GB1590317A

GB1590317A - Machine for making bags from plastics material

Info

Publication number: GB1590317A
Application number: GB47006/77A
Authority: GB
Original assignee: Printex
Current assignee: Printex
Priority date: 1976-11-12
Filing date: 1977-11-11
Publication date: 1981-05-28
Also published as: IT1080578B; FR2370580B1; DE2750392C2; FR2370580A1; DK497477A; DE2750392A1

Description

(54) MACHINE FOR MAKING BAGS FROM PLASTICS MATERIAL (71) We, PRINTEX, a Belgian body corporate, Neder-Over-Heembeek, Belgium, 62, Chaussée de Vilvorde, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:: This invention relates to a machine for making bags from plastics material, the machine being of the kind, in which at least one strip of plastics material is fed intermittently, and cut and fused by a movable fusing bar cooperating with a fixed member, and which machine further comprises a device for blowing pressurized on either side of a strip fed to the machine for moving the strip downstream of the fusing bar, means arranged at the machine outlet to form at least one stack of bags and including means for holding or releasing a formed bag stack at or from the machine outlet, and means for discharging a formed bag stack.

The invention aims to provide a machine of the kind referred to which is provided, at the outlet thereof, with an automatic device for piling bags which allows bags with bottom sealing (that is either a bag with bottom sealing and open mouth, or a so-called "jacket bag" with seals at both ends and in which a cut-out is made to form the bag handles) to be stacked correctly so that up to at least a hundred bags, according to the thickness of the material being worked, can be stacked in each stack while avoiding the danger of the bags sticking at the location of their bottom sealing as frequently happens in known machines of the kind referred to.

The invention also aims to provide said device with a system for discharging the formed bag stacks which ensures the retaining of suitable bag stacks up to the device outlet whatever the thickness of the plastics material used and the moving speed employed of those means for discharging the bag stacks.

According to the present invention there is provided a machine for making bags from plastics material, in which at least one strip of plastics material is fed intermittently, and cut and fused by a movable fusing bar cooperating with a fixed member, which machine also comprises a device for blowing pressurized air on either side of a strip fed to the machine for moving strip downstream of the fusing bar, means arranged at the machine outlet to form at least one stack of bags and including means for holding or releasing a formed bag stack at or from the machine outlet, and means for discharging a formed bag stack, the discharging means comprising conveying means adapted to be stationary for supporting a bag stack as the latter is being formed or movable for conveying a formed bag stack, when the latter has been released from the means for forming the stack and when the strip feeding is cut-off in the machine, over a predetermined distance along substantially the same direction as the direction along which the strip moves through the machine, said conveying means comprising two conveying sections, a first conveying section of which the bag stack is formed and the dimension of which as considered in parallel relationship with the strip movement direction, is at least equal to the dimension of a bag as considered in parallel relationship with said direction, said first conveying section being movable about an axis at right angles to said direction and adjacent to that conveying section end nearest the fusing bar, in such a way as to lie in two end positions, a first end position corresponding to the formation of the bag stack in which the upper surface of said first conveying section slants downwards relative to a substantially horizontal plane in which the upper surface of the second conveying section lies, and a second end position corresponding to the discharge of the bag stack, in which the upper surface of said first conveying section lies level with the upper surface of the second conveying section, means being provided to bring said first conveying section from the one to the other end position thereof and to impart motions to both said first and second conveying sections at substantially the same speeds.

Conveniently the first and second conveying sections are in the form of first and second endless belt conveyors, respectively, each endless belt conveyor comprising an endless belt adapted to run over a pair of spaced apart rotary guide members. Suitably the spacing between the axes of the rotary guide members of the first endless belt conveyor is fixed, the axis of the rotary guide member nearest the fusing bar and about which said first endless belt conveyor pivots being fixed, the axes of those rotary guide members of the second belt conveyor also being fixed.Alternatively, however, the spacing between the pair of rotary guide members of the first endless belt conveyor may be adjustable, the axis of that rotary guide member nearest the fusing bar and about which the first belt conveyor pivots, being fixed, the spacing between the axes of the pair of rotary guide members of the second belt conveyor being fixed, the axes of the pair of rotary guide members of the first and second belt conveyors being movable in parallel relationship with themselves along the movement direction of the material strip, means being provided to move and guide the axes of the movable rotary guide members of both endless belt conveyors in such a way that both said conveyors lie next to one another when the first endless belt conveyor lies in the second end position thereof, means being provided on the rotary guide members of the first endless belt conveyor to tighten the upper region of the first endless belt conveyor when the spacing between the axes of the lattermentioned rotary guide members is varied.

