US2874522A

US2874522A - Method and apparatus for manufacturing hermetically sealed electric switch

Info

Publication number: US2874522A
Application number: US378510A
Authority: US
Inventors: Cecil Z Mccabe; Thomas P Crawford; George D Mccabe
Original assignee: MERCOID CORP
Current assignee: MERCOID Corp
Priority date: 1953-09-04
Filing date: 1953-09-04
Publication date: 1959-02-24
Anticipated expiration: 1976-02-24

Description

Feb. 24, 1959 E. MCCABE METHOD AND APPARATUS FOR MANUFACTURING HERMETICALLY SEALED ELECTRIC SWITCH '7 Sheets-Sheet 1 Filed Sept. 4, 1953 INVENTOR. IRA E. M? 6455 Feb. '24, 1959 1. E. M CABE 2,874,522

- METHOD AND APPARATUS FOR MANUFACTURING HERMETICALLY SEALED ELECTRIC SWITCH Filed Sept. 4, 1953 7 Sheets sheet 2 I72 /75 I I74- I C I; a: i." u I77 IN V EN TOR.

1959 l. E. M CABE METHOD AND APPARATUS FOR MANUFACTURING HERMETICALLY SEALED ELECTRIC SWITCH Filed Sept. 4, 1953 '7 SheetsSheet 3 INVENTOR. /RA 5. MS (ABE BY Qzf/r I. E. M CABE Feb. 24, 1959 PPARATUS FOR MANUFACTURING HERMETICALLY SEALED ELECTRIC SWITCH Filed Sept. 4, 1953 METHOD AND A 7 Sheets-Sheet 4 I IN VEN TOR. IRA 5 MS CABE flzzj s INVENTOR.

diff r I. E. M CABE METHOD AND APPARATUS FOR MANUFACTURING HERMETICALLY SEALED ELECTRIC SWITCH Feb. 24, 1959 '7 Sheets-Sheet 5 Filed Sept. 4, 1953 I IRA ii/61985 Feb. 24, 1959 Filed Sept. 4, 1953 7 Sheets-Sheet 6 fiN V EN TOR.

m4 5.01s cnaz '7 Sheets-Shee t '7 Feb. 24, 1959 l. E. McCABE METHOD AND APPARATUSFOR MANUFACTURING HERMETICALLY sums ELECTRIC SWITCH Filed Sept. 4, 1953 3 r: 5 1 mm a 7 F l .l v.

F. ,v 8mm O 2 I I H. 2 2 :0. l

United States Patent METHOD AND APPARATUS FOR MANUFAC- TURING HERMETICALLY SEALED ELEC- rnrc SWITCH Ira E. McCabe, late of Chicago, 111.; Cecil Z. McCabe,

Thomas P. "Crawford, and George D. McCabe, co-

executors of said Ira E. McCabe, deceased, assignors vto The Mercoid Corporation, Chicago, 111., a corporafion of Delaware Application September 4, 1953, Serial No. 37 8,510

Claims. (Cl. 53-22) The invention relates to hermetically sealed electric switches of the mercury contact type such .as may be actuated by magnetic means or by tilting mechanisms and has reference more particularly to a novel method and to improved apparatus for carrying out the method in the desired sequence of steps for the production of said mercury switches in an automatic manner.

Mercury switches designed for actuation by either magnetic means or by tilting mechanisms have been manufactured, in part, by machine with certain operations being performed by hand such as the handling and .placement of the parts on the machine with certain steps in .the finishing procedures also being performed by hand such as exhausting the air from the interior of the glass enclosure of the switch, substituting a gas for reducing the are during operation, and injecting the mercury, all as clearly disclosed, for example, in the McCabe Patent No. 1,872,070 and in the Hunciker Patent No. 1,882,613. The manual procedures following the machine assembly of the switcli'par'ts within the glass enclosure and the handling of the product throughout the various manual operations has constituted an important item of cost in the manufacture of theswitches. In the magnetically actuated types which involve moving and spring tensioned .parts sealed within the switch enclosure, as in the Mo- Cabe Patents Nos. 2,325,785 and 2,442,981, the machine methods employed for sealing the operating mechanism have'so aifected the spring tensioned movable parts that 'in some instances calibration and adjustment for" the parts after sealing have been necessary in order to obtain the desired operation of the switch. This has been due to the high temperaturesrequired for the glass press sealing operation, which temperatures are developed over a period of time, thus producing a transfer offthe heat ,to the switch elements being sealed within the enclosure. One end of the glass enclosure is usually left open for possible and needed adjustments after sealing, said open end being subsequently sealed to prepare theswitch for mercury.

'In the methods of switch manufacture as exemplified by'the above patents, the sealing by pressing molten glass about a portion of the enclosed switch structure, and the means resorted to for exhausting and filling the switch interior with gas and mercury materially affected the overall length of the completed switch. Furthermore, the usual method of connecting lead wires to the switch by soldering the leads to terminals protruding from the sealed portion also contributed to the overall dimension of the switch so that these factors precluded the possibility of the manufacture of miniature, hermet- 'icaliy sealed, glass enclosed switches of the size now made possible by this invention. i i Accordingly, an object of the invention is to provide a method and apparatus for manufacturinghermetically ,sealed, :glass enclosed mercury switches of an improved :type characterized by metal fend capsyto providea method apparati s :a1s dest:rib ed which .will ,produce said 2,874,522 aten d F b- .1359

2 switches in miniature sizes heretofore impossible for this class of electric switch; and to provide a low cost manufacturing method which will employ relatively simple apparatus capable of automatic operation for producing said switches on a quantity basis.

