Patent Description:
Bag making apparatuses for successively making plastic bags from a continuous sheet panel and a continuous zipper are well known as disclosed in Patent documents <NUM> to <NUM>. The bag making apparatus includes a welding device configured to weld the sheet panel and the zipper to each other.

The welding device in each of Patent documents <NUM> and <NUM> includes a pair of pressure rollers opposing each other for pressurizing the sheet panel and the zipper, a feed device configured to intermittently feed the sheet panel and the zipper in their longitudinal direction through the pair of pressure rollers in a state in which they are superposed on each other, and a laser device configured to irradiate the zipper with a laser beam at a position upstream of the pair of pressure rollers.

Irradiating the zipper with a laser beam causes its irradiated part to be heat-melted by the laser beam. The sheet panel and the zipper are then guided to the pair of pressure rollers to be superposed on each other. When the sheet panel and the zipper pass through the pair of pressure rollers, they are pressurized by the pair of pressure rollers and thus welded to each other.

The temperature at the irradiated part is decreasing while this part is being fed from the irradiation position of the laser beam to the pair of pressure rollers. For proper welding, the molten state of the irradiated part should be maintained until the irradiated part reaches the pair of pressure rollers.

The sheet panel and the zipper are intermittently fed. This means that the sheet panel and the zipper are repeatedly fed and paused. During the pause phase of the intermittent feed cycle, the irradiated part which is located in the section from the irradiation position to the pair of pressure rollers cools down to return from the molten state to the non-molten state. When the sheet panel and the zipper are then fed again, the irradiated part is pressed in the non-molten state against the sheet panel by the pair of pressure rollers, and consequently fails to be welded to the sheet panel. In this way, the unwelded part, which was subject to the laser irradiation and the pressurization but failed to be welded, is generated every intermittent feed cycle. The unwelded part can be a cause of leakage in making bags, have an influence on the quality of the bags, and in addition, cause the loss of material.

Since the feed device of the welding device disclosed in each of Patent documents <NUM> and <NUM> not intermittently but continuously feeds the sheet panel and the zipper, there is no problem as described above. However, if the welding device stops its operation, the feed device also stops feeding the sheet panel and the zipper. Then, the irradiated part which is located in the section from the irradiation position of the laser beam to the pair of pressure rollers cools down to return to the non-molten state. If the feed device restarts to feed the sheet panel and the zipper in accordance with the restart of the operation of the welding device, this irradiated part passes in the non-molten state through the pair of pressure rollers. Therefore, the unwelded part is generated.

An object of the present disclosure is to provide devices and methods which allow for shortening an unwelded part.

The following disclosure serves a better understanding of the present invention. According to an aspect of the present disclosure, there is provided a welding device for welding a web and a continuous strip member to each other. The welding device includes: a pair of pressure members opposing each other for pressurizing the web and the continuous strip member; a feed device configured to intermittently feed the web and the continuous strip member in a longitudinal direction of the web and the continuous strip member through the pair of pressure members in a state in which the web and the continuous strip member are superposed on each other; a laser device configured to irradiate the web or the continuous strip member with a laser beam at a position upstream of the pair of pressure members so as to melt the web or the continuous strip member with the laser beam for welding of the web and the continuous strip member; and a movement device configured to move the pair of pressure members upstream with respect to the web and the continuous strip member during a pause phase of an intermittent feed cycle.

The movement device may be configured to, during a pause phase of an intermittent feed cycle, move the pair of pressure members upstream from a reference position and move the pair of pressure members back to the reference position.

The movement device may be configured to move the pair of pressure members upstream during a pause phase of an intermittent feed cycle such that at least one of the pressure members enters a path for the laser beam.

According to another aspect of the present disclosure, a welding device includes: a pair of pressure members opposing each other for pressurizing the web and the continuous strip member; a feed device configured to intermittently feed the web and the continuous strip member in a longitudinal direction of the web and the continuous strip member through the pair of pressure members in a state in which the web and the continuous strip member are superposed on each other; and a laser device configured to irradiate the web or the continuous strip member with a laser beam at a position upstream of the pair of pressure members so as to melt the web or the continuous strip member with the laser beam for welding of the web and the continuous strip member. The feed device is configured to, in an intermittent feed cycle, advance the web and the continuous strip member by a first length, retract the web and the continuous strip member by a second length which is shorter than the first length, and pause the web and the continuous strip member.

The welding device may further include a tension maintenance mechanism arranged upstream of the pair of pressure members and configured to maintain tension of the web.

The second length may be less than or equal to a distance between an irradiation position of the laser beam and a pressure position of the pair of pressure members.

According to yet another aspect of the present disclosure, a welding device includes: a pair of pressure members opposing each other for pressurizing the web and the continuous strip member; a feed device configured to continuously feed the web and the continuous strip member in a longitudinal direction of the web and the continuous strip member through the pair of pressure members in a state in which the web and the continuous strip member are superposed on each other; a laser device configured to irradiate the web or the continuous strip member with a laser beam at a position upstream of the pair of pressure members so as to melt the web or the continuous strip member with the laser beam for welding of the web and the continuous strip member; and a movement device configured to move the pair of pressure members upstream with respect to the web and the continuous strip member in response to the feed device stopping the web and the continuous strip member.

