P/00/009A Section 29 AUSTRALIA Patents Act 1990 INNOVATION PATENT SPECIFICATION Invention Title: PACKAGING MACHINE Applicant: Ishida Co., Ltd. The invention is described in the following statement: 1 7019 PACKAGING MACHINE PRIORITY CROSS-REFERENCE 100011 This application claims priority from Japanese Patent Application No. 2011-030642 filed on 16 February 2011, the contents of which are to be taken as incorporated herein by this reference. FIELD OF THE INVENTION 100021 The present invention relates to a packaging machine, and particularly relates to a packaging machine in which a conveyed packaging material is formed into a tubular shape, articles are dropped into the tubular shape, and the packaging material is then laterally sealed with the articles packaged therein. BACKGROUND TO THE INVENTION [00031 The following discussion of the background to the invention is intended to facilitate an understanding of the invention. However, it should be appreciated that a reference herein to a patent document or other matter which is given as prior art is not to be taken as an admission that that document or matter was, in Australia, known or that the information it contains was part of the common general knowledge as at the priority date of any of the claims. 100041 Vertical packaging machines are common as devices for packaging food products or other packaged articles by simultaneously manufacturing bags and loading packaged articles into the bags. 100051 In the pillow packaging machine disclosed in Japanese Laid-open Patent Publication No. 2004-142806, a sheet packaging material is formed into a tubular shape by a former and a tube. A vertical joint of the tubular packaging material is vertically sealed by a vertical 2 sealing means. The article is then loaded into the tubular packaging material, and a lateral seal is performed across the top part of the bag and the bottom part of the succeeding bag by a lateral sealing mechanism. The center of the laterally sealed portion is cut by a cutter. 100061 In packaging machines such as the one described above, the bag size must be reduced and the fill ratio increased in order to reduce packaging material cost and transportation cost. However, increasing the fill ratio leads to the risk of the packaged article fragmenting or becoming trapped in the sealed portion. 100071 It would therefore be desirable to provide a packaging machine whereby packaged articles can be prevented from fragmenting and becoming trapped in the sealed portion, and the fill ratio of packaged articles can be increased. SUMMARY OF THE INVENTION 100081 A packaging machine according to a first aspect of the present invention is a packaging machine that drops articles into a packaging material formed in a tubular shape and that seals the packaging material making a bag. The packaging machine includes a pair of sealing jaws and a pair of shutters. The pair of sealing jaws selectively holds the packaging material therebetween in a direction intersecting the conveyance direction of the packaging material and selectively seals the packaging material. The pair of shutters selectively holds the packaging material therebetween in a direction intersecting the conveyance direction and temporarily impedes the advancement of the packaged articles. The shutters operate in synchronization with operation of the sealing jaws such that the shutters hold the packaging material prior to holding and sealing by the sealing jaws. Upon the shutters holding the packaging material therebetween, the shutters advance a first distance in the conveyance direction, and further advance a second distance in the conveyance 3 direction while shaking the packaging material in the state in which the packaging material is held therebetween. 100091 In this packaging machine, since the shutters hold the packaging material therebetween and shake the packaging material, the packaged articles on the upstream side of the shutters aggregate toward the shutter side while the vibration of the shutters causes the gaps between the packaged articles to be filled. Since the packaged articles aggregate by inertia due to the vibration, fragmentation thereof is less likely than in a case in which the packaged articles are compressed by direct contact. 100101 A packaging machine according to a second aspect of the present invention is the packaging machine according to the first aspect, further comprising a cam for contacting and guiding a portion of the shutters in a predetermined path. A flat surface and a waved surface are formed in order in the conveyance direction on a surface of the cam. 100111 In this packaging machine, merely by the movement of a portion of the shutters on the waved surface of the cam, the shutters are shaken in accordance with the waved pattern. This configuration is achieved by a simple mechanism, and the ability to easily change the pattern of shaking by changing the waves on the cam surface gives the design a high degree of freedom. [00121 A packaging machine according to a third aspect of the present invention is the packaging machine according to the first aspect, wherein the shutters are coil springs. 