EP0329495A1 - Installation for manufacturing and stacking thermoplastic bags, etc. - Google Patents

Abstract

Installation for manufacturing and stacking thermoplastic bags, sachets etc., in which the lower jaw (8) is fixed and comprises on its downstream vertical face a transverse groove (55) one of whose edges serves as a counter-blade; the upper jaw (9) is driven by the locking pad (71) with the interposition of a return spring (85); the stacking table (67) is provided with an indexing device; the bag being made is pinned before the cutting; the stacking table (67) and the row of needles are manoeuvred by an additional lowering of the locking pad (71) after the cutting and return to their starting position under the effect of return springs (95, 103); the locking pad (71) can easily be swung upwards and in the upstream direction for maintenance. <IMAGE>

Description

The present invention relates to an installation for manufacturing and stacking bags, sachets, etc. made from a flattened thermoplastic sheath, installation of the type comprising:
- a horizontal guide channel of the sheath;
a pair of step-by-step transport rollers between which said sheath is pinched during its step-by-step transport and the lower roller of which is mounted at a stationary position and the upper roller of which is mounted so that it can move away from the lower roller under the action of a first control member;
- an intermittent sheath stop device provided upstream of the transport rollers and having a movable upper support pad and actuated by said first control member, and a fixed lower counter pad;
- a pair of welding jaws, one of which is disposed below and the other above the path of travel of the sheath downstream of the transport rollers and at least one of which is movable perpendicularly to said path being able to approach or move away from the other jaw, the lower jaw comprising a retaining shoulder at its upper and downstream part;
- a transverse cutting device provided downstream of the welding jaws and comprising an upper knife and a lower counter blade;
a stacking table situated downstream of the lower jaw, the upstream end of which is vertically movable relative to the lower jaw is disposed below the retaining shoulder, said table being capable of receiving between its upper upstream end and the underside of said retaining shoulder the upstream end of the stacked bags;
a needle holder disposed transversely under the upstream end of said table, movable relative to the lower jaw and supporting a transverse row of needles, or pins, the points of which point upwards slide in a row of aligned holes made in the upstream end of said table and skewer the upstream end of the stacked bags; and
- a vertically movable upper blocking pad under the action of a second control member, mounted so that the vertical path of its upstream face passes with little play in front of the vertical downstream face of said retaining shoulder, disposed downstream welding jaws and the cutting device, and capable of blocking the end part of the sheath projecting from the cutting device against said stacking table.

An installation of this kind is described in French patent 2,594,401. This installation includes a stacking table descending as the bags are stacked, a row of needles fixed during operation and placed under the retaining shoulder and a lower jaw moving upwards after cutting. of the last bag to allow the upstream end of it to fall back under the retaining shoulder and to be engaged on the row of needles.

The disadvantage of this installation is that the lower jaw is subjected to a reciprocating movement, which requires an additional control member consisting of cams keyed onto a shaft driven by the control shaft, and rollers mounted on rods connected to the lower jaw and sliding in guide boxes. On the other hand, the last cut bag is racked in after it has been cut, which requires suction and air blowing nozzles formed in the body of the lower jaw to allow "sleeping" perfect from the free upstream end of the last cut bag.

Indeed, the progress made in recent times in the field of extrusion of thermoplastic sheaths means that these sheaths have increasingly thin or thin walls and, consequently, less and less "memory or spring" for return to their starting position after being removed from it partially.

Patent DT 19 30 841 shows a stacking device in which the stack of bags on which the last cut bag rests, and the stacking table are lowered after cutting by an additional movement of the blocking pad, in order to spread said stack of bags from the retaining shoulder and allowing the upstream end of the last cut bag to fall back onto the stack of bags and the stack of bags to be held tight against the retaining shoulder as soon as the blocking shoe rises, the table also rising under the action of a return spring. The disadvantage of such a device is that the fact of almost permanently tightening the bags stacked between the stacking table and the retaining shoulder gives the ends of the bags incorrectly arranged permanent folds which subsequently hamper the opening of the bags .

European patent 0 050 339 presents a stacking device which has an additional application piece, vertically movable, situated under the sheath between the knife and the blocking pad which, during cutting serves as a counter blade for the knife, then rises to pass over the last cut bag and descends to play the role of retaining shoulder, before the blocking shoe rises. The disadvantage of this system is that it requires a synchronized movement of an additional piece in the bag manufacturing cycle, which does not allow a high rate. On the other hand, the upstream end of the bags is also kept permanently clamped by this additional application part.

European patent 0 084 880 also presents a stacking device comprising an additional application piece, vertically movable, situated above the sheath, which, during cutting creates additional tension on the sheath and, after cutting , causes the upstream end of the last bag cut out to be plugged into a row of needles. The disadvantage of this system is that this additional part has a variable displacement in time according to the thickness of the stack of bags, the stacking table being at a fixed post.