Conveniently the means provided for moving and guiding the axes of the movable rotary guide members of both belt conveyors comprise a fixed frame comprising two stringers in parallel relationship with the lengthwise axes of the endless belt conveyors and located on either side thereof, as well as a movable frame which is so arranged as to be movable on said stringers, said movable frame supporting the said rotary guide members of said second belt conveyor and an intermediate rotary guide member mounted between the pair of rotary guide members of the first belt conveyor, the axes of the one of said pair of rotary guide members of the first belt conveyor farthest away from the fusing bar and the axis of the said immediate rotary guide member being rigidly connected in such a way that the said one rotary guide member is freely pivotable about the axis of the intermediate rotary guide member to let that reach portion of the first endless belt conveyor lying between intermediate rotary guide member and the said one rotary guide member slant downward relative to that substantially. horizontal plane in which lies the upper reach of the second endless belt conveyor and the upper reach of that first endless belt conveyor portion lying between the said intermediate rotary guide member and the other of said pair of rotary guide members of said first belt conveyor located nearest the fusing bar, the spacing between said bar and the axis of the intermediate rotary guide member being adapted to be smaller than the bag dimension as considered in parallel relationship with the movement direction of the material strip, means being provided to move the movable frame relative to the fixed frame and to move that first endless belt conveyor portion lying between the intermediate rotary guide member and the said one rotary guide member, between the slanting position thereof and a position lying in the extension of the upper reach of the second endless belt conveyor and that first endless belt conveyor portion lying between the intermediate rotary guide member and the said other rotary guide member.

The invention will now be described by way of example with particular reference to the accompanying drawings, in which: Figure 1 is a diagrammatic elevation view of one embodiment of a machine according to the invention, Figure 2 is a view similar to Figure 1, with parts broken away, of another embodiment of a machine according to the invention, Figure 3 is an elevation view, partly in cross-section and on a larger scale, which shows details of the machines, shown in Figure 1 or Figure 2, and Figure 4 is a view along lines IV-IV in Figure 3 with parts broken away, some components being shown in a different position relative to Figure 3.

In the various figures, the same reference numerals pertain to similar elements.

The machine according to the invention as shown in the drawings is designed for making bags from plastic material, of the type called "jacket bag" the bottom and mouth of which are sealed, in which the strip 1 from plastic material is fed intermittently, and it is cut and sealed by fusing with a system known per se comprising a movable fusing bar 2 which performs simultaneously the sealing of a bag mount and the sealing of a bottom of an adjacent bag while cutting the strip 1 between both said sealings by means of a cutter 3, said bar 2 cooperating with a fixed member 4.Said machine comprises a device 5 for blowing during the feeding of the strip 1 on either side thereof, pressurized air which moves the strip downstream of the fusing bar 2, means 6 being arranged at the machine outlet to form at least one stack 7 of bags 8 comprising a predetermined number of bags, means 9 to release the formed bag stack 7 when said predetermined bag number is reached, and means 10 to discharge the bag stack. Said means 10 comprise endless belt conveying means on which the bag stack being formed is supported.The means 10 is controlled in a way known per se (and thus not shown) to move in a discontinuous or intermittent way and over a determined distance, along the same direction as the one along which strip 1 moves inside the machine, the belt movement occuring when the bag stack 7 is released by means 9 from the stack-forming means 6 and when the strip feeding is stopped inside the machine.The endless belt conveying means comprises two side by-side endless belt conveyors of sections 11 and 12, the first section 11 on which bag stack 7 is formed and that dimension of which as considered in parallel relationship with the movement direction of strip 1, is at least equal to the dimension of a bag as considered in parallel relationship with said direction, being movable about an axis 13 at right angle to said direction and located adjacent that end 14 of said section 11 nearest the fusing bar 2, so as to lie in two end positions, the one position (shown in Figures 1 and 2 in solid lines) corresponding to the formation of the bag stack, in which the upper reach 15 of the section 11 slants downwards relative to the subsantially horizontal plane in which lies the upper reach 16 of section 12 of the endless belt, and a second position (shown in dotted lines in figures 1 and 2), corresponding to the discharge of the bag stack, in which the upper reach 15 of section 11 is located in the extension of the upper reach 16 of section 12, means 17' being provided to bring said section 11 from the one to the other position thereof, as well as means known per se and thus not shown, for imparting to said sections 11 and 12 of the belt the same intermittent motion at the same speed. The means 6 arranged at the machine outlet to form and release the bag stack comprise fixed pointed elements or points 17 adjacent the fixed member 4 cooperating with the fusing bar 2 downstream of said bar. The points 17 extend below, and substantially at right angles to, the plane in which the material strip 1 moves.The means 6 further comprise a shaped section 18 mounted on the fusing bar 2 and provided with holes to let the points 17 through so as to stack the bags thereon when the fusing bar 2 engages member 4 with which it cooperates to seal material strip 1 to form the bags. The shaped section 18 can either be fastened to the fusing bar in such a way that a flange 19 thereof be located substantially in a horizontal plane passing through surface 20 of the fusing bar, or, as shown in Figures 1 to 3, be supported by a jack 21 the cylinder 22 of which is fastened to the fusing bar in such a way that when the fusing bar lies in the upper position thereof (position shown in Figure 3), the flange 19 of the shaped section 18 located somewhat higher than the horizontal plane passing through surface 20 of the fusing bar to prevent the material strip moving downstream thereof contacting said flange 19, the jack 21 pushing downwards said shaped section 18 when the fusing bar engages member 4, in such a way that flange 19 lies at the same level or somewhat lower than the horizontal plane defined above, to impale the bags on the points 17. The means 9 for releasing the bag stack 7 from the points 17 comprises a movable element 23 having a top surface 24 for supporting the stack 7, which element 23 extends in parallel relationship with the fusing bar 2, and a jack 25 to displace said movable element along a direction substatially in parallel relationship with the axis of points 17, between two end positions; a first end position in which the surface 24 of element 23 lies below the level of the top end of points 17 to allow piling the bags 8 thereon, and a second end position in which the upper surface 24 of said element lies above the level of the top end of points 17 to release the formed bag stack from said points. The machine according to the invention further comprises means 31 to join the bags 8 together when forming the stack 7.