According to yet another aspect of the present disclosure, a welding device includes: a pair of pressure members opposing each other for pressurizing the web and the continuous strip member; a feed device configured to continuously feed the web and the continuous strip member in a longitudinal direction of the web and the continuous strip member through the pair of pressure members in a state in which the web and the continuous strip member are superposed on each other; and a laser device configured to irradiate the web or the continuous strip member with a laser beam at a position upstream of the pair of pressure members so as to melt the web or the continuous strip member with the laser beam for welding of the web and the continuous strip member. The feed device is further configured to stop the web and the continuous strip member after retracting the web and the continuous strip member by a certain length.

According to yet another aspect of the present disclosure, there is provided a welding method for welding a web and a continuous strip member to each other, the welding method including: intermittently feeding the web and the continuous strip member in a longitudinal direction of the web and the continuous strip member through a pair of pressure members in a state in which the web and the continuous strip member are superposed on each other; irradiating the web or the continuous strip member with a laser beam at a position upstream of the pair of pressure members to melt the web or the continuous strip member with the laser beam for welding of the web and the continuous strip member such that the web and the continuous strip member are pressurized by the pair of pressure members to be welded to each other while the web and the continuous strip member pass through the pair of pressure members; and during a pause phase of an intermittent feed cycle, moving the pair of pressure members upstream from a reference position with respect to the web and the continuous strip member such that the web and the continuous strip member are pressurized by the moving pair of pressure members to be welded to each other and moving the pair of pressure members back to the reference position.

According to yet another aspect of the present disclosure, a welding method includes: intermittently feeding the web and the continuous strip member in a longitudinal direction of the web and the continuous strip member through a pair of pressure members in a state in which the web and the continuous strip member are superposed on each other; irradiating the web or the continuous strip member with a laser beam at a position upstream of the pair of pressure members to melt the web or the continuous strip member with the laser beam for welding of the web and the continuous strip member; and in an intermittent feed cycle, advancing the web and the continuous strip member by a first length, retracting the web and the continuous strip member by a second length which is shorter than the first length, and pausing the web and the continuous strip member.

The pair of pressure members may be a pair of pressure rollers. The web may be a continuous sheet panel for bags. The strip member may be a continuous zipper for the bags.

Welding devices and welding methods according to implementations will be described with reference to the drawings. The same or similar components in each implementation are indicated by the same numerals, and the explanations thereof are omitted.

[First implementation] <FIG> schematically illustrate a bag making apparatus. A welding device according to the implementation is provided in the bag making apparatus. The welding device is configured to weld a continuous strip member <NUM> to a web <NUM> (i.e., a continuous sheet). The strip member <NUM> has a narrower width than that of the web <NUM>.

As illustrated in <FIG>, the web <NUM> in this implementation is a continuous plastic film, specifically a continuous sheet panel from which sheet panels of bags <NUM> will be formed. The strip member <NUM> in the implementation is made of plastic and is a continuous zipper from which zippers of the bags <NUM> will be formed. The strip member <NUM> in the implementation has two surfaces <NUM> to be welded on the opposite sides thereof. As in Patent document <NUM>, a zipper as the continuous strip member <NUM> includes a male member <NUM> and a female member <NUM> which are detachably fitted to each other. Hereinafter, the strip member <NUM> (zipper) will be fed with the male member <NUM> and the female member <NUM> fitted to each other, and be welded to the webs <NUM>.

As illustrated in <FIG>, the welding device includes a pair of pressure rollers <NUM> as a pair of pressure members opposing each other for pressurizing the two webs <NUM> and the strip member <NUM>. As will be described below, the webs <NUM> and the strip member <NUM> are pressurized by the pair of pressure rollers <NUM> to be welded to each other.

The welding device further includes a feed device <NUM> configured to intermittently feed the webs <NUM> and the strip member <NUM> in their longitudinal direction (their continuous direction) and to superpose them on each other such that they pass through the pair of pressure rollers <NUM> in a superposed state. Thus, the webs <NUM> and the strip member <NUM> are repeatedly fed and paused by the feed device <NUM>. The reference sign Y in Figures designates the feed direction when the webs <NUM> and the strip member <NUM> are fed in the superposed state.

The feed device <NUM> includes at least one pair of drive rollers <NUM> arranged downstream of the pair of pressure rollers <NUM> to intermittently feed the webs <NUM> and the strip member <NUM>. The pair of drive rollers <NUM> rotates with the webs <NUM> and the strip member <NUM> sandwiched therebetween, and thereby intermittently feeds the webs <NUM> and the strip member <NUM> through the pair of pressure rollers <NUM> as well as the pair of drive rollers <NUM>. Only one pair of drive rollers <NUM> is illustrated in Figures for the purpose of convenience. However, for a large apparatus, a plurality of the pairs of drive rollers <NUM> are typically provided, and all of the pairs of drive rollers <NUM> are driven synchronously when intermittently feeding the webs <NUM> and the strip member <NUM>.

The feed device <NUM> further includes guide rollers <NUM> for guiding each of the webs <NUM> to the pair of pressure rollers <NUM>. Each web <NUM> is continuously unrolled from a roll thereof in a well-known manner. Alternately, a wide web may be continuously unrolled from a roll thereof, and slit in the longitudinal direction thereof into the two webs <NUM>. Then, feed of the webs <NUM> is properly converted by a dancer mechanism (not shown) from the continuous feed into the intermittent feed. The guide rollers <NUM> are arranged downstream of the dancer mechanism. Each web <NUM> is guided to the pair of pressure rollers <NUM> via the guide roller <NUM>.

