Ultrasonic welding method

Abstract

Provided is an ultrasonic welding method capable of suppressing an instantaneous increase in vibration amplitude of an ultrasonic horn when releasing sandwiching of a continuous body.　The present invention comprises: a conveyance step for conveying a continuous body (2); a sandwiching step for sandwiching the continuous body (2) between an ultrasonic horn (14c) and an anvil (16); a sandwiching release step for releasing the sandwiching of the continuous body (2); and a welding step for welding the continuous body (2) by applying ultrasonic vibration generated by the ultrasonic horn (14c) to the sandwiched portion of the continuous body (2). In the welding step, executed are a first step for generating the ultrasonic vibration (14x) after the start of the sandwiching step and setting the vibration amplitude of the ultrasonic vibration (14x) to a prescribed value (W) until immediately before the end of the sandwiching step, and a second step for reducing the vibration amplitude of the ultrasonic vibration (14x) after the end of the first step until the end of the sandwiching step.

Description

Ultrasonic welding method

[0001] The present invention relates to an ultrasonic welding method, and more particularly to a technique for welding a continuous body for manufacturing an absorbent article using an ultrasonic horn and an anvil.

[0002] For example, Patent Document 1 discloses that a continuous body for manufacturing disposable diapers is welded using a swing-type ultrasonic welding apparatus in which an anvil swings to open and close with respect to an ultrasonic horn. FIG. 12 is a diagram showing a rotary drum 105 of an ultrasonic welding apparatus 101 and its internal structure. FIG. 13 is a cross-sectional view showing an operating state of the ultrasonic welding apparatus 101.

[0003] As shown in FIGS. 12 and 13, a continuous body 130 for manufacturing disposable diapers is wound and conveyed in a folded state around an outer peripheral surface 105A of a rotary drum 105 of an ultrasonic welding apparatus 101, and the continuous body 130 is sequentially welded by a plurality of sets of ultrasonic horns 108 and anvils 114 that rotate integrally with the rotary drum 105.

[0004] The anvil 114 faces the ultrasonic horn 108 as shown in the upper part of FIG. 13 in synchronization with the rotation of the rotary drum 105, and swings between a closed position where the continuous body 130 is sandwiched between the ultrasonic horn 108 and the anvil 114 and an open position where it retreats in a direction away from the ultrasonic horn 108 as shown in the lower part of FIG. 13. When the continuous body 130 is sandwiched between the ultrasonic horn 108 and the anvil 114, ultrasonic vibrations generated by the ultrasonic horn 108 are applied to the continuous body 130 to weld the continuous body 130.

[0005] Patent Document 1 discloses that since vibration remains in the ultrasonic horn 108 even when the supply of electric energy for driving the ultrasonic horn 108 is stopped, the clamping of the continuous body 130 is continued even after the supply of electric energy for driving the ultrasonic horn 108 is stopped, and the clamping of the continuous body 130 is released after the vibration remaining in the ultrasonic horn 108 stops.

[0006] Furthermore, Patent Document 2 discloses that in adjacent pairs of ultrasonic horns and anvils, the periods for applying ultrasonic vibrations overlap when the rotating drum is rotating at high speed, but do not overlap when the rotating drum is rotating at low speed.

[0007] Patent No. 6286611 Patent No. 6307659

[0008] As described in Patent Document 1, if the clamping of the continuum 130 continues even after the supply of electrical energy to drive the ultrasonic horn 108 is stopped, depending on the combination of materials, material properties, thickness, etc. of the continuum 130, welding may proceed more than necessary, resulting in an excessively wide welded area or a thin welded portion.

[0009] Therefore, once a suitable welding state is achieved, it is conceivable to immediately release the clamping of the continuum 130.

[0010] However, when the clamping of the continuum 130 is released, the anvil 114 separates from the ultrasonic horn 108, and the constraint from the anvil 114 on the vibration of the ultrasonic horn 108 is momentarily removed. As a result, the vibration amplitude of the ultrasonic horn 108 increases momentarily when the clamping of the continuum 130 is released. If this causes the stress to exceed the allowable value, it can lead to damage to the ultrasonic horn 108 and other parts, as well as a decrease in durability and lifespan.

[0011] In view of these circumstances, the first problem that the present invention aims to solve is to provide an ultrasonic welding method that can suppress the instantaneous increase in the vibration amplitude of the ultrasonic horn when the clamping of a continuous body is released.

[0012] Furthermore, as described in Patent Document 2, depending on the speed mode of the rotating drum, the periods during which ultrasonic vibrations are applied to adjacent ultrasonic horn and anvil sets may or may not overlap, and the range of fluctuation in the electrical energy supplied to generate ultrasonic vibrations changes depending on the angular velocity of the rotating drum.

[0013] In view of these circumstances, the second problem that the present invention aims to solve is to provide an ultrasonic welding method that can ensure that the range of fluctuation in the electrical energy supplied to the ultrasonic horn to generate ultrasonic vibrations remains unchanged even when the angular velocity of the rotating drum changes.

[0014] To solve the above problems, the present invention provides an ultrasonic welding method configured as follows.