100131 In this packaging machine, since the pair of shutters descends while holding the packaging material therebetween and shaking, the inertial force at reversal of the shaking direction acts in the direction in which the shutters open. However, the shutters are coil 4 springs and therefore flex in response to the acting inertial force, and the shaking is kept from enlarging the gap between the shutters. [00141 A packaging machine according to a fourth aspect of the present invention is the packaging machine according to the second or third aspect, wherein portions of the shutters that contact the cam are rollers. [00151 There is a risk of noise or abrasion at the portion that contacts the cam surface when the speed at which the shutters descend increases, but in this packaging machine, contact via rollers suppresses noise and abrasion. [00161 A packaging machine according to a fifth aspect of the present invention is the packaging machine according to any of the first through third aspects, wherein the sealing jaws seal the packaging material while the shutters are advancing the first distance. [00171 In this packaging machine, since sealing is performed before the shutters begin shaking, fragments of the packaged articles are prevented from becoming trapped in the sealed portion even when fragments drop from the gap between the shutters after the shutters begin shaking. Advantageous Effects of Invention 100181 In the packaging machine of the present invention, since the shutters hold the packaging material therebetween and shake the packaging material, the packaged articles on the upstream side of the shutters aggregate toward the shutter side while the vibration of the shutters causes the gaps between the packaged articles to be filled. Since the packaged articles aggregate by inertia due to the vibration, fragmentation thereof is less likely than in a case in which the packaged articles are compressed by direct contact. 5 BRIEF DESCRIPTION OF THE DRAWINGS 100191 FIG. 1 is a perspective view showing a packaging machine according to an embodiment of the present invention. 100201 FIG. 2 is a perspective view showing the overall configuration of a bag-making and packaging unit of the packaging machine. 100211 FIG. 3 is a perspective view showing a vibration-imparting mechanism of the packaging machine. 100221 FIG. 4A is a side view showing a shutter mechanism of the packaging machine immediately before a first state. 100231 FIG. 4B is a side view showing the shutter mechanism in the first state. 100241 FIG. 4C is a side view showing the shutter mechanism in a second state. 100251 FIG. 5 is a side view showing a lateral sealing mechanism of the packaging machine, the lateral sealing mechanism including sealing jaws. 100261 FIG. 6 is a side view showing a trajectory of the sealing jaws. 100271 FIG. 7 is a plan view showing the area around the sealing jaws. 100281 FIG. 8 is an external perspective view showing a lateral drive mechanism of the sealing jaws. 100291 FIG. 9 is a chart showing synchronization of movements of the packaging machine, with the periods of discharge of the products, opening and closing of brushes of the vibration imparting mechanism, opening and closing of the shutter mechanism, and opening and closing of the sealing jaws being depicted graphically. 100301 FIG. 10 is a side view showing a shutter mechanism in a first state in the packaging 6 machine in accordance with a second embodiment. DESCRIPTION OF EMBODIMENT [00311 Embodiments of the present invention are described below with reference to the accompanying drawings. The embodiments described below are specific examples of the present invention and do not limit the technical scope of the present invention. (1) Configuration of the Packaging Machine 1 [00321 FIG. I is a perspective view showing a packaging machine according to an embodiment of the present invention. FIG. 2 is a perspective view showing the overall configuration of a bag-making and packaging unit of the packaging machine. In FIGS. I and 2, the packaging machine I is provided with a combination weighing device 2, a bag making and packaging unit 5, and a film feeding unit 6. 100331 The combination weighing device 2 weighs a packaged article and discharges a predetermined total weight thereof. The bag-making and packaging unit 5 is a main component for packing the packaged articles into bags. The film feeding unit 6 feeds a film F for forming bags to the bag-making and packaging unit 5. 10034] Operating switches 7 are provided on a front surface of the bag-making and packaging unit 5. A touch-panel display 8 for displaying operating states is positioned so as to be visible to a worker operating the operating switches 7. 