Another object of the invention resides in the pro vision or apparatus'for automatically assembling in an efiicient manner the parts of the present mercury switch which include a glass tube and metal end caps, the glass tube housing the contact or contact operating mechanism, whereas the caps serve is terminals for'circuit connections, and wherein said apparatus will operate on a step by step procedure ofmachine manufacture involving the automatic feeding of the several parts and their assembly in the proper order.

Another object is to provide automatic apparatus as above described which will incorporate high frequency induction heating for fusing the metal end caps to the glass tube, thereby localizing the application of heat for this purpose with the result that the time involved is so materially reduced that detrimental effects upon the operating parts are eliminated whereby said parts can thus be accurately calibrated prior to assembly, said apparatus also incorporating additional means in combination with said high frequency induction heating for controlling certain dimensional characteristics of the switch during the fusing operation.

' Other objects of the invention are to materially reduce manufacturing costs in the production of mercury switches of the present type, to improve the method of exhausting the completed switch, "or filling the same with gas, and the method of injecting the mercury into the switch.

With these and various" other objects in view, theinvention may consistof certain novel features of construction and operation, as will be more fully described and particularly pointed outin the specification, drawings and claims appended hereto.

In the drawings which illustrate an embodiment of the invention and wherein like reference-characters are used to designate like parts-- Figure 1 is a fragmentary top plan view of apparatus for assembling the various elements which comprise the present type of mercury switch, the said figure illustrating the several stations of theapparatus and the mechanism .at each station for performing the steps of the present method.

Figure 2 is an elevational view, parts being shown in I section, of a device employed in the performance of a series of operations on the switch, including the injection of an inert gas and the insertion of mercury.

Figure 3 is a sectional view taken substantially along line 3-3 of Figure 2.

Figure 4 illustrates in elevation the completed mercury switch, parts being broken away to show certain structural features.

Figures 5 and 6 are .views illustrating another type of mercury switch which may employ the improved method and apparatus of the invention for assembling the parts thereof.

Figure 7 isan elevational view, with parts being shown in section, of the mechanismcomprising station A of'the present apparatus.

Figure 8 is an elevational view, with parts being shown in section, of the mechanism comprising station E of said apparatus.

Figures 9, 10, 11 and 12 illustrate in detail the principal parts comprising the structure of station C.

Figure 13 is an elevational view illustrating the structure of station E for sealing theassembled elements of the switch by induction heating, the parts of said structure being shown in position prior to a heating operation.

Figure 1.4 'is a view similar to Figure 13 butshowing is relatively small in size.

the parts comprising the structure of station E in a position for a heating operation.

Figure is a sectional view illustrating certain parts of station E, andshowing in particular the switch mechanism for controlling the high frequency induction heating device; and I Figure 16 is a view on an enlarged scale illustrating in detail the relation of the assembled switch elements when 4 located within the induction heating coils.

Figure 4 of the drawings illustrates one type of mercury switch which may be assembled by the method and apparatus of the invention, the said switch 20 comprising a top cap 21 of any suitable metal, a glass tube or container 22, and a metal bottom cap 23, the said caps being fused to the glass tube by induction heating in a manner to be described in detail. has fixed thereto an electrode 24 which in assembled The top cap relation depends centrally within the glass tube, terminating short, however, of the bottom cap so as to The bottom cap 23 is provided with an opening 26, as best illustrated in Figure 2, and which In accordance with the invention the opening facilitates the flushing of the switch interior with a gas and the injection of the mercury 25, whereupon the opening is closed by an iron pin 28 to complete the switch and which is thus ready for com- ;mercial use.

switch parts for uniting them to form a unit is carried out at station E and the three stations following, namely, F, G and H, are provided with gas jets for directing gas flames onto the switch for annealing the glass container of the same. The completed switch is discharged at station K.

Referring more particularly to Figure 7, which illustrates the structure of station A in detail, it will be observed that the turntable 30 carries a number of part holders generally indicated by numeral 31 and consisting of a cup member 32 which is fixed to the spindle 33, said spindle being mounted by the member 34 for reciprocating movement, whereby the spindle can be elevated or lowered to properly position the cup member 'as the same is moved from station to station. At station A the feeding mechanism for the top caps is so located with respect to the turntable that elevation of the part holder is not required.

Said feeding mechanism essentially consists of a platform 35 suitably secured to and supported by the standard 36, said standard pivotally supporting at 37 the lever 38 adapted to be cam actuated against the tension of spring 40. Said spring is housed in the recess 41 and tensions the pin 42, causing the same to project outwardly into contact with the lever 38. The threaded plug 43 backs the spring and said plug is locked in adjusted position by the nut 44. The'chute 45 receives a supply of top caps 21 from a magazine feed, not shown, and from said chute the caps in inverted position are presented to a sliding push plate 46 operating in a grooved track 47 provided in the platform 35. The lever 38 is pivotally connected at 48 to the push plate and cam means, not shown, are provided to cause retraction of the lever and push plate to allow a cap 21 to be placed within the groove 47 in advance of the push plate. During the period the part holder 31, Figure 7, is positioned at station A, the cam means will release the lever and then pin 42 under the tension of spring 40 will produce clockwise movement of the lever and movement of the push plate to deliver the cap through the platform opening 49 to the cup member 32 of the part holder.