The feed device <NUM> further includes a guide roller <NUM> and a guide body <NUM> (<FIG>) for guiding the strip member <NUM> to the pair of pressure rollers <NUM>. The strip member <NUM> is unrolled from a roll thereof, guided to a space between the two webs <NUM> before being superposed, diverted in the direction Y via the guide roller <NUM>, and fed through the guide body <NUM> to the pair of pressure rollers <NUM>.

Therefore, the webs <NUM> and the strip member <NUM> are caused to be superposed on each other at a position right before the pressure position of the pair of pressure rollers <NUM>. At this time, one surface <NUM> of the strip member <NUM> comes into contact with one of the webs <NUM>, and the other surface <NUM> of the strip member <NUM> comes into contact with the other web <NUM>. The webs <NUM> and the strip member <NUM> are then fed through the pair of pressure rollers <NUM> in the superposed state.

As illustrated in <FIG> and <FIG>, the welding device further includes two laser devices <NUM> each configured to irradiate the strip member <NUM> with a laser beam <NUM> so as to melt the strip member <NUM> with the laser beam <NUM>. Each of the laser devices <NUM> includes a laser source and an optical system which are similar to those in Patent documents <NUM> and <NUM>. One of the laser devices <NUM> is arranged to irradiate one surface <NUM> of the strip member <NUM> with the laser beam <NUM>, and the other laser device <NUM> is arranged to irradiate the other surface <NUM> of the strip member <NUM> with the laser beam <NUM>. As in Patent documents <NUM> and <NUM>, each laser device <NUM> is arranged to irradiate the strip member <NUM> with the laser beam <NUM> at the irradiation angle q (<NUM>< q =< <NUM>). As illustrated in <FIG>, each surface <NUM> of the strip member <NUM> is made of a light absorption layer <NUM> which absorbs the laser beam <NUM>. This allows the surfaces <NUM> to absorb the laser beam <NUM>, generate heat and be melted. The wavelength of the laser beam <NUM> is appropriately selected. For example, this may be visible light or infrared light.

As in Patent document <NUM>, the laser device <NUM> interlinks the irradiation intensity of the laser beam <NUM> with the feed speed of the web <NUM> to maintain uniformity of the strength of the welding when welding with the laser beam <NUM> during the intermittent feed. It increases the irradiation intensity when the web <NUM> is fed at a higher speed, correspondingly it decreases the irradiation intensity when the web <NUM> is fed at a lower speed. In other words, the laser device <NUM> is configured to radiate the laser beam <NUM> while controlling the irradiation intensity of the laser beam <NUM> in accordance with the feed speed.

The example of this is illustrated in <FIG>. In the pattern <NUM>, the irradiation intensity is in complete proportion to the feed speed, which means that the irradiation intensity is zero (i.e., the laser beam <NUM> is not radiated) when the feed speed is zero. In contrast, in the pattern <NUM>, the irradiation intensity is in proportion to the feed speed but is controlled such that it is not less than the minimum predetermined value W<NUM> (<NUM> < W<NUM>W<NUM>; W<NUM> is the irradiation intensity value when the feed speed is maximum). This means that the laser beam <NUM> is radiated continuously while the web <NUM> is not only being fed but also being paused. The laser device <NUM> sets the output to zero for pattern <NUM>, whereas it does not set the output to zero for pattern <NUM>. Since the laser device <NUM> is generally subjected to the highest load when outputting from the zero-output state, the pattern <NUM>, which has lesser burden on the laser device <NUM> than the pattern <NUM>, is preferable.

As illustrated in <FIG>, the laser beams <NUM> are radiated onto the surfaces <NUM> (the light absorption layers <NUM>), so that the surfaces <NUM> are heat-melted by the laser beams <NUM>, respectively. The webs <NUM> and the strip member <NUM> are caused to be superposed on each other such that the surfaces <NUM> in the molten state come into contact with the webs <NUM>, respectively, and then pass through the pair of pressure rollers <NUM>. The webs <NUM> and the strip member <NUM> are pressurized by the pair of pressure rollers <NUM> while they pass through the pair of pressure rollers <NUM>. This causes one of the webs <NUM> and one of the surfaces <NUM> to be welded to each other, and also the other web <NUM> and the other surface <NUM> to be welded to each other. It is well-known that the surface <NUM> needs to be pressed in a molten state against the web <NUM> by the pair of pressure rollers <NUM> in order for welding to be guaranteed.

The welding device further includes a movement device <NUM> configured to move the pair of pressure rollers <NUM> downstream (in the feed direction Y) and upstream (in the opposite direction thereof). For example, the movement device <NUM> includes: support members which rotatably support the opposite ends of the rotation shafts of the respective pressure rollers <NUM>; guides which support the support members to guide them in the feed direction Y and the opposite direction thereof, respectively; and an actuator which moves the support members along the guides. Operation of the actuator allows the support members and the pair of pressure rollers <NUM> to move together along the guides upstream and downstream. The movement device <NUM> is not limited to this example.

As will be described below, the movement device <NUM> moves the pair of presser rollers <NUM> in synchronization with the intermittent feed performed by the feed device <NUM>. <FIG> illustrates the irradiation with the laser beam <NUM>. <FIG> only illustrates one of the webs <NUM> and one of the pressure rollers <NUM>. <FIG> separately illustrates the end part of the line L<NUM> irradiated with the laser beam <NUM> and the start part of line L<NUM> to be irradiated with the laser beam <NUM> for the purpose of convenience. As illustrated in <FIG>, the laser beam <NUM> having a spot-like cross section <NUM> is radiated at the irradiation angle θ onto the surface <NUM> of the strip member <NUM> through the vicinity of the part of the web <NUM> that is engaged with the pressure roller <NUM>. Thereafter, the irradiated surface <NUM> reaches the predetermined reference position P and is pressed against the web <NUM> by the pair of pressure rollers <NUM> at the reference position P.