100351 The combination weighing device 2, the bag-making and packaging unit 5, and the film feeding unit 6 are controlled in accordance with operations and settings inputted from the operating switches 7 and the touch-panel display 8. The operating switches 7 and the touch-panel display 8 are connected to a controller (not shown in the drawings) composed of 7 a CPU, ROM, RAM, and other components, and the controller takes in necessary information from various sensors provided to the combination weighing device 2 and the bag-making and packaging unit 5 and uses the information in various types of control. (2) Detailed Configuration (2-1) Combination Weighing Device 2 100361 The combination weighing device 2 is disposed on top of the bag-making and packaging unit 5, and after products C are weighed in a weighing hopper, the combination weighing device 2 combines the weighed values to achieve a predetermined total weight and sequentially discharges the products. (2-2) Film Feeding Unit 6 [00371 The film feeding unit 6 is a unit for feeding a sheet film F to a forming mechanism 13 of the bag-making and packaging unit 5, and is provided adjacent to the bag-making and packaging unit 5. A roll on which the film F is wound is set in the film feeding unit 6, and the film F is unwound from the roll. (2-3) Bag-making and Packaging Unit 5 100381 The bag-making and packaging unit 5 is composed of the forming mechanism 13, a pull-down belt mechanism 14, a vertical sealing mechanism 15, a shutter mechanism 16, a lateral sealing mechanism 17, a vibration-imparting mechanism 19, and a lateral drive mechanism 55. 100391 The forming mechanism 13 forms the film F conveyed in the form of a sheet into a tubular shape. The pull-down belt mechanism 14 conveys the tubular film E (hereinafter referred to as the tubular film Fm) downward. The vertical sealing mechanism 15 seals 8 overlapping portions (joints) of the tubular film Fm in the vertical direction. [00401 The shutter mechanism 16 holds the top part of the tubular film Fm therebetween to prevent the packaged article from being trapped in the sealed part before the sealed part is sealed by the lateral sealing mechanism 17, and the shutter mechanism 16 oscillates with the tubular film Fm in the clamped state. 100411 The lateral sealing mechanism 17 seals the top and bottom ends of the bag closed by sealing the tubular film Fm in the lateral direction. The vibration-imparting mechanism 19 imparts vibration to the tubular film Fm. The lateral drive mechanism 55 causes the shutter mechanism 16 and the lateral sealing mechanism 17 to move in reciprocating fashion. 100421 These mechanisms are supported by a support frame 12. The area surrounding the support frame 12 is covered by a casing 9. (2-3-1) Forming Mechanism 13 100431 The forming mechanism 13 has a former 13a and a tube 13b, and the combination of these two is generally referred to as a former. The tube 13b is a member extending in the vertical direction, a portion of the tube 13b being formed in a tubular shape, and the top and bottom ends thereof are open. The products C weighed by the combination weighing device 2 are placed in the opening at the top end of the tube 13b. The former 13a is provided so as to surround the tube 13b. The sheet film F unwound from the film roll is formed into a tubular shape as the sheet film F passes between the former 13a and the tube 13b. The former 13a and tube 13b of the forming mechanism 13 can be replaced according to the size of the bags, to be manufactured. (2-3-2) Pull-down Belt Mechanism 14 9 100441 As shown in FIG. 2, the pull-down belt mechanism 14 is a mechanism for adhering to the tubular film Fm wrapped around the tube 13b and continuously conveying the tubular film Fm downward, and is provided with belts 14c on the left and right sides of the tube 13b. In the puUl-down belt mechanism 14, belts 14c having adhesive capability are rotated by drive rollers 14a and following rollers 14b, and the tubular film Fm is thereby carried downward. In FIG. 2, a roller drive motor for rotating the drive rollers 14a and the like are not shown. (2-3-3) Vertical Sealing Mechanism 15 100451 The vertical sealing mechanism 15 is a mechanism for vertically sealing the overlapping portion of the tubular film Fm wrapped around the tube 13b by heating the overlapping portion while pushing the overlapping portion against the tube 13b with a certain pressure. The vertical sealing mechanism 15 is positioned in front of the tube 13b, and has a heater and a heater belt that is heated by the heater and placed in contact with the overlapping portion of the tubular film Fm. The vertical sealing mechanism 15 is also provided with a drive device (not shown in the drawings) for moving the heater belt toward and away from the tube 13b. (2-3-4) Vibration-imparting Mechanism 19 10046] As shown in FIG. 2, the vibration-imparting mechanism 19 is positioned above the shutter mechanism 16 and the lateral sealing mechanism 17. FIG. 3 is a perspective view showing the vibration-imparting mechanism. In FIG. 3, the vibration-imparting mechanism 19 is composed of a pair of cylindrical brushes 191, a motor 193 for rotating the brushes 191, and an air cylinder 195 for moving the brushes 191 horizontally. 