US3467832A - High-power high-frequency switch - Google Patents

Description

Sept. 16, 1969 C. F. DEPRlsco HIGH-POWER HIGH-FREQUENCY SWITCH '7 Sheets-Sheet 1 Filed March 20, 1967 v QAKNQQU Qv XKSG m o# om www QN 5 Sw .Rag Nm @WM wh Nnw l .l QW w ohm@ vv w mt Array/V516.

sept. 16, 1969 Q E DEPMSCO 3,467,832

HIGH-POWER HIGH-FREQUENCY SWITCH Filed March 20, 1967 7 Sheets-Sheet 2 CAPM/NE De/O/SCO Sept. 16, C. F DEPRSCQ HIGH-POWER HIGH-FREQUENCY SWITCH Filed March 20. 1967 7 Sheets-Sheet 3 JCR 2/5 Sept 16, 1959 c. F. DEPRlsco 3,467,332

HIGH-POWER HIGH-FREQUENCY SWITCH Filed March 2o, 1967 7 sheets-sheet 4 sept. 16, 1969 C, F. DEPRISCO HIGH-POWER HIGH-FREQUENCY SWITCH Filed March 20, 1967 7 Sheets-Sheet 5 l I I F/G.4C

'7 Sheets-Sheet 6 Nw? QS a s@ @gg J owl O x fm mw ma V w /mi n m C. F. DEPRISCO HIGH-POWER HIGH-FREQUENCY SWITCH sept. 16, 1969 Filed March 20, 1967 N ui in Q2 Sept 16 1969 c, F. DEPRlsco HIGH-POWER HIGH-FREQUENCY SWITCH 7 Sheets-Sheet '7 S NQN uw@ mm. @Px

United States Patent O 3,467,832 HIGH-POWER HIGH-FREQUENCY SWITCH Carmine F. DePrisco, Glen Mills, Pa., assignor to Aeroprojects Incorporated, West Chester, Pa., a corporation of Pennsylvania Filed Mar. 20, 1967, Ser. No. 624,505

im. C1. H023 3/14 U.s. C1. 307-41 14 Claims ABSTRACT F THE DISCLOSURE High power energy at ultrasonic frequencies is switched from an .active load to a dummy load on a highly repetitive time basis using inverse parallel silicon controlled rectiiiers controlled by a timer and electro-mechanical switches and gate circuit. As applied to ultrasonic frequency Welders, the circuitry reduces wear on the alternator and provides good stability.

high-repetition-rate ultrasonic welding, for example), a v

rapid, minimum-maintenance, and durable means is needed for switching kilowatts of energy at ultrasonic frequency. For example, each such weld is generally accomplished in an exceedingly short time interval (usually less than 1 second), and abrupt full power must be available when each weld is to be made. In a specific case, important considerations were speed, high duty cycle, small size, low power loss, long-term reliability, and environmental resistance. It was necessary to deliver 220 volts RMS, 70 to 90 amperes RMS, to a welding load designed to operate at about 15,000 cycles per second. The required repetition rate varied from about 300 to about 600 welds per minute, with a weld pulse duration of 0.095-second maximum (allowing an 0.105-second time interval-.at 300 welds per minute-for feeding or indexing).

In the electrical industry, remote-controlled magnetic contactors are often used for switching power at high levels, but these were found to have doubtful service life and to provide unsatisfactory response in the indicated application. Also, a vacuum switch was too sluggish for the required repetition rate. Available high-current solidstate switches proved unduly sensitive to the voltagecurrent phase relationship existing in the transmission line atithe instant of switching. Furthermore, a combination of available solid-state switches (for power-step response) and of magnetic contactors (as primary switching elements) proved insufficiently reliable.

It was found that the various requirements could be met by appropriate drivin-g of the power supply into a xed dummy load and by appropriate switching back and forthbetween that load and the welding load in a very short time interval (less than about 0.005-second in the described case). It was also possible to switch dummy resistors into and out of the power transmission line to provide step power Variations for power-programmed welding.

Therefore, it is a general object of the present invention to provide a high power ultrasonic switch.

It is another object of the present invention to provide a high power ultrasonic switch for rapidly switchingl energy in an ultrasonic Welding apparatus.'

It is yet another object of the present invention to provide .a high power ultrasonic energy source for ultrasonic ICC welding equipment that is capable of intermittently providing the energy requirements in rapid short bursts.

It is yet another object of the present invention to provide a novel silicon controlled rectifier circuit for rapidly and repeatedly switching high power ultrasonic electrical ener-gies.

Other objects will appear hereinafter.

For the purpose of illustrating the invention, there is shown in the drawings a form which is presently preferred; it being understood, however, that this invention is not limited to the precise arrangements .and instrumentalities shown.

FIGURE 1 is a schematic block diagram illustrating general electrical circuitry for an ultrasonic device.

FIGURE 2 is a schematic diagram illustrating the input power source.

