US3282670A

US3282670A - Method of and apparatus for making sealed switches

Info

Publication number: US3282670A
Application number: US309449A
Authority: US
Inventors: Chanowitz Harry; George F Weinreich
Original assignee: IXYS Integrated Circuits Division Inc
Current assignee: IXYS Integrated Circuits Division Inc; Arris Technology Inc
Priority date: 1963-09-17
Filing date: 1963-09-17
Publication date: 1966-11-01
Anticipated expiration: 1983-11-01
Also published as: GB1080235A; DE1218061B

Description

Nov. 1, 1966 H. CHANOWITZ ETAL 3,232,670

METHOD OF AND APPARATUS FOR MAKING SEALED swITcHEs Filed Sept. 17, 1963 5 Sheets-Sheet 1 Arrow/days 1966 H. cHANowrrz ETAL 3,

METHOD OF AND APPARATUS FOR MAKING SEALED SWITCHES 5 Sheets-Sheet 2 Filed Sept. 17, 1963 minimniitHHHIWHWW NOW 1966 H. CHANOW ITZ ETAL 3,232,670

METHOD OF AND APPARATUS FOR MAKING SEALED SWITCHES Filed Sept. 17, 1963 5 Sheets-Sheet 5 EN s a j RES: 635% 5 Sheets-Sheet 4 A/A/2/2Y O/AA/OW/TZ 4M0 GEORGE E WE/A/EE/C/J K Me/Lmwu fiLZMwwM W aw $8 $5 Em b6 358m N mu m mcblb NMEQQ mmSNu QZTRWQQ H. CHANOWITZ ETAL.

METHOD OF AND APPARATUS FOR MAKING SEALED SWITCHES E ii Nov. 1, 1966 Filed Sept. 17, 1963 1966 H. CHANOWITZ ETAL 3,

METHOD OF AND APPARATUS FOR MAKING SEALED SWITCHES 5 Sheets-Sheet 5 Filed Sept. 17, 1963 w M 3 h Hull 7/ f ffimz'ozhz fawozaw/W 4 ATTOEA/E Y5.

United States Patent M Filed Sept. 1'7, 1963, Ser. Noa 309,449 8 Claims. (Cl. 65-59) This invention relates to an apparatus for and a method of making switches and, more particularly, to a new and improved apparatus for and method of making switches of the type including a dielectric housing in which a pair of magnetic elements or reeds are sealed.

The substantial increase in the use of sealed magnetic reed switches due to their improved operating characteristics has resulted in a need for more efiicient and economical switch production. Initially, many of the switches were made by manual operations of the type described in United States Patent No. 2,882,648 in which the magnetic reeds were inserted into opposite ends of the dielectric housing or glass tube and the ends of the tube were then heated, usually in the presence of a controlled atmosphere, to seal the opposite ends of the tube and support the magnetic elements in their desired positions. The cost of the switch units manufactured by this method was substantially reduced by the use of automatic manufacturing equipment of the type shown in United States Patents Nos. 2,984,046 and 3,061,144. However, with even the automatic equipment shown in these patents, the switches are not produced as quickly and at as low a cost as desired.

Accordingly, one object of the present invention is to provide a new and improved method of making sealed switches.

Another object is to provide new and improved apparatus for making sealed switches of the type including a dielectric housing and a pair'of magnetic elements.

Anotherobject is to provide machinery for and a meth- 0d of automatically making sealed switches more economically and at an increased speed.

Another object is to provide a method of making sealed switches in which the formation of the upper and lower seals are overlapped at least in part.

Another object is to provide an apparatus for making sealed switches in which the heating of one end of the dielectric housing or tube is initiated before all of the parts of the switch are fed to the apparatus.

Another object is to provide a method of and an apparatus for supplying a high velocity jet of forming gas to the parts of the sealed switch following their assembly to free the interior of the switch of any foreign particles.

Another object is to provide a new and improved method of and apparatus for making sealed switches including means for heating the gas flow supplied to the sealed switch during its fabrication.