10047] The pair of brushes 191 face each other and hold the tubular film Fm therebetween. 10 The brushes 191 are formed by embedding resin bristles 191b in a cylindrical core 191a. The core 191a is attached to a rotary shaft of the motor 193 via a joint 192. Each of the brushes 191 defines a central axis. The rotary shaft of the motor 193 defines a rotational axis. The brushes 191 are attached so that the rotary shaft of the motor 193 (the rotational axis) and the central axis of the core 191a are spaced apart from one another by a predetermined distance, and the pair of brushes 191 are rotated by the driving of the motor 193 while being moved toward or apart from each other. Since the brushes 191 and the tubular film Fm are in contact with each other, the tubular film Fm is vibrated by the rotation of the brushes 191. 100481 The air cylinder 195 moves the brushes 191 and the motor 193 integrally with each other. The pair of brushes 191 can be moved by the air cylinder 195 in repeated reciprocal motion so as to alternate between moving toward each other in the direction of holding the tubular film Fm therebetween and moving in the direction away from each other. 100491 The predetermined quantity of packaged articles dropped from above the tube 13b generally passes into the tubular film Fm as a vertical stream, and is therefore prone to become bulky in the vertical direction. However, when the packaged articles are dropped while the tubular film Fm is being held between the brushes 191, the advancement of the leading end of the vertical stream of packaged articles is impeded, and the distance between the leading end and the trailing end is reduced. The vibration created by the rotation of the brushes 191 is also transmitted to the packaged articles, the gaps between packaged articles are filled, and an aggregation is formed in which the occupied space is further reduced. 100501 Since the rotation and reciprocal movement of the brushes 191 creates a rotation 11 which sends articles in the conveyance direction while vibrating the point of contact of the brushes 191 and the tubular film Fm, the articles are sent toward the lateral sealing mechanism 17 when the brushes 191 move apart from each other. (2-3-5) Shutter Mechanism 16 100511 The shutter mechanism 16 holds the top of the sealed portion of the tubular film Fm therebetween immediately in front of the lateral seal and stops the packaged articles so that packaged articles or fragments thereof are not trapped in the seal part during lateral sealing of the tubular film Fm. The shutter mechanism 16 repeatedly alternates between a first state of holding the tubular film Fm therebetween and descending, and a second state of moving away from the tubular film Fm until again holding the tubular film Fm therebetween. 100521 FIG. 4A is a side view showing the shutter mechanism immediately before the first state. FIG. 4B is a side view showing the shutter mechanism in the first state. FIG. 4C is a side view showing the shutter mechanism in the second state. In FIGS. 4A, 4B, and 4C, sealing jaws are indicated by dashed-dotted lines to facilitate understanding of the relationship between the shutter mechanism 16 and the lateral sealing mechanism 17. 100531 As shown in FIG. 4A, the shutter mechanism 16 is composed of a shutter cam 170 and a pair of mechanisms 160 which move along a cam surface of the shutter cam 170. The mechanisms 160 are each composed of a supporting member 161, a linking member 163, a roller 165, a shutter member 167, and a spring member 169. [00541 The shutter cam 170 has a cam surface 171 which includes a flat surface 171a and a waved surface 171 b, over which the roller 165 is driven. 100551 The supporting members 161 are members for supporting sealing jaws 51a, 51b, and 12 the supporting members 161 also support the linking members 163 so as to allow the linking member 163 to rotate. 