The next operation of the apparatus is to produce an index positioning of the'turntable 30, which moves all the part holders to their next adjacent station. Accordingly, the cup member 32 containing the top cap 21, is moved to station B and a glass cylinder is deposited thereon by the mechanism shown in Figure 8. The base plate 50 supports the standard 51 which in turn suitably supports the platform 52. The member 53 may be part of the platform or may be secured thereto by screws such as 54. The tubular supply chute 55 for the glass tubes 22 is fixed to said member 53 which has a vertical passage provided therethrough for receiving the glass tubes and for directing them to the apertured feed block 56. Said feed block 56 is mounted for movement between the platform 52 and member 53 and is pivotally connected at 57 to the lever 58 pivoted at 59 to the standard 51. Cam means, not shown, normally retracts the lever 58 and block 56 to a point where the aperture in said block aligns with the passage in the member and receives a glass tube. In said retracted position the pin 60 is caused to compress the spring 61 located within the recess 62 and backed by the screw plug 63.

Upon arriving at station E the spindle 33 of the part holder enters the jaws 64 of the lifter 65 which includes a supporting rod 66 mounted for vertical reciprocating movement by the tubular member 67 which is fixed to the base 50. At a predetermined time after the holder spindle 33 has entered the jaws 64, the lever 68 is actuated to elevate the lifter 65 and through the spindle 33 the part holder is also elevated to locate the cup member 32 thereof in close proximity to the underside of the platform 52 and in alignment with the discharge opening 70. The lever 58 is also actuated by the cam means, not shown, in a releasing direction permitting the pin 60 to move the lever clockwise and the feed block 56 forwardly until contact is made with the adjustment screw 71. The glass tube carried by the feed block is accordingly delivered through the opening 70 onto the top cap previously deposited in the cup member 32. After this assembling operation is completed the cam means functions to retract the lever 58 so that the feed block 56 is again located in position as shown in Figure 8 and the part holder is lowered by similar actuation of lever 68, for which purpose the spindle 33 carries the terminal screw 72. By means of the lips on the jaws 64 the screw is engaged as the lifter is lowered and the part holder is actually pulled down into its normal low position.

Following the operations taking place at station B as described, the turntable is again rotated to the extent of its indexing movement to progress all the part holders one complete station. Therefore the part holder 31, containing a top cap 21 and a glass tube 22 in assembled relation, is moved to station C for receiving a bottom cap 23. The feeding mechanism at station C is generally shown in Figure 1 with structural details thereof being shown in Figures 9 to 11 inclusive. In many respects the mechanism of station C is similar to that described in connection with station I, the same including a standard 74 supporting a platform 75 havinga special groove 76 formed in its top surface and which provides a ledge 77. The lever 78 is pivotally supported by the standard 74, said lever being cam actuated and having a pivot connection 79 at its top end with the push plate 80 which is slidable beyond the platform 77. The push plate 80, in accordance with the invention, is a double layered structure consisting of a top member 81 and a bottom member 82 having the bifurcated end providing the fingers '5 83. Top member 81 pf the push plate rides over the ledge 77, whereas bottom member 82 rides over the platform 75 with one side of member 82 within the groove 76 below ledge 77. The mechanism at station C also includes a chute 84 for continuously supplying the platform ledge 77 with end caps 23 and which are deposited thereon when the push plate 80 is retracted. Platform structure also includes an extension bar 85 which terminates a distance beyond the drop off front of the ledge 77, said extension bar serving as a positioning element 1 for the glass tube 22 as his indexed into position at the station. The projection 86 on the front end of the platform in alignment with the forwardly positioned extension bar 85 contributes to the correct and uniform positioning of the glass tubes when loc'ated at station C for final capping.

The part holders 31 are simply indexed into position at station (3 and as-shown-i-n Figure 9 they are not elevated beyond their normal at rest position. Upon actuation of the lever 78 to deliver a cap, the push plate 80 moves forwardly in a direction toward the right. The top member 81 slides on the ledge 77 to push'a cap 23 toward the drop off front of the ledge while the bottom member 82 slides underneath the ledge tofinally embrace the glass tube which has been indexed into position between the oppositelydisposed projections. While the glass tube is thus held in proper position the cap 23 is pushed off the ledge 77 and is deposited; over the'top of'the glass tube, being supported there by the fingered guide plate 82 which serves to maintain the cap over the end of the glass tube until final release. Said release takes place upon retraction of the guide plate 82, whereupon the cap drops into place upon the glass tube.

With the completion of the operations at station C all the switch elements will have been assembled and there remains only the fusing of the end caps to the glass tube and the annealing of the completed unit. The next indexing movement of the turntable 30 progresses the assembled parts on holder 31 to station D which is blank to permit visual inspection of the assembled parts before subjecting the same to induction heating at station E. Of course, it will be understood that the operations as described with respect to stations A, B and C take place simultaneously during the-period between indexing movements. When a top cap is'being delivered to a part holder at station A, a glass tube is being delivered at -B to another part holder which contains a top cap, and at C the bottom cap is being delivered to another part holder on which'has been deposited atop cap and glass tube. It will also'be appreciated that the various levers will be cam actuated in proper relation with each other and with the indexing movements of the turntable in order to accomplish the above operations, it being deemed unnecessary to show the cams for the levers as the same are conventional in structure and in mode of operation.

