JP6279024B2 - Ultrasonic welding anvil - Google Patents

Description

  The present invention relates to an anvil for ultrasonic welding.

  The principle of ultrasonic plastic film welding is that a plurality of plastic films are sandwiched between a horn that vibrates ultrasonically and a fixed anvil, and pressure is applied along with the ultrasonic vibration generated by the horn. This is because the frictional heat and the strain stress applied to the plastic film cause frictional heat between the molecular chains and melt.

Generally, the vibration frequency of the horn is 20 kHz to 80 kHz, and the amplitude is 50 μm to 5 μm. Further, according to the thickness of the plastic film, when the plastic film is thick, the welding strength can be increased in proportion to the pressure and amplitude.

Thus, when ultrasonically welding two ultra-thin plastic films having a thickness of 50 μm or less, the vibration of the horn penetrates the work and induces the vibration of the anvil. In addition, as the vibration of the horn increases and the time passes, distortion occurs in the vibration of the anvil, and as a result, the vibration of the anvil and the vibration of the horn cause a collision through the workpiece. This causes a rampage of the horn and anvil, leading to unstable welding. In some cases, the converter may be damaged.

  The present invention has been made in view of the above points, and in order to prevent the vibration of the anvil and the vibration of the horn from colliding with each other through the workpiece, the vibration of the anvil being welded is stabilized with a very small amplitude. Accordingly, an anvil for ultrasonic welding that can stabilize welding can be provided.

  Therefore, the present inventors have intensively studied to solve the above problems.

FIG. 3 is an amplitude graph when a metal rod having a resonance frequency of 60 kHz in the longitudinal direction is driven with a constant force at a frequency of 10 kHz to 125 kHz in the longitudinal direction. In the figure, the horizontal axis represents frequency and the vertical axis represents drive surface amplitude.

This analysis shows that the amplitude is minimized when a 60 kHz resonator is driven at 30 kHz and 90 kHz.

  That is, when a certain resonator is viewed as a mechanical resistance, the mechanical resistance is large and the amplitude is the smallest when driven at a frequency that is 1/2 or 1.5 times the resonance frequency.

In order to consider the movement of the ultrasonic horn and the anvil microscopically, consider the case where there is no work and the anvil is in direct contact.

In this case, the horn and the anvil do not always come into contact with each other in one cycle of the ultrasonic vibration, and the horn and the anvil come into contact only in about a quarter cycle. And only at the time of this contact, pressure is applied from the horn to the anvil (FIG. 4). Of course, the contact time (pressurization time) also varies depending on the horn amplitude and the applied pressure.

When this is regarded as an applied pulse, the driving force of the horn is a square wave other than Duty 50% (less than Duty 50%, Duty 50% or more) as shown in the graph of FIG. 5A, or as shown in the graph of FIG. 6A. It can be expressed as a square wave with a duty of 50%.

  In this study, a frequency of 10 Hz is used as a model.

  When the frequency analysis (frequency response analysis) is performed on the waveform of FIG. 5A using Fourier transform, the fundamental frequency (10 Hz) is doubled (20 Hz), tripled (30 Hz), and quadrupled (40 Hz). ) Can be decomposed into 5 times (50 Hz) frequency (FIG. 5B). Here, the vertical axis represents each amplitude amount.

  That is, it can be considered that a square wave other than Duty 50% (less than Duty 50%, Duty 50% or more) does not consist of one SIN frequency but consists of a plurality of SIN frequencies. That is, it includes harmonic components of an odd multiple (10 Hz, 30 Hz, 50 Hz...) And an even multiple (20 Hz, 40 Hz...) With respect to the fundamental frequency (10 Hz).

  On the other hand, in the case of a duty 50% square wave in FIG. 6A, when frequency analysis (frequency response analysis) is performed using Fourier transform, an odd multiple (10 Hz, 30 Hz, It is known that only a harmonic component of 50 Hz is included (FIG. 6B).

In other words, in the case of this study, a driving force square wave having a horn frequency (30 kHz) other than Duty 50% is generated, and as a result, the anvil is driven simultaneously at a resonance frequency of 2 times (60 kHz) and 3 times (90 kHz). Correspondingly, by providing the anvil with the specific frequency (60 kHz), it becomes possible to intentionally vibrate the anvil stably at the specific frequency (60 kHz).

  In addition, since the vibration is transmitted to the anvil through the workpiece, the vibration is small and stable without causing an increase in amplitude. In this case, the anvil amplitude is less than 1/50 of the horn amplitude.

