SU961902A1 - Method of automatic control of ultrasonic welding acoustic mode - Google Patents

Description

The invention relates to automatic control of technological regimes in ultrasonic processing and welding methods for various products in mechanical engineering and electronics and can be used in medicine during intraocular operations associated with dissecting the vitreous pathological structures of the body and coagulation of the retina to restore the visual function of the eye.

A known method of ultrasonic welding, in which acoustic contact is created between the instrument and the parts being joined, applies a force of normal pressure, excites pulsed ultrasonic welding vibrations}

The disadvantage of this method is the low quality of welding, which is explained by the lack of automatic control and monitoring of the welding mode under the action of various disturbances. ..

The closest in technical essence to the present invention is a method for automatically controlling the acoustic mode of ultrasonic welding, based on the determination

the quality factor of the oscillating system, creating a tight acoustic contact between the instrument and the connected elements by applying a normal pressure force, initiating periodic, controlled by the duration of the pulse ultrasonic welding vibrations and controlling the energy of the oscillations;

10 depending on the variation of the HarpySKji oscillatory system and its goodness-. ; 2J.

The disadvantage of this method is the low quality of welding,

15 determined by the absence of stabilization of heat radiation during welding.

The purpose of the invention is to improve the quality of welding due to the stabilization of the intensity of thermal radiation.

20 and providing the desired energy in the welding zone under the action of various disturbances, as well as automating the monitoring of the acoustic contact of the instrument and the connected elements.

25

The goal is achieved by the fact that, according to the method based on determining the quality factor of the oscillatory system, the creation of a tight acoustic contact between

30, using an instrument and connected elements, by applying a force of normal pressure, excitation of periodic, adjustable in duration pulsed ultrasonic welding oscillations and control of the energy of the oscillations depending on the change in the load of the oscillating system and its quality factor, after each pulse of excitation of the ultrasonic welding oscillations system for the number of cycles of its free oscillations and the measured value of the damping factor regulate the duration s subsequent excitation pulse ultrazvukovyhsvarochnyh oscillations.

In addition, before excitation of ultrasonic welding vibrations, complex low-power ultrasonic vibrations are formed, the redistribution of the nodes and antinodes of the longitudinal components of the ultrasonic oscillatory displacements in the waveguide part of the instrument, and the magnitude of the redistribution of the nodes and

: The antinodes determine the quality of the acoustic contact, after which they form ultrasonic welding oscillations with a given energy.

FIG. 1 shows a block diagram of a device that implements this method; in fig. 2 - voltage diagrams at the output of functional units of the device.

The evaluation of temperature in the contact zone and automatic stabilization of the intensity of thermal radiation are based on the peculiarities of free oscillations damping under viscous, dry (positional) and boundary friction, as well as changing the Q-factor of the main interconnected mechanical circuits as a function of changing the forces of normal pressure during welding, for example coagulation of the retina in the field of medicine. Variations of the force of the normal pressure are among the main destabilizing factors of temperature in the contact zone and are displayed as a function of changes in such Interconnected basic values as the damping factor, absorption coefficient, quality factor of interconnected mechanical circuits, and the number of free cycles; most varied character changes.

The concept of the quality factor of a mechanical circuit in this case is taken by analogy to electric circuits and is determined by the ratio of the total energy stored in an oscillating: system for a certain period of time to the energy given to overcome losses and payload. The magnitude is inverse to the goodness, there is a loss coefficient

The quality factor is related to the temporal attenuation coefficient in amplitude, the logarithmic decrement in the decay of free oscillations and the number of oscillation cycles, the amplitude of which damped free oscillations amount to a geometric or arithmetic progression and depends on the nature of the friction forces.

When, for example, coagulation of the retina is performed under conditions of viscous friction, the absorption coefficient in the contact zone does not depend on the amplitude of oscillations. In this case, the logarithmic decrement of the damping of the free oscillations is constant, and the successive amplitudes of the damped oscillations form a geometric progression.

In dry friction, the absorption coefficient depends on the amplitude, preferably, the logarithmic decrement is not constant, and the successive amplitudes of the damped ultrasonic oscillations do not constitute a geometric progression.