<FIG> illustrates the situation when the time is t<NUM> (see <FIG>), i.e., the moment the web(s) <NUM> and the strip member <NUM> have just started to be paused. The hatched part in line L<NUM> indicates the welded part. The surface <NUM> in the section P-S is melted as it has been irradiated with the laser beam <NUM>, but is not welded to the web <NUM>.

As illustrated in <FIG>, when the web <NUM> and the strip member <NUM> are paused, the pair of pressure rollers <NUM> is moved by the movement device <NUM> upstream (right direction on Figure) from the reference position P to the position P' with respect to the web <NUM> and the strip member <NUM> by the distance d. While the pair of pressure rollers <NUM> is moving in the section P-P', it presses the web <NUM> against the surface <NUM> which is in the molten state, thereby pressurizing the web <NUM> and the strip member <NUM> to weld them to each other in the section P-P' by the distance d. The movement device <NUM> then moves the pair of pressure rollers <NUM> back to the reference position P while the web <NUM> and the strip member <NUM> are being paused (by the time t<NUM> in <FIG>).

Then, at time t<NUM>, the feed device <NUM> starts to feed the web <NUM> and the strip member <NUM>. The laser beam <NUM> is radiated onto the surface <NUM> in its irradiation position (the section Q-S), so that the part of the surface <NUM> in the section Q-S is in the molten state. In contrast, the part of the surface <NUM> in the section P'-Q has already returned from the molten state to the not-molten state. Consequently, while this part of the surface <NUM> is passing through the pair of pressure rollers <NUM>, it is pressurized by the pair of pressure rollers <NUM> but fails to be welded to the web <NUM>. In other words, the unwelded area with length c, which is an area where the web(s) <NUM> and the strip member <NUM> are completely not welded to each other, is generated. The unwelded part, which is not welded although was subject to the laser radiation and the pressurization, has a length corresponding to the distance of the section P'-R (the part of the surface <NUM> in the section Q-R is partially welded and not partially welded due to the spot shape of the cross section <NUM> of the laser beam <NUM>). The downstream part with the length c in the unwelded part is the unwelded area defined as described above.

In this way, the movement device <NUM>, during the pause phase of the intermittent feed cycle, moves the pair of pressure rollers <NUM> upstream from the reference position P by the distance d and moves it back to the reference position P. This causes the web <NUM> and the strip member <NUM> to be pressurized by the moving pair of pressure rollers <NUM>, so that they are welded to each other by the distance d. The upstream movement of the pair of pressure rollers <NUM> must take place before the surface <NUM> returns from the molten state to the non-molten state. Therefore, the movement device <NUM> preferably starts to move the pair of pressure rollers <NUM> upstream immediately after the beginning of the pause of the feed. The pair of pressure rollers <NUM> is moved by the movement device <NUM> as described above during every intermittent feed cycle.

Since the welding device disclosed in Patent document <NUM> does not include the above movement device <NUM>, the unwelded area with the length b (<FIG>) is generated during every intermittent feed cycle. That is, the welding device and the welding method in the implementation allow for shortening the unwelded part by the movement distance d (= b - c) of the pair of pressure rollers <NUM>.

In the case where the laser device <NUM> keeps radiating the laser beam <NUM>, for example, according to the pattern <NUM> of the profile of the irradiation density as illustrated in <FIG>, the pair of pressure rollers <NUM> may be moved by the movement device <NUM> such that each pressure roller <NUM> enters the path for the laser beam <NUM> as illustrated in <FIG>. The pressure roller <NUM> prevents the surface <NUM> from being irradiated with the laser beam <NUM> during the pause phase of the intermittent feed cycle. In other words, the surface <NUM> in the section Q-S is prevented from being kept irradiated with the laser beam <NUM> during the pause phase of the intermittent feed cycle to become a super-molten state. Thus, at least a part of the pressure roller <NUM> which pressurizes the web <NUM> and the strip member <NUM> may be made of the material which reflects the laser beam <NUM>. For example, the pair of pressure rollers <NUM> may be moved from the reference position P to the position R. This results in welding the web(s) <NUM> and the strip member <NUM> to each other in the section P-R, since the surface <NUM> in the section P-S is in the molten state. Alternatively, the pair of pressure rollers <NUM> may be moved from the reference position P to the position S, so that the web(s) <NUM> and the strip member <NUM> are welded to each other in the section P-S.

As illustrated in <FIG>, the engaged part of the web <NUM> with the pressure roller <NUM> is irradiated with the laser beam <NUM>. However, its irradiation position is not the focus of the laser beam, and its energy is also weak. Since the web <NUM> in this implementation is transparent to the laser beam <NUM> (the web <NUM> has no light absorption layer), the web <NUM> is not damaged by the laser beam <NUM>.

As illustrated in <FIG>, just before the beginning of the feed of the web <NUM> and the strip member <NUM> (just before t<NUM>), the pair of pressure rollers <NUM> is moved back to the reference position P by the movement device <NUM>. At this time, a part of the web <NUM> still remains entering the path for the laser beam <NUM>. However, since the laser beam <NUM> passes through the web <NUM> as described above, it is radiated onto the surface <NUM> of the strip member <NUM>, and thereby heat-melts the surface <NUM>. Setting a larger movement distance d allows for welding with almost no unwelded area/part or with no unwelded area/part. The movement distance d is sufficient if it is at most the distance from the reference position P to the position S (the upstream end of the irradiation position).