Many other objects and advantages of the present invention will become apparent from considering the fol lowing detailed description in conjunction with the drawings, in which:

FIG. 1 is a top plan view of a switch making machine embodying the present invention;

FIG. 2 is an enlarged fragmentary elevational View of one switch making head included in the machine shown in FIG. 1;

FIG. 3 is a sectional view taken along line 3-3 in FIG. 2 illustrating the head in a position immediately prior to the time at which the dielectric housing or glass tube is fed to the head;

F164 is a fragmentary sectional view similar to FIG.

i atentecl Nov. 1, i956 3 illustrating a glass holding and heating means in a position in which the glass tube is fed thereto;

FIG. 5 is a fragmentary sectional view of the head in a position in which the parts of the switch are assembled during the manufacturing operation;

FIG. 6 is a timing diagram illustrating the different times at which the various components of the switch making apparatus operate during a cycle of operation; and

FIGS. 7-9 are schematic drawings illustrating the contraction of the switch making head.

Referring now more specifically to FIG. 1 of the drawings, therein is illustrated a machine or apparatus 10 which embodies the present invention and which is adapted to automatically manufacture sealed magnetic or reed switches 12 (FIG. 5). The switches 12 are formed of an upper magnetic element or reed 14 and a lower magnetic element or reed 16 which are inserted into and sealed within the opposite ends of a dielectric housing or glass tube 18 with their inner ends in an overlapping but spaced relationship. The interior of the housing18 is filled with a gas to protect and extend the life of the contact surfaces on the overlapping inner ends of the

magnetic elements

14 and 16.

The construction and arrangement of the switch making machine 10 (FIG. 1) is of the same type disclosed and described in detail in United States Patent Nos. 2,- 984,046 and 3,061,144. Accordingly, only those portions of the machine 10 that relate to the present invention are shown and described in detail herein. In general, the machine 10 includes a main supporting structure or bed 26 mounted on the floor and supporting a table 22 for continuous rotation through 360 of movement. The table 22 carries a plurality of heads 24 disposed at peripherally spaced positions relative to the axis of rotation of the table 22. The bed 20 also supports an assembly 26 for feeding the lower reed or magnetic element 16, an assembly 28 for feeding the upper reed or magnetic element 14-, and an assembly 30 for feeding the glass tubes or housings 18. The

assemblies

26, 28 and 30, which can be of the type described in the above-identified patents, are carried in a fixed position on the bed or frame 20 of the machine 10 and are adapted to feed the glass tube 18, the upper reed 14, and the lower reed 16 in sequence to each of the head assemblies 24 as these heads are rotated past the

feeding assemblies

26, 28 and 39 during operation of the machine 10.

Each of the head assemblies 24 (FIG. 2) includes an upper reed holding means or chuck 32, a lower magnetic element or reed holding means 34, and a centrally disposed glass holding assembly 36. The upper two holding means 32 and 36 are mounted for vertical sliding movement relative to each other and the holding means 34 by a plurality of guide rods 38 carried on the table 22. The holding means 32, 34, and 36 are moved relative to each other between an expanded position of the head 24 shown in FIG. 2 and a contracted position shown in FIG. 5 by a shoulder rod 39 (FIGS. 7-9) actuated by a follower roller 39a which engages a cam track 49 carried in a fixed position on the bed 20 of the machine 10. This construction can be of the type disclosed in the aboveidentified patents.

When the head assembly 24 is in the expanded position shown in FIG. 2, the upper reed chuck or holding assembly 32 is disposed in vertical alignment with the upper reed feeding assembly 28 and includes a chuck assembly 32a that is selectively moved between open and closed positions by fixed pins or actuators carried on the bed 20 to receive a reed supplied from the assembly 28. This reed is inserted into the open upper end of the glass tube 18 when the head assembly 24 is moved to its closed or contracted position. Similarly, the lower holding means 34 includes a lower reed chuck assembly 34a that is adapted to receive a magnetic reed from the lower reed feeding assembly 26 and is actuated between open and closed positions by fixed actuator-s disposed in the path of movement of the assembly 34a and carried at fixed positions on the bed 20. When the head assembly 24 is contracted, the lower reed carried by the chuck assembly 34a is inserted into the lower end of the glass tube 18. The glass holding means 36 includes a glass chuck 36a that is aligned with the glass feeding assembly 30 to receive and hold a glass tube in a proper position as the head assembly 24 passes the glass feeding assembly 30 during a cycle of rotation of the table 22. The

chucks

32a, 34a, and 36a can be of the type shown and described in detail in the above-identified patents.