The object of the present invention is to provide a plant for manufacturing and stacking thermoplastic bags of the type initially mentioned, which makes it possible to achieve high production rates, even with thin thermoplastic sheaths, in which the racking of the bags is carried out. before cutting the bag, the tightening of the stack of bags already made is limited and the point of the needles protrudes by a fixed and constant height above the stack of bags.

In an installation of this type, the goal is achieved because:
- the lower jaw is fixed,
the needle holder is arranged in line with the blocking shoe which has a row of vertical holes intended to receive the point of the needles when cutting the next bag,
the blocking pad is capable of carrying out an additional downward movement after cutting the last bag made and of causing the stacking table and the needle holder to move downwardly, which are urged upwards by return springs, so as to allow the upstream end of the last cut bag to fold down under the retaining shoulder of the lower jaw,
- the stacking table is provided with an indexing device which allows it to have a large clearance and to descend as the bags are stacked so that the height of the last stacked bag is constant when scrolling the sheath.

According to a feature of the invention, the indexing device of the stacking table comprises a horizontal hole of oblong shape arranged vertically in a vertical beam fixed under the table, in which slides a rod fixed to the movable end of a horizontal lever arm keyed onto a shaft, and a friction brake of which one of the flanges is keyed onto said shaft and the other flange is secured to the frame, the free movement of the table being limited by said oblong hole and said rod.

The needle holder is fixed to the free ends of two lever arms pivotable about a transverse axis which extend horizontally and longitudinally and which slide along a vertical cylinder rod and directed upwards from a fixed cylinder to the frame. The return springs of the needle holder are mounted around said cylinder rods and bear, on the one hand, against the upper flange of said cylinder and, on the other hand, against the underside of the corresponding lever arm. The clearance of said needle holder is limited and adjusted upwards by a nut fixed to the upper part of each jack rod and bearing against the upper face of the corresponding lever arm. The downward movement of said needle holder is provided by vertical beams integral with the blocking pad which are capable of pressing on the free ends of said lever arms after the bag has been cut during the further descent of said blocking pad.

According to another feature of the invention:
- the blocking shoe is fixed to two parallel lever arms extending laterally and horizontally upstream of the installation, keyed onto a pivot shaft mounted on the chassis and biased downwards by tension springs, drives the upper jaw with interposition of a return spring and carries said knife,
- the knife drive device comprises an angle gear fixed on one of said lever arms of the blocking shoe, said angle gear having a drive shaft whose axis coincides with said pivot shaft said blocking shoe and an output shaft whose axis is perpendicular to the plane of the drive pulley of the belt supporting the knife, and
- the dismantling of said tension springs makes it possible to rock as a block upwards and upstream of the installation, the blocking pad, the upper jaw and the cutting device.

The first control member and the second control member are cams keyed onto the carrier shaft of the lower transport roller which cooperate with rollers mounted respectively on the support levers of the upper transport roller and the support lever arms of the blocking pad, said rollers being held against their respective cam by elastic forces.

• - la figure 1 est une vue schématique en élévation, suivant les lignes I-I de la figure 2,
• - la figure 2 est une vue en plan de la partie amont de l'installation,
• - la figure 3 est une vue en plan de la partie antérieure et amont de l'installation,
• - la figure 4 est une vue en élévation du côté gauche de l'installation,
• la figure 5 est une vue schématique en plan de la partie aval de l'installation,
• les figures 6 à 8 sont des vues schématiques en élévation de coupes longitudinales verticales de la partie aval de l'installation à partir de la paire de rouleaux de transport, ces figures illustrant différentes positions de travail des mâchoires de soudure, du dispositif de découpe, du patin de blocage, de la table d'empilement et du dispositif d'embrochage.

Thanks to this design, the needles protrude above the stack of bags by a constant height and the upper face of the stack of bags is at a constant height when the sheath scrolls. The bag which is about to be cut is plugged in before it is cut and the stack of bags is only clamped between the table and the blocking shoe during part of the operating cycle. The upstream end of the cut bag has a very short length and quickly folds down by itself under the retaining shoulder which does not compress the upstream end of the stack of bags. The bag being racked up before cutting, the presence of suction and air blowing nozzles provided in the body of the lower jaw is not necessary. In addition, the number of parts which perform intermittent back and forth movements is limited compared to the solutions proposed by the state of the art, the blocking shoe always performs the same stroke of constant length and the maintenance of installation is facilitated by the possible tilting and blocking of the blocking pad, the upper jaw and the cutting device. Other characteristics and advantages of the invention will emerge from the description of an embodiment, made with reference to the appended drawings in which:

• FIG. 1 is a diagrammatic elevation view, along lines II of FIG. 2,
• FIG. 2 is a plan view of the upstream part of the installation,
• FIG. 3 is a plan view of the front and upstream part of the installation,
• FIG. 4 is an elevation view on the left side of the installation,
• FIG. 5 is a schematic plan view of the downstream part of the installation,
• FIGS. 6 to 8 are schematic elevation views of vertical longitudinal sections of the downstream part of the installation from the pair of transport rollers, these figures illustrating different working positions of the welding jaws, of the cutting device, blocking shoe, stacking table and racking device.