FIGURE 3 is a schematic block diagram illustrating the motor-alternator.

FIGURES 4A, 4B and 4C, when placed side by side with the ligure numbers in an upright position, comprise a detailed schematic of the static-type A-C switch.

FIGURES 5A and 5B, when placed side by side with the iigure numbers in an upright position, comprise a schematic illustrating the control section of the apparatus.

Referring now to the drawings in detail, wherein like numerals indicate like elements, there is shown in FIG- URE l a schematic block diagram of circuitry providing high-power alternating frequency in rapid sequential bursts to a load, designated generally as 10.

As shown, the load comprises a plurality of transducers 12 which convert current at ultrasonic frequency into mechanical vibratory energy. The vibratory energy may be used in apparatus such as ultrasonic welding apparatus in manners Well known in the art. The control section 14 provides overall control for the entire apparatus including on-off conditions, signaling, and switching of loads. In accordance with well known principles, the transducers 12 are polarized through a polarizing unit 16 which derives its electrical energy from the 60 cycle source 18 through the control section 14. The motoralternator 20 derives its energy from source 18. Motoralternator 20 is designed to provide the required current at a given nominal ultrasonic frequency (i.e., the frequency of the apparatus with which it is used). The motoralternator is preferably designed to be so stable (minimal fluctuation of frequency during operation) as to be capable of. being used as a timing base. The energy derived from the motor-alternator 20 is supplied to the transducers 12 through the control section 14.

Standard commercial motor alternators have slow power buildup to full load and lacking adequate frequency stability and control for the described application. The motor alternator 20 in the described embodiment comprises a modied version, incorporating a hard-drive system (to eliminate belt slip), a differential epicyclic-type transmission (to eliminate frequency sag and instability), and switch gear (to achieve full power with adequate promptness). Thus, motor alternator 20 in the described embodiment comprises an l8-kva, 15,000 cycle-per-second alternator 62, driven by a constant-speed transmission 60, coupled to a 60-horsepower, 480-volt, 3-phase synduction motor 38, with frequency adjustment over a narrow range being provided through a hard-drive variaable-speed coupling unit 58 between the motor and alternator, and with power level control being effected by adjustment of the alternator field current.

The electrical high-power ultrasonic frequency energy derived from the motor-alternator 20 is alternately applied to the transducers 12 and the dummy load 22 (which may be a bank of resistors) by a switching cir-V cuit contained within the control section 14. A timer 24 provides timing for the switching operation.

Referring now to FIGURE 2, the energy source 18 is shown in greater detail. Energy source 18 is connected to a three phase line L1, L2 and L3 which carries three phase 60 cycle alternating current from a power station. A three pole switch 26 having fuses 28, 30 and 32 is provided. The three phase line L1, L2 and L3 is connected to a reduced voltage starter for the three phase motor section 38 of the motor-alternator 20.

A transformer 40 has its primary side connected to the L2-L3 phase of the incoming power. Thus, the secondary of transformer 40 produces a single phase output through the conductors 42 and 44 at 115 volts which is used in the control section to energize the timer 24. The 115 volt alternating current from transformer 40 is also convereted into direct current and used to control the reed switches in the switching circuit to be described below. The timer 24 controls the flow of direct current to the control magnets of the reed switches.

The transformer 46 is connected across one phase of the three phase input to motor 38 and provides electrical energy through the conductors 48 and 50 which, as will be explained below, is rectified in the control section and used to energize the magnetic field of the alternator.

` Conductors 52 and 54 are connected to the L1-L2 phase of the source and conduct electrical energy through the control section, where appropriate operating indicators and fuses 55 and 57 are provided and then to the polarizer 16. Thus, the conductors 52 and 54 conduct energy for polarizing the transducers 12 in the well known manner recognized in the art. The circuitry for polarizer 16 will not be described in detail since such circuitry is well known to those skilled in the art.

A suitable motor-alternator system 20 is illustrated in FIGURE 3. The system receives its energy from the three phase source L1, L2 and L3 through the starter 36 in the manner explained above. The motor 38 is mounted on a heavy supporting base 56 and drives a variable speed differential transmission 58. The variable speed differential transmission 58 in turn is mechanically coupled to a speed matching transmission 60 also mounted on the supporting base '56. The speed matching transmission 60 is coupled to a high frequency alternator 62. If desired, as for example in connection with a 30-kva. (100 horsepower) rather than a 15-kva. unit, the speed matching transmission 60 may be maintained at a constant temperature by using the oil pump 64 to pump cooling oil through it and the heat exchanger 66. The motor-alternator 20 constructed as above indicated may typically have a continuous duty rating such as 200 volts at 75 amperes and 14,55() to 15,450 cycles per second. The elements of the motor-alternator 20, including the motor 38, variable speed differential transmission 58, speed matching transmission 60 and high frequency alternator 62, as well as the oil pump 64 and heat exchanger 66, are all well known items available on the open market. The output of the high frequency alternator is single phase.