The glass holding means 36 also includes means for heating the upper and lower ends of the tube 18 held in the chuck 36a to seal the

elements

14 and 16 in the upper and lower ends of this tube and additional means for supplying gas to the lower end of the tube. The heating means for sealing the lower reed 16 in the tube 18 is provided by a heating coil 40 that is mounted on a member 42 by dielectric means 44. The coil 40 is connected to a suitable source of electrical energy, such as a power transformer (not shown), forming a part of the head assembly 24. The member 42 is slidably mounted on the lower ends of a pair of guide rods 46 that are rigidly secured to a plate 48 forming a part of the glass holder assembly 36. A pair of compression springs 50 inter-posed between the plate 48 and the upper surface of the member 42 bias the member 42 downwardly against a pair of washers 52 carried on the lower ends of the guide rods 46. Therefore, the compression springs 50 bias the lower heating coil 40 to the lower position shown in FIG. 2 whenever the head assembly 42 is moved to its expanded position in which the glass tube 18 is to be fed to the glass chuck 36a. When the head assembly 24 is contracted by moving the upper holding means 32 and the glass holding means 36 downwardly, the member 42 engages a portion of the lower holding means 34 and compresses the springs 50 to move the coil 40, which is aligned with the tube 18 carried in the chuck assembly 36a, to a position encircling its lower end (FIG. In this manner, the expanded or contracted state of the head assembly 24 controls the position of the lower heating coil 40 relative to the lower end of the glass tube 18.

The top seal on the switch 12 is formed by an upper coil 54 that is mounted on a member 56 by one or a plurality of dielectric blocks 58. The axial opening in the heating coil 54 is aligned with the tube 18 held in the chuck assembly 36a, and the coil 54 is adapted to be energized by a suitable source forming a part of the head assembly 24. Energization of the coil 54 as well as that of the coil 40 preferably is controlled by switch means carried on the head assembly 24 and actuated by cam means and operators disposed in fixed positions on the bed 20 adjacent the path of movement of the head assembly 24. The member 56 on which the coil 54 is carried is normally biased to a position adjacent the plate 48 in which it encircles the upper end of a glass tube 18 held in the chuck assembly 36a by means of apair of tension springs 60 connected between a pair of members 62 carried on the block 56 and a plurality of pins or headed fasteners 64 carried on the plate 48.

Since the tension springs 60 tend to bias the member 56 downwardly toward the plate 48, the heating coil 54 is normally disposed in a position in which it impedes or interferes with the feeding of the glass tube 18 from the assembly 30 to the chuck 36a. To provide means for shifting the position of the upper heating coil 54, a cam follower roller 66 secured to one end of the member 56 so as to extend outwardly from the head assembly 24 is adapted to engage a somewhat V-shaped cam member 68 rigidly secured to a structure carried on the bed 20 of the machine 10, as by an intervening supporting structure 78.

The cam 68 includes an upwardly inclined surface 68a, a dwell surface 681), and a downwardly inclined portion 680 (FIG. 3).

In response to rotation of the bed 20, the roller 66 first engages the inclined surface 68a to move the member 56 upwardly toward the upper ends of the guide rods 46 against the action of the tension springs 60 from the position illustrated in FIG. 3 to the position illustrated in FIG. 4 in which the roller 66 engages the horizontally extending dwell portion 68b on the cam 68. In this upper or dwell position, the assembly 30 feeds a glass tube 18 to the open' chuck assembly 36a'which is released at that time to clamp and hold the tube 18 in the desired position. It is possible to feed the glass tube 18 in this position inasmuch as the upper heating coil 54 has been elevated to a position in which it does not impede the transfer of the tube from the assembly 30 to the chuck assembly 36a. During continuing rotation of the table 22, the roller 66 engages and moves along the downwardly inclined surface 680 on the cam during which the tension springs 60 move the member 56 downwardly so that the coil 54 is disposed around the upper end of the previously fed tube 18 held in the glass chuck assembly 36a.

The construction by which the upper heating coil 54 is continuously biased by the tension springs 60 to a position in which the coil 54 surrounds the upper end of the tube 18 held in the chuck assembly 36a substantially contributes to increased efficiency and speed at which the sealed switches 12 are manufactured by the machine 10.

The lower heating coil 40, for instance, is biased by the compression springs 50 away from the position encircling the lower end of the tube 18 held in the chuck assembly 36a so that whenever the head assembly 24 is in its expanded condition, the coil 40 cannot apply heat to the lower end of the tube 18. On the other hand, the coil 54 is biased to a position surrounding the upper end of the tube 18 held by the chuck 36a so that even though the head 24 is in its expanded position, the coil 54 is in a position in which it can be energized to heat the upper end of the tube 18 to begin the formation of the seal as soon as a glass tube 18 is fed to the chuck assembly 3611. The provision of the cam follower roller 66 and the cam means 68 briefly elevates the coil 54 to permit the feeding of the tube 18 by the assembly 30 and immediately restores the coil 54 to a position in which the heating of the upper end of the tube 18 can be initiated to start the formation of the upper seal.