As shown in the drawing, the plant for manufacturing and stacking thermoplastic bags comprises a frame whose lateral flanges bear the reference 1. A thermoplastic sheath 2 unwound from a storage coil, not shown, moves in the state flattened along a guide track 3 extending horizontally through the upper part of the installation. On the path of this guideway are provided, from upstream to downstream in the direction of travel of the sheath 2, an intermittent stop device 5 of the sheath 2, a pair of transport rollers 6, 7 intended to make advance the sheath 2 by a determined length, a pair of welding jaws 8, 9 intended to weld or seal together the two opposite faces of the flattened sheath 2 along a transverse line and, preferably, perpendicular to the longitudinal edges of the sheath flattened 2, a transverse cutting device 10 intended to cut the sheath 2 downstream and in the immediate vicinity of the weld joint produced by the jaws 8 and 9 and a stacking device 11 of the welded and cut bags.

The lower transport roller 6 is mounted mobile using bearings 13 keyed onto the drive shaft 14 which is itself mounted mobile on the flanges 1 of the frame using bearings 15. The shaft d drive 14 is connected to a continuous drive motor by means of a speed variator not shown and the lower transport roller 6 is connected to the same drive motor by a second speed variator speed driving the pulley 16 fixed to the end of the lower transport roller 6. The first speed variator is intended to adjust the speed of the machine and the second speed variator makes it possible to adjust the rotation speed of the lower transport roller and thereby the length of the bags.

The upper transport roller 7 is mounted idly on a support shaft 17 fixed to the downstream or front end of two levers 18 by means of bearings 19 keyed onto the shaft 17. The levers 18 pivot around an axis of transverse articulation 20 integral with the frame 1. The levers 18 are provided at their upstream end, opposite the upper transport roller 7 with a braking roller 21 provided above the sheath 2 and acting against a braking shoe, not shown, disposed below the path of the sheath 2 and fixed to the frame 1. The upstream end of the levers 18 is provided with an adjustable stud, not shown, which is pushed upwards by the action of 'a return spring not shown secured to the frame 1.

At the ends of the lower roller 6 are fixed pulleys 22a, only one of which is shown in the drawing, with a diameter slightly smaller than that of the roller. In the same way, the upper roller is provided at its ends with pulleys 22b intended to cooperate by friction with the corresponding pulleys 22a. These pulleys 22a and 22b are surrounded by a thin film or a bracelet of an elastic material such as rubber or neoprene which gives them a diameter slightly greater than that of the transport rollers 6, 7. In this way, the upper roller , which, when the sheath stops, deviates a few millimeters from the lower roller, is always driven by the lower roller. The two transport rollers rotate at the same speed and in a counter-rotating fashion and the sheath is not wrinkled when it is scrolled step by step.

At the ends of the support shaft 17 of the upper transport roller 7 are mounted idler cam rollers 23 of which only one is shown intended to cooperate each with a cam 24 keyed onto the drive shaft 14, carrying the lower roller 6. The cam 24 constitutes for the upper roller 7 the first control member.

The sheath feeder step by step 2 operates as follows. At each cycle of the installation, which corresponds to one revolution of the drive shaft 14, the cams 24 drive the rollers 23 in an alternating movement from top to bottom and from bottom to top. When the rollers 23 come in the high position, the upper roller 7 continues to rotate thanks to the pulleys 22a, 22b but it no longer cooperates with the lower roller 6, to pinch the sheath 2, on the other hand the levers 18 rock in the opposite direction of clockwise, the brake roller 21 lowers and presses the sheath 2 against the brake shoe, which causes the sheath to stop. The return spring tends to tilt the levers 18 in a clockwise direction, which allows the rollers 23 to follow precisely the contour of the cams 24. When the rollers 23 come in the low position, the roller braking 21 is raised and no longer presses the sheath against the brake shoe, while the upper roller 7 pinches the sheath against the lower roller 6, and the sheath is driven downstream of the installation. The two rollers 6 and 7 rotating at the same speed and in the opposite direction thanks to the pulleys 22a, 22, there is no wrinkling of the sheath during the drive thereof. The length of the sheath scrolled during a cycle is a function of the speed of rotation of the transport roller 6, supplied by the second variable speed drive.

Immediately downstream of the pair of transport rollers 6 and 7 is provided the pair of welding jaws 8 and 9.

The lower jaw 8 is stationary and fixed to the frame 1, so that its upper face 25 is located immediately below the path of the thermoplastic sheath (2).

The upper jaw 9 is movably mounted, above the lower jaw 8, in a manner described below, on a retractor 26 disposed downstream of the upper jaw 9.

