GB2127587A

GB2127587A - Ultrasonic welding control

Info

Publication number: GB2127587A
Application number: GB08325804A
Authority: GB
Inventors: George C Kramer; Eric G Quist; Richard F Schoonmaker
Original assignee: Branson Ultrasonics Corp
Current assignee: Branson Ultrasonics Corp
Priority date: 1982-09-27
Filing date: 1983-09-27
Publication date: 1984-04-11
Also published as: GB8325804D0; JPS5983615A; DE3334066A1

Abstract

An ultrasonic welding apparatus e.g. for plastics materials, includes a microprocessor for sequentially controlling the operation and monitoring the status of the welder. The microprocessor controls operations of a plurality of actuators 10 and power supplies. In addition, the status of the apparatus and the power provided from each power supply is monitored and displayed on units 22. Alarm indicators 36, 38 are activated in the event of incorrect welder operation or if the power supplied to a converter is outside a predetermined range of power levels. <IMAGE>

Description

SPECIFICATION Microprocessor controlled ultrasonic welding apparatus Background of the invention The invention refers to a microprocessor controlled ultrasonic welding apparatus wherein the sequence of operating and the monitoring of the status of an ultrasonic welding apparatus are achieved by means of a microprocessor. More specifically, this invention concerns an ultrasonic welding apparatus having a plurality of actuators which are independently controlled with regard to specific parameters by means of a single microprocessor.

The use of ultrasonic energy for welding plastic materials, inserting, staking, swaging and degating thermoplastic parts and sealing thermoplastic fabrics and films is well known. Ultrasonic welding apparatus for performing these operations is disclosed, for instance, in U.S.

Patent No. 3,790,057 issued to S. E. Jacke et al, dated February 4, 1974 entitled "Ultrasonic Apparatus". The basic ultrasonic welding apparatus comprises actuation means, such as dual palm button switches for activating the apparatus, a power supply for converting line power to a high frequency electrical signal, a piezoelectric converter for converting the high frequency electrical signal into high frequency mechanical energy, and a pneumatic system for causing the converter and a tool or horn coupled to the end of the converter to be for a predetermined time interval in forced engagement with a workpiece to be welded. The combination of the pneumatic system and the converter is commonly referred to as an actuator.

Ultrasonic welding apparatus of the type described includes adjustable control means for setting a predetermined weld time and hold time for accomplishing the welding operation. The weld time is the time interval during which high frequency mechanical energy, i.e. ultrasonic energy, is transferred from the horn to the workpiece. The hold time is defined as the time interval during which pressure is applied to the workpiece by the horn after termination of the weld time. In most apparatus, a trigger means is included to sense when a predetermined engagement force between the horn and the workpiece is manifest and responsive to the predetermined engagement force having been achieved the weld time interval commences.

It is also known to gang ultrasonic welding apparatus to perform multiple welds on the same workpiece. Usually several stand-aione units of the type described above are connected for independent operation in a timed sequence.

In the present invention, an ultrasonic welding apparatus having a plurality of actuators is controlled by a single microprocessor. In addition, functions such as power sensing and self diagnosis are accomplished by means of microprocessor software. The system is completely modular and expandable while being controlled by a single microprocessor. Any number of power supply modules and actuator/converters may be added to the system under the control of a single master control module which controls slaved additional control modules as required.

A principal object of this invention is, therefore, the provision of a microprocessor controlled ultrasonic apparatus.

Another important object of this invention is the provision of self diagnosis of an ultrasonic welding apparatus.

A further object of this invention is the provision of sensing the instantaneous power provided by each of a plurality of power supplies to associated converters and horns, and the storing of each of the peak power values sensed until the succeeding weld cycle.

Further and still other objects of this invention will be more readily apparent when the following specification is read in conjunction with the accompanying drawings.

Brief description of the drawings Figure 1 is a view of power supply modules and a control module in combination with a plurality of actuators, and Figure 2 is a schematical electrical circuit block diagram of the microprocessor circuitry contained in the control module.