100561 In each linking member 163, a long link 163a and a short link 163b are connected in a V shape, and a connecting part 163c thereof is rotatably supported by the supporting member 161. A roller 165 and a shutter member 167 are attached to a distal end of each long link 163a. One end of each spring member 169 is also connected to a distal end of a short link 163b, and the other end of each spring member 169 is fixed to a supporting member 161. Consequently, the linking member 163 is urged by the urging force of the spring member 169 in the direction in which the distal ends of the pair of long links 163a approach each other. [00571 The rollers 165 are attached so as to be able to rotate at the distal ends of the long links 163a of the linking members 163. The rollers 165 roll along the cam surface 171 of the shutter cam 170 during the period before and after lateral sealing. The cam surface 171 includes a flat surface 171a that extends a first distance in the conveyance direction of the tubular film Fm, and a waved surface 171b that extends a second distance after the flat surface 171a. 100581 When the rollers 165 roll over the flat surface 171a, the pair of shutter members 167 descend the first distance vertically while holding the tubular film Fm therebetween. When the rollers 165 roll over the waved surface 171b, the pair of shutter members 167 descend the second distance while oscillating and holding the tubular film Fm therebetween. 100591 For convenience in the description, the zone in which the rollers 165 roll over the flat surface 171a is referred to as the first zone, and the zone in which the rollers 165 roll over 13 the waved surface 171b is referred to as the second zone. Lateral sealing of the tubular film Fm is performed when the pair of rollers 165 is in the first zone. When the pair of rollers 165 is in the second zone, the tubular film Fm oscillates in a direction which intersects with the conveyance direction and the lateral direction. 100601 The shutter members 167 are longer than the width of the tubular film Fm, and both ends thereof are fixed at the distal ends of the long links 163a of the linking members 163. The pair of shutter members 167 hold the tubular film Fm therebetween earlier than the sealing jaws 51, and prevent the products C from falling above the sealed portion during lateral sealing of the tubular film Fm. At least the portion of the shutter members 167 that holds the tubular film Fm therebetween is a coil spring. (2-3-6) Lateral Sealing Mechanism 17 100611 FIG. 5 is a side view showing the lateral sealing mechanism. FIG. 6 is a side view showing the trajectory of the sealing jaws. As shown in FIG. 5, the lateral sealing mechanism 17 has a first sealing mechanism 50a and a second sealing mechanism 50b. The sealing mechanism positioned to the left of the tubular film Fm in FIG. 5 is the first sealing mechanism 50a, and the sealing mechanism positioned to the right of the tubular film Fm is the second sealing mechanism 50b. 100621 The first sealing mechanism 50a and second sealing mechanism 50b hold the tubular film Fm therebetween while causing the sealing jaws 51, 52, respectively, to turn in a D shape (see, for example, the trajectory of the sealing jaws indicated by dotted lines in FIG. 6). 100631 The sealing jaws 51, 52 have heaters in the inside thereof. Sealing surfaces of the sealing jaws 51, 52 are heated by the heaters, and a portion of the tubular film Fm held 14 between the sealing jaws 51, 52 is thereby sealed. 100641 For convenience in this description, the sealing jaw 51 on the side of the first sealing mechanism 50a is referred to as the first sealing jaw 51a, and the sealing jaw 51 on the side of the second sealing mechanism 50b is referred to as the second sealing jaw 51b. The first sealing jaw 51 a and the second sealing jaw 51b hold the tubular film Fm therebetween and press against each other to form a seal. 100651 In the same manner, the sealing jaw 52 on the side of the first sealing mechanism 50a is referred to as the first sealing jaw 52a, and the sealing jaw 52 on the side of the second sealing mechanism 50b is referred to as the second sealing jaw 52b. The first sealing jaw 52a and the second sealing jaw 52b hold the tubular film Fm therebetween and press against each other to form a seal. 100661 The term "sealing jaws 51, 52" is used when referring to components that are common to both sealing jaws. 100671 The sealing jaws 51, 52 are rotated about axes Cl, C2 by a drive motor (not shown). Specifically, the first sealing jaws 51a, 52a are rotated about the axis Cl, and the second sealing jaws 51b, 52b are rotated about the axis C2. [00681 FIG. 7 is a plan view showing the area around the sealing jaws. In FIG. 7, heaters 71 and a cutting mechanism 72 are built into the sealing jaws 51. The heaters 71 are inserted two each into the first sealing jaw Sa and the second sealing jaw 51b in the longitudinal direction thereof. The heaters 71 receive electrical power from electrical wiring 76a to generate heat, and heat the first sealing jaw 51a and second sealing jaw 51b to a sealing temperature that corresponds to the tubular film Fm. 15 100691 The cutting mechanism 72 is provided to the first sealing jaw 51 a on the side of the first sealing mechanism 50a, and has a cutter 72a and a cutter driving mechanism 72b. In accordance with the sealing timing of the tubular film Fm, the cutter 72a is advanced by the