US2813192A - Electrical welding apparatus - Google Patents

Description

1957 J. H. BROOKS ETAL ELECTRICAL WELDING APPARATUS 4- Sheets-Sheec 2 Filed April 25. 1955 o w a 5 u 8 5M .0 m 5 T 3 m 2 I V 5 m U m 7 5 8 8 5 5 5 9 5 3 .5 B 7 5 2 -w w w 8 n 5 H w w 6 6 m 2 6 -w .7-.. r g7 56 g i 2 4 m 0 8 9. 5 i .i 6 2 6 m6 w 5 I m/ (m a JOSEPH H. sRooks MARCELLUS N.GILBERT,JR.

CHARLES L. TOOMEY ATToRNtY FIG. 2

Nov. 12, 1957 J. H. BROOKS ETAL 2,813,192

ELECTRICAL WELDING APPARATUS Fild April 25. 1955 4 Sheets-Sheet 3 FIG. 5

INVENTOR.

c us ILBERT, JR. R s OMEY BY JOSEPH H. BROOKS,

ATTORNEY Nov. 12, 1957 J H. BROOKS ETAL ELECTRICAL WELDING APPARATUS 4 Sheets-Sheet 4 Filed April 25. 1955 lOl I02 v INVENTOR. JOSEPH H. BROOKS MARCELLUS N.GILBERT,JR.

CHARLES 1.. TOO'MEY BY ATTORNEY ELECTRICAL WELDING APPARATUS Joseph H. Brooks, Peabody, Marcelius N. Gilbert, Jr., Lynnfield, and Charles L. Toamey, Danvers, Mass, assignors to Sylvania Electric Products Inc, Satem, Mass, a corporation of Massachusetts Application April 25, 1955, Serial No. 503,575

2 Claims. (Cl. 219-130) This invention relates to the manufacture of electric lamps and more particularly to apparatus for electrically welding lead-in wires to external contacts of such lamps.

In electric lamps, lead-in wires connected to internal elements positioned within a glass envelope, project through the glass and are joined to external contact members adapted to form a connection with a suitable socket. In tubular fluorescent lamps, for example, a pair of leadin wires projects from each end of the envelope. Each wire of the pair is threaded through a hollow pin mounted on an end cap which is cemented to the end of the envelope. It has long been the practice to solder lead-in wires and contact pins at their outer ends to provide an electrical and mechanical bond between them. A similar practice has been followed in the manufacture of electron tubes and incandescent lamps.

The use of solder as a bond has many disadvantages. In the first place, the contact surfaces have a tendency to become corroded if an excess of flux is used. This results in a high resistance connection between the lamp and lamp-holder, and is especially objectionable in socalled rapid start lamps, in which a low voltage is used across the contact prongs for preheating the electrodes before starting. A high resistance connection is also objectionable in electron tubes where a variation of a few ohms may upset the operation of a circuit. Another disadvantage is that since the flow of the molten solder is difiicult to control, blobs of solder are often deposited on contact pins or lamp bases. As a result, it may be impossible to insert the lamp or tube into its lamp holder or socket besides giving the device an unsightly appearance.

In order to overcome the disadvantages of soldering, it

has been suggested that radio frequency gap welding be employed to unite lead-in wires to contact members. Apparatus heretofore used for this purpose has consisted essentially in an R. F. source and a high capacity charged condenser connected to a pair of fixed electrodes. As applied to tubular fluorescent lamps, for example, one electrode engages the contact pin to be welded while the other is positioned in spaced-apart relation with the end of the lead-in wire which projects slightly beyond the end of the hollow pin. In this position the R. F. source is triggered to ionize the air in the gap between the electrode and the lead-in wire. The arc of ionized air provides a path of low electrical resistance to the passage of the condenser discharge current which furnishes the heat necessary to weld lead-in wire to contact pin. It has been found, for example, that by using a gap of approximately inch, R. F. of 10,000 volts at approximately 200 kilocycles, and a condenser on the order of 40,050 microfarads having a charge of 70 to 90 volts, highly satisfactory results are obtained in welding steel lead-in wires to fluorescent lamp contact pins. However, tests have shown that all other factors remaining constant, the width of the gap is quite critical in determining characteristics of a particular weld. Too small a gap increases the amount of heat generated to the point of burning the nite rates atent O tip of the contact pin. On the other hand, with too large a gap, insuflicient heat is produced for a complete weld.

