JPH0425310Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a composite horn used in an apparatus for ultrasonically welding plastic members. In particular, the present invention is designed to weld a part of the plastic member to be welded that is in contact with the horn in a rectangular, trapezoidal, or circular shape, has a long side or circumference, and has a steeply rising part near the inner side of the machined surface. The present invention relates to a composite horn suitable for welding relatively large box-shaped or cylindrical plastic members.

[Conventional technology]

A method is known in which plastic members are welded by pressing the tip of a horn against the welded portion of laminated plastic members and applying ultrasonic longitudinal vibration from the other end. In addition to the ultrasonic welding method, there is a hot plate welding method, but this method requires processing time that is 30 times longer than the ultrasonic welding method, so it is not used much.

By the way, ultrasonic welding is generally used to weld film-like or sheet-like plastic members. However, recently there has been a demand for the assembly of box-shaped or cylindrical plastic parts, such as automobile or motorcycle headlamps, by ultrasonic welding.
Generally, the head lamp body is molded from ABS resin, and the lens member is made of acrylic resin or polycarbonate resin with good light transmittance, and the head lamp body and lens are welded together to maintain watertightness at each joint. They are integrated to form a headlamp.

This welding is performed by the method shown in FIG. That is, the lens portion 2 of the headlamp is placed on the holding jig 4, the lamp body 1 is placed on top of it, and the surrounding parts 3 to be welded are aligned. On the other hand, a welding tool horn 6 is screwed to a fixed horn 5 for transmitting ultrasonic vibrations from a vibrator (not shown). The tool horn 6 is a cylindrical column made of aluminum alloy with a diameter of 200 to 300 mm, and has a cavity 7 in which the lamp body 1 can be housed. The lower end surface of the tool horn 6 has the same planar shape as the welded part 3 of the lamp body 1, and if this is pressed against the welded part 3 and ultrasonic vibration is applied via the fixed horn 5, the lamp body 1 and the lens part will be separated. 2 is welded.

By the way, in general, in a cylindrical or prismatic tool horn, as the diameter or length of one side becomes more than 1/4 wavelength of the horn's resonant frequency (wavelength = sound speed of the horn material / resonant frequency), The vibration direction of each part on the lower end surface of the horn is not necessarily parallel to the central axis of longitudinal vibration, and the amplitude distribution also becomes uneven. This tendency is particularly noticeable around the lower end of the horn, where the diameter of the horn or the length of one side is 1/1/2.
If the wavelength exceeds 2, the horn may no longer resonate. This phenomenon is due to the fact that as the diameter of the horn that resonates in the longitudinal direction becomes larger than 1/4 wavelength, the amplitude of transverse vibration based on the vibration stress in the transverse direction increases at and near the nodes of longitudinal vibration. This is due to the fact that the lateral vibration stress restrains the longitudinal vibration inside the horn.

Therefore, the diameter of the horn or the length of one side is 1/2
If the wavelength exceeds the wavelength, attach approximately 1/4 to the side of the horn.
By passing vertical slits parallel to the central axis at wavelength intervals to reduce the effects of tension caused by lateral vibration stress between adjacent parts of the horn, the overall balance of the horn can be maintained. Conventionally, methods have been implemented in which vertical vibration is caused to occur. The tool horn 6 shown in FIG. 5 described above also has six slits 8 formed along its side surface, as shown in FIG. 6.

However, when the shape of the welded part 3 as shown in FIGS. 5 and 6 is rectangular, trapezoidal, circular, etc., and its one side or circumference is, for example, 200 mm or more, the inside vicinity of the welded part 3 is The tool horn 6 for welding a plastic member having a rising portion that suddenly reaches a height of, for example, 50 mm, includes:
A large cavity 7 is carved into the interior for accommodating plastic parts. Therefore, the cross-sectional shapes of the upper and lower horns are significantly asymmetrical around the nodal surface of longitudinal vibration, and there is also a large difference in the mass balance at the central axis of the horn (the central axis of longitudinal vibration). Although such conventional tool horns have slits, they have the disadvantage that the stress distribution due to the vibration of the horn is non-uniform, and the amplitude distribution at the lower end surface of the horn is also non-uniform. For example, the tool horn 6 in Fig. 6 is built vertically and horizontally inside a cylindrical aluminum alloy with a diameter of 210 mm and a resonance frequency of 15.1 KHz.
A cavity 7 of 170 x 110 mm and a depth of 50 mm is formed, but despite having six slits 8, the amplitude distribution at the lower end of the horn is scattered in the range of 15 to 25 μm and is extremely non-uniform. It was hot. Furthermore, the stress distribution due to horn vibration was uneven, and stress (mainly shear stress) was concentrated at the lower end 9 of the slit, especially at its square corner, and the horn 6 often broke from there. In order to prevent breakage, horns with similar shapes were used for welding with various changes in the shape and depth of the cavity, the number and position of slits, etc., but all of the horns broke after a short period of operation. In the case of a square horn, the breaking phenomenon was even more severe.