[0015] The ultrasonic welding method comprises: (i) a transport step of transporting a continuous body; (ii) a clamping step of clamping the continuous body between an ultrasonic horn and an anvil; (iii) a clamp release step of widening the gap between the ultrasonic horn and the anvil to release the clamping of the continuous body; and (iv) a welding step of applying ultrasonic vibrations generated by the ultrasonic horn to the portion of the continuous body that was clamped between the ultrasonic horn and the anvil in the clamping step, thereby welding the continuous body. In the welding step, (a) a first step of generating ultrasonic vibrations after the start of the clamping step and setting the amplitude of the ultrasonic vibrations to a predetermined value until just before the end of the clamping step; and (b) a second step of reducing the amplitude of the ultrasonic vibrations after the end of the first step and until the end of the clamping step.

[0016] According to the above method, the amplitude of the ultrasonic vibration of the ultrasonic horn decreases just before the end of the clamping process, and the amplitude of the ultrasonic horn's vibration at the time of releasing the clamping of the continuum is smaller than a predetermined value. Therefore, the instantaneous maximum value of the ultrasonic horn's vibration amplitude, which increases instantaneously when the clamping of the continuum is released, is smaller than when the amplitude of the ultrasonic horn's vibration is at a predetermined value up to the time of releasing the clamping of the continuum. Thus, it is possible to suppress the instantaneous increase in the amplitude of the ultrasonic horn's vibration when the clamping of the continuum is released.

[0017] In the first specific embodiment, in the transport step, the continuous body is wrapped around a rotating drum for transport; in the clamping step and the release step, multiple sets of the ultrasonic horns and anvils arranged along the rotating drum rotate together with the rotating drum; and in the clamping step, each set of the ultrasonic horns and anvils sequentially clamps the portion of the continuous body wrapped around the rotating drum in synchronization with the rotation of the rotating drum. In the welding step, the first rotation angle of the rotating drum when the ultrasonic vibration begins to be generated by the ultrasonic horn is greater when the angular velocity of the rotating drum is a first speed than when the angular velocity of the rotating drum is a second speed greater than the first speed.

[0018] In this case, the continuous material can be properly welded even if the angular velocity of the rotating drum changes.

[0019] In the specific second embodiment, in the transport step, the continuous body is wrapped around a rotating drum for transport; in the clamping step and the release step, multiple sets of the ultrasonic horns and anvils arranged along the rotating drum rotate together with the rotating drum; and in the clamping step, each set of the ultrasonic horns and anvils sequentially clamps the portion of the continuous body wrapped around the rotating drum 12 in synchronization with the rotation of the rotating drum. In the welding step, (a) the first rotation angle of the rotating drum when the ultrasonic vibration starts to be generated in the ultrasonic horn is the same in the first case where the angular velocity of the rotating drum is a first speed and in the second case where the angular velocity of the rotating drum is a second speed greater than the first speed; and (b) the second rotation angle of the rotating drum when the vibration amplitude of the ultrasonic vibration generated in the ultrasonic horn starts to decrease from a predetermined value is smaller in the first case than in the second case.

[0020] In this case, even if the angular velocity of the rotating drum changes, the initial rotation angle of the rotating drum when ultrasonic vibrations begin to be generated in the ultrasonic horn remains the same. Therefore, the range of fluctuation in the electrical energy supplied to the ultrasonic horn to generate ultrasonic vibrations does not change even if the angular velocity of the rotating drum changes. Furthermore, even if the angular velocity of the rotating drum changes, the continuum can be properly welded.

[0021] Preferably, the first rotation angle of the rotating drum is selected such that, in the first and second cases, the periods during which ultrasonic vibrations are generated in adjacent ultrasonic horns overlap.

[0022] In this case, regardless of whether it is a high-speed or low-speed mode, the oscillation periods of adjacent ultrasonic horns can be overlapped. This allows for a wider and more flexible setting of the welding time depending on the speed and material.

[0023] A specific third embodiment is as follows: In the conveying step, the continuous body is wrapped around a rotating drum for conveying; in the clamping step and the release step, multiple sets of ultrasonic horns and anvils arranged along the rotating drum rotate together with the rotating drum; and in the clamping step, each set of ultrasonic horns and anvils sequentially clamps the portion of the continuous body wrapped around the rotating drum 12 in synchronization with the rotation of the rotating drum. In the welding step, (a) the first rotation angle of the rotating drum when the ultrasonic vibration starts to be generated in the ultrasonic horn is the same or approximately the same in the first case where the angular velocity of the rotating drum is a first speed and in the second case where the angular velocity of the rotating drum is a second speed greater than the first speed; and (b) the third rotation angle of the rotating drum when the vibration amplitude of the ultrasonic vibration generated in the ultrasonic horn reaches a predetermined value is greater in the first case than in the second case.

[0024] In this case, even if the angular velocity of the rotating drum changes, the first rotation angle remains the same or approximately the same. Therefore, the fluctuation range of the electrical energy supplied to generate ultrasonic vibrations in the ultrasonic horn can be kept constant even if the angular velocity of the rotating drum changes. Furthermore, the continuous material can be properly welded even if the angular velocity of the rotating drum changes.

[0025] Preferably, the first rotation angle of the rotating drum is selected such that, in the first and second cases, the periods during which ultrasonic vibrations are generated in adjacent ultrasonic horns overlap.