Referring now to FIGURES A and 5B, the conductors 48 and 50, which carry energy from the secondary of transformer 46, are shown connected to the primary of transformer 68. The secondary output of transformer 68 is connected to a full wave rectifier 70. Full wave rectifier 70 includes, in addition to the usual 4 diodes, the thyrector 72 which provides protection against surge currents. The output of full wave rectifier 70 is connected to the ammeter 74. Meter 74 may be a direct current meter having a range of 0 to 1 milliamperes. The meter is provided with shunt resistors 76 and 78 which in the indicated embodiment are 2,500 ohms, l watt and 2 ohms, 55 watts respectively. The output side of rectifier 70 not connected to meter 74 is connected to ground. A pair of conductors 80 and 82 carry current from the full wave rectifier 70 to the alternator 62 and provide energy for the alternators magnetic field.

Current is taken from the secondary of transformer at 115 volts and conducted by the conductors 42 and 44 to the timer 24 which in the preferred embodiment, is a cycle counter of any well known construction. The cycle counter-timer 24 is operated by the energy conducted from transformer 40.

Conductors 42 and 44 are also connected to a transformer 84 which reduces the voltage to 24 volts AC. The secondary of transformer 84 is connected to a full wave rectifier 86 whose output is connected through a lter consisting of inductor 87 and grounded capacitor 90 to the cycle counter-timer 24.

As shown in FIGURE l, the output of motor-alternator 20 is conducted by the coaxial cable 88, 90 to the control section 14 illustrated in FIGURES 5A and 5B. A shielded or coaxial cable 88, 90 is provided so as to prevent leakage of the 15 kc. current being conducted therethrough. The alternator high output line is connected through terminal 90 to the solid state switch through capacitors C160-C162. The grounded line is connected to the solid state switch through terminal 94. In the embodiment described, there are six transducers 12. Conductors L10I, L103, L105, L107, L109 and S111 go to high side, while conductors L102, 1.104, L106, L108, L110 and S112 go to ground.

The welding apparatus disclosed herein is also provided with a dummy load. The conductors leading to the grounded side of the dummy load and connected to conductor 90 are designated D-102, D104, D-106, D-108,

. D-110 and D-112. The conductors connecting the ungrounded side of the dummy load to the circuit are designated D-101, D-103, D-105, D-107, D109 and D*- 111. It is to be understood that although most of the conductors shown in FIGURE 5B are illustrated as a single line, they may in fact actually be representative of several conductors (example, 12 from terminal 94). However, since these are common current carriers they have been illustrated as a single conductor.

Ultrasonic frequency current in the conductor 88 is passed to the high power ultrasonic frequency switch and then to the transducer load through conductors L101- L109 and S111 or to the dummy load through conductors D101-D111, depending on the switching condition of the high power ultrasonic frequency switch. A general description of the function of the switch will be given, followed by a detailed description of its circuitry.

In the embodiment described, the ultrasonic switch is used to apply 15-18 kilowatts at 15 kilocycles to an array of six transducers being used in a welding operation. The particular welding operation employs 300 events every minute with the switch being required to turn the transducers on for .095-second and off for 0.105-second during each event. Although the switch is described in regard to this example, it will readily be recognized by those skilled in the art that the switch is completely capable of performing at a higher or lower rate depending upon the requirements of the system.

As explained above, the requirement was for transfer of power from one load to the other in about 0.2-second, i.e., at a minimum repetition rate of 300 events per minute, alternately to a welding array and to a resistive dummy load. It has been fou-nd that if the alternator is required to absorb this type of loading and unloading its speed varies with resultant frequency variation. This creates two problems. First, the transducer-coupling systems are not operating at optimum frequency for the complete weld interval, and secondly severe torsional stress reversals are applied to the coupling shafts of the motor-alternator. It has been found that these problems can be eliminated if the alternator is maintained under a constant load. Therefore, a dummy load (approximately 9 kilowatts in this instance) has been provided an a high power ultrasonic frequency switch developed to transfer power rapidly fr-om the dummy load to the welding load.

Overall control of the system is brought about by opera tion of the line switch 114 and the spot switch 116. Both the line and spot switch are operated 300 times per minute or 5 times per second by a mechanical transfer device which is simultaneously transferring units to be welded into position beneath the welding apparatus and removing said units when the weld has been completed. By way of example, the machine may be transferring rolled aluminum sheets which are to be seam welded into cylinders for manufacturing cans. Such a machine may first move a can into position beneath an ultrasonic welding device where it is spot welded on closure of the spot switch 116. The spot welded cylinder is then moved to a position beneath another ultrasonic welding device where the line or seam weld is provided. In actual operation, the apparatus will be line and spot welding different units at the same time. Thus, a unit is first spot welded at either end of the seam and then moved by the manufacturing mechanism to a position where it is line welded.