The means 25 comprise heated pointed members or points 26 in parallel relationship with the points 17 and staggered relative thereto, said heated points 26 being mounted on the fusing bar 2 and movable relative thereto. A jack 27, the cylinder 28 of which is fixed relative to the fusing bar 2, is provided to move the heated points 26 along a direction in parallel relationship to the axis thereof, between two end positions; a first end position in which the ends 29 of the heated points 26 facing the bag stack being formed lie higher than the flange 19 of section 18 pushing the bags onto the points 17, and a second end position in which the ends 29 of the heated points 26 lie lower than the flange 19.The jack 27 is so controlled as to bring the heated points 26 from the first end position thereof the the second position after impaling a predeter mined number of stacked bags on the points 17 so as to join the bags together by fusing, during the sealing of a bag. The stroke of the heated points 26 is longer than the thickness of said predetermined number of stacked bags. The heated points 26 are advantageously so arranged as to have their axes lying in a vertical plane which passes through the axes of points 17, the flange 19 of section 18 being provided with holes therethrough to let the points 26 through.It is possible to provide for an adjustment in position of the points 17 relative to member 4 along a direction in parallel relationship with the movement direction of strip 1, so as to make it possible to adjust the location where the bags are impaled relative to the bag mouth according to the type and dimensions of the bags to be made. This is also true for the points 26 which can be made unoperative depending on the type of bags made. For instance to make bags with bottom seal and with open mouth, the points 17 will lie as near as possible to the member 4 and the heated points 26 will be made in operative by cutting-off the supply to the jacks 27.It would also be possible to assemble all of the bags in the stack impaled on the points 17, in a single operation, when the. material strip is stopped inside the machine and when the fusing bar 2 lies in the top position thereof as well as the shaped section 18, the heated points 26 then being pushed through the complete bag stack by the jacks 27.

The slanting of section 11 of belt 10 during the formation of the bag stack has various advantages resulting in the bags at the location of the bottom seal thereof, not sticking strongly together whatever the thickness of the stack. In previous machines, in view of the manufacturing rate of the bags, the seals made by fusing the material do not have time enough to cool and the stacking of the bags results at the seals in an actual sealing of the bags together, which causes either substantial rejects, or manpower costs not to be belittled for separating by hand the bags. By providing the slanting section 11, the sticking or sealing together of the bags near the bottom seals thereof is prevented or reduced for a plurality of reasons.First the fall time of that bag end provided with the bottom seal is lengthened which in view of the pressurized-air driving system for the material strip 1 downstream of the fusing bar, allows a better cooling of the seal on that bag which has just been manufactured, before said seal is laid down on previously stacked bag. Second, the slanting position of the bag stack in the location of the bottom seals reduces the weight of the seals on top of one another which decreases the danger of sticking particularly where the bag stacks contain a large number of bags. Third, the position of the bags impaled on the points 17 which lie vertically and bear on the slanted section 11 of the belt, allows a slight staggering of the bottom seals relative to one another, which further decreases the danger of sticking.Finally the slanting of section 11 of the belt allows the formation of stacks which comprise a large number of bags while still retaining smooth stacks, which is not possible on a horizontal belt as the bags the bottom of which has a much greater thickness at the seal location than in the middle portion thereof, form a bulge which interfers with pressurized-air conveying of strip 1 downstream of fusing bar 2.