In the implementation, the pressurizing force required for welding is sufficient if it is about 2N to 3N. A large pair of pressure rollers is not required. For example, the pair of pressure rollers <NUM> is preferably made of lightweight material such as carbon. Selecting such material allows for easy movement of the pair of pressure rollers <NUM> with respect to the web(s) <NUM> and the strip member <NUM>.

The irradiation angle θ is determined as appropriate in the way as disclosed in each of Patent documents. The irradiation angle θ is preferably <NUM>° or close to <NUM>° from the viewpoint of improvement of the irradiation intensity (i.e., prevention of blurry of the focus). On the other hand, the larger the irradiation angle <NUM> is, the further the irradiation position is away from the pair of pressure rollers <NUM>, resulting in the longer unwelded part. Therefore, the irradiation angle θ is, for example, <NUM>° to <NUM>°, in particular <NUM>° to <NUM>°. This is also the same for the following implementations.

The feed device <NUM>, the laser devices <NUM> and the movement device <NUM> are operated in conjunction with one another by a control device (comprising a controller, etc.) not shown in Figures.

The welding device is incorporated into the bag making apparatus as described above. As illustrated in <FIG>, the bag making apparatus further includes a seal device <NUM>, a seal device <NUM> and a cutting device <NUM>. After the welding, the two sheet panels (webs) <NUM> are sealed to each other along the side thereof by the seal device <NUM>, so that the sealed part <NUM> (<FIG>) is formed. Also, the sheet panels <NUM> are sealed to each other in the width direction thereof by the seal device <NUM>, so that the sealed part <NUM> (<FIG>) is formed. These sealings may be in the form of heat-sealing or ultrasonic-sealing. The sheet panels <NUM> and the zipper (the strip member) <NUM> are cut in the width direction thereof by the cutting device <NUM>, and thereby the bag <NUM> is shaped. The cutting may be in the form of shear or fusing. The bags <NUM> in the implementation are plastic bags.

The bag making apparatus may be a multi-line bag making type, which means that two or more bags <NUM> are shaped every time the cutting device <NUM> cuts the sheet panels <NUM> and the zipper <NUM>. The bag making apparatus may partially seal the panel sheets (webs) <NUM> and the zipper (strip member) <NUM> to crush the zipper <NUM>, thereby forming the crushed parts <NUM> (<FIG>) at the opposite ends of the zipper <NUM> of the bag <NUM>. The crushed parts <NUM> are similar to those disclosed in Patent document <NUM> and ensure the sealability of the bag <NUM> at the ends of the zipper <NUM>. The bag making apparatus preferably forms the crushed parts <NUM> such that the aforementioned unwelded area/part is included in the crushed part <NUM>. This can reduce the loss of material. Instead of the example in <FIG>, the crushed part <NUM> may be completely included in the sealed part <NUM> if the unwelded part is short. The unwelded part can be a cause of leakage in making bags, have an influence on the quality of the bags, and in addition, cause the loss of material. Therefore, the welding device is especially advantageous when it is incorporated into a bag making apparatus.

[Second implementation] As illustrated in <FIG>, the welding device in this implementation does not include the movement device <NUM> (<FIG>). The pair of drive rollers <NUM> of the feed device <NUM> is configured to be rotatable in the forward and backward directions. <FIG> illustrates the relationships between the feed speed and the irradiation intensity in this implementation. As illustrated in the feed speed profile in <FIG>, in one intermittent feed cycle, the feed device <NUM> rotates the pair of drive rollers <NUM> forward to advance (feed) the webs <NUM> and the strip member <NUM> in the feed direction Y by the first length, rotates the pair of drive rollers <NUM> backward to retract (return) the webs <NUM> and the strip member <NUM> by the second length which is shorter than the first length, and then halts the pair of drive rollers <NUM> to pause the webs <NUM> and the strip member <NUM>. The feed device <NUM> intermittently feeds the webs <NUM> and the strip member <NUM> in this manner every cycle. Thus, with "p" as the net pitch of the intermittent feed, "f<NUM>" as the first length, and "f<NUM>" as the second length, p = f<NUM> - f<NUM> (f<NUM> > f<NUM>) is completed.

The example of the operation of the welding device and the welding method when the laser device <NUM> changes the irradiation intensity according to the pattern <NUM> of the profile in <FIG> will be described below.

<FIG> illustrates the situation when the time is t<NUM> (<FIG>), i.e., the moment the irradiation of the laser beam <NUM> has just been stopped. At this time, the web(s) <NUM> and the strip member <NUM> have already been advanced in the direction Y by the net pitch p, and thereby welded to each other by the net pitch p. The surface <NUM> in the section P-S has already been irradiated with the laser beam <NUM>, and is therefore in the molten state.

Then, the feed device <NUM> further rotates the pair of drive rollers <NUM> in the forward direction without halting the pair of drive rollers <NUM> to further advance the web <NUM> and the strip member <NUM> in the direction Y by the second length f<NUM>. This causes the part of the surface <NUM> in the section P-P' in <FIG> to be fed to the pair of pressure rollers <NUM>, and to be pressed against the web <NUM> by the pair of pressure rollers <NUM>. Consequently, the web <NUM> and the strip member <NUM> are additionally welded to each other by the pair of the pressure rollers <NUM> by the length f<NUM>.