A serious difficulty has been encountered in maintaining optimum spacing between the lead-in wire and an electrode in the form which has heretofore been used. These have been rods of tungsten, carbon or other suitable material having an end surface spaced from the lead-in wire. Each time that a weld is made small particles of molten metal from the weld are deposited upon this surface. The accumulation of these deposits with continued operation of the apparatus reduces the gap between the end of the electrode and the end of the lead-in wire. Consequently, this type of electrode requires constant attention and adjustment in order to avoid the spoilage of lamps at a final operation in their manufacture.

Our invention is specifically concerned with an improved electrode construction for use in R. F. gap welding circuits.

A general object of our invention is the production of uniform welds between lead-in wires and contact members in electric lamps and similar devices.

A more particular object of our invention is an electrode arrangement capable of operating for extended periods of time without readjustment.

Still another object is an electrode Whose cleanliness is easily maintainable during continuing operation.

It is a feature of our invention that a circular electrode employed at the gap is rotated slightly for each weld thereby presenting a new arcing surface for each operation of the apparatus.

It is another feature of our invention that a brush has been incorporated in our apparatus to clean that part of the circular electrode which has been indexed away from the welding position.

Other objects and novel features of our invention will be more fully understood from the detailed description in connection with the accompanying drawings in which:

Figure 1 is a plan view of the apparatus;

Figure 2 is a view in cross-section taken along line 22 of Figure 1;

Figure 3 is a view in cross-section taken along line 33 of Figure 2;

Figure 4 is a plan view of one of the trigger switches and its actuating arm;

Figure 5 is a view in side elevation of an electrode according to our invention applied to welding the side wire of an incandescent lamp;

Figure 6 is a simplified diagram of a typical electric circuit which is used in conjunction with our invention.

Although apparatus according to our invention is applicable to the manufacture of a variety of products in a wide range of machines, it has been shown in Figures 1 through 4 as applied to the welding of lead-in wires to contact pins of tubular fluorescent lamps on a lamp basing machine of the type disclosed in U. S. Patent 2,264,304, owned by the assignee of this application.

The inclusion of the pin welding operation among those performed on this machine has necessitated a change in its mode of operation to require a full revolution of the carrier to complete the basing of each end of a lamp. As the machine is employed, during one revolution of the carrier an end cap is bonded to one end of the lamp, lead-in wires projecting through contact pins are cut to length and each lead-in wire is welded to its contact pin. The lamp is then turned end for end and during a second revolution the same operations are performed on the other end. In order to suit these new conditions one of the wire trimming mechanisms has been removed, heating and cooling manifolds have been rearranged, and one of the manifold supports 19 has been replaced by base 16, Figure l of this application.

In Figure 1, there are two complete welding devices, one for each contact pin on one end of a tubular fluorescent lamp. Both devices are adjustably mounted on base 16, above the basing machine carrier. In Figure l, the path travelled by the axis of a lamp 135 (Fig. 2) has been shown as circular are 11. Each lamp 135 is oriented on the carrier in a basing head whichmain tains contact pins 12 and 13 disposed in a radial plane. The first welding head designated by reference character 16 has a circular electrode 17 of tungsten, copper or other suitable material positioned above the path of inner contact pin 12. Similarly, Welding head 18 has a circular electrode positioned above the path of outer contact pin 13. Each of heads 16, 18 is vertically adjustable by means of a positioning screw 20 retained against axial motion in plate 21secured to base 11) by a pair of screws 22. To provide the necessary adjustment, positioning screw 29 is threaded into a tapped hole in housing 23 which is then secured by screws 24 to base 10 in the case of head 16 and to bracket 25 in that of head 18.

The electrodes 17 and 19 are kept clean by a longbrittle wire brush 26 mounted above and in contact with both electrodes. Shorting of the electrodes through the brush 26 is avoided .by-cutting'away two sectors of wire bristles, leaving two tufts I disposed somewhat in the manner of the blades or a propeller. The relative positions of electrodes 17,19 and brush 26 and the size of these tufts are such that onlyone electrode is engaged by crush 26 at any one time as the brush is being rotated. Brush 26 is insulatedly mounted for rotation with shaft 29 by means of adapters 27 and 28 and'nut-3tl in threaded engagementwith the end'of the shaft. Adapters 27 and 23 are of fibre or other suitable. non-conductive material. Shaft 29 is mounted for rotation in a selfaligning ball bearing fitted in block 104 which is adjustable vertically by positioning screw 31 threaded into plate 32 fast on slide 130 (Figure 2), by screws 33. A screw 131 (Figure 2) projects through a slot 132 in slide 130 and is threaded into block 194 to retain it in its adjusted position. Shaft 29, positioned above'shafts 50, is rotated by motor 34 through universal joint 35.