[0026] In this case, regardless of whether it is a high-speed or low-speed mode, the oscillation periods of adjacent ultrasonic horns can be overlapped. This allows for a wider and more flexible setting of the welding time depending on the speed and material.

[0027] Preferably, in the welding process, the controller sends an operation signal to the ultrasonic horn based on a signal sent from a higher-level control device to generate the ultrasonic vibrations.

[0028] In this case, the vibration characteristics of the ultrasonic horn tip can be finely adjusted solely by adjusting the higher-level control unit.

[0029] According to the present invention, it is possible to suppress the instantaneous increase in the vibration amplitude of the ultrasonic horn when the clamping of the continuum is released. Furthermore, even if the angular velocity of the rotating drum changes, the fluctuation range of the electrical energy supplied to the ultrasonic horn to generate ultrasonic vibrations can be kept constant.

[0030] Figure 1 is a schematic diagram of an ultrasonic welding apparatus. (Example 1) Figure 2 is a schematic cross-sectional view along line II-II in Figure 1. (Example 1) Figure 3 is a block diagram of the control system of the ultrasonic welding apparatus. (Example 1) Figure 4 is a timing chart showing the ultrasonic welding method. (Comparative Example 1) Figure 5 is a timing chart showing the ultrasonic welding method. (Example 1) Figure 6 is a timing chart showing the ultrasonic welding method. (Example 1) Figure 7 is a timing chart showing the ultrasonic welding method. (Example 2) Figure 8 is a timing chart showing the ultrasonic welding method. (Example 2) Figure 9 is a timing chart showing the ultrasonic welding method. (Example 2) Figure 10 is a timing chart showing the ultrasonic welding method. (Example 2) Figure 11 is a block diagram of the control system of the ultrasonic welding apparatus. (Example 3) Figure 12 is a diagram showing the rotating drum and its internal structure of the ultrasonic welding apparatus. (Conventional Example 1) Figure 13 is a cross-sectional view showing the operating state of the ultrasonic welding apparatus. (Conventional Example 1)

[0031] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0032] First, the configuration of the ultrasonic welding apparatus 10 used in the ultrasonic welding method of the present invention will be described. Figure 1 is a schematic diagram of the ultrasonic welding apparatus 10. Figure 2 is a schematic cross-sectional view along line II-II in Figure 1.

[0033] As shown in Figures 1 and 2, the ultrasonic welding apparatus 10 has multiple sets of ultrasonic horns 14c and anvils 16 arranged along the rotating drum 12 at intervals from each other. The ultrasonic horns 14c are positioned radially inward of the rotating drum 12, and the anvils 16 are positioned radially outward of the rotating drum 12.

[0034] The rotating drum 12 rotates around the rotation center 12x in the direction indicated by arrow 13. The continuous body 2 is wrapped around the cylindrical outer surface 12s of the rotating drum 12 via guide rolls 4 and 6, and the continuous body 2 is conveyed in the direction indicated by arrows 3 and 7.

[0035] The ultrasonic horn 14c and the anvil 16 rotate together with the rotating drum 12. That is, the ultrasonic horn 14c and the anvil 16 rotate around the rotation center 12x of the rotating drum 12 in the direction indicated by arrow 13 at the same angular velocity as the rotating drum 12.

[0036] The ultrasonic horn 14c is positioned such that its tip surface 14s is exposed through an opening 12k formed on the outer circumferential surface 12s of the rotating drum 12.

[0037] As shown in Figure 2, the anvil 16 is supported so as to be able to swing around the support shaft 16x, and as indicated by the arrow 17, it swings between the retracted position K0 shown by the solid line and the clamping position K1 shown by the dashed line.

[0038] The anvil 16 is configured to repeatedly oscillate in conjunction with the rotation of the rotating drum 12, for example, using a cam mechanism (not shown). As shown in Figure 1, the continuous body 2 is wrapped around the rotating drum 12 in the winding section from rotation position A to rotation position B in the direction indicated by arrow 13. The anvil 16 is in a clamping position K1 in the section from rotation position P in the winding section to rotation position Q in the direction indicated by arrow 13, and is retracted to a retracted position K0 in the other sections.

[0039] In Figure 2, the continuum 2 is shown separated from the outer circumferential surface 12s of the rotating drum 12, the tip surface 14s of the ultrasonic horn 14c, and the opposing surface 16s of the anvil 16. However, in reality, the continuum 2 is supported by the outer circumferential surface 12s of the rotating drum 12 and is clamped between the tip surface 14s of the ultrasonic horn 14c and the opposing surface 16s of the anvil 16 at the clamping position K1. The continuum 2 is ultrasonically welded by applying ultrasonic vibrations 14x generated by the ultrasonic horn 14c to the continuum 2 from the tip surface 14s of the ultrasonic horn 14c to the clamped portion of the continuum 2.

[0040] The continuum 2 is, for example, a continuum for manufacturing absorbent articles such as disposable diapers, napkins, and pads, and the individual segment regions that are to become individual segments of absorbent articles are connected in the longitudinal direction. The continuum 2 is folded in half so that the boundaries of the individual segment regions overlap, and is wrapped around the rotating drum 12, and is conveyed as the rotating drum 12 rotates.