The mechanical closing of line switch 114 and spot switch 116 completes a circuit to ground from the full wave rectifier 86 through the timer 24, through the contact relays 120, 122, 124, 126 and 128.

Energization of contact relays 120-128 results in the simultaneous closing of two groups of five normally open contacts 134 and 135 and the simultaneous opening of two groups of six normally closed contacts 136 and 137 as well as the closing of two normally open contacts 138. In the preferred embodiment, the contacts may be reed switches which are energized to their respective opened and closed position by the application of a magnetic eld provided by relays 120-128. Such switches are well known and noted for their speed and reliability. In the embodiment shown, energization of contact relay 120 causes the closing of tive normally open contacts 134 and the ener gization of contact relay 122 results in the closing of five normally open contacts 135. Energization of contact relay 124 results in the opening of six normally closed contacts 136 and the energization of contact relay 126 results in the opening of six normally closed contacts 137. Contact relay 128 is associated with the spot switch 116 and closes the two normally open contacts 138 associated therewith.

The contacts 134-138 are part of the gate circuit for silicon controlled rectiers connected as an inverse-parallel, or back-to-back, static alternating current switch. The closing or opening of the reed switches either triggers or initiates blocking by the silicon controlled rectifier switches. The normally open contacts 134 and 135 are associated with silicon controlled rectifier switches which control the application of ultrasonic energy to the transducers of the line welding arrays. In the same way, the two normally open contacts 138 are associated with the trigger circuit of a silicon controlled rectifier switch connected as inverse-parallel, or back-to-back, static alternating current switch for the spot welding array. The twelve normally closed contacts 136 and 137 are similarly connected in the trigger circuit of silicon controlled rectifier switches for controlling application of energy to the dummy load.

A detailed description of the inverse-parallel, or backto-back, static alternating current switches is given below. It should be pointed out that although the present invention is -disclosed in an embodiment incorporating both a line and spot switch for overall circuit control, either more or less switches can be used. Thus, it is within this invention that only the line switch should be used and the circuitry associated with the spot switch eliminated. In the embodiment with which this invention is disclosed, the line and spot switch are not to be operated simultaneously, although both are to complete the operation within the required 0.9 second. In one operational sequence, the 0.2-second on period is divided into 360 elements. rI`he line switch may be on from 0 to 180 of these elements while the spot switch is on for 150 to 255 of these elements. For this reason, the line switch controls the two normally open contacts 138 apart from the ten normally open contacts 134 and 135. Thus, the transducer associated with the spot welders may be separately controlled.

As shown in FIGURES 5A and 5B, the normally closed contacts 136 and 137 are connected by the conductors 140 and 142 to the gate control circuitry represented schematically by the blocks 144, 146, 148, 150, 152 and 154. The trigger control circuitry 144-154 is connected to the 6D switches through the conductors 156 and 158. It will be noted that when the six SCR switches 6D are in the on condition, ultrasonic frequency current flows through the conductor 88, through the power factor correcting capacitors and 162, through the conductor 164, through the six 6D switches, through the conductor 168 to the the input side of the dummy load D101-D111. Thus, when the line and spot switches are open, energy from the alternator is directed to the dummy load.

Upon closing of the line switch 114, the contact relays 120, 122, 124 and 126 are energized thereby closing the contacts 134, 135 and opening the contacts 136, 137. The opening of contacts 136, 137 breaks the gating circuit thereby opening the six SCR switches 6D. The closing of contacts 134 and 135 completes the gating circuit for tive SCR inverse-parallel switches schematically represented as 5L in FIGURE 5B. The circuit is completed through conductor 88, power factor correcting capacitors 160 and 162, conductor 170, gate control circuits represented by the block diagram 172, 174, 176, 178 and 180, conductor 184, and conductor 186 to the line conductors L101-L109. The completion of this circuit turns on the inverse-parallel static alternating current switches 5L which then permit ultrasonic frequency current to flow through conductor 88, power factor correcting capacitors 160 and 162, conductor 164, switches 5L, conductor 188, and conductor 186v to the line transducers through conductors L10-1-L109.

Upon closing of the spot switch 116, a circuit is completed through one of the gate control blocks 182 to close the inverse-parallel SCR switch S. This completes a circuit for the ultrasonic frequency current to the spot welding transducer through conductor S111.

It should be noted that the pulse switches 5L, S and 6D are only schematically shown in FIGURE 5B. The purpose of FIGURES 5A and 5B is merely to illustrate the general circuit diagram in as simplified form as possible and thereby facilitate the understanding of the invention.

The cycle counter-timer 24 is connected through conductor 196 to the input side of the ultrasonic frequency current from motor-alternator 20. The cycle counter 24 is adjusted to count 1,350 cycles which equal .O9-second, the on time for the transducers. At the end of 1,350 cycles the cycle counter opens switches 190 thereby breaking the circuit to contact relays 120-128 and turning oif the transducers. The use of the cycle counters renders the on time of the transducers semi-independent of the line and spot switches 114 and 116. Thus, if the line and spot switches 114 and 116 should remain on beyond the weld period of .O9-second, the timer-cycle counter 24 will turn off the transducers. Of course, if the line and spot switches 114 and 116 open before the end of the 0.2-second on time, the transducers will be turned olf and the dummy load brought into the circuit.