  FIG. 7 is a conceptual diagram at that time, and shows that the anvil is stable at a frequency twice the horn frequency and with a small amplitude.

  FIG. 8 shows a vibration mode in the case where the anvil is square in the axial cross-sectional shape.

  FIG. 8A shows a case where a square in the axial cross-sectional shape extends in the vertical direction, and FIG. 8B shows a case where the square extends in the left-right direction.

When the axial cross-sectional shape is a square, the same vibration mode can be maintained at any position when viewed in cross-section even if the length changes (FIG. 8C).

As the anvil size, a thickness (length in the vertical direction) of about 60 mm is suitable for a 20 kHz horn, and the vicinity of 40 mm is suitable for a 30 kHz horn.

These can be determined from the speed of sound of the material used, as well as the design of the horn. However, since the thickness of 60 mm at 20 kHz is considerably large when viewed from an automatic machine, it can be expected that another frequency can be used at a triple frequency and around 40 mm.

Also, even if the anvil is manufactured with a specific resonator, if the anvil is supported incorrectly, resonance or forced vibration at other frequencies will occur between the anvil and the holder, and the machine body. Stable welding cannot be obtained.

Therefore, it is desirable to support the anvil in a floating manner on the anvil holder, and this application is held by a sheet-like member that is elastic, viscous, and durable so that direct metal contact does not occur between the anvil and the anvil holder. It was decided to. Thereby, vibrations at other frequencies can be prevented.

The anvil has a concave portion formed on the left and right side surfaces of the anvil so that the anvil can be stably fixed without contact, and an anvil holder sandwiched from the left and right generates a downward pressing force and stabilizes the anvil.

The present invention has been completed based on the knowledge of the results of the above-mentioned earnest studies.

And Thus, it is an aspect of the present invention consists an anvil body and anvil holder for supporting this, the anvil body, twice for the horn having a resonance frequency of 80kHz from 20kHz for use with the anvil body Alternatively, an anvil body with a resonance frequency of 4 times is formed, and in order to stabilize the resonance state of the anvil body, the anvil body is floated on the anvil holder with an elastic and viscous sheet-like member interposed therebetween. An anvil for ultrasonic welding, characterized in that it is supported.

  Further, in the above configuration, as a means for floatingly supporting the anvil body on the anvil holder, the anvil body is formed in a square shape in the axial cross-sectional shape and formed with a recess along the axial direction on each of the left and right side surfaces. The holder is composed of a pair of left and right anvil holder pieces, and each of the pair of anvil holder pieces has an inverted T-shaped axial cross section, and the left and right side surfaces of the anvil main body are opposed to each vertical portion. Forming a convex part along the axial direction that respectively enters the concave part of the pair of anvil holder pieces and an anvil main body, between the opposing surfaces of the pair of anvil holder pieces and an elastic and viscous sheet-like member is interposed, Thus, the anvil body may be supported in a floating manner on the anvil holder.

The present invention is such a structure described above, consists of a anvil body and anvil holder for supporting this, the anvil body, twice or four times for a horn having a resonance frequency of 80kHz from 20kHz for use with the anvil body In order to stabilize the resonance state of the anvil body and to support the anvil body in a floating manner with an elastic and viscous sheet-like member interposed between the anvil body and the anvil body. Therefore, the vibration of the anvil main body during welding can be stabilized with a very small amplitude and constant, so that the welding can be stabilized. In addition, the anvil can be downsized.

It is a perspective view of the anvil for ultrasonic waves concerning the embodiment of the present invention. It is the same front view. It is principle explanatory drawing discovered in the research process of this invention, and is an amplitude graph when a 60 kHz resonator is driven with a fixed force with the frequency of 10 kHz to 125 kHz. It is explanatory drawing of the contact time of the horn and anvil in 1 period of the same ultrasonic vibration. FIG. 4A shows the driving force of the horn when the pressurization from the horn to the anvil in FIG. 4 is regarded as an applied pulse, with 10 Hz as a model and a square wave other than Duty 50%, and Fourier transform of the waveform. It is the figure (b) which performed frequency response analysis using. FIG. 4A shows the driving force of the horn when the pressure from the horn to the anvil in FIG. 4 is regarded as an applied pulse, and the waveform is Fourier-transformed using 10 Hz as a model and a 50% duty square wave. It is the figure (b) which performed frequency response analysis using. It is a figure which shows that an anvil is stable with a small amplitude and a double frequency with respect to the frequency of the horn. It is a figure showing the vibration mode in case the anvil is a square in axial cross-sectional shape.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

  1 and 2, reference numeral 1 denotes an ultrasonic welding anvil.