[0041] The continuous body 2 is sequentially sandwiched between the ultrasonic horn 14c and the anvil 16 that rotate integrally with the rotating drum 12, and the ultrasonic vibration 14x generated by the ultrasonic horn 14c is applied thereto, and welding is performed along the boundary line of the individual piece region.

[0042] The continuous body 2 discharged from the ultrasonic welding device 10 is cut at the boundary line of the individual piece region, whereby individual pieces of the absorbent article are formed.

[0043] Next, the control system of the ultrasonic welding device 10 will be described while referring to the block diagram of FIG. 3.

[0044] As shown in FIG. 3(a), a host control device 18 that overall controls the manufacturing line of the absorbent article including the ultrasonic welding device 10 sends an amplitude command signal 18x and an oscillation timing signal 18y to the controller 15. The controller 15 sends an operation signal 15x for operating the ultrasonic device 14 including the ultrasonic horn 14c so as to generate ultrasonic vibration 14x in the ultrasonic horn 14c.

[0045] As shown in FIG. 3(b), the ultrasonic device 14 is, for example, connected in series with a transducer 14a, a booster 14b, and an ultrasonic horn 14c. The transducer 14a generates mechanical vibration based on the operation signal 15x from the controller 15. The booster 14b amplifies the mechanical vibration transmitted from the transducer 14a and transmits it to the proximal end of the ultrasonic horn 14c. Thereby, ultrasonic vibration 14x is generated in the ultrasonic horn 14c.

[0046] The ultrasonic device 14 further includes a vibration amplitude detection sensor 14d that detects the vibration amplitude of the ultrasonic vibration 14x of the ultrasonic horn 14c and sends out a feedback signal 14y. The vibration amplitude detection sensor 14d can also be omitted.

[0047] The controller 15 receives a rotation angle signal 12y obtained by detecting the rotation angle of the rotating drum 12 with an encoder or the like, a feedback signal 14y from the vibration amplitude detection sensor 14d, and an amplitude command signal 18x and oscillation timing signal 18y sent from the higher-level control device 18. The controller 15 operates according to a predetermined program and generates an operation signal 15x to generate ultrasonic vibrations 14x of a desired vibration amplitude in the ultrasonic horn 14c based on the input signals 12y, 14y, 18x, and 18y, and sends the operation signal 15x to the transducer 14a.

[0048] The vibration characteristics of the tip of the ultrasonic horn can be finely adjusted simply by adjusting the amplitude command signal 18x and the oscillation timing signal 18y sent from the higher-level control device 18.

[0049] Next, the ultrasonic welding method of the present invention will be described with reference to Figures 4 to 10.

[0050] Figures 4 and 5 are timing charts illustrating the ultrasonic welding method, where the horizontal axis represents the rotation angle of the rotating drum 12 and corresponds to the rotational position of the rotating drum 12. In Figures 4 and 5, X represents the operation of the anvil 16, and Y represents the manipulated amount for the ultrasonic horn 14c (for example, the adjustment amount for the output of the ultrasonic device 14). Z represents the controlled amount, i.e., the vibration amplitude of the ultrasonic vibration 14x generated by the ultrasonic horn 14c.

[0051] <Comparative Example 1> Figure 4 is a timing chart for Comparative Example 1. In Comparative Example 1, the application of ultrasonic vibration 14x to the continuum 2 is started while the continuum 2 is being clamped, and the application of ultrasonic vibration 14x is stopped simultaneously with the release of the clamping of the continuum 2.

[0052] As shown in Figure 4, the anvil 16 becomes a clamping position K1 in the section from rotation position P to rotation position Q, and clamps the continuum 2. At rotation position S between rotation position P and rotation position Q, the manipulative amount Y changes in a stepwise manner from zero to a predetermined value V, and at rotation position Q, the anvil 16 releases its grip and the manipulative amount Y becomes zero.

[0053] In this case, the controlled variable Z changes in accordance with the manipulated variable Y, and reaches a predetermined value W in the interval between rotational position S and rotational position Q. More precisely, the controlled variable Z reaches the predetermined value W with a delay from the rise of the manipulated variable Y.

[0054] When the rotation position Q is reached, the clamping of the continuum 2 is released, and at the same time, the manipulated amount Y becomes zero. At this time, the anvil 16, which had been restraining the vibration of the ultrasonic horn 14c, retracts from the clamping position K1 to the release position K0, so the restraint from the anvil 16 on the vibration of the ultrasonic horn 14c is momentarily eliminated. Also, even when the manipulated amount Y becomes zero, the vibration amplitude of the ultrasonic horn 14c does not immediately become zero.

[0055] Therefore, as schematically shown in Figure 4, when the rotation position Q is reached, the controlled amount Z (vibration amplitude of the ultrasonic horn 14c) instantaneously increases, reaches a first peak 40 that exceeds a predetermined value W, and then decreases.

[0056] When the vibration amplitude of the ultrasonic horn 14c increases instantaneously in this way, the stress may exceed the allowable limit, potentially leading to damage to the ultrasonic horn and other components, as well as a decrease in durability and lifespan.

[0057] <Example 1> Figure 5 is the timing chart for Example 1.