T he mechanism of station E is shown in Figures l3, 14, 15 and 16. The base plate 88 supports the standard 89, having the platform '90 suitably secured thereto in overhanging relation as by means of securing screws 91. The base plate 88 also supports the cylindrical member 92. A second standard 93 supports .the platform 94, secured thereto by screws "95. A lifter, generally indicated by numeral 96, is located at station E and which issimilar in construction and mode ,of operationto the lifter described in connection with station ,B. Said lifter 96 includes a supporting rod 97 mounted for vertical movement by thecylindrical member 92. The lifter proper is provided with the jaws within which the spindle 33 and terminal screw 72 of the part holder 31 are located when thesame is positioned at station E. However, the lifter, at this station is additionally characterized by the transverse member 100 which is suitably fixed to the sup- ,porting rod 97 and positioned to project on respective sides, of 'thefrod. The right hand projection is provided with a plate 101 which'has associated relation-with the holding pin 102 mounted by the cyiindricalmember 103 in the platform 94 for vertical reciprocating movement. The pin 102 projects some distance below member 103 and below the platform 94, the said projecting portion being provided with the collar 104 having spaced flanges and said portion is also provided with the flange 105' at the extreme lower end of the pin. The pin 102 is provided for the purpose of aligning the part holders with the station mechanisms following each indexing movement of turntable 30. As the lifter 96 is elevated from its position in Figure 13 to its raised position, as shown in Figure 14, it will be understood that the pin 102 is caused to enter one of the openings 106, provided for the purpose in the turntable. Such an opening is located in associated relation with each part holder, being equally spaced around the turntable as are the part holders so that insertion of pin 102 in an opening 106 at station B will operate to hold the turntable .in proper indexed position with respect to the mechanisms at all the stations. As the lifter 96 is elevated the pin is raised by positive contact of plate 101 with collar 104. -When lifter 9,6 is lowered at the end of an induction heating operation the pin is resiliently withdrawn by the action of the Urshaped spring 107 fixed to the underside of platform 94 by the member 168 and which additionally functions as a guide for the free end of spring 107. The said free end ,of spring 107 has associated relation with pin 102 between the flanges provided by the collar 104 and thus the pin is resiliently withdrawn upon lowering of lifter 96. However, positive action also takes place to withdraw the pin should the spring fail in its retracting operation since it will be seen that plate 101 will eventually contact the flange lllS, thus withdrawing the pin into its retracted position as illustrated in Figure 13.

Transverse member 100 on the left side thereof is Provided with a plate 110 which .is slotted at 111 for the reception of rod 112,. Said rod 112 is pivotedto the lifter as at' 113 and the end 114 is disposed under the spindle 33, being adapted to have contact with terminal screw 72 in a manner and for purposes which will be presently described. The left end of rod 112 carries the Weight 115 which may be located in adjusted position along the length of the rod to yieldingly bias the'end 114 in an upward direction. The purpose of the pivoted rod 112 is to apply a yielding force to spindle 33 and to its part holder 31. The part holder at station E is elevated as described in connection with holding pin 102, said rod .112 having pivotal movement on axis 113 when the lifter 96 is so elevated, causing a lifting of weight 115 .totheextent as permitted by slot 111. This results from the downward force exerted by spindle 33 against end 114 as the lifter is raised from its low position, Figure 13, to its elevated position, as shown in Figure 14. During theinduction heating operation the action of end 114m applying a yielding upward force tospindle 33 and thus to its part holder is to maintain the parts of the switch structure in firm contact whereby to facilitate joining .of the end caps to the glass tube during this sealing operation, and in part to control the finished dimensions of the switch. The above action of the weighted rod 1-1'2takes place in conjunction with a weighted top cap holder, which structure will now be described in detail.

Platform 90 is provided with the collar 118 which extends through the platform, being suitably secured thereto by the locking nuts 1 19. The collar mounts the bearing sleeve 120 for verticalreciprocating movement'so that the sleeve moves toward and from the part holders 31. The top projecting end of bearing sleeve 120 'is provided with a weight 121 in the form of a cup-shaped housing, the same being secured to that end ofthe sleeve projecting immediately above collar 118. A shaft 122 is disposed within the bearing sleeve and which is of a length substantially equal to that of the sleeve. The weight 123 is suitably-secured to the top end of shaft 122 and said :shaft atits lower end'has fixed thereto a direction.

i 7 top cap holder 124, there being provided above the holder the limit nut 125, which is adapted to contact the end of sleeve 120 under certain conditions to cause upward movement of the sleeve and elevation of the housing 121. When the assembled parts of the present switch are yieldingly held between the cup member 32 and the top cap holder 124 the same will be properly positioned with respect to

coils

126 and 127, Figure 16, of a conventional induction heating device generally indicated by numeral 128, Figure 1, said coils having connection with the device through terminals 129. The device 128 has connection with a source of electric current through lead L and L and said device supplies the

coils

126 and 127 with high frequency alternating current in the vicinity of 27 to 28 megacycles, although this may vary depending on the nature of the seal being made. A powerful alternating current'field is thus created in the immediate vicinity of the end caps 21 and 23, since it will be observed that the top coil 126 of the induction device is horizontally positioned with respect to the bottom cap 23, whereas the bottom coil 127 is horizontally positioned with respect to the top cap 21. The holders, including the cup member 32 and the top cap holder 124, are made of ceramic material so that they are not affected by the high frequency electric field. However, as is well known in the art of induction heating, the metal of the end caps is heated to a high temperature and also due to the dielectric losses in the glass of the tube the said glass will also 'be heated. However, only the top and bottom edges will attain a fusion temperature primarily due to the reflection of the heat from the end caps. The heating of the glass to a softening temperature is attained rather quickly and fusion of the switch parts accordingly takes place. However, during this action the said switch parts are under yielding pressure by reason of weight 123 acting downwardly through shaft 122 on the top cap holder 124, and, further, as a result of the weight 115 acting upwardly through the lever end 114 and spindle 33 on the cup member 32.' The mode of operation of the weighted parts will now be described.