Further, ultrasonic welding anvil 1 is made from the anvil holder 3 for supporting the anvil body 2, the anvil body 2, for a 20kHz for use with the anvil body 2 in horn having a resonance frequency of 80kHz In order to make the anvil body 2 or 4 times the resonance frequency, and to stabilize the resonance state of the anvil body 2 , the anvil body 2 is interposed by interposing an elastic and viscous sheet-like member 4 having durability. the those formed by floatingly supported on the anvil holder 3.

  Further, in the present embodiment, as a means for floatingly supporting the anvil body 2 to the anvil holder 3, the anvil body 2 is formed into a square in the axial cross-sectional shape and recessed along the axial direction on each of the left and right side surfaces. 2a and 2b, while the anvil holder 3 is composed of a pair of left and right anvil holder pieces 3A and 3B, and each of the pair of anvil holder pieces 3A and 3B has an inverted T-shaped axial cross section, Convex portions 3a and 3b extending in the axial direction respectively entering the concave portions 2a and 2b on the left and right side surfaces of the anvil body 2 are formed on the opposing surfaces of the respective vertical portions 3A 'and 3B', and the pair of anvil holder pieces Between the opposing surfaces of 3A and 3B and the anvil body 2, there is an elastic and viscous sheet-like member 4 that is durable and interposed.

  The pair of anvil holder pieces 3 </ b> A, 3 </ b> B is installed on the base plate 5 and fixed with a set bolt 6.

  Thus, according to the above-described embodiment, the vibration of the anvil body 2 being welded can be reduced with a very small amplitude by the action as has been found as a result of research for solving the problems of the conventional ultrasonic welding anvil. In addition, it is possible to stabilize and stabilize the welding. In addition, the anvil can be downsized.

In other words, since a resonator having a certain frequency has a minimum vibration amplitude when driven at a constant force driving frequency of ½ with respect to that frequency , the anvil body 2 can be It is as hereinbefore for the 20kHz for use with anvil body 2 in horn having a resonance frequency of 80kHz designed twice or four times the resonant frequency, and in this case, about half the thickness of the length of a half wavelength horn It becomes the anvil body 2. Therefore, the vibration amplitude of the anvil body 2 can be extremely reduced.

Further, as a method of supporting the anvil body 2 itself to the anvil holder 3, avoiding metal contact, floating and supporting it with a sheet-like member 4 that is elastic and viscous like a resin and has durability. A collision occurring between the anvil body 2 and the anvil holder 3 can be avoided. Further, the viscosity of the sheet-like member 4 hinders the growth of the vibration amplitude of the anvil body 2, and the anvil body 2 can be vibrated with a stable amplitude of a very low amplitude (one tens of horn amplitudes). It is. This causes a frontal collision with the anvil main body 2 once every two times of vibration of the horn, but the amplitude of the anvil main body 2 is extremely small, and the anvil main body 2 itself is large with respect to the drive frequency. Since the amplitude behavior is similar to that of a mass anvil, the welding can be stabilized.

DESCRIPTION OF SYMBOLS 1 Ultrasonic welding anvil 2 Anvil main body 2a, 2b Concave 3 Anvil holder 3A, 3B A pair of anvil holder piece 3a, 3b Convex part 4 Sheet-like member 5 Base plate 6 Set bolt

Claims (2)

It consists anvil holder for supporting the anvil body and which, the anvil body, together form a double or quadruple the anvil body of the resonance frequency for the horn having a resonance frequency of 80kHz from 20kHz for use with the anvil body, Ultrasonic welding characterized in that in order to stabilize the resonance state of the anvil body, the anvil body is floatingly supported on the anvil holder by interposing an elastic, viscous and durable sheet-like member Anvil. The anvil body has a square shape in the axial cross section and is formed with a concave portion along the axial direction on each of the left and right side surfaces, and the anvil holder is composed of a pair of left and right anvil holder pieces, and the pair of anvil holder pieces Are formed in a reverse T-shaped axial cross section, and on the opposing surfaces of the respective vertical portions, convex portions along the axial direction respectively entering the concave portions on the left and right side surfaces of the anvil body are formed, and the pair of anvils 2. An elastic, viscous, and durable sheet-like member is interposed between opposing surfaces of the holder piece and the anvil body so that the anvil body is supported in a floating manner by the anvil holder. An ultrasonic welding anvil as described.

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