[Problem that the invention attempts to solve]

The object of the present invention is to provide a composite horn for ultrasonic welding that can be stably used for welding relatively large box-shaped or cylindrical plastic members for a long period of time.

[Means for solving problems]

The composite horn for ultrasonic welding according to the present invention includes a driving horn integrally formed with one edge of a plurality of plate-shaped arms joined around the central axis of longitudinal vibration, and each plate of the driving horn. It consists of a plate-shaped welding horn that is attached to the lower end face of the arm so as to intersect with each other, and a cavity is formed inside the welding horn by the plurality of welding horns.

The composite horn of the present invention maintains mass balance around the central axis of longitudinal vibration, and has a symmetrical cross-sectional shape above and below the nodal surface of longitudinal vibration.
Of course, the drive horn and each welding horn may be provided with slits in the conventional manner. If the plate thickness of each plate arm of the drive horn and each welding horn is 1/8 wavelength or less, the length can be approximately 2 wavelengths by providing slits at intervals of approximately 1/4 wavelength. , almost uniform and stable longitudinal vibration can be obtained over the entire lower end surface of the horn.

In the present invention, the number of plate-like arm parts constituting the driving horn may be two or more, and can be arbitrarily determined in consideration of the shape of the welding horn to be attached thereto. However, in order to easily balance the mass around the central axis of longitudinal vibration, the drive horn is made up of an even number of plate-like arms, in particular four plate-shaped arms, which form a pair every two. It is preferable that the plate-like arms are arranged linearly with the central axis in between. In this case, it is preferable that the welding horns attached to the plate-like arms be located symmetrically with respect to the central axis and have the same shape.

The plate-like arm that constitutes the drive horn is a flat plate with a predetermined thickness and no curve, but the welding horn is not limited to such a flat plate, but can also be used depending on the shape of the workpiece to be welded. It may also be a shape that is curved together, for example, a cylinder divided into several pieces in the vertical direction.

〔Example〕

Next, specific examples of the present invention will be described with reference to the drawings.

1 to 3 show one of the preferred specific examples, in which the driving horn 10 has four plate-like arm portions 1.
Each edge of 1a, 11b, 11c, and 11d is formed in a cross shape at the lower end of the fixed horn 5 so that one edge thereof coincides with an extension of the center line of the fixed horn 5. A pair of plate-like arms 11a-11b and 11c-11d arranged linearly with the fixed horn 5 in between have the same length, but adjacent plate-like arms, for example 11a and 11c, are shown in FIG. They don't have to be the same length.

A plate-shaped welding horn 12a,
12b, 12c, and 12d are crossed and screwed together. In order to rotate and screw the welding horn into the plate-like arm portion, in the specific example shown, the four corners of the two opposing welding horns 12a and 12b are cut. Of course, the welding horns can also be screwed in by increasing the distance between the two opposing welding horns without cutting the four corners. In addition, opposing welding horns 12a-12b
and 12c to 12d have the same shape and are arranged at equal distances from the central axis. The lower end surfaces of all the welding horns 12a, 12b, 12c, and 12d are rectangular and are pressed against the welded portion of the plastic member. If the width of the lower end face of the welding horn is wider than the width of the part to be welded, the welding horn is processed so that only the inner rectangular portion of the lower end face protrudes as shown in the figure.
In this example, all welding horns 12
A, 12b, 12c, and 12d form a box-shaped cavity with a rectangular bottom inside.