Detailed description of the invention Referring now to the figures and Figure 1 in particular, there is shown a table upon which a plurality of four actuators 10 are securely fastened via suitable support means. Each of the actuators incorporates an ultrasonic converter 12 (partially visible), such as the converter described and illustrated in U.S. Patent No. 3,524,085 issued to A. Shoh, dated August 11, 1 970 entitled "Sonic Transducer", for converting high frequency electrical energy into mechanical energy. Coupled to the output end of the converter at an antinodal region of longitudinal motion of the vibratory energy travelling through the converter is an ultrasonic horn 14. The horn is dimensioned to be resonant as a half wavelength resonator at the system frequency.Typically the horn and converter are dimensioned to be resonant at a frequency in the range between 10 and 100 kHz, and particularly, at a frequency of 20 kHz or 40 kHz.

Each actuator includes a pneumatic motion system which causes the horn and converter assembly to travel from the raised position shown downward toward the workpieces W1 and W2 to be welded. The workpieces are disposed upon a suitable anvil 1 5. Each actuator 10 also includes an adjustable trigger means which senses the presence of a predetermined engagement pressure between the horn frontal surface and the workpieces, see for instance, U.S. Patent No.

3,493,457 issued to J. Jugler dated February 3, 1970 entitled "Control Circuit for Tool Driven by Sonic Energy". When the predetermined engagement force is sensed, a trigger switch signal is provided which commences the system weld time and hold time as described hereinafter.

Actuators of the general type described are commercial items available from Branson Sonic Power Company, Danbury, Connecticut.

The actuators are adjustable with regard to vertical stroke and angle to the workpieces in order to conform to the contour and dimensions of the workpieces. The actuators may also be used on a rotary table or with multiple horns as the application requires. In a further modification, a single pneumatic system may be used to drive a plurality of converters.

The power supply modules and control panels are contained in drawers of a remotely disposed cabinet 20. One drawer contains a control panel 16 and one or more power supply modules 28.

Additional drawers containing power supply modules 28 can be added with all the power supply modules 28 being controlled by the same control panel 16. The control panel 16 includes a microprocessor, an adjustable hold time control 26, a store mode switch 24, a power switch 18 and sequence indicators 22.

The on/off power switch 18 on the panel 16 activates the unit. A series of seven indicators 22 indicates the status of the apparatus for diagnostic purposes. The store mode switch 24 is used in conjunction with power indicating means on each power supply module 28 for storing of the peak power supplied to the actuator 10 as will be described.

The hold time control 26, shown as adjustable digital thumbwheel switches, is adjusted by the operator to a predetermined hold time common to all of the actuators 10 measured from the time the last power supply module 28 completes its weld cycle. At the conclusion of the predetermined hold time all the actuators 10 cause, via their respective pneumatic systems, the horns 14 to be removed from contact with the workpieces thereby allowing the operator to remove the welded product and insert subsequent workpieces to be welded. While the controls are shown as digital switches it will be apparent that other controls, such as potentiometers, may be used equally as well.

There is one power supply module 28 associated with each actuator 10. In each drawer of the apparatus there is a rectifier and regulator for preconditioning the line power. Each power supply module 28 includes a power supply circuit for converting the preconditioned line power to a high voltage high frequency electrical signal for activation of a respective converter 12. An LED bar display 30, divided into twenty segments, displays the instantaneous power provided by the particular power supply module to the associated converter 12 for monitoring welding power by the particular converter/horn assembly. Two adjustments 32, 34 are provided on the module 28 for setting the upper power level and lower power level of a power window range.As will be explained, a power window alarm indicator 38 is actuated if power outside the predetermined power window range is provided by a respective power supply module 28 to an actuator 10. Each power supply module 28 further includes an adjustable weld time control 40 for setting a predetermined weld time interval during which interval power is provided from the respective power supply module to the associated converter 12. When the converter 12 is activated and a horn 14 coupled to the converter is in contact with a workpiece, welding takes place. In addition, an overload alarm indicator 36 provides an alarm indication if the power supply is overloaded by providing excess power or if the power supply oscillatory circuit shifts to a frequency outside the normal operating frequency range. A typical overload circuit is described in U.S.Patent No. 3,946,280, issued to E. Quist, dated March 13, 1976 entitled "Overload Protection Circuit".

A portion of the microprocessor circuitry contained in control panel 16 is shown schematically in Figure 2. In a preferred embodiment the microprocessor 50 is a model 8039 microprocessor manufactured by Intel Corporation. The microprocessor 50, in combination with the crystal time base 51 and an internal timer, controls all timing and logical functions under the control of the program in the program storage module 58. The operational program is stored in a PROM or preferably an EPROM such as a model 2716 manufactured by Intel Corporation. The microprocessor 50 interfaces with the various display and control sections by means of a parallel interface 52 and serial interface 54. An I/O decoding logic module 56 completes the control circuitry. A suitable bus driver is included to drive the power supply interface circuitry located on each power supply module 28.Address and data signals are communicated between the control components by means of suitable bus lines. While specific components manufactured by Intel Corporation have been listed, other microprocessors and associated circuitry manufactured by Intel or others may also be used.