[0058] As shown in Figure 5, in Example 1, similar to Comparative Example 1, the clamping of the continuum 2 begins at rotation position P, and when it reaches rotation position S, the manipulated amount Y becomes a predetermined value V, and the controlled amount Z follows the manipulated amount Y to a predetermined value W.

[0059] Unlike Comparative Example 1, when the rotation position T is reached just before the rotation position Q that releases the grip of the continuum 2, the manipulated amount Y decreases from the predetermined value V.

[0060] Here, the rotation position T immediately before reaching the rotation position Q is appropriately selected such that, for example, D is 1% or more and 20% or less of C, preferably 3% or more and 10% or less of C, where C is the length of the section from the rotation position P where the continuum 2 is held to the rotation position Q, and D is the length of the section from the rotation position T to the rotation position Q.

[0061] As shown in Figure 5, when the manipulated variable Y gradually decreases from a predetermined value V, the controlled variable Z decreases accordingly.

[0062] Then, when the rotation position Q is reached to release the clamping of the continuum 2, the manipulated variable Y becomes Vx, which is smaller than the predetermined value V, and the controlled variable Z becomes Wx, which is smaller than the predetermined value W. In this state, the anvil 16, which had been restraining the vibration of the ultrasonic horn 14c, retracts from the clamping position K1 to the release position K0, and the restraint from the anvil 16 on the ultrasonic horn 14c is instantaneously released. As schematically shown in Figure 5, the controlled variable Z instantaneously increases, reaches a second peak 42, and then decreases.

[0063] The instantaneous maximum value of the controlled variable Z at the second peak 42 is smaller than the instantaneous maximum value of the controlled variable Z at the first peak 40 in Comparative Example 1 shown in Figure 4. This is because the value Wx at the point when the rapid increase in the controlled variable Z begins is smaller than the value W at the point when the rapid increase in the controlled variable Z begins in Comparative Example 1.

[0064] By making the instantaneous maximum value of the vibration amplitude of the controlled quantity Z at the second peak 42 smaller than the instantaneous maximum value of the controlled quantity Z at the first peak 40, damage to the ultrasonic horn 14c and other components, as well as a decrease in durability and lifespan, can be suppressed.

[0065] The manipulated variable Y is, for example, gradually decreased from a predetermined value V in proportion to the rotation angle, so that the value Vx when the rotation position Q is reached is 0% or more and 90% or less of the predetermined value V, preferably 5% or more and 80% or less of the predetermined value V.

[0066] The manipulated variable Y may decrease linearly, curvedly, or in steps, as shown in Figure 5. The manipulated variable Y may continue to decrease after passing the rotation position Q and may become zero at an appropriate timing.

[0067] Figure 6 shows timing charts for multiple sets of ultrasonic horns 14c and anvils 16. For the i-th set of ultrasonic horns 14c and anvils (i = 1, 2, ...), the rotation angle is shown as Xi and the manipulated variable as Yi.

[0068] As shown in Figure 6, the multiple sets of ultrasonic horns and anvils are arranged with staggered timing according to their spacing, and similar to Figure 5, when the i-th set of anvils 16 of the ultrasonic horns 14c and anvils 16 begins gripping the continuum 2 at rotational position Pi and reaches rotational position Si, the manipulated amount Yi for generating ultrasonic vibrations 14x in the i-th set of ultrasonic horns 14c of the ultrasonic horns 14c and anvils 16 becomes a predetermined value V. When the rotational position Ti is reached just before reaching the rotational position Qi where the gripping of the continuum 2 is released, the manipulated amount Yi decreases. Then, when the rotational position Qi where the gripping of the continuum 2 is released is reached, the manipulated amount Yi becomes a value smaller than the predetermined value V.

[0069] In response to the manipulated amount Yi, ultrasonic vibrations 14x are generated in the i-th pair of ultrasonic horns 14c of the ultrasonic horns 14c and anvil 16, similar to Figure 5. This suppresses the instantaneous increase in the vibration amplitude of the ultrasonic horns 14c when the clamping of the continuum 2 is released in each pair of ultrasonic horns 14c.

[0070] The controller 15 determines a predetermined value V for the manipulated variable Yi based on the amplitude command signal 18x from the higher-level control device 18. The controller 15 also generates the manipulated variable Yi based on the oscillation timing signal 18y so that the manipulated variable Yi changes at rotational positions Si and Ti.

[0071] If the rotational position Si shown in Figure 6 remains unchanged even when the angular velocity of the rotating drum 12 changes, then the first state occurs where the periods L during which ultrasonic vibrations are generated in adjacent ultrasonic horns overlap.

[0072] In the first state, compared to the second state described later, the welding time can be set more freely and broadly depending on the angular velocity of the rotating drum 12 and the material of the continuum 2. In addition, errors can be prevented by reducing the peak of the ultrasonic vibration before the start of the release of clamping.

[0073] On the other hand, for example, in Figure 6, the ultrasonic welding apparatus 10 can be configured such that i = 1 and 3 remain, but i = 2 and 4 are not. In this case, even if the angular velocity of the rotating drum 12 changes, the period L during which ultrasonic vibrations are generated in adjacent ultrasonic horns does not overlap and is separated, resulting in a second state. In the second state, since it is not necessary to supply electrical energy to the two ultrasonic horns simultaneously, the fluctuation range of the electrical energy supplied to generate ultrasonic vibrations in the ultrasonic horns is smaller than in the first state.