Then, the feed device <NUM> reversely rotates the pair of drive rollers <NUM> to retract the web <NUM> and the strip member <NUM> by the length f<NUM>, and halts the pair of drive rollers <NUM> to pause the web <NUM> and the strip member <NUM>. Thereby, this additionally welded part is moved back to the section P-P' (<FIG>).

Then, at time t<NUM>, the next intermittent feed cycle begins.

As can be seen from the above, this implementation can shorten the unwelded part by the retraction length f<NUM> (second length). It is also possible to reduce the unwelded area/part to substantially zero depending on setting of the length f<NUM>. The length f<NUM> is sufficient if it is less than or equal to the section P-S (the distance between the pressure position of the pair of pressure rollers <NUM> and the irradiation position (more specifically, the position of its upstream end) of the laser beam <NUM>).

As illustrated in <FIG>, a part of the web <NUM> may enter the path for the laser beam <NUM> depending on the length f<NUM>. As described above, the web <NUM> is not damaged by the laser beam <NUM> and does not prevent the surface <NUM> of the strip member <NUM> from being irradiated with the laser beam <NUM>.

As described above, the pressurizing force of the pressure rollers <NUM> may be as small as about 2N to 3N. It is therefore possible to retract the web <NUM> and the strip member <NUM> without any problem.

As illustrated in <FIG>, the welding device in this implementation may include a tension maintenance mechanism <NUM> (hereinafter simply referred to as "maintenance mechanism"). The maintenance mechanism <NUM> may be provided for each of the webs <NUM>. The maintenance mechanism <NUM> is arranged upstream of the pair of pressure rollers <NUM> (<FIG>), more specifically upstream of the guide roller <NUM> (see <FIG>) and downstream of the dancer mechanism. The maintenance mechanism <NUM> is configured to maintain the tension of the web <NUM>. The maintenance mechanism <NUM> is of a well-known type. For example, the maintenance mechanism <NUM> includes an application roller <NUM> for applying tension, two guide rollers <NUM> located upstream and downstream of the application roller <NUM>, an actuator <NUM> for moving the application roller <NUM> in the direction Z, and a sensor (not shown) for detecting the position of the application roller <NUM>. The maintenance mechanism <NUM> operates the actuator <NUM> based on the detection by the sensor to adjust the position of the application roller <NUM> such that the tension is maintained constant. A maintenance mechanism <NUM> may also be provided for the strip member <NUM>, arranged upstream of the irradiation position of the laser beam <NUM>, and configured to maintain the tension of the strip member <NUM>. The maintenance mechanism(s) <NUM> absorbs the change of the tension of the web <NUM>/the strip member <NUM> when the feed device <NUM> intermittently feeds the web(s) <NUM> and the strip member <NUM> according to the feed speed profile in <FIG>.

In the previous implementation, the laser device <NUM> intermittently radiates the laser beam <NUM> according to the pattern <NUM> of the irradiation intensity profile in <FIG>, but may continuously radiates the laser beam <NUM>. Thus, the laser device <NUM> may radiate the laser beam <NUM>, for example, according to the pattern <NUM> of the irradiation intensity profile in in <FIG>. This case also allows for shortening the unwelded part.

The feed device <NUM> and the laser devices <NUM> in this implantation are also controlled by the control device such that they operate in synchronization with each other.

[Third implementation] <FIG> illustrates a bag making apparatus including a welding device in this implementation. In this implementation, the pair of drive rollers <NUM> of the feed device <NUM> of the welding device continuously rotates to not intermittently but continuously feed the webs <NUM> and the strip member <NUM> in their longitudinal direction Y. The bag making apparatus further includes another pair of drive rollers <NUM> which is disposed downstream of the pair of drive rollers <NUM> to intermittently feed the webs <NUM> and the strip member <NUM> in their longitudinal direction Y. In this implementation, the dancer mechanism <NUM> is therefore disposed downstream of the pair of drive rollers <NUM> and upstream of the pair of the drive rollers <NUM> to appropriately convert the continuous feed into the intermittent feed.

The feed device <NUM> continuously feeds the webs <NUM> and the strip member <NUM> while maintaining their feed speed constant. The strip member <NUM> is (its surfaces <NUM> are) melted by the laser beams <NUM> at a position upstream of the pair of pressure rollers <NUM>. The webs <NUM> and the strip member <NUM> are then caused to be superposed on each other and to be pressurized by the pair of pressure rollers <NUM> so as to be welded to each other. This is same as in Patent documents <NUM> and <NUM>.

The welding device in the implementation includes the movement device <NUM> as in the first implementation. If the feed device <NUM> that is continuously feeding the webs <NUM> and the strip member <NUM> in the direction Y, receives the input indicating the stop of the feed, it halts the pair of drive rollers <NUM> to stop the webs <NUM> and the strip member <NUM>. As illustrated in <FIG>, in response to the feed device <NUM> stopping the web(s) <NUM> and the strip member <NUM>, the movement device <NUM> moves the pair of pressure rollers <NUM> upstream from the reference potion P to the position P' by the distance g with respect to the web <NUM> and the strip member <NUM>, and then moves the pair of pressure rollers <NUM> back to the reference position P. This causes the web <NUM> and the strip member <NUM> to be welded to each other in the section P-P' by the moving pair of pressure rollers <NUM> by the distance g.