Bracket 36 is fastened at its inner end to base 10 by screws 37 and is forked at its outer end for .the'pivotal mounting of lever 38 on hinge pin 39. Lever 38 is adjustably loaded by compression spring 46 mounted on stud 31 between nut 42 and shoe 43 which is free to slide on stud 41. Similarly lever 44 is pivotally mounted on hinge pin 45 in bracket 25 and adjustably loaded by compression spring 46 on a stud 47 between nut 48 and shoe 49. The functions of levers 38 and 44 are set forth below.

Details in the construction of heads 16 and 18, which are alike, will now be described with reference to Figure 2 which shows the component parts of head 16. Electrode 17 is clamped fast on shaft 59 between contact rings 51 and 52, fitted to telescoping bushings 53 and 54 between opposed washers 55 and nuts 56. Bushings 53 and 54, of suitable non-conductive material, serve to insulate electrode 17 from shaft 50. A pair of slots 57 in bushing 53 engages a pin 58 in shaft 50 to prevent relative rotation between bushing 53 and shaft 50.

Rotation of shaft 50, which is mounted in ball bearings 59, is affected by the engagement of worm 60 with a worm wheel, not shown, which is fast on'shaft 50. Inner bearing 59 is retained in place in housing 23 by a cap 104 fastened by screws 195. Inner race 67 of bearing 68, spacer 66, and worm 61) are retained on shaft 61 by washer 65, lock washer 64 and nut 63. A key 62 is provided to prevent rotation of shaft 61 relative to worm 60. At its lower end shaft 61 is mounted in bearing 70, whose inner race 69 is positioned against a shoulder in the shaft 61 by star-wheel 71 retained by set screw 72. A cover 1136 closes the upper end of housing 23.

A plurality of lamp holders 197 is mounted on the basing machine carrier (not shown) which moves continuously. Each holder 107 is adapted to transporting one lamp supported between an upper basing head 15 fixedly positioned on its column 73 and a spring loaded lower basing head (not shown). Each column 73 is affixed to the basing machine carrier. Rotation of shaft 61 and consequently of electrode 17 effected by the engagement of star wheel 71 and columns 73 as shown in Figure 3 presents a clean electrode surface for each successive weld. Alternatively, electrode 17 can be revolved continuously by coupling shaft 50 to its own motor drive when the apparatus is employed on a different machine. The speed of rotation of the electrode relative to the motion of the machine carrier should be such that terminal points of successive welding arcs are distributed over the entire periphery of the electrode.

Contact pin 12 is shown in Figure 2 after the welding operation has been completed. Pin 13 on the other hand, is shown before welding, lead-in wire 168 projecting slightly above the upper end of the pin 13. In the welding process lead-in wire 10%, whose length above pin 13 is exaggerated for clarity in Figure 2, and the upper end of the contact pin are melted and fused into a iemispherical end shown at contact pin 12. Under ideal conditions, the welding operation takes place as a contact pin 12 is moved by the basing machine carrier through a relatively short distance bisected by the vertical axial plane of electrode 17 and is initiated by the closing of switch as pin 12 moves into this welding area or zone.

Switch 85, which is fixedly mounted on the underside of base 1%, is closed by the pressure of operating screw 36 upon its actuator plunger 96, thereby forming a connection between lines 101 and 102. Screw 86 is adjusted in the upper end of pivotally mounted lever 38 (Figure 4) and locked by nut 94 to actuate switch 85 as pin 12 in contact with plate 92 enters the welding area. The. plate 92 is aflixed to the underside of lever 38, its outer edge 109 acting as a cam surface which is engaged by each pin 12 as it approaches the welding zone. As head 15 continues its counter-clockwise motion, pin 12 being in contact with plate 92, screw 86 engages actuator button 96, and effects a'closure of switch 85 as pin 12 enters the welding area. The welding process itself will be described below with particular reference to Figure 6.