[0074] In other words, if the angular velocity of the rotating drum 12 changes and the rotational position Si at which ultrasonic vibrations begin to be generated in the ultrasonic horn remains the same, then the period L during which ultrasonic vibrations are generated in adjacent ultrasonic horns will either be in a first state where they overlap, or in a second state where they do not overlap and are separated.

[0075] <Example 2> Next, Example 2, in which the angular velocity of the rotating drum 12 of the ultrasonic welding apparatus 10 is different, will be explained with reference to the timing charts in Figures 7 to 10.

[0076] (1) First Embodiment Figures 7 and 8 show the first embodiment of Embodiment 2. In Figure 7, the horizontal axis is the rotation angle of the rotating drum 12 and corresponds to the rotation position of the rotating drum 12. In Figure 8, the horizontal axis is time. In Figures 7 and 8, Xi indicates the operation of the i-th pair of anvils 16 of the ultrasonic horn 14c. Yi indicates the manipulated amount Yi of the i-th pair of ultrasonic horns 14c and anvils.

[0077] Figures 7(a) and 8(a) show the case where the angular velocity of the rotating drum 12 is at a first speed (low speed), while Figures 7(b) and 8(b) show the case where the angular velocity of the rotating drum 12 is at a second speed (high speed) which is greater than the first speed.

[0078] As shown in Figures 7 and 8, similar to Embodiment 1, from rotation position Pi to rotation position Qi, the i-th pair of anvils 16 of the ultrasonic horn 14c is in a clamping position K1. When the rotation position Si between rotation position Pi and rotation position Qi is reached, the manipulated amount Yi for generating ultrasonic vibration 14x in the i-th pair of ultrasonic horns 14c of the ultrasonic horn 14c and anvil 16 increases to a predetermined value V. When rotation position Ti is reached, the manipulated amount Yi decreases, and when rotation position Ri is reached, the manipulated amount Yi becomes zero.

[0079] As shown in Figure 7, the rotational position Si when the angular velocity of the rotating drum 12 is at the first speed (low speed) is greater than the rotational position Si when the angular velocity of the rotating drum 12 is at the second speed (high speed). That is, as shown in Figure 8, when the rotation is at the first speed (low speed), the manipulated amount Yi increases more slowly than when the rotation is at the second speed (high speed).

[0080] As shown in Figure 8, even if the angular velocity of the rotating drum 12 changes, the continuous body 2 can be properly welded by ensuring that the time for which the manipulated amount Yi is at a predetermined value V remains approximately the same.

[0081] In the first aspect of the second embodiment, in adjacent pairs of ultrasonic horns 14c and anvils 16, when the rotating drum 12 rotates at a second speed (high speed), the periods for applying ultrasonic vibrations 14x to the continuum 2 overlap, and when the rotating drum 12 rotates at a first speed (low speed), the second state, i.e., the periods for applying ultrasonic vibrations 14x to the continuum 2 do not overlap, may occur.

[0082] (2) Second Embodiment Figure 9 shows a second embodiment of Embodiment 2. In Figure 9, as in Figure 7, the horizontal axis is the rotation angle of the rotating drum 12, and Xi indicates the operation of the i-th pair of anvils 16 of the ultrasonic horn 14c and anvil. Yi indicates the change in the manipulated variable Yi for generating ultrasonic vibration 14x in the i-th pair of ultrasonic horns 14c of the ultrasonic horn 14c and anvil. Figure 9(a) shows the case where the angular velocity of the rotating drum 12 is a first speed (low speed), and Figure 9(b) shows the case where the angular velocity of the rotating drum 12 is a second speed (high speed) which is greater than the first speed.

[0083] As shown in Figure 9, Xi and Yi change in much the same way as in Figure 7, but the rotational position Si at which the manipulated amount Yi begins to increase is the same whether the angular velocity of the rotating drum 12 is at the first speed or at the second speed. As a result, even if the angular velocity of the rotating drum 12 changes, the first rotation angle of the rotating drum 12 when the ultrasonic horn 14c starts generating ultrasonic vibrations 14x remains the same, so the range of fluctuation in the electrical energy supplied to the ultrasonic horn 14c to generate ultrasonic vibrations 14x does not change even if the angular velocity of the rotating drum 12 changes.

[0084] Furthermore, the rotation angle corresponding to the rotation position Ti when the manipulated amount Yi begins to decrease from a predetermined value V is smaller when the rotating drum 12 is at a first speed than when the rotating drum 12 is at a second speed. By selecting the rotation position Ti such that the time for which the manipulated amount Yi is at a predetermined value V is approximately the same and generating the manipulated amount Yi, the continuum 2 can be properly welded even if the angular velocity of the rotating drum 12 changes.

[0085] It is preferable to select the first rotation angle of the rotating drum 12 so that it reaches the first state, that is, so that the periods during which adjacent ultrasonic horns generate ultrasonic vibrations overlap. In this case, the oscillation periods of adjacent ultrasonic horns can be overlapped regardless of whether it is a high-speed or low-speed mode. This allows the welding time to be set more freely and broadly depending on the speed and material compared to the second state. Furthermore, by controlling the vibration amplitude of the ultrasonic vibrations of the ultrasonic horns to decrease just before the end of the clamping process, the occurrence of errors can be prevented.