cutter driving mechanism 72b toward the second sealing jaw 51b from inside a slide space formed in the first sealing jaw 5Ia. 100701 An air cylinder is employed in the cutter driving mechanism 72b to reciprocally move the cutter 72a in a predetermined direction. Therefore, between the first sealing jaw 51 a and the second sealing jaw 51b, or between the first sealing jaw 52a and the second sealing jaw 52b, the cutter 72a presses on the position of the sealed portion substantially at the center in the width direction thereof, and the sealed portion is cut. As a result, one bag at a time is separated off and discharged to a chute conveyor 23 (refer to FIG. 1). (2-3-7) Lateral Drive Mechanism 55 100711 FIG. 8 is an external perspective view showing the lateral drive mechanism of the sealing jaws. In FIG. 8, the first sealing mechanism 50a is supported by a first horizontal movement plate 61a, and the second sealing mechanism 50b is supported by a second horizontal movement plate 61b. The first horizontal movement plate 61a and the second horizontal movement plate 61b are moved horizontally by the lateral drive mechanism 55 shown in FIG 8. 100721 As shown in FIG. 8, the lateral drive mechanism 55 has a drive mechanism 65 for moving the first horizontal movement plate 61a and the second horizontal movement plate 61 b toward or away from each other. 100731 The drive mechanism 65 has a ball screw 80a, a first nut 81, a second nut 82, a first 16 connecting rod 83, a second connecting rod 84, third connecting rods 85, and a fourth connecting rod 86. 100741 The ball screw 80a is rotated by a servo motor 80 (refer to FIG. 3). The first nut 81 and the second nut 82 are screwed onto the ball screw 80a. The first connecting rod 83 and the second connecting rod 84 are provided so as to be orthogonal to the ball screw 80a in the horizontal direction. The pair of third connecting rods 85 are provided in the direction of movement of the first horizontal movement plate 61a and the second horizontal movement plate 61b. The fourth connecting rod 86 is provided parallel to the third connecting rods 85. [00751 The first connecting rod 83 is connected to the third connecting rods 85 via a joint 87, and distal ends of the third connecting rods 85 are fixed to a lateral end surface of the second horizontal movement plate 61b. The third connecting rods 85 are passed through the first horizontal movement plate 61a so as to be able to slide. 10076] The second connecting rod 84 is connected to the fourth connecting rod 86 via a joint 88, and a distal end of the fourth connecting rod 86 is fixed to a lateral end surface of the first horizontal movement plate 61a. 100771 The portion of the ball screw 80a on which the first nut 81 is screwed and the portion of the ball screw 80a on which the second nut 82 is screwed are threaded in opposite directions each other. [00781 Through the drive mechanism 65 described above, the first horizontal movement plate 61 a and the second horizontal movement plate 61 b can be moved toward or away from each other by rotation of the ball screw 80a. (3) Operation of the Packaging Machine 1 17 100791 The sequence of operations of the packaging machine 1 will next be described. Packaged articles (hereinafter referred to as products C) weighed by the combination weighing device 2 are sequentially dropped into the top open end of the tube 13b. At this time, the outer periphery of the tube 13b is covered by the tubular film Fm for packaging the products C. [00801 The products C pass through the tube l3b, and are discharged from the bottom open end of the tube 13b. Below the bottom open end, the pair of brushes 191 hold the tubular film Fm therebetween and temporarily block the passage of the products C. 100811 FIG. 9 is a chart showing synchronized operation of the periods of discharge of the products C, opening and closing of the brushes, opening and closing of the shutter, and opening and closing of the sealing jaws. Here, "closed" means that the tubular film Fm is held closed so that products C are not allowed to pass through, and "open" means that the closing off of the tubular film Fm is released and products C are allowed to pass through. 100821 In FIG. 9, the brushes 191 are closed from before the products C are dropped, and the brushes 191 begin to open when the controller receives a signal (discharge completion signal) indicating that products C have been discharged from the combination weighing device 2. Therefore, the period during which advancement of the products C is stopped by the brushes 191 is short. During this short period, the distance between the leading end and the trailing end of the products C advancing as a vertical stream is reduced, vibration created by rotation of the brushes 191 is transmitted to the packaged articles, and the gaps between products C are filled. The brushes 191 move apart from each other and send out the products C while vibrating the tubular film Fm by the rotation and reciprocal movement. 