The configuration of the heating coils 40 and 54 also contributes to the eflicient formation of scaled switches 12 having the desired operating characteristics. In prior constructions, such as those shown in the above-identified patents, the heating coils are formed as a single helix which is adapted to be disposed about the upper or lower end of the glass tube. These coils are energized from an alternating current source so that when the coils are disposed about the ends of the tube and the

magnetic elements

14 and 16 are inserted (FIG. 5), the alternating current energization of the coils tends to induce vibration in the

magnetic elements

14 and 16 with the result that the magnetic elements tend to become misaligned or the seals formed between these elements and the glass of the tube 18 are not satisfactory. These deficiencies are overcome in themachine 10 by forming the

coils

40 and 54 in a noninductive form comprising double helices. By virtue of the parallel and interleaved convolutions of the

coils

40 and 54 carrying oppositely directed currents, the electromagnetic field produced by the energization of these coils is substantially cancelled, and the

magnetic elements

14 and 16 are not subjected to pulsating or varying electromagnetic forces during the heating operation. This permits the formation of satisfactory seals at an accelerated speed.

Each of the glass holding assemblies 36 also includes means for supplying a gas flow through the tube 18 during the formation of the switch. To accomplish this, the

member 42 is provided with an opening 72 (FIGS. 2 and 5) which is aligned with the lower reed 16 and the glass tube 18 and which is placed in communication with a fluid conveying means or cavity 74 in the member 42 by. a plurality of upwardly inclined orifices 76. The fluid conveying means 74 is connected to a gas source 78 through a conduit 81 (FIG. 2) coupled at one end to the conveying means 74 in the member 42 and passing through a gas supply control means 82. The gas supply control unit 82 is of the same general type disclosed in the above-identified patents and operates to vary the flow of gas from the source 78 to the glass holding means 36 at different times during a cycle of revolution of the head assembly 24 under the control of the switch means carried on the head 24 and operator means disposed at peripherallyspaced positions along the path of movement.

The control unit 82, however, provides a different sequence and type of gas flow than those used before. More specifically, the control 82 includes means for providing a relatively large volume of flow of gas during the interval in which the

magnetic elements

14 and 16 and the glass tube 18 are fed and assembled followed by a high velocity, very large volume flow or jet of short duration immediately after the

magnetic elements

14 and 16 are inserted into the opposite ends of the tube 18. This high velocity jet of gas clears contaminants and any foreign particles from the interior of the tube 18. The control unit 82 then reduces the flow to a low level in the interval in which the upper seal is completed and the lower seal is formed.

Since gas from the source 78 is continuously supplied to the tube 18 during the formation of the upper and lower seals, the interior of the glass tube or housing 18 is filled with the gas after the upper and lower seals have been completed. Since one or both of the heating coils 40 and 54 is energized during the time in which the gas the glass holder 36 and the lower reed holding means 34 in the head 24 remain in adjacent positions.

During this expanding movement of the head 24, the point is reached at which the relative separation of the upper reed holder 32 and the glass holder 36 is completed. At this time, the glass holder 36 starts to move vertically upward away from the lower reed holder 34. As the glass holder 36 moves upwardly, the compression springs 59 act on the member 42 to hold this member in a fixed position relative to the lower reed holder 34 so that the lower heating coil 41) is separated from the glass chuck 36 (see line 7). The upper heating coil 54 does not move relative to the glass chuck 36a inasmuch as this coil is biased downwardly by the tension springs 60. After approximately of movement from the assumed starting point, the compression springs 50 have biased the member 42 against the stop washers 52 on the rods 46 so that the separation of the lower heating coil from the glass chuck 36a is completed (see line 7). The continuing expansion of the head 2 (see line 1) raises the member 42 and the lower heating coil 40 from the lower reed chuck 34a so that the feeding of the lower reed 16 to this chuck is not impeded.