As shown in Figure 1, the spacing between axes 13 and 30 of those rotary guide members or shafts bearing the ends 14 and 32 of belt section 11 is fixed, the axis 13 about which swings said section 11 being fixed as well as the axes 33 and 34 bearing the ends 35 and 36 of belt section 12; the spacing between axes 13 and 30 being of course at least equal to the maximum length for the bags which are to be stacked on the belt.On the other hand, as shown in Figure 2, it is possible to adapt the length of section 11 to the length of the bags being manufactured, the spacing between the axes 13 and 30 of those shafts bearing the ends 14 and 32 of endless belt section 11 then being adjustable, the axis 13 of that shaft nearest the fusing bar 2 and about which swings the section 11 being fixed, the spacing between the axes 33 and 34 of those shafts bearing the ends 35 and 36 of the second section 12 of the endless belt being fixed, the axes 33 and 34 being movable in parallel relationship with themselves along the movement direction of material strip 1, means 37 being provided to move and guide the axes of the movable shafts of both belt sections 11 and 12 in such a way that both these sections lie next to one another when the first section lies in the second end position thereof, and means 38 being provided to tighten the upper reach 15 of belt section 11 on the shafts bearing the ends thereof when the spacing between the axes 13 and 30 of said latter shafts is varied.

The means 37 provided for moving and guiding the axes 30, 33 and 34 of the movable shafts of belt section 11 and 12 comprise a fixed frame 39 having two stringers 40 in parallel realtionship with the endless belt lengthwise axis and arranged on either side thereof, as well as a movable frame 41 so arranged as to move on the stringers 40. The frame 41 supports the axes 33 and 34 of those shafts bearing the ends 35 and 36 of belt section 12 and the axis 42 of an intermediate shaft mounted between the axes 13 and 30 of those shafts bearing the ends 14 and 32 of belt section 11 in parallel relationship with said shafts.The axis 30 of that shaft bearing the end 32 of belt section 11 and the axis 42 of the intermediate shaft are rigidly connected through links 43 in such a way that the axis 30 of the shaft bearing that end 32 of belt section 11 is freely rotatable about the axis 42 of the intermediate shaft to let that portion 15' of the upper reach 15 of the section 11 lying between the intermediate shaft and the shaft bearing the end 32 of said first section 11, slant downwards relative to that substantially horizontal plane in which lies the upper reach 16 of belt section 12 and the portion 15" of the upper each of that portion of belt section 11 which lies between the axis 42 of said intermediate shaft and the fixed axis 13 of that shaft bearing the end 14 of said section 11.The spacing between the fusing bar 2 and the axis 42 of the intermediate shaft is shorter than the dimension of the bag as considered in parallel relationship with the movement direction of the material strip.

Means such as screws (not shown) are provided to move the movable frame 41 relative to the fixed frame 39 as well as means comprised of jacks 44 acting on the links 43 made fast to the ends of the axis 42 of the intermediate shaft which freely rotates about said shaft 42 to move that portion of belt section 11 lying between the axis 42 of the intermediate shaft and the end 32 of said section 11, between the slanting position thereof and the position thereof where it lies in the extension of section 12 and of that portion of section 11 lying between said axis 42 and the axis 13 of that shaft bearing the end 14 of said section 11.

Between the ends 32 (section 11) and 35 (section 12), there is provided a bridge 46 which is fixed relative to section 12, to facilitate the passage of the bag stacks from section 11 to section 12 of the belt when the section 11 lies in the position thereof in which that portion 15' of the upper reach thereof lies in the extension of its reach 15" and reach 16 of belt section 12.

As for the manufacturing of the "jacket bags", there is a rather wide spacing between the points 17 and member 4 and thereby the free portion of the stacked bags located between said member 4 and points 17 might interfer with the conveying of strip 1 in front of said member 4. Means 47 are thus provided to push downwards that portion of a bag which has just been formed and impaled on points 17, which lies between said points 17 and fixed member 4, so as to have said portion lying below the horizontal plane passing through the top end 48 of said member 4.Moreover to prevent, as mentioned above regarding the seals at the bag bottom, the sticking or sealing of the "jacket bags" at the location of the seal made at the bag mouth during the piling-up, the machine comprises means 49 so arranged as to space during the bag stack formation, the free end of said portion of the bag formed and impaled on points 17, from the free end of the corresponding portion of the following bag.The means 47 designed for pushing downwards the bag portion comprise a distributor 50 for blowing pressurized air which is fastened in parallel relationship therewith, to the fusing bar 2 downstream thereof, in such a way that the air stream is directed substantially in parallel relationship with the movement direction of the fusing bar, the lengthwise axis of the distributor being located in a vertical plane at right angles to the movement direction of strip 1 and lying substantially at the same distance from the points 17 on which the bags are impaled, and the fixed member 4 with which cooperates the fusing bar to form the bags. The means 49, so arranged as to space the free end of a formed bag from the corresponding free end of the following bag, comprise a movable cage 51 located between the fixed member 4 and the points 17 on which the bags are impaled.The cage is arranged below a horizontal plane passing through the root of said points 17. The cage, the length of which corresponds substantially to the length of the fixed member, is comprised of two circular end plates or cheeks 52 between which are made fast rods 53 in parallel relationship with fixed member 4, with an equal spacing on a circle the center of which lies on the axis of cage shaft 56 which lies in parallel relationship with said member 4.