However, if the frictional force is proportional to the contact pressure, which, in turn, is proportional to the displacement (positional friction), then the decrement of oscillations is constant, and therefore, exactly as with viscous friction, the successive amplitudes in this case are geometric progression. ,

Thus, the damping factor varies with the quality factor of the mechanical circuit during load aariation. The change over time of the number of cycles —free oscillations directly related to the quality factor of the main circuit of the system, reflects the law of change in the efforts of the normal pressure — which is the basis for automatic control and stabilization of the intensity of thermal radiation in the contact zone.

The proposed method of automatic control of the acoustic mode of ultrasonic welding is carried out as follows.

A device that implements the method provides two basic modes of automatic control of ultrasonic vibrations: during ultrasound cutting of materials and during their ultrasonic welding, when dissecting the pathological structures of the vitreous body of the eye and during coagulation of the retina.

A device that implements this method (Fig. 1) contains a typical ultrasonic generator, consisting

from the master oscillator 1, the amplitude amplifier 2, the amplifier 3 power and system 4 stabilization of the resonant frequency and a given amplitude electronic switch 5, which provides alternate connection of the piezoelectric transducer 6 either to the excitation circuit of the ultrasonic vibrations or to the registration circuit (measurement) of the number of free oscillations cycles, Piezoelectric transducer b for exciting ultrasonic vibrational displacements of the working part of the instrument through an exponential concentrator 7, transducer 8 acoust natural emission, control amplifier 9 and control signal generation. The detection circuit of the number of cycles of free oscillations includes a signal amplifier 10, a detector 11, a limiter amplifier 12, an electronic switch 13, a controlled trigger 14, a counter 15, a code-voltage converter 16, a comparison circuit 17, an amplifier 18, a sawtooth generator 19 voltage, the threshold element 20, the differentiating element 21, as well as the block 22 of automatic time control of the impact of powerful ultrasonic vibrations.

To enhance and simultaneously transform the longitudinal vibrational displacements excited by the transducer 6 on the working part of the tool, the exponential concentrator 7 is made with twisted grooves connected by a jumper, like a drill, which, in addition to the amplification of ultrasonic vibrations, transforms the longitudinal vibrations into complex vibrations the predominance of the torsional component.

Let us consider an example of the implementation of the proposed method in relation to eye surgery, since it is intraocular operations that place greater demands on the reliability and accuracy of controlling the acoustic mode of ultrasonic welding, for example, when the retina coagulates to the vascular and sclera to restore the visual function of the glaa.

The inclusion of predetermined low-power complex ultrasonic vibrations of 3-5 µm excludes molecular coupling and use them as a signal carrying information about the tool loading and the moment of switching on complex powerful vibrational displacements with an amplitude of 35-40 µm while creating a load on the tool, for example. , when dissecting the dense pathological structures of the vitreous body, are performed automatically, for which purpose they register

the redistribution of nodes and antinodes of the longitudinal and bending components of the oscillatory displacements by means of a converter 8 mounted on the waveguide part of the tool, and

form the control signal.

 In order to form an oscillation amplitude control signal, the signal of the converter 8 is amplified by the control amplifier 9, and with its help, a gain control signal of the amplifier 2 is generated.

Powerful ultrasonic vibrations on the working part of the Instrument (with an amplitude of 2A - 35-40 µm) destroy

5 dense vitreous structures

body, eliminating (reducing) thereby the load on the working part of the tool, and, consequently, the control signal on

The Q output of the transducer is 8, and low-power ultrasonic vibrations (with an amplitude of 2A - 3-5 µm) are switched on again in the system.

Thus, the moment of inclusion

5 powerful ultrasonic (US) oscillations, the time of their action until the complete guaranteed cutting of the strands (unloading) is determined automatically by means of a feedback circuit consisting of a transducer

0 8 and the amplifier 9 control and the formation of the control signal.