At the time that the glass holder 36begins to move upwardly relative to the lower reed holder 34, a switch means in the control unit 82 is actuated to provide the sustained heavy flow of gas through the conduit 80 and the nozzle openings 76 (see line 9). In addition, the

switch means carried on the head 24 are engaged by opis supplied and in view of the fact that the heated portions of the glass tube 18 retain some heat after the seals are formed and the energization of the

coils

40 and 54 is terminated, there is a possibility that a blowout may occur in the softened glass during the cooling of the seal-s. This is due to the fact that the gas contained within the housing 18 is expanded by the heat absorbed from the tube 18 and coils 40 and 54. This tendency to blowout is corrected in the machine 10 by providing heating means 84 (FIG. 2) for preheating the gas supplied to the head 24 to the point at which any further expansion of the gas occasioned by its heating within the tube 18 is not sutficient to produce blowouts. The heating means can comprise any suitable construction but preferably comprises an electrical resistance means having an axial opening through which the conduit 80 passes. The heating means 84 provides suflicient heat so that the gas supplied to the lower end of the tube 18 has been expanded considerably in volume and is not appreciably further expanded by the heating encountered during the forn1a- 1 tion of the seals between the tube 18 and the

magnetic elements

14 and 16.

A typical cycle of operation of one head assembly 24 of the machine 10 during the production of a single sealed switch unit 12 is illustrated schematically by the timing diagram in FIG. 6. At a starting point arbitrarily assumed to be 0, the head 24 is in a contracted condition (see line 1 in FIG. 6), the glass chuck 36a and the lower chuck 34a are in an open condition (see lines 2 and 6), and the upper chuck 32a (see line 5) is closed to grip the upper magnetic element 14 of the sealed switch 12 formed during the preceding cycle of rotation of the table 22. During the following rotation of the table 22, the cam actuated means for controlling the position of the head assembly 24 is operated to initiate the elevation of the upper holding means 32 which is effective because of the closed condition of the chuck 32a to lift the previously completed sealed switch 12 out of the coils 40 and 54 (see line 1). During this initial expanding movement,

erator means carried on the bed or frame 20 of the machine to energize the upper heating coil 54 so that the preheating of the coil is initiated (see line 4).

After slightly less than 50 of rotation, a fixed position actuator engages the upper reed chuck 32a (see line 5) to operate this chuck to an open condition. In doing so, the previously formed switch 12 is released and is discharged from the machine 10 through a chute (not shown). This operation also prepares the upper reed chuck 32a to receive the reed 14 to be used in forming the next sealed switch. At substantially the same time as the upper chuck 32a is opened, the follower 66 on the member 56 engages the leading edge of the cam surface 68a. During the following rotation of the table 22 (see line 3), the member 56 is moved to its uppermost position in which the follower 66 dwells on the horizontal surface 68b of the cam and the expansion of the head 24 is completed (see line 1). During this interval, the glass feeding assembly 30 feeds a glass tube to the glass chuck 36a, and this chuck is operated to its closed condition (see line 2). During the next few degrees of rotation of the table 22, the follower 66 now passes down the surface 680 on the cam so that the tension springs 60 return the member 56 to its lower normal position in which the upper end of the tube 18 that is now held in the glass chuck 36a is disposed Within the upper heating coil 54 (see line 3). Since the upper heating coil 54 has been previously energized, the heating of the upper end of the tube 18 is initiated to soften the glass for the formation of the upper seal prior to the time at which the upper magnetic element or reed 14 is fed to the chuck assembly 32a.

After the upper heating coil 54 has been restored to its normal position, the table 22 advances the head 24 to the position at which the assembly 28 feeds the upper magnetic element or reed 14 to the upper chuck assembly 32a, and this chuck assembly is actuated to close and hold this reed in a position spaced above the upper end of the tube 18 held in the glass chuck 36a (see line 5). The continuing rotation of the table 22 next advances the head 24 into alignment wit-h the assembly 26 for feeding Thecam means provided in the machine 10 now initiates the contraction of the head 24. (see line 1) during which the lower heating coil 40 is moved upwardly relative to the glass chuck 36a (see line 7) so that the lower end of the tube 18 is received within the lower heating coil 40. During this contraction of the head 24, the upper reed 14 'is inserted through the upper coil 54 into the open upper end of the tube 18 which has been partially softened by the heating that has taken place during the feeding of the

magnetic elements

14 and 16. In addition, the lower reed or magnetic element 16 is inserted through the lower heating coil 40 into the lower end of the tube 18 held in the glass chuck 36a, and the gas nozzle formed by the openings 76 in the member 42 is disposed in proximity to this lower end of the tube 18. When the contraction of the head 24 is completed (see line 1), the components of the switch 12 and of the machine 10 are in the position illustrated in FIG. 5.