18 100831 In FIG. 9, since the shutter members 167 are closed from before the brushes 191 begin to open, the products C are stopped between the brushes 191 and the shutter members 167, and during this time, the products C are vibrated by the rotation of the brushes 191 so that the gaps between the products C are further filled. The shutter members 167 descend the first distance vertically in the closed state, and then descend the second distance while oscillating. The oscillation of the shutter members 167 is transmitted to the products C, and the gaps between the products C are further filled. [00841 In FIG. 9, while the shutter members 167 are closed, the first sealing jaw 5]a and the second sealing jaw 51 b hold and laterally seal the tubular film Fm therebetween, the tubular film Fm being positioned below the shutter members 167. Lateral sealing is performed while the shutter members 167 descend the first distance, the top part of a bag and the bottom part of the succeeding bag are formed, the center of the sealed part is simultaneously cut, and a bag packed with products C is completed. (4) Characteristic Features (4-1) 100851 In the packaging machine 1, since the pair of shutter members 167 holds the tubular film Fm therebetween and shakes the tubular film Fm, the packaged articles on the upstream side of the shutter members 167 aggregate toward the side of the shutter members 167 while the vibration of the shutter members 167 causes the gaps between the packaged articles to be filled. Since the packaged articles aggregate by inertia due to the vibration, fragmentation thereof is less likely than in a case in which the packaged articles are compressed by direct contact. 19 (4-2) 100861 In the packaging machine 1, merely by the movement of the rollers 165 on the waved surface 171b of the shutter cam 170, the shutter members 167 are shaken in accordance with the waved surface 171b. This configuration is achieved by a simple mechanism, and the ability to easily change the pattern of shaking by changing the waves on the cam surface gives the design a high degree of freedom. Since the portions that contact the shutter cam 170 are rollers 165, noise and abrasion are suppressed. (4-3) 100871 In the packaging machine 1, since the pair of shutter members 167 descends while holding the tubular film Fm therebetween and shaking, the inertial force at reversal of the shaking direction acts in the direction in which the shutters open. However, the shutter members 167 are coil springs and therefore flex in response to the acting inertial force, and the shaking is therefore kept from enlarging the gap between the shutter members 167. (4-4) 100881 In the packaging machine 1, the sealing jaws 51 seal the tubular film Fm while the pair of shutter members 167 is advancing the first distance. Specifically, since sealing is performed before the shutter members 167 begin shaking, fragments of the packaged articles are prevented from becoming trapped in the sealed portion even when fragments drop from the gap between the shutter members 167 after the shutter members 167 begin shaking. (5) Modifications 100891 In the embodiment described above, the cam surface 171 of the shutter cam 170 is not left-right symmetrical about the central axis thereof in the longitudinal direction, but this 20 configuration is not limiting, and the cam surface 171 may be left-right symmetrical. 100901 FIG. 10 is a side view showing the shutter mechanism in the first state in the packaging machine according to a modification. In FIG. 10, the cam surface 171 is left-right symmetrical about the central axis CO. Consequently, when the pair of rollers 165 descends at the same height position, the shutter members 167 are opened by the peaks of the waved surface. Since the shutter members 167 are thereby unable to cause the tubular film Fm to oscillate, the height position is varied so that when one of the pair of rollers 165 is facing a peak, the other is facing a valley. As a result, the shutter members 167 can oscillate while closing the tubular film Fm. Industrial Applicability [00911 Through the present invention, the amount of packaging material used can be reduced while fragmentation of packaged articles and trapping of fragments of packaged articles in the sealed portion are suppressed. The present invention is therefore useful in packaging machines in general. [00921 Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. It is understood that the invention includes all such variations and modifications which fall within the spirit and scope. [00931 Throughout the description and claims of the specification the word "comprise" and variation of the word, such as "comprising" and "comprises", is not intended to exclude other additives, components, integers or steps. 21