In contrast to the cutting mode of various materials (in this case, dissection of dense structures of the vitreous body) during the welding process (coagulation of the retina), the load on the working part of the tool always exists due to the presence of an increase in the normal pressure required

0 to create a tight acoustic contact. In this connection, in the process of retinal coagulation (welding), the moment of switching on powerful ultrasonic vibrations is carried out automatically by means of

5 of the circuit formed by blocks 8 and 9, similar to the cutting-cutting mode, and the time of action of powerful oscillations followed by automatic shutdown is controlled by

contour of the system formed by blocks 10-22.

Tight acoustic contact of the surfaces to be welded is created by applying normal pressure forces through a working tool equipped with an excitation oscillator 6 and a register 8 and redistribution of nodes and antinodes of the longitudinal component of the oscillatory movements

0 parts of the tool with load variation. Moreover, depending on the technological capabilities, requirements and conditions of welding, the creation of a dense acoustic contact can produce, without excitation, on the working part of the tool, low-power oscillations with an amplitude of 3-5 µm. In such a case, the moment of switching on high-power ultrasonic vibrations is carried out manually or, according to a predetermined program, acting on the control amplifier 9, which controls the setting of the gain factor of the multi-voltage amplifier 2. Time-to-power powerful ultrasonic vibrations, determining the energy required to form a reliable connection, are monitored by the unit 22 for recording the times of exposure to powerful ultrasonic vibrations, with which, after a predetermined time, powerful ultrasonic vibrations are automatically turned off by the amplifier 9 controlling the amplifier 2 tightness.

In order to stabilize the intensity of thermal radiation in the contact zone with varying normal pressure forces (pressure), the excitation of powerful ultrasonic vibrations is carried out periodically in a pulsed mode using automatic switching by an electronic switch 5 of converter 6 of K of the excitation circuit to the output of amplifier 3, then to signal input the amplifier 10 of the measurement circuit of the registration of the damping decrement or the number of cycles of free oscillations formed by the sequence; signal-activated amplifier 10, detector 11, amplifier limiter 12, electronic key 13, trigger controlled 14. with a counting input, counter 15 in a binary-ten code, and a code-voltage converter.

Free oscillations from the piezoelectric transducer b through the electronic switch 5 are fed to amplify the input of the signal amplifier 10, after which they are detected by the detector 11, then amplified by the limiting amplifier 12 to an amplitude limit, i.e. convert them into rectangular pulses of the same amplitude and, via a controlled electronic key 13, trigger 14 is fed to read into the input of counter 15. The latter reads the number of pulses corresponding to the number of free oscillations | ry that change with the quality factor of the mechanical circuit. and by the converter the code - voltage 16 forms the control signal in analog form, which varies in proportion to the number of cycles of free oscillations, which vary with the change in the quality factor anicheskogo tool contour at normal pressure variations efforts at its working part.

The control signal at the output of block 16, which is proportional to the number of cycles of free oscillations and, consequently, the variations of the efforts of the normal pressure, is in principle possible to be used to stabilize the intensity of radial radiation by the following control methods: controlling the magnitude of the ultrasonic vibrational displacements, for example, changing the coefficient amplifying the amplifier 2 by varying the voltage by varying the frequency of the following rectangular pulses that control the frequency of excitation of powerful

5 ultrasonic vibrations, for example, by changing the oscillation frequency of the generator 19 of the sawtooth voltage, keeping other parameters constant; change pulse duration

Q is the effect of powerful ultrasonic vibrations, using the principle of the pulse-width modulation, an example of which is shown in FIG. one.

However, in all cases, the excitation of powerful ultrasonic vibrations is carried out periodically. Moreover, in one half-period, powerful ultrasonic vibrations are excited, and in the second half, the decrement decrement or the number of cycles of free oscillations are recorded and a control signal is generated that is proportional to the load variation, then during the next half-period of excitation, powerful ultrasonic oscillations automatically correct (change) the duration pulse of intense ultrasound exposure.