It will be observed by reference to Figure 13 that a gap, indicated by the space S, exists between the end of sleeve 120 and the limit nut 125. It will also be observed that the slot 111 has a definite length for limiting the pivotal movement of the weighted rod 112. As the lifter 95 is elevated to position the assembled switch elements for the induction heating operation the cap 23 will engage the top holder 124 which is yieldingly biased into its extreme downward position by the weight 123 and thereafter rod 112 will be rotated in a direction to elevate weight 115.

rendering the same operative through end 114 to yieldingly bias the spindle 33 and the part holder in an upward Continued upward movement of the lifter will move the top cap holder upwardly into engagement with the cap holder 124, effecting elevation of the weight 123, which movement can continue to the extent of gap S. When the space represented by gap S has been taken up further movement of the lifter will cause the weighted bearing sleeve 120 to *be elevated, in which position it is clamped in a manner hereinafter described. When the parts assume this position the induction heating operation can be initiated. As the end caps reach a high temperature and the top and bottom edges of the glass tube become soft the top cap holder and the cup member, both weighted in a direction to cause movement toward each other, exert their force upon the heated switch structure. This maintains the parts in finm contact and in addition limits shrinkage in one instance to the extent of gap S and in the other instance to the extent of the slot 111, taking into consideration the movement of end 114, due to the lever ratio. As a result the overall length of the completed switch is controlled.

The mechanism at station E additionally includes switch means for starting the induction heating operation after the parts have been properly positioned with respect to the coils and after gripping by spring energized jaws for the purpose of holding the switch structure and steadying the same during the heating step. The platform has suitably secured thereto a bracket which carries the mercury switch 131 at its right hand end, said switch being releasably held to the bracket through the instrumentality of the spring clips 132. The said switch 131 is connected to the control circuit L and L, of the induction heating device 128 so as to control the supply of electric current thereto. Actuation of the switch is effected by means of a magnet 133 fixed to and carried by arm 134 which is mounted for oscillating movement since the arm is suitably fixed to the vertically disposed shaft 135.

The shaft 135 is journalled for rotation, being mounted at its top end in the collar 136 in platform 90 and at its terminal lower end in the base member 137. As best shown in Figure 15, the left hand end of the arm 134 is in engagement with the set screw 138 carried by arm 139 of the cam actuated lever 140. Said lever 140 and arm 139 are suitably secured to pivot shaft 141 extending vertically in parallel relation to standard 89 and being mounted for rotation by the platform 90 at its top end and by support 142 at its lower end, Figure 13. The cam 143 is adapted to actuate cam lever 140 to eflect oscillating movement of arm 134 whereby the magnet 133 is positioned close to switch 131 or is retracted, being spaced therefrom. When the magnet is located close to the switch the switch is effective to close the electric circuit to the induction heating device, rendering the same operative.

Simultaneously with the closing of the switch 13 spring energized jaws, including the top pair 144 and the bottom pair 145, are caused to close to resiliently engage the bearing sleeve 120 and the glass tube 22, respectively. In accordance with the invention shaft 135 is provided with an intermediate flat blade portion 146, the said portion extending above jaws 144 and below jaws 145 and being disposed between the jaws of each pair. On respective sides of the jaws there is provided a plate member such as 148 and 150, the said plates being suitably secured with cap screws 153 to the platform 96 so as to depend therefrom, and providing the support for the base member 137. The rods 151 for the pair of jaws 144 and the rods 152 for the pair of jaws 145 extend through their respective jaws to project on opposite sides thereof and said rods also extend through the

plate members

148 and 150. Collars 154 are disposed on the rods on both sides of their jaws and said collars provide seats for the coil springs 155 which are confined between said seats and their respective plate members. As a result of the structure above described, each pair of

jaws

144 and 145 is resiliently urged in a closing direction as a result of which the left end of the jaws will have clamping action with respect to their particular element. However, each pair of jaws is normally held in an open separated relation as a result of the flat blade portion 146 which is normally positioned so as to cam the jaws into said open spaced relation. When cam 143 has rotated to where the cam portion 156 is in contact with roller 157 of the lever 140 the action is such as to allow arm 134 to rotate the blade portion 146 parallel to the jaws to bring magnet 133 into close proximity to switch 131. The arm 134 has a natural tendency to rotate in this direction due to the resilient biasing action of springs 155 on the fiat blade portion 146. Accordingly, it'will be seen that when switch 131 is closed to start operation of the induction heating device the fiat portion 146 will simultaneously assume a position parallel to the jaws of each pair, allowing the jaws to close under the tension of coil springs 155. Therefore upon initiation of the induction heating the bearing sleeve 120 and the glass tube 22 are gripped by the

jaws

144 and 145 respectively so that the force applied to each of the caps by the weights 115 relation.

ncreases and 123, as previously described, isrto the degree limited only by the extent of the slot 111'in lifter'i96 an'dt he gap S established with respect to the movement ofzweight 123. By holding =the glass and the sleeve, the force of weight 115 is applied only to the bottomcap while the force of weight 123 .is applied'only to the upper cap. .Moreover, since sleeve 120 is movable heyond the limited independent movement of the-shaft 122, it is necessary to prevent movement-of the sleeve during the gauged movement of the weight-123.