The retractor 26 comprises a plate 27 arranged transversely in front of the upper jaw 9, fixed near its lateral ends to two simple lever arms 28, in the shape of an inverted L, arranged outside the flanges 1 of the frame, located in the upper part of the installation, s' extending upstream and pivoting about an axis 29 fixed transversely and upstream on the flanges 1 of the frame. Near the downstream end of the horizontal part of each of the lever arms 28, a cam roller 30 is mounted idly on a stud 30a fixed to the lever arm 28. This guide roller 30 cooperates with a second cam 31 keyed onto the drive shaft 14 carrying the lower transport roller 6. The cam 31 constitutes the second control member of the installation.

On one of the lever arms 28 is fixed a bevel gear 32 whose input shaft 33 is aligned on the pivot axis 29 of the lever arms 28 of the retractor 26, as seen on Figures 2 to 4. The drive shaft of the bevel gear 32 is moved by a continuous movement synchronized with the speed of rotation of the cam drive shaft 14. The output shaft 34 of the bevel gear angle 32 is perpendicular to the general plane of the plate 27 and drives a pulley 35 wedged on it which in turn drives, thanks to a toothed belt 36, a pulley 37 keyed onto a shaft 38 mounted on bearings 39, 40, integral of the lever arm 28. The shaft 38 is intended to rotate the cutting system 10 of the sheath 2, which is mounted on the retractor 26. The angle transmission system 32 is constituted in a known manner by bevel gears and will not be further explained in this application.

Each guide roller 30 is biased downwards by a tension spring, not shown, which is easily removable, fixed, on the one hand, at its upper end, to the upstream part of the lever arms 28 of the retractor 26 and, on the other hand leaves at their lower end, to the frame 1 of the installation. The retractor 26 can thus be tilted upwards and upstream of the installation after the disassembly of said tension springs and without disassembly of the drive system of the cutting device thanks to the return corner 32.

The lower roller 6 comprises a series of annular grooves 45 (FIG. 2) intended to receive and allow passage to the blowing pipes 46 (FIG. 1) provided horizontally at the upper part of the lower roller 6 below the sheath 2 and extending to the vicinity of the rear or upstream face of the jaws 8, 9. These blowing pipes 46 are intended to produce an air sheet below the sheath 2 and to prevent the latter from remaining stuck to the lower jaw 8. In addition, this first layer of air serves to support and propel the end of the sheath 2 beyond the jaws 8, 9 and of the transverse cutting device 10. The upstream ends of the tubes of supply air 46 are supplied by an air distributor, not shown, fixed to the frame 1.

The lower jaw 8 is more precisely arranged in such a way that the air blown by the blowing pipes 46 passes over its upper face 25.

The almost vertical upward and downward movements of the retractor 26 are caused during an operating cycle of the machine, that is to say a rotation of the drive shaft 14, by the cam 31 which drives the cam roller 30 against the tension spring not shown. The movement of the plate 27 is low during operation and preferably between three and five centimeters. This movement is small because the installation does not have air blowing pipes above the path of the sheath 2, which avoids creating a slight depression above the sheath downstream of the transport rollers 6, 7, which would tend to lift the sheath further downstream of the welding jaws 8, 9.

As can be seen in FIGS. 6 to 8, the lower jaw 8 has a transverse weld line 53 on its upper face 25 and has, at its upper part and below this weld line 53, a retaining shoulder in projection 54 directed downstream and comprising on its downstream front face 54a a horizontal transverse groove or groove 55 which is open at its two lateral ends and towards the front, that is to say downstream, and extends perpendicular to the longitudinal edges of the sheath 2 and parallel to the horizontal cutting path of the knife 56 of the device cutout 10. This transverse groove 55, in particular by its upper front edge 55a, acts as a knife counter blade 56 which extends from downstream to upstream and is capable of penetrating said groove or groove 55 to starting from one end of the latter and, passing rapidly therethrough, cutting the sheath 2, that is to say the upstream end of a bag, very close to the horizontal underside of the retaining shoulder 54 of the lower jaw 8.

It should be noted that the vertical front face 54a of the shoulder 54 serves during the cutting of the sheath 2 at least partially as a support plane for the latter as can be seen more particularly in FIG. 7. This arrangement is very advantageous for rapid cutting of the sheath 2 and horizontal coating of the upstream end of the bag which has just been cut.

The cutting device 10 mounted downstream and in the immediate vicinity of the upper jaw 9 comprises two notched return pulleys not shown around which passes a notched support belt 61 comprising two strands at least the lower strand of which is guided parallel to the groove or front groove 55 of the lower jaw 8 by means of a transverse guide bar 57 provided on its lower face with a horizontal guide groove 57a in which the lower strand of the toothed belt 61 moves. on its free outer face at least one horizontal fixing lug 62 for the knife 56, the blade of which extends from this lug 62 horizontally upstream so as to be able to penetrate into the groove 55 and be in a perpendicular plane to the substantially vertical support plane of the sheath 2, support plane determined by at least the upper edge 55a of the transverse groove 55 of the cutting device 10. One of the pulleys c of the cutting device 10 is driven in continuous rotation from the main shaft of the installation via the angle transmission system 32 and the tree 38 described above.