After the weld is completed, head 15 carrying thelamp progresses in a counter-clockwise direction, pin 12 moving out of engagement with plate 92. When this occurs lever 38, under the pressure of compression spring 40, is rotated in a clockwise direction on hinge pin 39 until stop screw 90 threaded into'lever 38 and adjustably locked by nut 91 comes to rest against bracket 36. Screw 90 is so adjusted that outer edge 109 of plate 92 will lie in the path of the pin 12 of the next lamp on the basing machine carrier, thus allowing the switching operation to be repeated for each successive lamp.

The operation of lever 44 shown only partially in Figure 1, is similar at welding head 18 to that of lever 38 at head 16. Lever 44- also carries a plate, similar to that designated by reference numeral 92, which is engaged by pin 13 as it approaches its welding zone beneath electrode 19. By this engagement lever 44 is rotated in a counter-clockwise direction, thereby exerting pressure by means of operating screw 124 upon actuator button 125 to close a switch, not shown. Screw 124 is in threaded engage 'ment in the innerend of lever 44 and locked 'by nut 126.

This switch performs in the circuit of head'18 the same function of initiating the welding operation as that effected V by switch S5 at head 16.

In order to provide welding current across the gap between electrode 17 and the lead-in wire which projects above pin 12, it is necessary that electrical communication be established between line 103, the ground side of the welding circuit (Figure 6) and plate 92 which serves as a ground terminal and also between lines; and

live electrode 17. Line 103 is connected to base 10 and wire 122 by screw 121. The electrical path between line 103 and plate 92 consists in base 10, line 93 secured to base 10 by screw 120 at one end and to lever 38 at the other by screw 99, and lever 38 to which plate 92 is attached. Wire 122 links line 103 and lever 44 to which it is attached by screw 123. It has already been explained that a plate similar to plate 92 is mounted on lever 44 and performs the same functions.

Our invention may be applied, with slight modifications, to the welding of lead-in wires and similar articles, as is indicated at Figure 5. In this view electrode 17, its :axis vertically disposed, is applied to the welding of lead-in wire 98 to base 97 of incandescent lamp 100, which is being moved in a base-up position on a basing machine carrier (not shown) commonly employed in the manufacture of such lamps. Plate 76, like plate 92 which has been described above, serves as a ground terminal and is part of a trigger switch operating mechanism.

Although electrode 17 is shown in Figure as it is employed in the manufacture of incandescent lamps, the manner in which it is connected to its electrical circuit will be described as though it were part of Welding head 16. Brush 75, of carbon or other suitable material, is biased into engagement with contact ring 51 by the pressure of leaf spring 74. Post 78 provides a mount for spring 74 and a junction for line 81 and one end of wire 77 which is connected to brush 75 at its other end. The pressure exerted by spring 74 may be adjusted by the :axial positioning of post 78 in yoke 82 which is clamped around a projection 129 on housing 23. A screw 79 and two nuts 80 fasten spring 74, wire 77 and line 81 to post 78 which is made of polystyrene or other suitable insulating material. Line 81 extends to terminal post 33 (Figure 1) where it is connected to line 84 between nuts 127. Post 83 is mounted on insulator block 128 which is affixed to base 10. Electrical communication between live line 84 and electrode 17 is therefore through line 81, wire 77, brush 75 and contact ring 51.

The operation of the electrical circuit will now be described with reference to Figure 6. The circuit shown in this view is in electrical communication with welding head 16 but it will be understood that a like circuit, identical in its operation, is provided for head 18. A transformer 110 permits operation at 115 volts A. C. from a 230 volt A. C. line. With no lamp in the welding zone and hence no connection between lines 101 and 102, switch 85 being open, relay coil 114 is de-energized and contacts of its switch 113 occupy their normally closed position. Rectifier 119 is connected to the 115 volt output of transformer 110 through the closed contacts of relay switch 113. The direct current output of rectifier 119, which is preferably controlled by means of a rheostat or variably tapped autotransformer charges condenser 118 to about 80 volts. It has been found as already mentioned that a condenser 118 having a capacity of approximately 40,000 microfarads, rated at 100 volts, and charged to between 70 and 90 volts provides a sufficient discharge to perform a welding operation in our apparatus. While condenser 118 is being charged oscillator 115, which may be either of the vacuum tube or spark gap variety is inoperative, its connection to the output side of transformer 110 being interrupted by open switch 85. Thus when contact pin 12 first engages plate 92 and before switch 85 is closed a potential difference of approximately 80 volts, the charge on condenser 118 is present across the gap between pin 12 and electrode 17. There is no current flow across the gap since it presents an effectively infinite resistance to the discharge of condenser 118.