Whereas, the induction heating. operation is initiated by closing the terminals of the magnetic switch 131, it will be understood that said operation is terminated'by the heating device itself which employs timing mechanism ;for accurately timing the duration of. the heating period.

The mechanismat station B will remaininthepositions assumed during the heating step untilcam143 has rotated to actuate cam lever140 and oscillate lever 134 to with- .draw magnet133 from themagnetic switch131. Opening of the switch occurs simultaneously with rotation of ;the fiat blade portion 146-to cause opening ofthe jaws.

The space between the two pairs ofjaws accommodating lowpositiomthe holding pin 102 i s simultaneously withdrawn from its'opening in the turntable. .The turntable cannow be indexed to progress the work holders with -respect to all the stations and the assembled switch previously at station E is moved to station P .where it is subjected to gas fiames produced by the gas jets158. Similar gas jets are located at station G and at :station H so that for the next two indexing movements of the turntable the assembled switch housing will be subjected .to gas fiames'for the purpose of annealing the, glass tube of the housing. Station I is blank and at station K the ,switch housing is discharged'uponactuation. of the lever 460. The switch housing is nowreadyfor thefiushing operation and for the injection of mercury, whereupon a .iinabsealing operation completes themanufacturing operations on the switch.

The apparatusforflushing the interior of the switch 'housingand injecting mercury into the, same-is shownin {Figure 2. The member 161 is cored at 162 and pro- ,yidedswith nipple 163 adaptedto connect with asupply ofrgassuch as. hydrogen and the like. A similar cored ,pas'sage 164 is also formed in member 161, towhich is .joined the connectionlfiS leading to a supply of mercury. 'Member -161 additionally forms a base and ,supporting structure for a needledike projection indicated in its I entirety by numeral 166 and whichcomprises three separate 1 tubes of relatively small size each of which is Qfiattened to providetwo flat surfaces at anangle of approximately 120 degrees. fso formed are thenplaced together and drawn through The three lengths 1 of tubing a collar 167 which functions to hold them in assembled Below the collar each length of tubing is separated tromthe otherto providethree extremities, one

of which,.narnely, .168, is anchored in member1'61, to have communicating relation with passage16 2. Another .length oftubing170 is similarly anchored in member 161 andhas communicating relation with passage 164. The third length of tubing, namely, 171, terminates above member 161 and accordingly communicates with the atmosphere. The opening 26, as previously described in connection with the bottom cap 23, is relatively small'in 'size although large enough to receivethe tripled tubed, needle-like projection 166, whichmeasures approximately one-thirty-second inch'in diameter. The next operation on theswitch housing is to place the same on the 'pro- J jection =166 with the :projection extending 'well inside the 'switch structure. .The flushing operation is initiated hy admittinggas-throughthe gas passage-162, the same :fiowing through tubing 168 to enter the switch housing. Since the gas is under pressure'it will force the air from the housing,'which air-is conveniently vented through tubing 171 and discharged to the atmosphere. After theinterior of the switch has been adequately flushed the gas is valved off and a metered. quantity of mercury -is injected through tubing 176. switch is then removed from the needle projection 166 and inaccordance with the invention the mercury will close opening 26 since the opening is small enough in The mercury loaded size to prevent release of the mercury. Accordingly,

the mercury forms a seal, closing off opening 26 and trapping the gas within the switch housing. The switch is held'ina positionwherein the mercury seals the opening until an iron pin suchas 28 is inserted in the opencury'for the purposeof reducing the contact resistance between the mercury and the end cap, which become ing and welded to hermetically sealthe switch. The iron pin su'ch as 28 may project some distance into themeroxidized during the sealing operation. In those cases where resistance is an important factor with respect to the use of the switch, special metals and other means may be employed to insure good contact between the mercury, electrode and end cap.

The -switch 20 is now complete and ready for use.

When interposed in an electric circuit the same will 'open'th'e'circuit when tilted so that the mercury flows out of contact with metal cap '23. However, the circuit will be closed through the switch when the same is tilted so that the mercury fiows into the'end cap 23 and additionally maintains contact with electrode 24. The product of the invention comprises a miniature switch of the mercury type which may be as small as ninesixteenths of an inch in length with a maximum diameter of three-'eights of an inch. Such a switch Will have many uses in the automotive and appliance field. The

advantages of themetal to glass seal, together with the machine method of assembling the component parts of the switch, and the simplified method of flushing with gas and injecting mercury, results in the production of a mercury switch wherein the length of the switch is not any greater than that needed to enclose operative switch structure. In addition the cost of manufacture is-greatly reduced in comparison to the cost when old methods are employed. It is to be-recognized that the invention may be employed in the manufacture of switches of larger size, the size changebeing that resulting from the character of the "switch parts necessitated by the current capacity rating of the switch and the operating methodof theswitch structure. Furthermore, the basic principles of switch manufacture covered by this invention makespossible a simplified and less costly manufacture of switches incorporating mechanisms sensitive to the high temperatures attained in the sealing operations, all

of which can afiect the operating characteristics of calibrated and adjusted segments of the operating structure made prior to-the final sealing operation.