Energy will be directed to the dummy load for 0.110- second, during which the timer 24 will reset itself and close the switch 190. At the same time, the mechanism operating the line switch 114 and spot switch 116 will reset itself so as to be prepared to close the switches at the end of the reset time period.

FIGURES 4A, 4B and 4C illustrate in detail the switch and timing circuit.

As shown in FIGURE 4A, the input ultrasonic frequency current from the motor-alternator 20 is passed through the power factor adjusting capacitors 160 and 162. In operating the apparatus, it was found that occasionally one of the static switches would not restore blocking and would operate for a few milliseconds past the preset weld time interval or until voltage was removed. The source of this problem was found in the nature of the welding array, which does not present constant electrical characteristic to the power source. Adjustment of the welding array to obtain a to 15% leading power factor cured the problem.

As shown, ultrasonic frequency current in conductor 88 is divided and conducted through six static alternating current switches which are normally in a blocking condition. These switches are S1D, S2D, SSD, S4D, SSD and S6D. Current passes through the switches and to the dummy load through conductors D101-D111. Thev current ofcourse passes through the dummy load and cornpletes the circuit to conductor 90 through conductors When the line switch 114 and spot switch 116 are closed, the contact relays 120', 122, 124, 126 and 128 are energized and the reed switches 134a-134e and 135g- 135e close in response to relays 120 and 122. Similarly, reed switches 136a-136f` and reed switches 137a-137f open in response to relays 124 and 126. Contact relay 128 is connected with spot switch 116 and controls the closing of reed switches 138a and 138b upon energization. So as to rapidly illustrate association with the particular static alternating current switch, the reed switches have been generally designated 1L, 2L, 3L, 4L, 5L and 6S. These reed switches 1D, 2D, 3D, 4D, 5D and 6D are associated with the static alternating current switches SID, S2D, S3D, S4D, SSD and S6D respectively.

The contact relay 120 operates the reed switches 134g- 134e. The contact relay 122 operates the reed switches 135a-135e. The contact relay 128 operates the reed switches 138a and 138b. The contact relay 124 operates the reed switches 136a-136f and the contact relay 126 operates the reed switches 137a-137f, It will be noted that the reed switches having like letters, such as 136c- 137e, are connected in parallel. As thus connected, operation of either switch will serve to open or close the circuit. The purpose in providing parallel switches is to ensure completion of the circuit on closing of the line switch 114 and spot switch 116. The problems of contact bounce and minor delay in operation of the contact relays are thereby avoided.

A complete circuit for one of the line switches and one of the dummy switches will now be described in detail. As all of the switches are identical in circuitry, the description of the circuitry for the remaining switches will be incorporated by reference. As previously explained, when line switch 114 and spot switch 116 close, a circuit is completed thereby energizing the contact relays 120-128 through switch 190 of timer 24. This closes reed switches 6S, lL-SL and opens reed switches 1D-6D.

The closing of reed switches 1L, completes a gate circuit through conductor 300, conductor 302, resistor 220, conductor 304, reed switch 1L, conductor 306, conductor 308, resistor 218, the load transducer connected to conductor L10I, and back to the alternator through conductors L202 and 90. Resistors 218 and 220 are connected to the gate terminals of the inverse-parallel con'- nected silicon controlled rectiers SCR 200` and SCR 201. The value of resistors 218 and 220 is chosen so as to bias SCR 200 and SCR 201 into a conducting condition upon completion of the circuit described above. Of course whether SCR 200l or SCR 201 is in the conducting state will depend upon whether the voltage across resistors 218 and 220` is negative or positive, and this is determined by the ultrasonic frequency alternating current. SCR200 and SCR201 are identical in type and are capable ofturning on and off at the required rate. Such silicon controlled rectiers are available on the market as by way of example, the General Electric SCR ZJ255D silicon controlled rectifier.

The inverse-parallel static alternating current switch using silicon controlled rectiers and described herein,Y is a modication of a static alternating current switch shown and described in SCR Manual, Third Edition, General Electric Company, 1964, pages 103 and 104.

As shown in FIGURE 4A, a diode D212 is connected in parallel with resistor 218 and a diode D213 is connected in parallel with resistor 220. The diodes D212 and D213 assure that the proper polarity of voltage is applied to the gate of silicon controlled rectiers SCR200 and SCR201.