When pin 12 enters the welding zone switch 85 is closed, effecting a connection between lines 101 and 102, and thereby energizing relay coils 112 and 114. Switch 113, operated by relay coil 114, opens instantly, disconnecting rectifier 119 from transformer 110 and terminating the charging of condenser 118. Switch 111, on the other hand, is of the time delay variety. Consequently after coil 112 is energized, switch 111 remains closed for a brief interval, then it opens. During this interval oscillator 115 is connected to the 115 volt side of transformer 110 through switch 11 and closed trigger switch 85. The output of oscillator 115, 10,000 volts at 200 kilocycles, ionizes the 'air in the gap between pin 12 and electrode 17, allowing condenser 118 to start discharging across the gap.

A D. C. blocking condenser 116 presents a low impedance to the R. F. output of oscillator 115 while preventing the discharge of condenser 118 through the oscillator 115. An R. F. choke 117 isolates condenser 118 from the R. F. output of oscillator 115 and is of sufficiently low resistance to have little effect upon the discharge of condenser 118 across the gap. After the discharge has started switch 111 opens rendering oscillator 119 once again inoperative. The discharge of condenser 118 continues, however, its voltage decreasing, until it is insufficient to maintain ionization. The welding operation is complete by the time the arc across the gap is extinguished. As already explained, pin 12 moves out of engagement with plate 92, opening switch 85. Thereupon coils 112 and 114 are de-energized and switches 111 and 113 assume their normally closed position. Open switch presents an open circuit between oscillator 115 and transformer so that oscillator remains inoperative. However, rectifier 119 is connected to transformer 110 through switch 113 and its output charges condenser 118 for another welding operation which will be initiated when switch 85 is closed, as already explained, when pin 12 of the next lamp on the basing machine carrier enters the welding zone.

Now that we have disclosed a preferred embodiment of our invention, a number of variations within its scope will be obvious to those skilled in the art. For example, the live electrode need not be cylindrical or circular in form nor must it be rotated continuously. This electrode could be a flat plate reciprocable between a welding position and a cleaning position. Again the electrode might be in the form of a polygon with one side positioned parallel to the path described by the outer end of the contact pin as the lamp is moved on the basing machine carrier. Such an electrode could readily be indexed periodically, the surface which has already seen welding service moving to a cleaning station and being replaced by a clean surface in the welding zone. Since many modifications are possible within the spirit of the invention, it will be understood that we do not intend to be limited to the specific construction shown but to depend rather upon the definition presented in the appended claims.

What we claim is:

1. In apparatus for welding a lead-in wire to a contact on each of a succession of electric lamps, the combination of: a disk-shaped electrode, a portion of the periphery of which defines a welding zone with the wire and related contact of a given lamp during a welding operation, said wire and said contact being spaced from said electrode in said zone by a gap suitable for welding; a source of radio frequency energy and a source of welding current connected to said electrode; means actuated by entry of said wire and said contact into said zone for triggering said source of radio frequency energy to ionize the air in said gap to allow said welding current to discharge through said ionized air, to said wire and said contact; a brush in cleaning engagement with the periphery of said electrode at a distance from said zone; means for slightly rotating said electrode to present a fresh welding surface for each welding operation; and means for revolving said brush continuously for cleaning each portion of the periphery of said electrode which has been employed for a given welding operation before that portion is again employed for a subsequent welding operation.

2. In apparatus for welding a lead wire to a contact on each of a succession of electric lamps, the combination of: an electrode, a portion of which defines a welding zone with the wire and contact of a lamp during a welding operation, said wire and said contact being spaced from said electrode in said zone by a gap suitable for welding; a source of radio frequency energy and a source of welding current connected to said electrode; and means, actuated by the entry of said wire and said contact into said zone, for triggering said source of radio frequency energy for ionizing the air in said gap to permit the discharge of said welding current through said ionized air, to said wire and said contact whereby welding of the Wire to the contact is efi'ected by a single continuous pulse of electrical energy of relatively short duration.

' References Cited in the file'of this patent 7 UNITED STATES, PATENTS Gravell -a Apr. 15, 1919. Fechheimer et a1. Feb. 11, 1941 'Rava Mar. 18, 1941 Larsen -2. Dec. 11, 1945 Defienbaugh Jan. 12, 1954 Muller June 15, 1954 FOREIGN PATENTS, Germany July 1, 1922

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