Before operation of the welding apparatus commences, the hold time is set on hold time control 26. Each power supply module 28 is then adjusted by setting weld time controls 40 and by setting the power maximum level adjustment 32 and power minimum level adjustment 34 for providing a predetermined power window range.

Each power supply module is connected via analog multiplexer 62 and analog-to-digital converter 64 to the microprocessor 50. By virtue of the EPROM 58 the weld time signals are sensed through the serial interface 54 and the power level signals sensed from each power supply module is fed through the multiplexer 62 and analog-to-digital converter 64 for processing by the microprocessor 50.

An electrical cable connects the circuitry in cabinet 20 to each of the actuators 10. When welding is to be commenced, an actuation signal is provided via the parallel interface 52 as an input to the microprocessor 50. In a manually loaded arrangement the operator must simultaneously depress dual palm button switches (not shown) to activate the welder and the microprocessor control. The operator cannot remove either hand from the switches until all the trigger switches have provided a signal to the microprocessor. In the event of a premature removal of either one or both of the hands, the system will abort. In an automatic workpiece feed arrangement, a suitable actuation signal indicative of the workpiece being disposed for welding will be provided to the microprocessor.In an alternative arrangement, a pre-trigger signal will be provided to the microprocessor prior to the horn having attained a predetermined engagement force with the workpiece.

Upon receipt of the actuation signal the microprocessor 50, under the control of the program stored in EPROM 58, provides a signal to the solenoid control 60 which transmits a corresponding signal to the solenoid drives in the pneumatic systems of each actuator 10. In response to the solenoid drive signals each horn 14 is urged into forced engagement with the workpiece W1. When the predetermined engagement force between the horn and workpiece W1 is achieved, trigger switch signals are transmitted from the actuators to the parallel interface 52. Upon receipt of the actuation signal and all the trigger switch signals, each power supply 28 is activated responsive to its associated trigger switch for energizing its associated converter 12. Upon activation of a respective power supply the weld time interval of the respective power supply is measured.At the completion of a respective weld time interval the particular power supply 28 is deactivated. The hold time interval is measured commencing upon completion of the last weld time interval. At the end of the hold time interval another signal from microprocessor 50 to the solenoid control 60 causes all the actuators 10 to raise the horns 14 from the workpiece W1.

During the welding cycle, the microprocessor 50 monitors the instantaneous power level of each power supply module 28. The power level signals are received by microprocessor 50 via multiplexer 62 and analog-to-digital converter 64 from each power supply module 28. A visual indication of the instantaneous power monitored is displayed on the respective bar display 30.

When the switch 24 is in the store mode, the maximum power is stored on the display 30 until the next weld cycle is initiated. If a power level outside the predetermined power window range is measured, a signal is provided from the serial interface 54 to illuminate the respective power window alarm indicator 38. During the welding cycle a plurality of sequence indicators 22, such as the seven lights shown, illuminate in sequence according to programmed instructions to provide for diagnosis of the system.For example, a first light illuminates when the actuation signal is received, a second light illuminates when the solenoid is activated, a third light illuminates when a power supply is triggered, a fourth light illuminates when all the trigger switches are closed, a fifth light illuminates at the beginning of the hold cycle, a sixth light illuminates at the end of the hold cycle, and a seventh light illuminates when any system fault occurs or any overload alarm 36 or window alarm indicator 38 is activated. If there is an incomplete weld cycle, the last sequentially illuminated light 22 remains lit to aid in trouble shooting and diagnosing the system fault.

The sequence of operation is as follows: the hold time control 26 and each weld time control 40 are adjusted to respective predetermined values and the store switch 24 is set to store or non-store mode. The power maximum and minimum level adjustments 32 and 34 are set for each power supply. The dual palm button switches are simultaneously depressed or an automatic actuation signal is provided to the microprocessor 50. The solenoid control 60 is then activated for lowering the horns toward the workpiece. As the trigger switch in each actuator provides a trigger signal indicative of a predetermined engagement force between a respective horn and the workpiece, the information is received and processed by microprocessor 50.