When the switch S1L is biased into a conducting condition by the closure of reed 'Switches IL ,current then flows through conductor 312, `switch S1L',`condu`ctor 314, conductor 310, the transdu'ci-`""lo'ad connectedto conductor 'L101, land returns' v'to the source" 'throughl conductor L102 and conductori90.z

As soon v,as currentiiows, thetiiner V24 ebegins `to count cycles received through thepickup; lead""1'96. At the end of 1,350 cycles, -or any other tirnepe'riod, the.timer opens switch 190 thereby de-energizing contact rela'ys 120 and 122 and opening reed switches 134a and 135a. Resistors 218 and 220 therefore'are ro'longe'r"capable of applying a voltage ofproper polarity yto thesilicon controlled rectitiers SCR200`and SCR201, Thus switch SIL is restored to a blockingfcondition andl current no longer vtlows through the' transducers. 4 4

With theopening"` f's'witch 190` relays l122 Vand 124 de-energize and reed switches 1D`6D"close'. n l

' When reed switch 1D is restored touits normallylclosed position, a circuit is completed 'from' conductor l88thr'ough capacitors 160and 162, conductor 300, resistor 200, conductor '318, reed, switch 1 D, co'ndu,` ".ftor 320, toI resistor 202, conductor 322 to the dummy load connectedu'to conductor D101. This provides for gating the inverse-parallel silicon controlled rectifier switch into a conducting condition. In this instance, the switch is designated S1D. As shown, the conductor 316 connectsthe resistor 200 to the silicon controlled rectifier SCR 217. Similarly, the resistor 202 is connected to the gate of ,the silicon controlled rectiiier SCR 216 by conductors '.320 and 324.

vWith the static alternating current switch S1D gated on, ultrasonic frequency current now Hows from the conductor 88 through conductor 326, switch S1D, and conductorD101 to the dummy load.` i

Each of the resistors 200 and V202 is connected in parallel with a diode D200 and D201 respectively. These diodes provide blocking for the reverse current -flow in accordance` 4with the principles discussed above. i r

The foregoing has been a detailedl description of. the operation of switches S1Lan d SID so ashto provide cur-v rent either to a transducer or a dummy load accordance with the operation of the` lineswitch '114 and spot switch 116 and timer 24. Since each of the static alternating cur-` rent switches has identically thesaniecircuits, no additional description is provided. These' switches operate inv exactly the same way and with'exactly the same func-I tion. It should be pointed out,'how`ev''r, that trigger or gating control of switch S6S is provided by reed switch 6S. This switch in turn' is controlled by Contact re1a`y\128 f which is'energized by spot switch 11m-Therefore' spot switch 116 may operate at a diierenttime'sequence than line switch 114 and thereby e'nergizethey transducerconnectedto conductors. S111 and- S112 at a diierenttime.

Present day silicon controlled rectiiers, particularly thosenwith the highspeed switching.requirementsof -the present invention, do-not `have the `necessary, current-carrying capacity. To successfullycarry suicient current, lit is necessary to provide several parallelconnected, silicon controlled rectiers. However,` .when the rectiiiers were connected in parallel, it was found that the rst, silicon controlled rectifier to lire removed the drive from thev other silicon controlled rectiers. To overcome this vprobs` lem both the load carrying silicon controlled rectifier static switches and the dummy load static switches are divided into six individual electric segments, thereby permitting the use of the inverse-parallel static switches without misre. Six of the static switches furnish 18 kilowatts to the welding array, and six provide 9 kilowatts to the dummy load.

The segmented parallel connection is best shown in FIGURE B where the blocks 144-154 and 172-182 are shown connected to the common conductor 170, from which gating control for the static switches is provided.

Static switch S2L consists of SCR202 and SCR203. The'gating control circuitry for switch S2L consists of diodes D214 and D215 connected in parallel with resistors 221 and 223. Switch S3L comprises SCR204 and SCR205. The gating control circuit for switches S3L include diodes D216 and D217 connected in parallel with resistances 224 and 226. Switch S4L comprises silicon controlled rectiers SCR206 and SCR207. The gating control circuitry for switch S4L includes diodes D218 and' D219 connected in parallel with resistances 227 and 229. Switch SSL includes silicon controlled rectiiiers SR208 and SCR209. The gating control circuitry for switch SSL includes diodes D220 and D221 connected in parallel with resistances 230 and 232. Switch S6L comprises silicon controlled rectifers SCR210 and SCR211. The gating control circuitry for switch S6L includes diodes D222 and D223 connected in parallel with resistances 233 and 235.

In the dummy load control circuit, switch S2D includes silicon controlled rectiers SCR218 and SCR219. The gating control circuit for switch S2D includes diodes D202 and D203 connected in parallel with resistances 203 and 205. Switch S3D includes silicon controlled rectiers SCR220 and SCR221. The gating control circuit forswitch S3D includes diodes D204 and D205 connected in parallel with resistances 206 and 208. Switch S4D includes silicon controlled rectifiers SCR222 and SCR223. The gating control circuit for switch S4D includes diodes D206 and D207 connected in parallel with resistances 209 and 211. Switch SSD includes silicon controlled rectiers 212 and 213. The gating lcontrol circuit for-switch SSD includes diodes D208 and D209 connected in parallel with resistances 212 and 214. Switch S6D includes silicon controlled rectifiers SCR214 and SCR215. The gating control circuit for switch 86D diodes D210 and D211 connected in parallel with resistances 215 and 217.