Means 54 and 55 are provided to rotate the cage 51 about the axis thereof over one step which corresponds to the spacing of two directly adjacent rods 53, at each formation cycle for one bag, said means 54 being so arranged as to cause on the one hand a stepwise movement of the rods 53 during the bag stacking, along the same direction as the movement of strip 1 (means 54) and on the other hand, the movement of rods 53 to occur continuously (means 55) along the direction opposite to the movement direction of material strip 1 to release the bags from the cage, when the bag stack has been formed, the feeding of the material strip being stopped inside the machine, said continuous movement of the cage occuring before releasing the stack from the points 17, the spacing between said points 17 and the nearest cage rod being shorter than the spacing between said points 17 and the free end of said bag portions.

The means 54 for driving stepwise the cage 51 are comprised of a ratchet wheel 58 fast to the cage shaft 56, which is driven by a pawl 59 the pivot 60 of which is mounted on a part 61 which swings freely on shaft 56 and is operated by a jack 62 which is hinged on a fixed pivot 63. The jack 62 releases the pawl 59 from the ratchet wheel 58 at each operation to let the shaft 56 be freely driven in the opposite direction by means 55 which are comprised of an electric motor (not shown), which drives a pinion 64 which is loose on shaft 56 and drives same through a coupling 65.

The machine further comprises means 66 which are so arranged as to bear on the upper surface of the bag stack when it is formed, and when the cage 51 is about to be driven continuously to release the bags and belt section 11 lies in the extension of section 12. Control means (not shown) are provided to impart to the means 66 an alternating motion to bring same closer to and away from said upper surface, said means 65 being so arranged as to have the portion thereof engaging the upper stack surface move at the same linear speed as the belt and along the same direction.The means 66 comprise a cylinder 67 in parallel relationship with the belt and the axis of which lies at right angle to the movement direction of the material strip 1, the cylinder 67 being mounted on a shaft 68 which is supported by the fixed frame 39 (in the embodiment as shown in Figure 2), to rotate freely about the axis of said shaft, means not shown being provided to rotate said cylinder about the shaft thereof with the same linear speed as the belt 10.

It should be understood that the invention is in no way limited to the above embodiments and that many changes can be brought there without departing from the scope of the invention as defined by the appended claims.

For instance, it would be possible to provide for improving the separation of the free bag ends 69 by the movable cage 51, a blowing nozzle 70 the air stream of which is directed towards the upper rods 53 of said cage.

There could further be provided, to enhance the action of the heated points 26, a helical spring 71 which surrounds each such point 26 and which is mounted on a part 72 which moves together with said point 26.

The spring end 73 is provided with a washer 74 lying lower then the end of point 26 and does not project relative to the shaped section 18 when same lies in the top position thereof together with the point. The flange 19 of shaped section 18 has holes of size large enough to let spring 71 through for bearing on the upper bag surface to compress the bags about the area where the point 26 operates.

WHAT WE CLAIM IS: 1. A machine for making bags from plastics material, in which at least one strip of plastics material is fed intermittently, and cut and fused by a movable fusing bar cooperating with a fixed member, which machine also comprises a device for blowing pressurized air on either side of a strip fed to the machine for moving the strip downstream of the fusing bar, means arranged at the machine outlet to form at least one stack of bags and including means for holding or releasing a formed bag stack at or from the machine outlet, and means for discharging a formed bag stack, the discharging means comprising conveying means adapted to be stationary for supporting a bag stack as the latter is being formed or movable for conveying a formed bag stack, when the latter has been released from the means for forming the stack and when the strip feeding is cut-off in the machine, over a predetermined distance along substantially the same direction as the direction along which the strip moves through the machine, said conveying means comprising two conveying sections, a first conveying section on which the bag stack is formed and the dimension of which, as considered in parallel relationship with the strip movement direction, is at least equal to the dimension of a bag as considered in parallel relationship with said direction, said first conveying section being movable about an axis at right angles to said direction and adjacent to that conveying section end nearest the fusing bar, in such a way as to lie in two end positions, a first end position corresponding to the formation of the bag stack in which the upper surface of said first conveying section slants downwards relative to a substantially horizontal plane in which the upper surface of the second conveying section lies, and a second end position corresponding to the discharge of the bag stack, in which the upper surface of said first conveying section lies level with the upper surface of the second conveying section, means being provided to bring said first conveying section from the one to the other end position thereof and to impart motions to both said first and second conveying sections at substantially the same speeds.