The switching frequency from the excitation mode to the measurement mode is set

40 by a sawtooth voltage generator 19, and the duration of the excitation pulse is formed on the basis of a comparison of the output signal of the block 16 code - voltage with analog

J signal setting unit permissible temperature at the second input of the circuit 17 comparison with the subsequent addition of the received differential signal by the adder 18 with the signal sawtooth voltage

generator output 19. Using the principle of pulse-width conversion, rectangular pulses of variable duration are formed with the help of threshold element 20, which control the switching frequency of the electronic to the Mutator 5, and differentiated link 21 by means of a pulley of rectangular pulses controlling the reset input of the counter 15

 and the operation of the electronic key 13

by trigger 14 by the counting input, updated for each half-period the counter 15, and hence the output control voltage at the output of the converter 16

The code is the voltage depending on the load variation.

The optimal duration of the rectangular excitation pulses of the powerful ultrasonic oscillations is set as an analog voltage at the second input of the comparison circuit 17, at the first input of which an analog voltage is fed in as feedback, proportional to the load variation.

Thus, changing the divider of the rectangular pulses, which provide the excitation time of powerful ultrasonic vibrations by the transducer b, proportional to the variation of the active component of the load, associated with the variation of the normal pressure force, stabilizes the intensity of the thermal radiation in the contact zone.

Then, by controlling the time of exposure to powerful ultrasonic vibrations, the unit 22, at a constant intensity of thermal radiation, determines (controls) the optimal thermal energy necessary to form a reliable connection.

The time of exposure to intense stabilized thermal radiation in the contact zone is recorded by reading a specified number of rectangular pulses with the aid of the exposure time control unit 22. When a predetermined number of rectangular pulses are reached at the second input of the block 22 corresponding to the optimum temperature in the contact zone, a signal that turns off the excitation of powerful ultrasonic vibrations by acting on the amplifier 9 through control. the control input of the amplifier 2 is a variable voltage.

The proposed method makes it possible to fully automate the process of controlling the acoustic mode of operation of the ultrasonic generator for a wide variety of technological processes, indirectly control and maintain the optimum temperature in the contact zone without using any temperature-sensitive elements, stabilize the intensity of thermal radiation in the contact zone with significant variation of normal effort pressure.

These possibilities greatly expand the scope of application of the method of controlling the acoustic regime in various areas of the national economy. The most effective use of the method for the ultrasonic welding of elements in radio-microelectronics, computing and, especially, in medical practice

The proposed method of controlling the acoustic mode of ultrasonic welding with the use of a special ultrasonic instrument and a device for its implementation allow intraocular operations for the category of patients who were previously considered non-operable, in which vitreal films, weights and moorings in the vitreous body retain the detached retina and do not allow replicate it in place, and also perform the operation under ophthalmoscopic control.

0

Claims (2)

1. The method of automatic control of acoustic mode of ultrasonic welding, based on the determined. Research Institute of the quality factor of the oscillating system, creating a tight acoustic contact between the instrument and the connected elements by applying normal pressure, initiating periodic, adjustable in duration pulsed ultrasonic welding vibrations and control of oscillation energy in. 5 depending on the change in the load of the oscillating system and its quality factor, characterized in that, in order to improve the quality of welding by stabilizing the intensity of thermal radiation and providing a given energy in the welding zone under the action of various disturbances, after each excitation pulse of ultrasonic welding vibrations 5, the damping factor of the oscillatory system is measured according to the number of cycles of its free oscillations, and the duration of the subsequent ultrasonic excitation pulse is measured by the measured value of the damping factor. 0 welding fluctuations. 2. The method according to claim 1, I differ from the fact that, in order to automatically control the acoustic contact of the instrument and the connected 5 elements, before excitation of ultrasonic welding {4 {oscillations), form complex low-power ultrasonic vibrations, determine the redistribution of nodes and antinodes of the longitudinal components of ultrasonic vibrational displacements on the waveguide part of the instrument, and determine the quality of the acoustic 5 contact-, then form ultrasonic welding vibrations with a given energy. Sources of information taken into account in the examination 0 1.Volkov S.S., Orlov Yu.N., Chern to B.Ya. Welding plastics by ultrasound .M. / Chemistry, 1974, pp.213-214. 2. USSR author's certificate for application number 2975814 / 25-27, cl. At 23 K 20/10, 1980 (prototype). five Ulla All Lll A t. 2