In connection'with the foregoing, reference is made to Figures 5 and 6 which illustrate certain manufacturing procedures designed especially for mercury switch structures of the magnetic type wherein a spring actuated-electrodeis supported from one of the metal end caps. In

-magnetic switch structure of this type the spring actuated electrode is properly adjusted for a particular operation,

and it will be appreciated that upon being subjected to "intense heat its operating characteristics could be materially changed since heat will affect the tension of the spring and also the strength of the magnet mounted upon the springactuatedelectrode. According to the method of the invention a metal end cap 172 can be fused to the :glass'container 173 by means of induction heating efifected through coils 1 74 which are'suitably energized by the induction heating device175, under control of switch 131, all as shown in Figure 5. The operating switch mechanism, generally designated by numeral 176, can be secured to the electrode stem such as 177, fixed to and protruding from the metal end cap 172. After adjustment of the switch mechanism a second end cap 178 is applied to the opposite end of the tube and the switch structure 180 is again subjected to induction heating which, in this instance, is confined to the end cap 178. This last induction heating operation requires that the switch structure be inverted, all as clearly shown in Figure 6. As a result the heat sensitive mechanism of the switch is removed from the area where heating takes place for fusing the final cap to the glass tube. With the heat being localized, and the heating period of relatively short duration, it will be understood that the critical parts of the switch are accordingly not injured by excessive heat. Following the completion of this last fusing operation the switch housing is flushed in a manner as explained in connection with Figure 2, for which purpose the metal end cap 178 is provided with a small opening, the same as end cap 23. Mercury is then injected into the switch structure and following this operation the opening in the metal end cap 178 is sealed by inserting a metal plug and welding the same in place.

The invention is not to be limited to or by details of construction of the particular embodiment thereof illustrated by the drawings, as various other forms of the device will of course be apparent to those skilled in the art without departing from the spirit of the invention or the scope of the claims.

What is claimed is:

1. In the manufacture of a mercury switch wherein metal end caps are sealed to respective ends of a glass tube, the steps which include the assembling of the parts by placing a glass tube on a bottom cap and depositing a top cap on the opposite end of the tube, subjecting the assembled parts to induction heating to fuse the glass tube to the metal end caps whereby to provide a unitary switch housing, flushing the interior of the switch housing by injecting a gas into the housing through an opening in one of the end caps, then injecting a quantity of mercury into the switch housing through the same opening, and finally closing said opening while the same is sealed by the mercury by inserting a member therein and welding the member in place.

2. In the manufacture of a mercury switch wherein metal end caps are hermetically sealed to respective ends of a glass tube, the steps which include the assembling of the parts by depositing a glass tube on a bottom cap and then depositing a top cap on the opposite end of the tube, subjecting the assembled parts to an induction heating to hermetically join the glass tube and the metal end caps whereby to provide a unitary switch housing, flushing the interior of the switch housing by injecting a gas into the housing through an opening in one of the end caps and simultaneously therewith discharging the air from the switch housing through the same opening, then injecting a quantity of mercury into the switch housing through said opening, and finally closing said opening while the same is sealed by the mercury by inserting a member therein and welding the member in place.

3. In the manufacture of a mercury switch wherein metal end caps are hermetically sealed to respective ends of a glass tube, the steps which include the assembling of the parts, subjecting the metal end caps to induction heating while holding the parts in assembled relation, whereby to hermetically join the metal end caps to the glass tube and provide a unitary switch housing, flushing the interior of the switch housing by injecting a gas into the housing through an opening in one of the end caps and simultaneously therewith venting the air from the switch housing through the same opening, then injecting a quantity of mercury into the switch housing through said opening, and finally closing said opening while the 'sameis sealed by'the mercury by inserting a metal plug therein and welding the metal plug in place.

4. In the manufacture of a mercury switch wherein metal end caps are hermetically sealed to respective ends of a glass tube, the steps which include the assembling of the parts, subjecting the metal end caps to induction heating while holding the parts in assembled relation, applying pressure to force the end caps into contact with the glass tube during the induction heating step whereby to hermetically join the metal caps to the glass tube and provide a unitary switch housing, flushing the interior of the switch housing by injecting a gas into the housing through an opening in one of the end caps and simultaneously therewith venting the air from the switch housing through the same opening, then injecting a quantity of mercury into the switch housing through said opening, and finally closing said opening while the same is sealed by the mercury by inserting a member therein.

5. In the manufacture of a mercury switch wherein metal end caps are hermetically sealed to respective ends of a glass tube, the steps which include the assembling of the parts by bringing them into juxtaposed relation in the proper order, subjecting the metal end caps to induction heating while holding the parts in assembled relation, applying pressure to each end cap to force the same into firm contact with the glass tube during the induction heating step, controlling the pressure to control the shrinkage of the glass tube due to the fusion taking place at the ends thereof with the metal end caps, whereby the parts are hermetically joined and a unitary switch housing is provided, flushing the interior of the switch housing by injecting a gas into the housing through an opening in one of the end caps and simultaneously therewith venting the air from the switch housing through the same opening, then injecting a quantity of mercury into the switch housing through said opening, and finally closing said opening while the same is sealed by the mercury by inserting a member therein.