The movement of the toothed belt 61 is synchronized with the movement of the retractor 26 so that the knife 56 makes a whole number of journeys during each operating cycle of the installation, that is to say for one revolution. of the drive shaft 14, and is present at a good height near the entry end of the horizontal groove 55 of the lower jaw 8 only when the welding jaws 8, 9 are in the low welding position (Figure 7) in which the welding faces of the jaws 8, 9 bear one against the other. The specific design of the cutting device 10 is described in French patent application 2,597,402, entitled "Device for cutting a sheath in an installation for manufacturing bags or sachets, etc. made of thermoplastic material" and to which may refer for more details to the fact that the present description will remain limited to the elements necessary for the understanding of the present invention. We can also refer to the cutting device described in US Patent 4,230,029.

Below and upstream of the retaining shoulder 54 of the lower weld jaw 8 is provided a stacking device 11 comprising a table 67 and a bag racking device.

The table 67 comprises an almost horizontal plate 101 supported upstream by support beams 102 disposed laterally on vertical return springs 103 fixed to the lower part of the frame, and downstream by collars 104 mounted on a shaft 105 parallel to the drive shaft 14 and mounted idly in bearings 106 fixed to the lateral flanges of the frame 1. The upstream end 107 of the horizontal plate 101 is disposed in the immediate vicinity and below the retaining shoulder 54 of the jaw lower 8 and is overlapped by the greater part of the lower face thereof. The plate 101 is slightly inclined up and down upstream. The table 67 is pivotable around the shaft 105 and the spring 103 tends to keep in the high position.

The support beam 102 is provided with an oblong hole 108 directed parallel to the rotation shaft 105 of the table 67 whose lower 109 and upper 110 ends are intended to cooperate with a horizontal rod 111 mounted fixed and laterally on a arm 112 extending, under the plate 101 and downstream, parallel to the general direction of the sheath 2. This arm 112 is keyed in its middle part on a shaft 113 parallel to the shaft 105 connected to one of the flanges 1 of the frame by a bearing 114 and to the other flange by a mechanical friction brake 115 consisting of a fixed part 116 secured to the chassis and a movable part 117 keyed onto the shaft 113. During operation of the installation, the movable part 117 is held in friction against the fixed part 116 by an electromagnet not shown. When this electromagnet is de-energized, the brake 115 no longer acts and the table switches clockwise under the action of the return springs 103, until the downstream end of the arm lever 112 comes to press on an adjustable stop 118.

The return spring 103 tends to keep the upstream end 107 of the table 67 in the high position. When a vertical force is applied to this end 107, the table switches counter-clockwise. The rod 111 slides in the oblong hole 108 until it comes to abut against the upper face 110. An additional descent of the table causes the displacement of the rod 111 so that the arm 112 rotates around the axis 113 clockwise which drives the moving part 117 of the friction brake 115. The friction forces of the brake 115 are calculated so that the friction torque of the brake 115 is greater than the torque of the return springs 103. Thus the rod 111 retains the position it had acquired at the time of the descent of the table 67, and when the vertical force on the upstream end 107 is removed, the return spring 103 moves the table up to that the underside 109 of the oblong hole 108 abuts against the rod 111 which is now in a slightly lower position. It is thus noted that the table descended during this maneuver.

Near the upstream end 107 of the table 67 is disposed, above the plate 101 and transversely, an elastic damping cushion 67c, for example of rubber, the vertical upstream face of which is slightly downstream, but very close to the plane passing through the vertical front face 54a of the retaining shoulder 54 of the lower jaw 8.

The stacking device 11 further comprises a blocking pad 71 vertically movable and capable of passing very close in front of the front face 54a of the shoulder 54, to be applied against the upper face of the damping cushion 67c of the table stacking 67 and thus block the end part of the sheath against the damping cushion 67c of said table 67 very close to the transverse groove 55 of the cutting device 10 and the shoulder 54, the downstream end of said sheath 2 resting freely on the stack of bags already supported for the most part by table 67.

The blocking pad 71 has the form of a right angle angle whose horizontal lower flange 71a extends from downstream to upstream, at a relatively low height and constitutes the blocking pad itself and whose l vertical wing 71b, constituting the plate 27 of the retractor 26, is connected to the downstream end of the lower wing 71a and serves to support the transverse guide bar 57 of the lower strand of the toothed belt 61, this bar guide 57 being fixed on the vertical wing 71b so that its horizontal guide groove 57a is open downwards towards the horizontal wing 71a. Thus the lower strand of the toothed belt 61, the horizontal knife 56 and the fixing lug 62 of the latter on said belt 61 are protected against any untimely access.