A rapid, minimum-maintenance and durable means have been provided for switching kilowatts of energy at ultrasonic frequencies from one load to another. In the disclosed embodiment, the load equipment comprises an ultrasonic Welder and a dummy load. However, it is readily apparent that the switch is applicable to other types of loads. The ultrosonic Welder of the disclosed embodiment requires a minimum of 300 weld units per minute with a' cycle of 0.09-second on and 0.1l0second olf. The nominal frequency is 15 kilocycles. The switch incorporates a unique arrangement of high speed silicon controlled rectiers (General Electric Company SCRZIZSSD) The Silicon controlled rectiers are not parallelled, and to avoid misre by the first SCR removing gate drive from the other SCRs, the welding, array and dummy load have been divided into six individual electrical segments, thereby permitting the use of the inverse-parallel static switches: six to provide 18 kilowatts to the welding array, and six to provide 9 kilowatts to the dummy load.

As explained above, the load switching is necessary so as to maintain the motor-alternator under a continuous, if varying, load. Under these conditions, the motor-` alternator is capable of producing a stable frequency current.

The gate circuits of the welding array silicon controlled rectiers are completed by reed relays with normally open contacts, while the dummy load silicon controlled rectiers incorporate another bank of reed relays with normally closed contacts. The relay contacts are parallel with two contacts being used for each lstatic switch. This arrangement minimizes transfer time and contact bounce.

The inclusion of a Weld timing device, comprising a pre-set cycle counter 24, permits initiation by the material feeder and re-set during the interval that power is being delivered to the dummy load.

The value of the switch circuit elements used to achieve the foregoing results are as follows:

Diodes D200-D223 GE 1N540. Re-sistances 200-23'4 100 ohms, l watt 5%. SCR200-SCR223 GE ZJ255D.

The foregoing circuitry provides an ultrasonic Welder using high speed silicon controlled rectiers as circuit elements of a high frequency static switch, and permits continuous operation with the motor-alternator power supply.

The present invention may be embodied in other specic forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specication as indicating the scope of the invention.

I claim:

1. An ultrasonic frequency switch comprising a first set of static alternating current switches, a second set of static alternating current switches, each said set of swtitches including a plurality of two terminal static alternating current switches, one terminal of each switch in said first and second set being commonly connected to each other and to the other set, means for connecting said common connection to a source of ultrasonic frequency current, means for connecting the other terminal of each static switch in said first set to one of a plurality of first loads, means for connecting the other terminal of each static switch 'in said second set to one of the plurality of second loads, means for controlling whether said first Set of static lswitches is in a conductive or non-conductive condition, means for controlling whether said second set of static switches is in a conductive or non-conductive condition, and means for rendering said iirst set of switches conductive when said second set of switches is non-conductive and rendering said iirst set of switches non-conductive when said second set is conductive.

2. An ultrasonic frequency switch in accordance with claim 1 wherein each said alternating current static switch in said rst and second sets includes a pair of inverse-parallel connected silicon controlled recti-ers, one terminal of said rectiiiers being connected to one of said loads, and the other terminal of said rectiers being connected to said common connection.

3. An ultrasonic frequency switch in accordance with claim 1 wherein each said static alternating current switch includes a pair of inverse-parallel connected silicon controlled rectiers, said controlling means includingy a gate control circuit for said silicon controlled rectifiers, said gate control circuit including gate switch means fo-r electrically connecting the gate of one of said pair of silicon controlled rectiers to lthe gate of the other of said pair of silicon controlled rectifiers, the gate switch means for static alternating current switches in said first set being normally on and the gate switch means for the static alternating current switches in said second set being normally closed, and means for substantially simultaneously closing said normally open gate switches and opening said normally closed gate switches.

4. An utrasonic frequency switch in accordance with claim 3 wherein said gate switches are reed switches, and said means for simultaneously closing said normally open gate switches and opening said normally closed gate switches includes magnetic means for controlling said reed switches.

5. An ultrasonic frequency switch in accordance with claim 1 wherein said plurality of iirst loads are ultrasonic transducers, and said plurality of second loads are dummy loads.

6. An ultrasonic frequency switch in accordance with claim 1 wherein said means for controlling whether said first set of static switches is conductive or non-conductive and said means for controlling whether said second set of static switches is conductive or non-conductive includes a time responsive switch.

7. An ultrasonic frequency switch in accordance with claim 1 wherein said means for controlling whether said lirst set of static switches is conductive or non-conductive and said means for controlling whether said second set of static switches is conductive or non-conductive includes a time responsive switch, said time responsive switch including a cycle counter for counting cycles of ultrasonic frequency current ilowing in the switch circuit, said cycle counter including means to 4cont-rol said time responsive switch in response to a predetermined number of cycles counted.