In the specific example shown in Figures 1 to 3, the lower end surfaces of the four welding horns attached to the cross-shaped driving horn are rectangular, but the length of each plate-like arm of the driving horn is By appropriately designing the length and mounting position of each welding horn, the lower end surfaces of the welding horns can be set in a square or trapezoid shape, etc., in line with the shape of the part to be welded of the plastic member. I can do it.

The shape of the driving horn is also as shown in Figures 1 to 3.
Not limited to the example shown in the figure, the number of plate-like arms can be changed from 4 to 5.
As explained above, the number can be changed to 1, 6, or 3.

As an example, three plate-like arm portions 11e, 1 are shown in FIG.
A bottom view of a composite horn in which 1f and 11g are arranged at equal intervals around the central axis is shown. In this example, three welding horns 12e, 12f, and 12g are mounted at equal distances from the central axis, and their lower end surfaces form an equilateral triangle.

Furthermore, the welding horn does not need to be flat; if the welding horn in the specific example of FIG. 3 or 4 is replaced with a curved plate, the lower end surface of the welding horn may be circular or oval. The hollow portion formed inside them also has a cylindrical or elliptical shape.

The plate thickness, width, height, etc. of the driving horn and the welding horn can be appropriately selected depending on the size of the plastic member to be processed and the processing frequency.

A composite horn shown in FIG. 1 was formed from an aluminum alloy. The cross-shaped driving horn of this composite horn has a plate thickness of 60 mm and a horn height of 163.5 mm, and of the two pairs of linear plate-shaped arms, the short one has a total length of 230 mm, and the long one has a total length of 230 mm. The length was 270mm. The four welding horns have a plate thickness of 40 mm, a horn height of 163.5 mm, and two of them have a length of 120 mm.
and the other two had a length of 170 mm. In addition, slits were bored in the driving horn and the welding horn at intervals of 1/4 wavelength of the resonant frequency.

The composite horn constructed by screwing a welding horn to the lower end surface of a cross-shaped driving horn as shown in Fig. 1 has a resonance frequency of 15.10 KHz, and the amplitude of the lower end surface of the welding horn is equal to that of the fixed horn tip surface. same as amplitude
22 μm, and the amplitude deviation over the entire lower end surface of each welding horn was ±1.5 μm. In addition, fatigue fractures due to stress concentration, which frequently occur with conventional cylindrical tool horns, as shown in Figure 6, did not occur, and stable welding could be continued for a long period of time, and the welding of plastic parts was also good. .

[Effect of idea]

According to the present invention, the part to be welded is rectangular, trapezoidal, circular, etc., has a long side or circumference, and has a relatively large box-like, cylindrical, etc. shape with a steeply rising part near the inner side of the part to be welded. A composite horn suitable for welding plastic members is provided. Moreover, this composite horn has a uniform amplitude over the entire lower end surface of the welding horn that is pressed against the part to be welded of the plastic member, and there is no breakage due to stress concentration, so it can be used stably for a long period of time.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a specific example of the composite horn for ultrasonic welding of the present invention, FIG. 2 is a side view of the composite horn of FIG. 1, and FIG. 3 is a bottom view of the composite horn of FIG. 1. It is a diagram. FIG. 4 is a bottom view of another specific example of the composite horn of the present invention. FIG. 5 is a partially sectional view showing the welding process of a headlamp using a conventional tool horn, and FIG. 6 is a partially cutaway side view of the conventional tool horn used in FIG. 5... Fixed horn, 6... Tool horn, 7...
Hollow portion, 8...Slit, 10...Driving horn, 11a, 11b, 11c, 11d, 11e,
11f, 11g...Plate arm portion, 12a, 12b,
12c, 12d, 12e, 12f, 12g... welding horn.

Claims (1)

[Claims for Utility Model Registration] (1) A driving device that is integrally formed by joining one edge of a plurality of plate-like arms to the lower end of a fixed horn on an extension of the center line of the fixed horn. horn and
Ultrasonic welding consists of a plate-shaped welding horn attached to the lower end surface of each plate-shaped arm of the drive horn, and a cavity is formed inside the welding horn by these plurality of welding horns. Composite horn for. (2) The drive horn is composed of an even number of plate-shaped arms, which are arranged in pairs every two, and the pair of plate-shaped arms are arranged linearly with the central axis in between.
Composite horn for ultrasonic welding in item (1).