2. A machine according to claim 1, in which said first and second conveying sections are in the form of first and second conveying sections are in the form of first and second endless belt conveyors, respectively, each endless belt conveyor, comprising an endless belt adapted to run over a pair of spaced apart rotary guide members.

3. A machine according to claim 2, in which the spacing between the axes of the rotary guide members of the first endless belt conveyor is fixed, the axis of the rotary guide member nearest the fusing bar and about which said first endless belt conveyor pivots being fixed, the axes of those rotary guide members of the second belt conveyor also being fixed.

4. A machine according to claim 2, in

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

59 from the ratchet wheel 58 at each operation to let the shaft 56 be freely driven in the opposite direction by means 55 which are comprised of an electric motor (not shown), which drives a pinion 64 which is loose on shaft 56 and drives same through a coupling 65.

The machine further comprises means 66 which are so arranged as to bear on the upper surface of the bag stack when it is formed, and when the cage 51 is about to be driven continuously to release the bags and belt section 11 lies in the extension of section 12. Control means (not shown) are provided to impart to the means 66 an alternating motion to bring same closer to and away from said upper surface, said means 65 being so arranged as to have the portion thereof engaging the upper stack surface move at the same linear speed as the belt and along the same direction.The means 66 comprise a cylinder 67 in parallel relationship with the belt and the axis of which lies at right angle to the movement direction of the material strip 1, the cylinder 67 being mounted on a shaft 68 which is supported by the fixed frame 39 (in the embodiment as shown in Figure 2), to rotate freely about the axis of said shaft, means not shown being provided to rotate said cylinder about the shaft thereof with the same linear speed as the belt 10.

It should be understood that the invention is in no way limited to the above embodiments and that many changes can be brought there without departing from the scope of the invention as defined by the appended claims.

For instance, it would be possible to provide for improving the separation of the free bag ends 69 by the movable cage 51, a blowing nozzle 70 the air stream of which is directed towards the upper rods 53 of said cage.

There could further be provided, to enhance the action of the heated points 26, a helical spring 71 which surrounds each such point 26 and which is mounted on a part 72 which moves together with said point 26.

The spring end 73 is provided with a washer 74 lying lower then the end of point 26 and does not project relative to the shaped section 18 when same lies in the top position thereof together with the point. The flange 19 of shaped section 18 has holes of size large enough to let spring 71 through for bearing on the upper bag surface to compress the bags about the area where the point 26 operates.

WHAT WE CLAIM IS: 1. A machine for making bags from plastics material, in which at least one strip of plastics material is fed intermittently, and cut and fused by a movable fusing bar cooperating with a fixed member, which machine also comprises a device for blowing pressurized air on either side of a strip fed to the machine for moving the strip downstream of the fusing bar, means arranged at the machine outlet to form at least one stack of bags and including means for holding or releasing a formed bag stack at or from the machine outlet, and means for discharging a formed bag stack, the discharging means comprising conveying means adapted to be stationary for supporting a bag stack as the latter is being formed or movable for conveying a formed bag stack, when the latter has been released from the means for forming the stack and when the strip feeding is cut-off in the machine, over a predetermined distance along substantially the same direction as the direction along which the strip moves through the machine, said conveying means comprising two conveying sections, a first conveying section on which the bag stack is formed and the dimension of which, as considered in parallel relationship with the strip movement direction, is at least equal to the dimension of a bag as considered in parallel relationship with said direction, said first conveying section being movable about an axis at right angles to said direction and adjacent to that conveying section end nearest the fusing bar, in such a way as to lie in two end positions, a first end position corresponding to the formation of the bag stack in which the upper surface of said first conveying section slants downwards relative to a substantially horizontal plane in which the upper surface of the second conveying section lies, and a second end position corresponding to the discharge of the bag stack, in which the upper surface of said first conveying section lies level with the upper surface of the second conveying section, means being provided to bring said first conveying section from the one to the other end position thereof and to impart motions to both said first and second conveying sections at substantially the same speeds.
2. A machine according to claim 1, in which said first and second conveying sections are in the form of first and second conveying sections are in the form of first and second endless belt conveyors, respectively, each endless belt conveyor, comprising an endless belt adapted to run over a pair of spaced apart rotary guide members.
3. A machine according to claim 2, in which the spacing between the axes of the rotary guide members of the first endless belt conveyor is fixed, the axis of the rotary guide member nearest the fusing bar and about which said first endless belt conveyor pivots being fixed, the axes of those rotary guide members of the second belt conveyor also being fixed.
4. A machine according to claim 2, in