The upper machine 9 is mounted mobile on the blocking pad 71 and for this purpose, two vertical guide columns 80 are fixed laterally and above the horizontal wing 71a and of the guide bar 57 on the vertical wing 71b of the blocking shoe 71 using an upper clamp 81 and said vertical wing 71b and a bore 82 located on the upper part of the bar 57 .

The upper end of the two vertical columns 80 protrudes from the upper clamp 81 by a height at least equal to half the vertical distance separating the clamp 81 and the bar 57. The front downstream face of the upper jaw 9 is provided with two superimposed guide bearings 83, 84 whose vertical and axially aligned bores are traversed respectively by the upper part and the lower part of a corresponding guide column 80. A return spring 85 is placed on each guide column 80 and bears against, on the one hand, the lower horizontal face of the upper clamp 81 and, on the other hand, the upper horizontal face of the lower guide bearing 84 so that the upper jaw 9 is constantly urged towards the bottom under the effect of said return spring 85. Between the upper clamp 81 and the upper guide bearing 83 is provided an adjustment stop nut 86 which is made ground idaire of the blocking shoe 71 by screwing on a threaded part of the guide column 80 and which serves to adjust the vertical spacing between the underside of the upper jaw 9 and the underside of the blocking shoe 71 and to drive said jaw upper 9 during the upward stroke of the blocking shoe 71.

The upper jaw 9 has on its lower face a transverse weld line 87 which aligns with the weld line 53 of the lower machine during the descent of the retractor 26. This weld line 87 is constituted in known manner by an electrical resistance wire. The same applies to the weld line 53 of the lower jaw 8.

The blocking pad 71 is also intended to cooperate during operation with the bag racking device and for this purpose two beams 88 are fixed vertically on the upstream and lateral faces of the vertical wing 71b of the pad. blocking 71. These beams 88 extend downward and on each side of the table 67 and are intended in operation to cooperate with a transverse row of needles 89.

The needles or pins 90 are fixed, the point directed upwards, on a horizontal and transverse needle holder beam 91, which is arranged under the table 67 in line with the shock cushion 67c, and is pivotally mounted on the pivot shaft 105 of the table using two longitudinal lever arms 92, 93 extending under the table 67, fixed upstream at one end of the needle holder beam 91 and downstream to the pivot shaft 105.

The ends of the arms 92, 93, in the immediate vicinity of the beam 91, are provided with a vertical bore 94 traversed by the cylinder 95 of a release cylinder 95a fixed to the lower part of the frame 1 by a nut 96. The arms 92, 93 can slide freely along the cylinder 95. A return spring 97 is placed on each cylinder 95 and bears, on the one hand on the upper shoulder of the release cylinder or on the nut 96 and on the other hand on the underside of the corresponding arm 92, 93. The vertical clearance of the needle holder beam is limited by a nut 98 mounted on the upper part of the cylinder 95 which is threaded and above the lever arm 92, 93 This nut 98 serves both as an upper stop for the needle holder beam 91 and for adjusting the maximum height of the upper needle tip 90. In operation, the return springs tend to hold the needle holder beam 91 and the cylinder 95 of the release cylinder 95a at p high position. The beams 88 are arranged above the upstream part of the lever arms 92, 93 supports of the needle holder 91.

The needles 90 pass through a transverse row of vertical holes 99 made in the table 67 and the shock absorbing cushion 67c and protrude above this cushion and the bags already inserted of a low height, which can be adjusted by the nuts 98 and the stops 118. A transverse row of vertical holes 100 is provided in the lower part 71a and upstream of the blocking pad 71. This row of holes is aligned with the row of holes 99 on the table and is intended to receive the upper point of the needles 90 during operation during the racking-in and stacking phases of the bag being finish.

The blocking pad 71, an integral part of the retractor 26, is arranged such that the vertical path of the upstream vertical face 71a ′ of its horizontal wing 71a passes very close to the front vertical face 54a of the retaining shoulder 54 and is spaced therefrom by a distance equal to a few thicknesses of the sheath 2, for example 2 to 5 double thicknesses of said sheath 2. The tip of the knife 56 slightly protrudes from the upstream face 71a ′ of the wing horizontal 71a of the blocking pad 71 when said knife engages in the groove 55. The blocking pad 71 thus fulfills a protective function of the knife 56 on the lower strand 61, in addition to its function of elastic support, guiding and control of the upper machine 9 which is integral with the retractor during part of the path thereof.

The main function of the blocking pad is to hook the end of the sheath 2 onto the row of needles, to block it against the stack of bags being formed, to bring a section of sheath in an approximately vertical position against the vertical face 54a of the retaining shoulder 54 and to actuate the stacking and racking-in devices.

According to the invention, the cams 24 which operate the sheath feeder 2 step by step and the cams 31 which operate the retractor are designed and arranged so that, in an operating cycle, when the retractor 26 is in the high position, the sheath 2 is driven downstream above the table 67, and that when the retractor 26 makes its vertical movement from top to bottom and then from bottom to top, the sheath is stopped by the brake roller 21.