When the insertion of the magnetic elements '14 and 16 into the opposite ends of the tube 18 has been completed and when the head assembly 24 is in its contracted condition (FIG. a fixed operator on the frame or bed 20 of the machine engages switch means included in the forming gas control 82 to operate thiscontrol so that a momentary high velocity and large volume jet of gas is passed through the interior of the tube 18 from its lower open end to its upper open end (see line 9). This high velocity jet removes any foreign particles from the interior of the tube 18 and the enclosed portions of the

magnetic elements

14 and 16 that might cause switch contamination or a high resistance contact between the overlapping ends of the

magnetic elements

14 and 16.

After approximately ten additional degrees of rotation of the table 22, the normal or sustained high flow of forming gas is reduced by the control unit 82 to a low sustained flow (see line 9). At this time, the switch controlling the energization of the lower heating coil 40 is also actuated by an operator carried on the bed 20 so that the lower heating coil (see line 8) is energized along with the previously energized upper heating coil 54 (see line 4). Thus, for approximately the next 70 of rotation of the table 22, the upper and lower ends of the tube 18 are being heated with the reduced flow of gas from the control 82 to complete the formation of the upper seal between the magnetic element 14 and the glass tube 18. During this movement of the table 22, a cam means of the type disclosed in the above-identified patents shifts the bottom reed 16 relative to the axis of rotation of the table 22 until it touches the overlapped portion of the upper reed 14.

When around 150 of rotation of the table 22 has been completed, a fixed operator on the bed 20 engages the upper chuck assembly 32a so that this assembly is opened (see line 5) and, immediately following this, the switch means controlling the upper heating coil 54 is actuated to terminate the energization of this coil (see line 4). This completes the heating of the upper end of the tube 18 held in the glass chuck 36a. At this time, the glass at the upper end of the tube 18 has been heated sufficiently to flow inwardly and to form a seal, although soft, between the upper magnetic element 14 and the tube 18. At substantially this position, the lower magnetic element or reed 16 moves into the field of a permanent magnet means 90 (FIG. 1) carried on the bed or frame 20 of the machine 19. This field is applied through the overlapping ends of the

magnetic elements

14 and 16 and, if

necessary, moves the released upper reed 14 to insure proper mating orientation of the two

elements

14 and 16. It is possible for the magnetic element 14 to be shifted. or aligned at this time even though the upper seal has been completed because the glass forming the seal has not cooled appreciably and is in a somewhat softened condition. The permanent magnet means 90 now holds the reed 14 in proper position relative to the reed 16 while the glass of the upper seal solidifies.

8 After approximately 225 of rotation, the head assembly 24 moves beyond the field of influence of the permanent magnet means to release the magnetic holding of the upper magnetic element 14 which now remains in position because the glass forming the upper seal has cooled and solidified sufficiently to rigidly retain this element in its desired position. As the head assembly 24 moves beyond the point at which the permanent magnet means 90 is eifective, a cam mechanism of the type disclosed in the above-identified patents acts on the lower chuck assembly 34a to shift the lower reed 16 a predetermined distance relative to the axis of rotation of the table 22 to provide the desired spacing between the previously engaged ends of the

magnetic elements

14 and 16.

When approximately 265 of rotation of the table 22 have been completed, the switches controlling the gas control unit 82 and the energization of the lower heating coil 40 are actuated to terminate the flow of gas through the nozzle openings 76 (seeline 9) and to terminate the energization of the heating coil 40 (see line 8). With the lower and upper seals now completed, the remaining rotation of the table 22 is utilized to cool the upper and lower seals. As the end of this cycle of rotation of the table 22 is approached, actuators carried on the bed 20 of the machine 10 engage the operators for the glass chuck 36a and the lower chuck assembly 34a to release these two chucks (see lines 2 and. 6) and to re'close the upper chuck 32a (see line 5) so that the completed switch is supported only from the upper chuck assembly 32a. This completed switch 12 is ejected from the machine 10 at the beginning of the next cycle of rotation of the head assembly 24 in the manner described above.