which the spacing between the said pair of rotary guide members of the first endless belt conveyor is adjustable, the axis of that rotary guide member nearest the fusing bar, and about which said first belt conveyor pivots, being fixed, the spacing between the axes of the said pair of rotary guide members of the second belt conveyor being fixed, said axes of the said pair of rotary guide members of the first and second belt conveyors being movable in parallel relationship with themselves along the movement direction of the material strip, means being provided to move and guide the axes of the movable rotary guide members of both belt conveyors in such a way that both said conveyors lie next to one another when the first endless belt conveyor lies in said second end position thereof, means being provided on the rotary guide members of the first endless belt conveyor to tighten the upper reach of the first endless belt conveyor to tighten the upper reach of the first endless belt conveyor when the spacing between the axes of said latter-mentioned guide members is varied.
5. A machine according to claim 4, in which said means provided for moving and guiding the axes of the movable rotary guide members of both belt conveyors comprise a fixed frame comprising two stringers in parallel relationship with the lengthwise axis of the endless belt conveyors and located on either side thereof, as well as a movable frame which is so arranged as to be movable on said stringers, said movable frame supporting the said rotary guide members of said second belt conveyor and an intermediate rotary guide member mounted between the said pair of rotary guide members of the first belt conveyor, the axis of the one of said pair of rotary guide members of the first belt conveyor farthest away from the fusing bar and the axis of the said intermediate rotary guide member being rigidly connected in such a way that the said one rotary guide member is freely pivotable about the axis of the said intermediate rotary guide member to let that upper reach portion of the first endless belt conveyor lying between the said intermediate rotary guide member and the said one rotary guide member slant downwards relative to that substantially horizontal plane in which lies the upper reach of the second endless belt conveyor and the upper reach of that first endless belt conveyor portion lying between the said intermediate rotary guide member and the other of said pair of rotary guide members of said first belt conveyor located nearest the fusing bar, the spacing between said bar and the axis of the said intermediate rotary guide member being adapted to be smaller than the bag dimension as considered in parallel relationship with the movement direction of the material strip, means being provided to move the movable frame relative to the fixed frame and to move that first endless belt conveyor portion lying between the said intermediate rotary guide member and the said one rotary guide member, between the slanting position thereof and a position lying in the extension of the upper reach of the reach of the second endless belt conveyor and that first endless belt conveyor portion lying between the said intermediate rotary guide member and the said other rotary guide member.
6. A machine according to any of claims 2 to 5, in which means are arranged between the ends of both endless belt conveyors positioned nearest one another to make easier the passage of the bag stacks from the first endless belt conveyor to the second endless belt conveyor, when said first endless belt conveyor lies in the second end position thereof.
7. A machine according to any of the preceding claims 1 to 5, in which the means arranged at the machine outlet for forming at least one bag stack comprise fixed pointed elements adjacent, but downstream of, the said fixed member, said pointed elements extending below, and substantially at right angles to, that plane in which the material strip is adapted to move, a shaped section mounted for movement with the fusing bar and provided with holes to let said pointed elements through for impaling the bags thereon when the fusing bar is moved to engage the fixed member with which it cooperates to form the bags, a movable element having an upper surface for supporting the bag stack being formed and which extends in parallel relationship with the fusing bar, and means to move said movable element between two end positions, a first end position in which the upper surface thereof lies below the top ends of said pointed elements to allow piling the bags thereon, and a second end position in which the upper surface of the moveable element lies above the level of the tops of the pointed elements for enabling a bag stack formed on the pointed elements to be released therefrom.
8. A machine according to any of the preceding claims, which further comprises means for assembling bags together during the formation of a bag stack.
9. A machine according to claim 8, when dependent upon claim 7, in which the means for assembling the bags together comprise heatable pointed members which extend in a direction parallel to, but which are staggered relative to, said pointed elements, said heatable pointed members mounted on the fusing bar and movable relative thereto, means being provided to move said heatable pointed members para llel to said parallel direction between a first end position in which the end so the pointed members which are adapted to face the bag stack being formed lie above the part of the shaped section which has the holes therein through which said pointed elements can pass, the said shaped section being provided with further holes to let the heatable pointed members pass through, and a second end position in which the ends of said heatable pointed members lie below the said part of the shaped section, said means for moving the heatable pointed members being so controlled as to bring the heatable pointed members from their first end position to their second end position after impaling a predetermined number of bags on said fixed pointed elements so as to join together said predetermined number of bags by sealing during the sealing of a bag, the stroke of said heatable pointed members being longer than the thickness of said predetermined bag number, in such a way that by joining together said predetermined number of bags, said bags are joined by sealing to the already joined bags.
