is switched off. By setting three-level switch 34 into position V, a.c. motor 38 is set into rotation and continues to run, until cam contact 40 returns into position a and disconnects the motor. When this happens, potentiometer slider 37 is returned into its initial position.

In order to adjust the distance between the two contact paddles, the second contact paddle 3 is removed from the first contact paddle 2. To accomplish this, arm-moving electromagnet 53 is switched off so that supporting arm 54 is set free. Support 47b of the paddle-clamping device swings into the position shown in FIG. 7. At the same time, arm 54 rests with its bevelled portion 55 on cam wheel 52. In this position, lower heater winding 25 receives current from program-controlled variac 30 and transformer 29 (FIG. so that the glass assumes a viscosity of Poise and the second contact paddle can be embedded in the relatively soft glass. After that, switch 31 in the circuit of the lower heater winding 25 is opened so that additional resistor 32 becomes effective. The heating effect of heater winding 25 decreases to an extent that the glass viscosity increases to 10 Poise.

Three-level switch 34 (FIG. 8) for paddlemagnetizing coil 24 is then put into position V1 so, that paddle-magnetizing coil 24 is connected to the adjustable constant-current source 41 via switch arms S1 and S2. In this way, a magnetic field equivalent to the nominal operating field of the reed switch is generated in the area of glass tube 1.

When the magnetic field is applied, motor 51 actuating cam wheel 52 begins to rotate in the direction of arrow B. Cam wheel 52 moves arm 54 upward over bevelled portion 55 and hence lifts support 47b of the paddle-clamping device so that second contact paddle 3 is moved toward first contact paddle 2. When this occurs, second contact paddle 3 moves in the paste-like glass melt which is denoted by la in FIG. 10. When the two contact areas and 3aare located in a certain distance a (FIG. 10), the effect of the magnetic field generated by paddle-magnetizing coil 24 becomes so great that the contact areas engage, i.e., the contact is closed under bending of the embedded contact sections. This, in turn, disconnects motor 51, i.e., the sec- 0nd paddle 3 remains fixed at a distance a from the first contact paddle. Y

The heater current through heater winding 25 is switched off at the same time. The glass solidifies and the embedding of the second contact paddle 3 ends. Length fb (FIG. 10) of the embedded section of contact paddle 3 determines the extent to which the reed switch bends when it responds. Length b is identical to the length which is effective when the distance is adjusted.

When, upon engagement of the two contact paddles, coil 24 is de-energized and motor 51 is disconnected, the two contact areas of the paddles disengage. The bent sections of the contact paddles straighten, and the distance between the contact areas returns to the value a (FIG. 10). That portion of the second contact paddle 3, which is immersed in the paste-like glass melt, remains in the proper embedding position and is retained in that position in the ensuing solidification of the glass (after the heating has been switched off).

Once the glass has solidified, the reed switch can be removed from the device. By rotating arm 7, which had been previously supplied with new components, the production steps can be repeated from the position shown in FIG. 2.

FIG. 6 shows a section of another embodiment of the device, in which the production process is modified. This device servesfor the manufacture of reedswitches whose glass tubes contain a compressed gas or have been evacuated. In this case, the contact paddle must be embedded in a high-pressure gas atmosphere or in vacuum. The device is equipped with vacuum unit 58 consisting of a base plate 59 with an opening 60, a bell jar 61 resting on the base plate, and a packing 62 between the bell jar and the base plate. Bell jar 61 is provided with two spaced windows 63 and 64. After the first contact paddle 2 has been inserted into the glass tube, the bell jar is placed on top of the device and rests on packing 62. After that, bell jar 61 is filled with compressed gas via opening 60, or vacuum is produced in the bell jar by evacuating the air through opening 60.

(FIG. 10)

FIG. 6 shows, in addition, means used for a modified melting process. The contact paddles are embedded with the aid of infrared heating focused on the glass tube. Two polished reflecting mirrors 65 and 66 are attached to supporting member 23 of the melting device so that the mirrors are located in the upper and lower areas of glass tube 1, respectively, at the side opposite windows 63 and 64 in the bell jar. The mirror surfaces face the windows. A quartz-iodine lamp 68 is mounted in the focal plane of a reflector 67 located outside the bell jar. Lamp 68 can be moved up and down as indicated by double arrow G. Lamp 68, whose power consumption amounts to about 600W, generates a focused infrared beam 69 as indicated by an arrow in the figure. When infrared beam 69 is directed onto the upper end of glass tube 1 (FIG. 6), the beam focused by reflecting mirror 66 heats the glass tube so that it becomes soft and contact paddle 2 is embedded.

During the following steps of the process, which is continued as described above, reflector 67 with quartziodine lamp 68 is lowered so that the infrared beam focused by reflecting mirror 65 melts the lower end of glass tube 1 around contact paddle 3. In order to move contact paddle 3 in the paste-like melt as provided by the invention, a resistor is inserted into the circuit of the quartz-iodine lamp. The intensity of the infrared beam can be controlled in a fashion similar to the control of the heater current supplied to the lower heater winding 25 (circuit diagram of FIG.

According to the invention, infrared heating for melting the glass can be used even when no compressed gas is to be introduced into the glass tube or when the glass tube need not be evacuated, i.e., when the device does not comprise the bell jar. It is an advantageous feature of infrared melting that the times required for the melting are reduced and that no disturbing alternating magnetic fields are generated when the lower contact paddle is adjusted by means of the magnetic field generated with paddle-magnetizing coil 24.

The present invention is not restricted to the production steps described above and the corresponding devices. Within the scope of the invention, the paddle supporting means can be actuated pneumatically instead of electrically. The mechanism for moving the second contact paddle with respect to the first paddle can be driven and controlled in various ways. The important feature is that the contact paddle moves in the paste-like melt and that the motion is stopped when the two contact paddles are in engagement.

The method of the invention can be modified insofar as the second contact paddle can be moved away from the first contact paddle in a magnetic field for distance adjustment. One of the contact paddles moves in the paste-like glass melt, until the two paddles have separated. Separation of the contact paddles can be used to stop the motion of the second paddle. However, since the contact paddles open in a magnetic field which is weaker than that in which the contact is closed, in this modification of the process one must generate an appropriate magnetic field in the coil, with the ampereturn value of that field being necessarily lower than that of the magnetic field used for the actual operation of the reed switch.

We claim:

1. A method of producing a reed switch comprising: providing a first contact embedded in one end of a glass tube, positioning a second contact through the other end of said glass tube, controlling the temperature of said other end to embed a portion of said second contact in viscous glass, applying a magnetic field to said contacts, moving said second contact with respect to said first contact until said reed switch is actuated in said magnetic field, and cooling said other end of said glass tube to harden said glass and hold said second contact.

2. Themethod as claimed in claim 1, wherein the step of applying a magnetic field comprises applying a magnetic field having a strength corresponding to the strength of the operating field for said reed switch.

3. The method as claimed in claim 1, wherein said step of moving said second contact comprises the step of moving said second contact toward said first contact.

4. The method as claimed in claim 1, including the step of demagnetizing said contacts before said step of applying said magnetic field.

5. The method as claimed in claim 4, wherein said demagnetizing step comprises exposing said contacts to a gradually decreasing alternating magnetic field.

Claims

2. The method as claimed in claim 1, wherein the step of applying a magnetic field comprises applying a magnetic field having a strength corresponding to the strength of the operating field for said reed switch.