The construction of the machine 10 and the method of making the sealed switches 12 is such that these switches can be fabricated in a time on the order of one-half of that required by the automatic machines shown in the above-identified patents. In other words, the table 22 in the machine 10 on which the assembling and fabricating head. assemblies 24 are carried rotates at a speed substantially twice that of the prior machines. One of the important factors that tacilitates this rapid production of the sealed switches 12 is the preheating'of the upper heating coil 54 and the overlapped heating of the upper and lower ends of the tube 18 by the heating coils 54 and 40. In a machine 10 constructed in accordance with the present invention, the upper coil is preheated for around 34 of rotation of the table 22 prior to the time at which the upper heating coil 54 is lowered to a position encircling the upper end of the tube 18 in the glass chuck assembly 36a. Heat is then applied to the upper end of the tube 18 for around 112 of rotation, during 63 of which the lower heating coil 40 is concurrently energized to apply heat to the lowerend of the tube 18. Following the termination of the heating of the upper coil 54, the lower coil 40 remains energized for an additional 104 of rotation to complete the formation of the lower seal. Thus, heat is applied to one or both of the upper and lower ends of the tube 18 for around 216 of rotation of the table 22 or 60% of a single cycle of operation with the overlapped heating of the upper and lower ends of the tube occupying approximately 20% of a full cycle of operation of the machine 10 or around 30% of the period in which heat is applied to one or both of the upper and lower ends of the tube 18.

Because the flow of gas from the aspirator openings 76 around the lower end of the tube 18 and the presence of the mass of the member 42 results in heat loss from the lower end of the tube 18, the lower coil 40 is energized through 167 of rotation of the table 22 or substantially longer than the 112 of rotation of this table during which heat is applied by the upper heating coil 54 to the upper end of the tube 1 8. It appears that one reason for being able to reduce the time during which heat is applied to the upper end of the tube 18 by the heating coil 54 is the fact that the reed 14 is not inserted into the open upper end of the tube 18 until after the heating has been initiated with the attendant reduction in the loss of heat from the upper coil 54 due to conduction through the reed 14 to the chuck assembly 32a. Thus, the overlapped heating of both the upper and lower ends of the tube 18 comprises around 60% of the interval in which heat is applied to the upper end of the tube 18 and only 40% of the time in which heat is applied to the lower end of the tube 18.

Although the present invention has been described with reference to a single illustrative embodiment thereof, it should. be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A method of making a sealed switch from a glass tube and a pair of switch elements in which the elements are partially inserted into opposite ends of a glass tube and sequentially sealed therein by heating the opposite ends of the tube until a seal is formed between the glass and the elements, the method also including the step of displacing a given one of the elements after the other element has, been sealed in the tube, the improvement which comprises the steps of heating one end of the glass tube to start the softening of the glass before the said other switch element is inserted so that the heat loss occasioned by conduction through the said other element is reduced; starting the heating of the other end of the glass tube, in which end the said given one of the elements has been inserted, prior to the termination of the heating of the one end; and terminating the heating of the one end of the tube during the heating of the other end of the tube to start the cooling of the seal at the said one end of the tube prior to the displacement of said given one of the elements.

2. In a method of making sealed switches using a tube and a pair of magnetic elements in which the magnetic elements are inserted into the opposite ends of the tube, the opposite ends of the tube are heated to produce seals at the opposite ends of the tube between the magnetic elements and the tube, and a stream of gas is introduced into the tube during the heating, the improvement which comprises the step of heating the gas prior to introducing the gas into the tube to the extent necessary to avoid excessive expansion of the gas within the tube and to prevent displacement of the heated tube by the expansion of gas therein.

3. The method set forth in claim 2 including the step of briefly increasing the volume of the stream of gas introduced into the tube to a level sufficient to discharge from the interior of the tube particles or material introduced therein by the insertion of the magnetic elements, the increasing of the volume of the gas stream being done after the insertion of the magnetic elements and before the formation of the seals.

4. In a machine for making sealed switches from a dielectric tube and a pair of magnetic elements, which machine is of the type having a support movable over a fixed path, a tube chuck carried on the support, a pair of magnetic element chucks carried on the support and disposed on opposite sides of the tube chuck, first and second heating means carried on the tube chuck and disposed on opposite sides of the tube chuck to heat opposite ends of a tube carried in the tube chuck, the first and second heating means being movable toward and away from the tube chuck, tube and magnetic element feeding stations disposed at fixed points along the path of movement of the support for feeding a tube and two magnetic elements to the chucks, a control linkage coupled to the tube chuck and the magnetic element chucks for separating these three chucks to receive the tube and the two magnetic elements and for moving these three chucks together to insert the magnetic elements into the opposite ends of the tube in the tube chuck, said movements of the chucks occurring during movement of the support along the path, and first means coupled to the first heating means to move the first heating means away from the tube chuck when the tube chuck and the magnetic element chucks are separated to permit the feeding of the tube to the tube chuck, said first means holding the first heating means spaced from the tube chuck until the tube and magneticelement chucks are moved together, the improvement comprising second means coupled to the second heating means for momentarily moving the second heating means away from the tube chuck during the interval in which the tube chuck and the magnetic element chucks are separated so that the tube can be fed to the tube chuck and the second heating means returned to a position for heating one end of the tube in the tube chuck prior to moving the chucks together.