10. A machine according to claim 9, in which means are provided for adjusting the position of those pointed elements relative to the fixed member cooperating with the fusing bar for forming the bags along a direction in parallel relationship with the movement direction of the material strip, and adjusting the position of the heatable pointed members relative to the fusing bar along a direction in parallel relationship with said strip movement direction.
11. A machine according to any one of claims 7 to 10, which further comprises for pushing downwards that portion of a bag which has just been formed and impaled on said pointed elements and which lies between said pointed elements and the fixed member with which cooperates the fusing bar to form the bags, in such a way that said portion is adapted to lie below that horizontal plane passing through the top end of said fixed member.
12. A machine according to claim 11, which further comprises means for separating, during the formation of a bag stack, the free end of said portion of a bag, formed and impaled on the pointed elements, from the free end of the corresponding portion of a following bag.
13. A machine according to claim 11 or 12, in which the means for pushing downwards said bag portion comprises a distributor positioned downstream of, and substantially parallel to, the fusing bar for blowing pressurized air in a stream directed substantially parallel to the movement direction of the fusing bar, the lengthwise axis of said distributor lying in a vertical plane at right angles to the movement direction of the material strip and spaced approximately equally the said pointed elements and from the fixed member with which said fusing bar cooperates for forming the bags.
14. A machine according to claim 12 or claim 13 when dependent upon claim 12, in which the means for spearating said free end of a following bag, comprise a rotatable cage arranged between said fixed member and said pointed elements and below a horizontal plane passing through the bottoms of said pointed elements, said cage having an axial length corresponding substantially to the length of the fixed member and comprising two circular end plates between which are fastened rods disposed parallel to the fixed member and space apart equally on the surface of a cylinder having its axis lying on the cage axis, and means provided to rotate the cage about its axis, either stepwise in a first direction, one step corresponding to the spacing between an adjacent pair of said rods, at each cycle during the formation of a bag, or continuously in the opposite, second direction, stepwise rotation of the cage in the first direction being adapted to occur during piling-up of the bags to give the rods in the upper part of the cage a component of movement in the movement direction of the material strip, and continuous rotation of the cage in the second direction being adapted to give the rods in the upper part of the cage a component of movement in the direction opposite to the movement direction of the material strip for releasing bags from said cage when a bag stack has been formed and the strip feeding has been stopped inside the machine, said continuous movement of the cage occuring before the release of the bag stack from said pointed elements, the spacing between said pointed elements and the nearest cage rod therebelow being shorter than the spacing between said pointed elements and the free end of said bag portions.
15. A machine according to any of the preceding claims, which further comprises means for bearing on the upper surface of a bag stack when the stack is being formed and when the first conveying section lies in said second end position, and control means for imparting to said bearing means an alternating motion to bring the bearing means closer to and away from said upper surface, said bearing means so designed that a portion thereof which is adapted to enagage the said upper surface of the stack is adapted to move with the same linear speed as the conveying means and in the same direction.
16. A machine according to claim 15, in which the means for bearing on the upper stack surface comprises a cylinder having its axis parallel to the conveying means and at right angle to the movement direction of said material strip, said cylinder being mounted on a shaft so as to rotate freely about the axis thereof, means being provided to rotate said cylinder about the shaft thereof with the same linear speed as the conveying means.
17. A machine according to claim 12 or any of claims 13 to 16 when dependent upon claim 12, which further comprises a nozzle for blowing pressurized air which is located between said separating means and said fixed member, said nozzle being so arranged for directing the air stream towards said separating means.
18. A machine according to claim 9 or 10 or any of claims 11 to 17 when dependent upon claim 9 or 10, which further comprises a helical spring arranged around each heatable pointed member with its axis parallel to the extending direction of the heatable pointed member, said spring being mounted on a part that moves together with the heatable pointed member and having one of its ends lying below the pointed end on the pointed member, the said further holes being sufficiently large to let said spring pass therethrough to enable them to bear on the upper surface of a stack of bags to compress the stack of bags in the regions where said heatable pointed members operate.
19. A machine constructed and arranged substantially as herein described with reference to and as illustrated in Figure 1 as modified by Figures 3 and 4 or Figure 2 as modified by Figures 3 and 4 of the accompanying drawings.