During the downward travel of the blocking pad 71, the downstream end 71a comes to apply the end of the sheath 2 against the downstream face 54a of the retaining shoulder 54 of the lower jaw 8. This downward movement of the retractor 26 keeps under tension the downstream part of the sheath 2 which is stopped upstream by the braking roller 21. Then the lower face of the upper jaw 9 is applied against the lower jaw 8 and is maintained in this position under the action of the springs 85 during the additional descent of the retractor 26. Almost at the same time, the underside of the blocking pad is in the vicinity of the upper end of the needles 90 which will skewer the sheath 2. The blocking shoe continues a slight descent until the knife 56 is in alignment with an open side face of the groove 55. The plugged sheath part is then pressed against the stack of bags already stacked on the needles 90, the table 67 is slightly lowered and the needles 90 are held in their starting position by the action of the return springs 97, the beams 88 fixed to the retractor being at immediate vicinity of the lever arms 92, 93 of the racking device. The retractor temporarily stops its downward stroke. The part of the sheath (2) between the welding jaws and the blocking pad is then stretched and almost vertically pressed against the face 54a of the retaining shoulder. The tips of the needles 90 are housed in the holes 100 of the blocking shoe 71 and the knife 56 continues to run in the groove 55, which has the effect of cutting out the bag which has just been racked in, as can be seen on Figure 7.

As seen in Figure 8, the retractor continues its downward stroke, after cutting the last finished bag, over a distance of 5 to 15 mm. The blocking pad 71 causes the table 67 to tilt as has already been described, and the beams 88 tilt the needle holder beam 91. This additional descent of the retractor is such that the underside of the retaining shoulder 54 located slightly above the free upstream end 120 of the bag which has just been cut and which is still pressed against the stack of bags or the shock absorbing cushion 67c of the stacking table 67 by the blocking pad 71. In this low position of the stack of bags, the free upstream end very short 120 of the cut bag, free end 120 with a length of the order of 5 to 10 mm, folds down automatically and quickly under the effect of its stiffness or of its "memory".

When the retractor 26 is raised, the hands 90 return to their initial position under the action of the return springs 97. The table 67 also rises and takes, for the following cycle, a position slightly lower than that which it had at the start of the cycle, thanks to the action of the friction brake 115 as already described. Finally, the blocking shoe 71 rises in its high position while driving with it the upper jaw 9 in order to free the path of advance of the downstream end of the sheath 2 which, under the action of the pair of rollers transport 6, 7 and supported by the sheet of blown air leaving the blowing pipes 46 is advanced by a step corresponding to the length of a bag.

It should be noted that the stacking table 67 is slightly lowered by the blocking pad 71 before the sheath 2 is cut so as to sufficiently tension the sheath portion between the welding jaws 19, and the blocking pad 71 and to facilitate the cutting of the sheath by the knife.

It should be noted that, from one cycle to another, the upper ends of the needles 90 protrude above the stack of bags by a constant length which can be adjusted by the nuts 98. Thus the position upper end of the last racked bag is always constant and the upstream free ends of the stacked bags are cantilevered upstream of the shock-absorbing cushion 67c of the stacking table 67 and are not compressed or pressed against the retaining shoulder 54.

Finally, it should be noted that the upper ends of the needles are arranged above the damping cushion 67c in the vicinity and slightly below the groove 55 of the retaining shoulder 54, and cannot damage the sheath 2 during its advancement.

It should also be noted that during a large part of the operating cycle, the bags are skewered on the needles without being permanently tightened between the table 67 and the blocking pad 71 or the retaining shoulder 54.

The installation is provided with a bag counting device constituting a stack. When the desired number of bags is reached, a bell prompts the operator to remove the stack of bags that has just been made. At this time, the installation stops, the retractor being in the high position and the sheath being kept stationary by the braking roller 21.

The release cylinder 95a is then actuated in such a way that the cylinder 95 moves downward, which causes the needle holder beam 91 to descend. The amplitude of the descent of the cylinder 95 is determined so that in the low or release position, the point of the needles 90 is located below the upper face of the shock absorbing cushion 67c and preferably in the holes 99 made in the table 67.

The operator can then manually remove the stack of bags that has just been made. However, the retaining shoulder 54 can hinder the removal of the stack, so the cylinder 95 undergoes an additional downward movement, which rocks both the needle holder beam 91 and the table 67 counterclockwise. a watch around the axis 105 against the return springs 97 and 103 and the friction brake 115.

To this end, the lever arms 92, 93 are each provided with a not shown stud which extends towards the support beams 102 of the table 67 and which comes to bear, during the additional descent of the cylinder 95, on a stud not shown attached to the support beam 102 of the table 67 below the corresponding stud of the lever arm 92, 93.

This additional descent from the table 67 allows the stack of made-up bags to be released from the retaining shoulder 54 of the lower jaw 8.