5. The machine set forth in claim 4 in which the second means includes a resilient means for biasing the second heating means toward the tube chuck and cam means for moving the second heating means against the bias of the resilient means to separate the second heating means from the tube chuck.

6. The machine set forth in claim 4 including means for initiating heating of the second heating means prior to the feeding of the tube to the tube chuck.

7. The machine set forth in claim 4 in which the tube feeding means is disposed prior to the magnetic element feeding means considered relative to the direction of the path of movement of the support, and which includes means for initiating the heating of the second heating means prior to the feeding of the tube to the tube chuck, said initiation of the heating of the second heating means also being prior to the insertion of the magnetic element into the end of the tube.

8. In a method of automatically making a sealed switch from a glass tube and at least one magnetic element in which the magnetic element is at least partially inserted into one end of the glass tube and the one end of the glass tube is heated until a seal is formed between the glass and the magnetic element, the improvement which comprises the step of heating the one end of the tube suflicient to start the softening of the glass before inserting the magnetic element so that the heat loss occasioned by conduction through the magnetic element is reduced.

References Cited by the Examiner UNITED STATES PATENTS 1,740,443 12/1929 Donat 6532 2,397,408 3/1946 Crosby et al. 338-62 X 2,984,046 I 5/1961 Brewer et al. 65-276 X 3,150,952 9/1964 Alcott et al. 6532 X DONALL H. SYLVESTER, Primary Examiner. G. R. MYERS, Examiner.

Claims

1. A METHOD OF MAKING A SEALED SWITCH FROM A GLASS TUBE AND A PAIR OF SWITCH ELEMENTS IN WHICH THE ELEMENTS ARE PARTIALLY INSERTED INTO OPPOSITE ENDS OF A GLASS TUBE AND SEQUENTIALLY SEALED THEREIN BY HEAT THE OPPOSITE ENDS OF THE TUBE UNTIL A SEAL IS FORMED BETWEEN THE GLASS AND THE ELEMENTS, THE METHOD ALSO INCLUDING THE STEP OF DISPLACING A GIVEN ONE OF THE ELEMENTS AFTER THE OTHER ELEMENT HAS BEEN SEALED IN THE TUBE, THE IMPROVEMENT WHICH COMPRISES THE STEPS OF HEATING ONE END OF THE GLASS TUBE TO START THE SOFTENING OF THE GLASS BEFORE THE SAID OTHER SWITCH ELEMENT IS INSERTED SO THAT THE HEAT LOSS OCCASIONED BY CONDUCTION THROUGH THE SAID OTHER ELEMENT IS REDUCED; STARTING THE HEATING OF THE OTHER END OF THE GLASS TUBE, IN WHICH END THE SAID GIVEN ONE OF THE ELEMENTS HAS BEEN INSERTED, PRIOR TO THE TERMINATION OF THE HEATING OF THE ONE END; AND TERMINATING THE HEATING OF THE ONE END OF THE TUBE DURING THE HEATING OF THE OTHER END OF THE TUBE TO START THE COOLING OF THE SEAL AT THE SAID ONE END OF THE TUBE PRIOR TO THE DISPLACEMENT OF SAID GIVEN ONE OF THE ELEMENTS.

4. IN A MACHINE FOR MAKING SEALED SWITCHES FROM A DIELECTRIC TUBE AND A PAIR OF MAGNETIC ELEMENTS, WHICH MACHINE IS OF THE TYPE HAVINGG A SUPPORT MOVABLE OVER A FIXED PATH, A TUBE CHUCK CARRIED ON THE SUPPORT, A PAIR OF MAGNETIC ELEMENT CHCUKS CARRIED ON THE SUPPORT AND DISPOSED ON OPPOSITE SIDES OF THE TUVE CHUCK, FIRST AND SECOND HEATING MEANS CARRIED ON THE TUBE CHUCK AND DISPOSED ON OPPOSITE SIDES OF THE TUBE CHECK TO HEAT OPPOSITE ENDS OF A TUBE CARRIED IN THE TUBE CHUCK, THE FIRST AND SECOND HEATING MEANS BEING MOVABLE TOWARD AND