When the trigger switch signals are received the weld time intervals of the respective power supply modules 28 commence and the power supplies are activated for energizing each converter 12 which, in turn, provides ultrasonic energy to the horns 14 coupled to the converters 12 for welding the workpieces. At the conclusion of a respective weld time interval the respective power supply module 28 is deactivated. When the weld time intervals of all the power supplies 28 are concluded, the hold time interval commences. At the end of the hold time interval, after the workpieces are welded, the solenoid control 60 receives a signal from microprocessor 50 causing the pneumatic system in each actuator to raise all the horns 14 from the workpieces.

During the weld cycle, the instantaneous power of each power supply module is measured and displayed on the associated indicator 30. If the store mode is selected by switch 24, the peak value of the applied power of each power supply module 28 is stored on the respective display 30 until the next weld cycle.

The overload circuit is part of the power supply module. In the event of an overload condition, the overload alarm indicator 36 on the respective power supply module 28 is illuminated.

If the measured power level for a power supply module 28 is less than the power window minimum level or in excess of the power window maximum level, the respective power window alarm indicator 38 will be illuminated.

Concurrently, with the operation of the apparatus, sequence indicators 22 will be illuminated as described above.

After the part is welded and no power window alarm or overload alarm indicator is activated, the apparatus is reset, the welded part is removed and new workpieces are placed in position for being welded. Upon actuation of the dual palm buttons or receipt of an actuation signal the next welding cycle commences.

While a preferred embodiment of a microprocessor controlled ultrasonic welding apparatus has been described and illustrated it will be apparent to those skilled in the art that modifications and variations thereof may be made without deviating from the broad principle of the invention.

Claims

1. A microprocessor controlled ultrasonic welding apparatus comprising: a plurality of actuators each including an ultrasonic converter and a pneumatic system for causing said converter to travel toward and away from workpieces to be welded; a plurality of power supply means each being coupled to a respective one of said actuators for selectively energizing an associated one of said converters; actuation means for providing a first signal for commencing welding; trigger switch means for providing a second signal from each of said actuators upon the occurrence of a predetermined condition for commencing welding; adjustable weld time means associated with each of said power supply means for providing a respective weld time signal for each of said power supplies;; adjustable hold time means for providing a signal indicative of a predetermined hold time for said actuators, and microprocessor means coupled to said actuators, power supply means, actuation means, trigger switch means, adjustable weld time means and adjustable hold time means for: a. providing a second signal to initiate said pneumatic systems responsive to receipt of said first signal; b. providing a signal to activate said power supply means responsive to the receipt of said first signal and said second signals for selectively providing a high frequency electrical signal to each of said converters; c. providing a signal to deactivate a respective power suppply means after said respective weld time; d. providing a signal to deactivate said pneumatic systems after said predetermined hold time; and e. controlling the sequence of the signals in steps a to d above.

2. A microprocessor controlled ultrasonic welding apparatus as set forth in claim 1, further including: power indicating means for sensing and displaying the power supplied by each of said power supply means to a respective converter during welding, and said microprocessor being coupled to said power indicating means for causing said display.

3. A microprocessor controlled ultrasonic welding apparatus as set forth in claim 2, further including storage means for causing said display to store the peak value during each weld cycle.

4. A microprocessor controlled ultrasonic welding apparatus as set forth in claim 2, further including: power level adjustment means for setting predetermined power levels of power to be supplied by each of said power supply means during welding, and said microprocessor providing a signal when said power exceeds or is less than said predetermined power level.

5. A microprocessor controlled ultrasonic welding apparatus as set forth in claim 1, further including: diagnosis means for indicating the status of the welding apparatus responsive to signals from said microprocessor.

6. A microprocessor controlled ultrasonic welding apparatus as set forth in claim 5, said diagnosis means comprising a plurality of indicators which are activated in a predetermined sequence responsive to the condition of the welding apparatus.

7. A microprocessor controlled ultrasonic welding apparatus having a plurality of actuators and which is controlled by a single microprocessor.

8. An apparatus according to claim 7 in which power sensing is accomplished by means of microprocessor software.

9. An apparatus according to claim 7 or 8 in which self diagnosis is accomplished by means of microprocessor software.

10. An apparatus according to any one of claims 7 to 9 substantially as hereinbefore described with particular reference to figures 1 and 2.