[0086] (3) Third Embodiment Figure 10 shows a third embodiment of Embodiment 2. In Figure 10, the horizontal axis is the rotation angle of the rotating drum 12. In Figure 10, Xi shows the operation of the i-th pair of anvils 16 of the ultrasonic horn 14c. Yi is the manipulated amount Yi for generating ultrasonic vibration 14x in the i-th pair of ultrasonic horns 14c of the ultrasonic horn 14c of the anvil. Figure 10(a) shows the case where the angular velocity of the rotating drum 12 is a first speed (low speed), and Figure 10(b) shows the case where the angular velocity of the rotating drum 12 is a second speed (high speed) which is greater than the first speed.

[0087] As shown in Figure 10, the rotational position Si at which the manipulated amount Yi begins to increase is the same in the first case, where the angular velocity of the rotating drum 12 is the first speed, and in the second case, where the angular velocity of the rotating drum 12 is the second speed. Unlike the first and second embodiments of Embodiments 1 and 2, the manipulated amount Yi gradually increases and reaches a predetermined value V at rotational position Ui.

[0088] Therefore, the first rotation angle of the rotating drum 12 when the ultrasonic vibration 14x starts to be generated in the ultrasonic horn 14c is the same or approximately the same in the first case and the second case.

[0089] Furthermore, the rotation angle corresponding to the rotation position Ui when the manipulated amount Yi reaches a predetermined value Vi is larger in the first case than in the second case. Therefore, the third rotation angle of the rotating drum 12 when the vibration amplitude of the ultrasonic vibration generated by the ultrasonic horn 14c reaches a predetermined value is larger in the first case than in the second case.

[0090] Even if the angular velocity of the rotating drum 12 changes, the first rotation angle at which ultrasonic vibration 14x is generated in the ultrasonic horn 14c is constant. Therefore, the range of fluctuation in the electrical energy supplied to the ultrasonic horn 14c to generate ultrasonic vibration 14x can be kept constant even if the angular velocity of the rotating drum 12 changes. Furthermore, even if the angular velocity of the rotating drum 12 changes, the continuous body 2 can be properly welded by selecting the rotation position Ui so that the time for which the manipulated amount Yi is approximately the same as a predetermined value V, thereby generating the manipulated amount Yi.

[0091] It is preferable to select the first rotation angle of the rotating drum 12 so that it reaches the first state, that is, so that the periods during which adjacent ultrasonic horns generate ultrasonic vibrations overlap. In this case, the oscillation periods of adjacent ultrasonic horns can be overlapped regardless of whether it is a high-speed or low-speed mode. This allows the welding time to be set more freely and broadly depending on the speed and material compared to the second state. Furthermore, by controlling the vibration amplitude of the ultrasonic vibrations of the ultrasonic horns to decrease just before the end of the clamping process, the occurrence of errors can be prevented.

[0092] <Example 3> Figure 11 is a block diagram of the control system in Example 3.

[0093] As shown in Figure 11, the controller 15, which operates the ultrasonic horn 14c of the ultrasonic device 14 to generate ultrasonic vibrations 14x, is equipped with a memory 15a. The controller 15 receives an oscillation timing signal 18y and a memory retrieval signal 18z from a higher-level control device 18 that controls the entire manufacturing line. Based on the memory retrieval signal 18z, the controller 15 reads a set value from the memory 15a and generates an operation signal 15x that changes the manipulated amount Yi, as in Example 1 or Example 2, based on the rotation angle signal 12y detected by an encoder or the like for the rotation of the rotating drum 12 and the oscillation timing signal 18y.

[0094] For example, the memory 15a contains the rotation angles θ corresponding to the rotation positions Pi, Qi, Ri, Si, Ti, and Ui of the rotating drum 12. Ｐｉ , θ Ｑｉ , θ Ｒｉ , θ Ｓｉ , θ Ｔｉ , θ Ｕｉ The system stores the setting values ​​of parameters appropriately selected from a predetermined value V of the manipulated amount Yi and the value Vx of the manipulated amount Yi when the gripping of the continuum 2 is released.

[0095] Memory 15a may store multiple combinations of setting values ​​in advance, or setting values ​​may be written to memory 15a from the higher-level control device 18, or setting values ​​stored in memory 15a may be overwritten.

[0096] Using memory 15a, the mode in which ultrasonic vibrations are applied can be easily changed.

[0097] <Modification> Two or more embodiments of Examples 1 to 3 may be combined. For example, as in the third embodiment of Example 2, the manipulated amount Yi is gradually increased, and the rotation angle corresponding to the rotational position Ui of the rotating drum 12 when the manipulated amount Yi becomes a predetermined value V is changed according to the angular velocity of the rotating drum 12, while the rotation angle corresponding to the rotational position Ti of the rotating drum 12 when the decrease in the manipulated amount Yi begins is changed according to the angular velocity of the rotating drum 12, as in the second embodiment of Example 2.

[0098] <Summary> As explained above, by reducing the vibration amplitude of the ultrasonic vibration 14x of the ultrasonic horn 14c just before the clamping of the continuum 2 is released, the vibration amplitude at the time the clamping of the continuum 2 is released is reduced, thereby suppressing the instantaneous increase in the vibration amplitude of the ultrasonic horn 14c when the clamping of the continuum 2 is released.