6. In the manufacture of mercury contact switches, the method of assembling the parts of the switch housing by machinery including step by step movements wherein the first step consists in depositing a metal end cap on a part holder at the first station of said machinery, moving the part holder to the next station by an indexing operation, depositing a glass tube onto the metal end cap so that the parts are in proper juxtaposed relation for closing the bottom end of the tube, again indexing the part holder to the third station, placing a second metal end cap on the glass tube to close the top thereof and simultaneously holding the glass tube to assure proper positioning thereof, again indexing the part holder to locate the assembled switch parts at another station, fusing the metal end caps to the glass tube by subjecting the end caps to an ultra high frequency electric discharge, applying yielding pressure to the end caps respectively to press them into contact with the glass tube during the fusing step, then indexing the part holder through successive stations for subjecting the switch housing to an annealing process by directing gas flames against the glass tube, and finally removing the completed switch housing fromv the part holder.

7. Apparatus for use in the manufacture of mercury switches of the type wherein metal end caps are sealed to respective ends of a glass tube, the combination with mechanisms located at various stations, of a turntable adapted to be periodically indexed with respect to said stations, a plurality of part holders carried by the tumtable and which are moved from station to station by said indexing of the turntable, the mechanism at one station comprising means for depositing an end cap on a part holder, the mechanism at the next station comprising means for placing a glass tube on the said end cap, the mechanism at the next station comprising means for depositing another end cap and for placing the same on the top end of said glass tube, and mechanism at still another station for fusing the end caps to said glass tube, said last mentioned mechanism including a top cap holder adapted to contact the said top end cap for holding the assembled switch parts between the same and the part holder, and said last mentioned mechanism additionally including induction heating coils and a high frequency electric device for energizing the coils, said holders presenting the as sembled switch parts to said coils to effect an induction heating of the end caps for fusing said caps to the respective ends of the tube.

8. Apparatus for use in the manufacture of mercury switches as defined by claim 9, wherein said last mentioned mechanism aditionally includes spring energized jaw members for gripping and holding the glass tube of the assembled switch parts during the fusing operation, a rotatable blade member for effecting opening and closing action of the jaw members, an electric switch for initiating operation of the high frequency electric device, and means fixed to and actuated by the blade member for controlling the operation of said electric switch.

9. Apparatus for use in the manufacture of mercury switches of the type wherein metal end caps are sealed to respective ends of a glass tube, the combination with mechanisms located at various stations, of a turntable adapted to be periodically indexed with respect to said stations, a plurality of part holders carried by the turntable and which are moved from station to station by said indexing of the turntable, the mechanism at one station comprising means for depositing an end cap onto a part holder, said means including a platform having a groove, a magazine feed supplying said end caps to said groove and a push plate slidably mounted in the groove for reciprocating movement, the mechanism at the next station comprising means for placing a glass tube on the said end cap, the mechanism at the next station operating to deposit another end cap and place the same on the top end of said glass tube, said mechanism including a platform having a groove, a magazine feed for supplying the last mentioned end caps to said groove, a push plate slidably mounted in the groove for reciprocating movement, said push plate including top and bottom members, the bottom member having a bifurcated forward end whereby the end cap delivered to the drop off edge of the platform by the top member is deposited onto the bottom member which places it on the glass tube upon retraction of the push plate, and mechanism at still another station for fusing the end caps to said glass tube, said last mentioned mechanism including a top cap holder adapted to contact the top end cap for holding the assembled switch parts between the same and the part holder, and said last mentioned mechanism additionally including induction heating coils and a high frequency electric device for energizing the coils, said holders presenting the assembled switch parts to said coils to effect an induction heating of the end caps for fusing said caps to the respective ends of the tube.

10. Apparatus for use in the manufacture of mercury switches of the type wherein metal end caps are sealed to respective ends of a glass tube, the combination with mechanisms located at various stations, of a rotatable turntable adapted to be periodically indexed with respect to said stations, means operative at the end of each indexing operation for locking the turntable in position, a plurality of part holders carried by the turntable and which are moved from station to station by said indexing of the turntable, the mechanism at one station comprising means for depositing an end cap onto a part holder, said means including a platform having a groove, a magazine feed supplying said end caps to said groove and a push plate reciprocable in the groove for feeding the end caps individually, the mechanism at the next station comprising means for placing a glass tube on the said end cap, the mechanism at the next station operating to deposit another end cap and place the same on the top'end of said glass tube, said mechanism including a platform having a groove, a magazine feed for supplying the last mentioned end caps to said groove, a push plate reciprocable in the groove for feeding the said end caps individually, said push plate including top and bottom members separated by a platform ledge, the bottom member having a bifurcated forward end whereby the end cap feed to the terminal end of said ledge by the top member is deposited onto the bottom member which places it on the glass tube upon retraction of the push plate, and mechanism at still another station for fusing the end caps to said glass tube, said last mentioned mechanism including a top cap holder adapted to contact the top end cap for holding the assembled switch parts between the same and the part holder, said last mentioned mechanism additionally including induction heating coils and a high frequency electric device for energizing the coils, said holders presenting the assembled switch parts to said coils to effect an induction heating of the end caps for fusing said caps to the respective ends of the tube, and yielding pressure means combined with said holders respectively for applying yielding pressure to the end caps to force them into contact with the glass tube during the fusing operation.

References Cited in the file of this patent UNITED STATES PATENTS 1,895,177 Staley Jan. 24, 1933 2,048,556 McArthur July 21, 1936 2,101,092 Payne Dec. 7, 1937 2,160,367 Maxfield May 30, 1939 2,210,017 Wetherby-Williams et al. Aug. 6, 1940 2,298,178 Staley Oct. 6, 1942 2,305,414 Gerisch Dec. 15, 1942 2,324,595 Pollard July 20, 1943 2,482,734 McKenzie et al Sept. 20, 1949 2,522,990 Cartun Sept. 19, 1950