Thereafter, if the feed device <NUM> receives the input indicating the start of the feed, it restarts to feed the web(s) <NUM> and the strip member <NUM>. The laser device <NUM> irradiates the surface <NUM> in the section Q-S with the laser beam <NUM>. The part of the surface <NUM> in the section P'-Q was in the molten state due to the previous irradiation with the laser beam <NUM> but has already cooled down and returned to the non-molten state at the restart of the feed. Due to this, the part of the surface <NUM> in the section P'-Q fails to be welded in restarting the feed. As a result, the unwelded area with the length c is generated. This length c is shorter than the length b of the unwelded area which is generated by the conventional device and method, by the movement length g (c = b - g). Therefore, this implementation also allows for shortening the unwelded part. As in the first implementation, setting the longer movement length g allows for the shorter length of the unwelded area/part, and also can make the length of the unwelded area/part substantially zero.

[Fourth implementation] The welding device in this implementation does not include the movement device <NUM>. The feed device <NUM> continuously feeds the webs <NUM> and the strip member <NUM> in their longitudinal direction. If the feed device <NUM> receives the input indicating the stop of the feed, it stops the webs <NUM> and the strip member <NUM>. Specifically, after receiving the input, the feed device <NUM> retracts the webs <NUM> and the strip member <NUM> by the length h and then stops them. More specifically, the feed device <NUM> switches the pair of drive rollers <NUM> from forward rotation to backward rotation to retract the webs <NUM> and the strip member <NUM> by the length h, and then halts the pair of drive rollers <NUM> to stop the webs <NUM> and the strip member <NUM>. As illustrated in <FIG>, this causes the already welded part of the web(s) <NUM> and the strip member <NUM> to be retracted upstream from the pair of the pressure rollers <NUM> by the length h in the process of stopping the web <NUM> and the strip member <NUM>. As a result, the welded part is located in the section P-P'.

Then, if the feed device <NUM> restarts to feed the webs <NUM> and the strip member <NUM> in response to receiving the input indicating the start of the feed, the unwelded area with length c is generated as in the third implementation. The length c of this unwelded area is shorter than the length b of the conventional unwelded area by the length h (c = b - h). In this way, this implementation also allows for shortening the unwelded part. As in the second implementation, setting the longer retraction length h allows for the shorter length of the unwelded area/part and also can make the length of the unwelded area/part substantially zero.

The preferred implementations of the present invention have been described above.

The strip member <NUM> is irradiated with the laser beam <NUM> in each of the implementations. Alternatively, the web <NUM> may have a light absorption layer, and be irradiated with the laser beam <NUM> so as to weld the web <NUM> and the strip member <NUM> to each other.

As illustrated in <FIG>, each laser device <NUM> in the respective implementations may be fixed to a base shaft <NUM> which may be supported by a stage (not shown). The stage may be configured to be movable together with the base shaft <NUM> in the feed direction Y and its opposite direction with respect to the pair of pressure rollers <NUM>. The base shaft <NUM> may be supported by the stage to be movable in width direction X of the web <NUM> with respect to the pair of pressure rollers <NUM>. The base shaft <NUM> may also be supported by the stage to be movable with respect to the pair of pressure rollers <NUM> in the direction Z which is perpendicular to the directions X and Y. The base shaft <NUM> may be supported by the stage to be rotatable around its axis (direction Φ). These allow for free adjustment of the position and orientation of the laser device <NUM>, and thus of the irradiation position and irradiation angle θ (see <FIG>, etc.) of the laser beam <NUM>.

There are several factors that should be adjusted in order to irradiate the strip member <NUM> with the laser beam <NUM>. It is preferable that the factors that a user has to adjust are minimized. Therefore, it is preferable to provide a user with the welding device as a product in which the directions Y, Z, Φ (and thus the irradiation angle θ and the irradiation distance) have been adjusted and fixed in advance. This is because a user only has to adjust the irradiation position in the width direction X of the web <NUM> for welding. This is user-friendly.

The laser device <NUM> may have a function to radiate a laser beam <NUM> of visible light with low output. A user can easily adjust and check the irradiation position in advance using such a laser beam <NUM> as an indicator before welding.

As illustrated in <FIG>, a camera <NUM> may be attached to the laser device <NUM> such that the irradiation position of the laser beam <NUM> is within its imaging range. A display may indicate the image acquired by the camera <NUM> on the real time basis. A user can check the irradiation of the laser beam <NUM> at a position away from there on the real time basis.

As illustrated in <FIG>, each of the pressure rollers <NUM> includes a part <NUM> for pressuring the web(s) <NUM> and the strip member <NUM>, and parts <NUM> adjacent to the part <NUM>. The pressure roller <NUM> is generally made of carbon, and in this case, the part <NUM> may be thicker than the parts <NUM>. Alternatively, only the part <NUM> is made of the material (such as metal) with higher stiffens than carbon. The part <NUM> made of carbon has a problem that it is bent when pressurizing so that its cross section is deformed into an elliptical shape. The above configuration solves this problem.

Since the carbon absorbs the laser beam <NUM>, the surface of the part of the pressure roller <NUM> where the laser beam <NUM> passes by may have a color which reflects the laser beam <NUM>. Such color may include, for example, white or silver. For example, a foil made of material such as aluminum which reflects the laser beam <NUM> may be pasted or wound on the main body of the pair of pressure rollers <NUM>. The web <NUM> which is transparent to the laser beam <NUM>, has a possibility that the carbon of the pressure roller <NUM> absorbs the laser beam <NUM> to generate heat, resulting in heating the web <NUM>. The above configuration solves this problem.