[0099] Furthermore, for each set of ultrasonic horns 14c and anvils 16, by keeping the rotation angle of the rotating drum 12 constant, which corresponds to the rotation position Si of the rotating drum 12 when the supply of electrical energy to generate ultrasonic vibrations 14x in the ultrasonic horn 14c begins, it is possible to ensure that the range of fluctuation in the electrical energy supplied to the ultrasonic horn to generate ultrasonic vibrations remains unchanged even if the angular velocity of the rotating drum 12 changes.

[0100] It should be noted that the present invention is not limited to the embodiments described above, and can be implemented with various modifications.

[0101] For example, the ultrasonic welding apparatus 10 can be of an appropriate configuration. For instance, an ultrasonic welding apparatus may be used in which the anvil moves radially along the rotating drum 12 while maintaining a state parallel to the rotational axis of the rotating drum 12.

[0102] Alternatively, the continuous body 2 may be transported and stopped repeatedly, and ultrasonic welding may be performed while the continuous body 2 is stopped.

[0103] 2. Continuous 12. Rotating drum 14c. Ultrasonic horn 14x. Ultrasonic vibration 15. Controller 16. Anvil W. Predetermined value

Claims

1. An ultrasonic welding method comprising: a conveying step of conveying a continuous body; a clamping step of clamping the continuous body between an ultrasonic horn and an anvil; a clamping release step of widening the gap between the ultrasonic horn and the anvil to release the clamping of the continuous body; and a welding step of welding the continuous body by applying ultrasonic vibrations generated by the ultrasonic horn to the portion of the continuous body that was clamped between the ultrasonic horn and the anvil in the clamping step, wherein the welding step includes: a first step of generating the ultrasonic vibrations after the start of the clamping step and setting the amplitude of the ultrasonic vibrations to a predetermined value until just before the end of the clamping step; and a second step of decreasing the amplitude of the ultrasonic vibrations after the end of the first step and until the end of the clamping step.

2. The ultrasonic welding method according to claim 1, wherein in the conveying step, the continuous body is conveyed by wrapping it around a rotating drum; in the clamping step and the clamping release step, a plurality of sets of ultrasonic horns and anvils arranged along the rotating drum rotate together with the rotating drum; in the clamping step, each set of ultrasonic horns and anvils sequentially clamps the portion of the continuous body wrapped around the rotating drum in synchronization with the rotation of the rotating drum; and in the welding step, the first rotation angle of the rotating drum when the ultrasonic vibration starts to be generated by the ultrasonic horn is greater when the angular velocity of the rotating drum is a first speed than when the angular velocity of the rotating drum is a second speed greater than the first speed.

3. The ultrasonic welding method according to claim 1, wherein in the conveying step, the continuous body is conveyed by wrapping it around a rotating drum; in the clamping step and the clamping release step, a plurality of sets of ultrasonic horns and anvils arranged along the rotating drum rotate together with the rotating drum; in the clamping step, each set of ultrasonic horns and anvils sequentially clamps the portion of the continuous body wrapped around the rotating drum in synchronization with the rotation of the rotating drum; in the welding step, the first rotation angle of the rotating drum when the ultrasonic vibration starts to be generated in the ultrasonic horn is the same in the first case where the angular velocity of the rotating drum is a first speed and in the second case where the angular velocity of the rotating drum is a second speed greater than the first speed; and the second rotation angle of the rotating drum when the vibration amplitude of the ultrasonic vibration generated in the ultrasonic horn starts to decrease from a predetermined value is smaller in the first case than in the second case.

4. The ultrasonic welding method according to claim 3, wherein the first rotation angle of the rotating drum is selected such that, in the first case and the second case, the periods during which ultrasonic vibrations are generated in adjacent ultrasonic horns overlap with each other.

5. The ultrasonic welding method according to claim 1, wherein in the conveying step, the continuous body is conveyed by wrapping it around a rotating drum; in the clamping step and the clamping release step, a plurality of sets of ultrasonic horns and anvils arranged along the rotating drum rotate together with the rotating drum; in the clamping step, each set of ultrasonic horns and anvils sequentially clamps the portion of the continuous body wrapped around the rotating drum in synchronization with the rotation of the rotating drum; in the welding step, the first rotation angle of the rotating drum when the ultrasonic vibration starts to be generated in the ultrasonic horn is the same or approximately the same in the first case where the angular velocity of the rotating drum is a first speed and in the second case where the angular velocity of the rotating drum is a second speed greater than the first speed; and the third rotation angle of the rotating drum when the vibration amplitude of the ultrasonic vibration generated in the ultrasonic horn reaches a predetermined value is greater in the first case than in the second case.

6. The ultrasonic welding method according to claim 5, wherein the first rotation angle of the rotating drum is selected such that, in the first case and the second case, the periods during which ultrasonic vibrations are generated in adjacent ultrasonic horns overlap with each other.

7. The ultrasonic welding method according to any one of claims 2 to 6, wherein, in the welding step, the controller sends an operation signal to the ultrasonic horn based on a signal sent from a higher-level control device to generate the ultrasonic vibrations.

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