8. An ultrasonic frequency switch in accordance with claim 1 wherein each said static alternating current switch includes a pair of inverse-parallel connected silicon controlled rectiiiers, said controlling means including a -gate control circuit for said silicon controlled rectifiers, said gate control circuit including gate switch means for electrically connecting the gate of one of said pair of silicon controlled rectifiers to the gate of the other silicon controlled rectiiiers, said -gate switch means for the static alternating current switch in asid rst set 4being normally on and said gate switch means for the static alternating current switch in said second set being normally closed, said control means including a switch responsive to a predetermined number of cycles counted by a cycle counter for simultaneously closing said normally on gate switches and opening said normally closed gate switches.

9. A method of intermittently providing ultrasonic frequency energy to a plurality of ultrasonic frequency transducers including the steps of sequentially rendering a static alternating current switch for each transducer in a conductive and nonconductive condition at a switching rate greater than or equal to an integer number of times per second, intermittently providing energy to a plurality of dummy loads by rendering a plurality of static alternating current switches non-conductive and conductive at a rate equal to the switching rate of said static alternating current switches for said transducers, rendering said transducer static switches conductive when said dummy load static switches are nonconductive, and rendering said transducer static switches nonconductive when said dummy load static switches are conductive.

10. An ultrasonic apparatus comprising means for generating ultrasonic frequency current and means for controlling the flow of ultrasonic frequency current alternately to a plurality of ultrasonic transducers and to a dummy load, said control means including a rst and second set of static alternating current switches, each said set of switches including a plurality of two terminal static alternating current switches, one terminal of each switch in said first and second set being commonly connected to each other and to one terminal of said source of ultrasonic frequency current, one terminal of each of said transducers and each of `said dummy loads being connected to the other terminal of said source of ultrasonic frequency current, the other terminal of each of said transducers being connected to the other terminal of one of each of said static alternating current switches in said tirst set, the other terminal of each of said dummy loads being connected to the other terminal of each of said static switches in said second set, each said static alternating current switch including a pair of inverse-parallel connected silicon controlled rectiers, gate control means for said silicon controlled rectiiiers, said gate control means for each static alternating current switch including at least one reed switch, and means for alternately closs ing the reed switches connected with said first set of static alternating current switches and for simultaneously opening the reed switches associated with said second set of alternating current switches, said means including a switch sequentially opening and closing to energize a magnetic eld for affecting opening and closing of said reed switches, said means further including a cycle counter and a switch responsive to a predetermined number of counted cycles, said last mentioned switch being connected to said magnetic means for deenergizing the same.4v

11. An ultrasonic frequency switch for switching ultrasonic frequency energy between first and second loads comprising a rst static alternating current switch, a second static alternating current switch, said first static alternating current switch being connected between a source of ultrasonic frequency and said first load, said second static alternating current switch Ibeing connected between said source of ultrasonic frequency energy and said second load, control means for rendering said rst static alternating current switch conductive and non-conductive at a predetermined switching rate, said control means rendering said second static alternating current Iswitch nonconductive and conductive at the same rate as said first static alternating current switch so that said first static alternating current switch is conductive when said second static alternating current switch is non-conductive and said irst static alternating current switch is non-conductive when said second static alternating current switch is conductive.

12. An ultrasonic frequency switch in accordance with claim 11 wherein said static alternating current switches are silicon controlled rectiiiers connected in inverse parallel relation.

13. An ultrasonic frequency switch in accordance lwit claim 11 wherein said first load is an ultrasonicftr psducer and said second load is a dummy resistive la 14. An ultrasonic frequency switch comprising a first static alternating current switch, a second static alternating current switch, each of said first and second static alternating current switches including a two terminal static alternating current switch, one terminal of each of said rst and second switches being commonly connected to each other, means for connecting said common connection to a source of ultrasonic frequency current, means for connecting the other terminal lof said rst static alternating current switch to a first load, means for connecting the other terminal of said second static alternating current switch to a second load, first switch control means for controlling whether said iirst switch is in a conductive or non-conductive condition, second switch control means for controlling whether said second switch is ina conductive or non-conductive condition, and initiating means for controlling said rst and second switch control means so that said rst switch is conductive when said second switch is non-conductive and said iirst switch is non-conductive when said second switch is conductive.l l

References Cited UNITED STATES PATENTS 3,205,378 9/ 1969 Kline 307-252 X 3,258,613 6/ 1966 Felcheck et al. 307-252 3,263,157 7/1966 Klein 323-24 X 3,284,667 ll/l966 Harris et al 307-252 X 3,337,741 8/ 1967 Mislan 307-41- ROBERT K. SCHAEFER, Primary Examiner T. B. J OIKE, Assistant Examiner Us. C1. Xn.

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