Although the welding devices in the respective implementations are incorporated into the bag making apparatus in <FIG> or <FIG>, they may be incorporated into other types of bag making apparatuses. For example, the welding devices may be incorporated into a pillow-bag making apparatus in <FIG>.

In the pillow-bag making apparatus illustrated in <FIG>, as a continuous sheet panel <NUM> (web) is intermittently or continuously fed in the longitudinal direction Y thereof, the sheet panel <NUM> is guided by a well-known sheet panel guide mechanism (not shown) to be folded into a cylindrical shape such that one side part <NUM> thereof and the other side part <NUM> thereof face each other. The side parts <NUM> and <NUM> are then guided by the sheet panel guide mechanism to the pair of pressure rollers <NUM>. The zipper <NUM> (strip member) in <FIG> is also guided by the guide roller <NUM> and the guide body <NUM> to be interposed between the side parts <NUM> and <NUM> and to pass though the pair of pressure rollers <NUM>. This causes the side parts <NUM> and <NUM> and the zipper <NUM> to be superposed on each other and to be fed through the pair of the pressure rollers <NUM> in a superposed state. The two laser devices <NUM> are arranged to irradiate both surfaces <NUM> (<FIG>) of the zipper <NUM> with the laser beams <NUM> at a position upstream of the pair of pressure rollers <NUM>.

Therefore, the side part <NUM> of the sheet panel <NUM> and one surface <NUM> of the zipper <NUM> are caused to be welded to each other by the pair of pressure rollers <NUM>, and at the same time, the side part <NUM> of the sheet panel <NUM> and the other surface <NUM> of the zipper <NUM> are caused to be welded to each other by the pair of pressure rollers <NUM>.

Thereafter, the side parts <NUM> and <NUM> may be sealed to each other by the seal device <NUM> in the longitudinal direction thereof along a section which is closer to the edge than the zipper <NUM>. Although not illustrated, contents are then filled in the sheet panel <NUM>. The sheet panel <NUM> is then sealed in the width direction thereof, so that the sealed part <NUM> is formed. The sheet panel <NUM> and the zipper <NUM> are then cut in the width direction thereof. Thereby, the plastic bag <NUM>' illustrated in <FIG> is shaped. In the case where the aforementioned unwelded part is generated, it is preferably included in the sealed part <NUM>.

An exemplary pillow-bag making apparatus illustrated in <FIG>, which does not form part of the invention but illustrated for understanding the invention, makes plastic bags <NUM>' having no zipper. In this implementation, a surface of the side part <NUM> facing the other side part <NUM> is made of the light absorption layer. One laser device <NUM> irradiates this surface with the laser beam <NUM> to melt this surface. The side parts <NUM> and <NUM> are pressurized by the pair of the pressure rollers <NUM> to be welded (sealed) to each other. This implementation requires only one laser device <NUM> and can dispense with the downstream seal device <NUM> (<FIG>). Therefore, the bag making apparatus can be made smaller and simpler as a whole.

The laser beam <NUM> may be radiated to the side part <NUM> from the inside of the sheet panel <NUM> as illustrated in <FIG> which does not form part of the invention but illustrated for understanding the invention. In the case where the side part <NUM> is transparent to the laser beam <NUM>, the laser beam <NUM> may be radiated to the side part <NUM> through the side part <NUM> as illustrated in <FIG> which does not form part of the invention but illustrated for understanding the invention. For this, the side part <NUM> is, for example, made of material which is highly transparent to the laser beam <NUM>, and printed on using ink with high transparency.

Instead of the plastic film, the web <NUM> may include, for example, a base made of paper and a film or resin material partially or entirely laminated to the base. The web <NUM> may be made of any one or more materials as long as it at least partially has a surface weldable to the strip member <NUM>.

Instead of the zipper which includes the male member <NUM> and the female member <NUM> fitted to each other, the strip member <NUM> may be, for example, a male member of a zipper, a female member of a zipper, a male member of a hook-and-loop fastener, a female member of a hook-and-loop fastener, a hook-and-loop fastener (which includes a male member and a female member engaged with each other), an adhesive tape, a seal tape, a tape-like reinforcing member, a tape-like decorative member, a tape-like header of a bag, and so on. The strip member <NUM> may be made of any one or more materials, as long as it at least partially has a surface weldable to the web <NUM>.

The pair of pressure members <NUM> may have other configurations than the pair of pressure rollers.

Claim 1:
A welding device for welding a web (<NUM>) and a continuous strip member (<NUM>) to each other, the welding device comprising:
a pair of pressure members (<NUM>) opposing each other for pressurizing the web (<NUM>) and the continuous strip member (<NUM>);
a feed device (<NUM>) configured to intermittently feed the web (<NUM>) and the continuous strip member (<NUM>) in a longitudinal direction of the web (<NUM>) and the continuous strip member (<NUM>) through the pair of pressure members (<NUM>) in a state in which the web (<NUM>) and the continuous strip member (<NUM>) are superposed on each other; and
a laser device (<NUM>) configured to irradiate the web (<NUM>) or the continuous strip member (<NUM>) with a laser beam (<NUM>) at a position upstream of the pair of pressure members (<NUM>) so as to melt the web (<NUM>) or the continuous strip member (<NUM>) with the laser beam (<NUM>) for welding of the web (<NUM>) and the continuous strip member (<NUM>);
characterized in that the welding device further comprises a movement device (<NUM>) configured to move the pair of pressure members (<NUM>) upstream with respect to the web (<NUM>) and the continuous strip member (<NUM>) during a pause phase of an intermittent feed cycle.