After removing the stack of bags, the operator must return the table 67 and the needle holder beam to the high position before starting to make the next stack. This is done by releasing the cylinder 95a and de-energizing the electromagnet which held the movable flange 117 of the friction brake 115 against the flange 116 fixed to the frame. The return springs 97 rotate the needle holder 91 until the lever arms 92, 93 abut against the nuts 98. The return springs 103 rotate the table 67 until the lever arms 112 abut against the stop rod 130.

The invention is not limited to the embodiment described above and made by way of example. modifications can be made thereto without departing from the protective framework defined by the appended claims.

Claims (7)

1.- Installation for manufacturing and stacking bags, sachets, etc. made from a flattened thermoplastic sheath, installation of the type comprising:
- a horizontal guide track (3) of the sheath (2);
- a pair of step-by-step transport rollers (6, 7) between which said sheath (2) is clamped during its step-by-step transport and the lower roller (6) of which is mounted in a fixed position and the upper roller (7 ) is mounted so as to be able to move away from the lower roller (6) under the action of a first control member (24);
- an intermittent stop device (5) of the sheath (2) provided upstream of the transport rollers (6, 7) and having an upper support pad (21) movable and actuated by said first control member (24 ), and a fixed lower backing pad;
- A pair of welding jaws (8, 9), one of which (8) is arranged below and the other (9) above the path of travel of the sheath downstream of the transport rollers (6, 7) and at least one of which is movable perpendicular to said path so as to be able to approach or move away from the other jaw, the lower jaw (8) comprising a retaining shoulder (54) at its upper and downstream part ,
a transverse cutting device (10) provided downstream of the welding jaws and comprising an upper knife (56) and a lower counter blade (55),
a stacking table (67) located downstream of the lower jaw (8) whose upstream end vertically movable relative to the lower jaw (8) is disposed below the retaining shoulder (54), said table (67) being capable of receiving between its upper upstream end (107) and the lower face of said retaining shoulder (54) the upstream end (120) of the stacked bags;
- a needle holder (91) disposed transversely under the upstream end (107) of said table (67), movable relative to the lower jaw (8) and supporting a transverse row needles (90) or pins whose points directed upwards slide in a row of aligned holes (99) formed in the upstream end (107) of said table (67) and skewer the upstream end (120) stacked bags; and
- An upper blocking pad (71) vertically movable under the action of a second control member (31), mounted so that the vertical path of its upstream face (71a) passes with little play in front of the vertical face (54a) downstream of said retaining shoulder (54), disposed downstream of the welding jaws (8, 9) and of the cutting device (10), and capable of coming to block the end part of the sheath (2) projecting from the device cutting (10) against said stacking table (67);
installation characterized in that:
- the lower jaw (8) is fixed;
- the needle holder (91) is arranged in line with the blocking pad (71) which comprises a row of vertical holes (100) intended to receive the point of the needles (90) during the cutting of the next bag;
- the blocking pad (71) is capable of carrying out an additional downward movement after cutting the last made-up bag and of causing the stacking table (67) and the needle holder (91) in its downward movement which are urged upwards by return springs (97, 103), so as to allow the upstream end (120) of the last cut bag to fall back under the retaining shoulder (54) of the lower jaw ( 8); and
- The stacking table (67) is provided with an indexing device which allows it to have a large clearance and to descend as the bags are stacked, so that the height of the last stacked bag is constant when the sheath scrolls (2). 2.- Installation according to claim 1, characterized in that the indexing device of the stacking table (67) comprises a horizontal hole of oblong shape (108) formed vertically in a vertical beam (102) fixed under the table (67), in which slides a rod (111) fixed to the mobile end of a horizontal lever arm (112) keyed onto a shaft (113), and a friction brake (115), one of the flanges (117) is keyed onto said shaft (113) and the other flange (116) is integral with the frame (1), the free movement of the table (67) being limited by said oblong hole (108) and said rod ( 111). 3.- Installation according to one of claims 1 or 2, characterized in that:
- the needle holder (91) is fixed to the free ends of two lever arms (92, 93) pivotable about a transverse axis (105) which extend horizontally and longitudinally and which slide along a rod vertical cylinder (95) and directed upwards of a cylinder (95a) fixed to the frame (1),
the return springs (97) of the needle holder (91) are mounted around said jack rods (95) and bear, on the one hand, against the upper flange of said jack (95a) and, on the other hand, against the underside of the corresponding lever arm (92, 93),
- The travel of said needle holder (91) is limited and adjusted upwards by a nut (98) fixed to the upper part of each jack rod (95) and bearing against the upper face of the corresponding lever arm (92 , 93), and
- the downward movement of said needle holder (91) is ensured by vertical beams (88) integral with the blocking pad (71) which are capable of pressing on the free ends of said lever arms (92, 93) after the cutting the bag during the additional descent of said blocking pad (71). 4.- Installation according to one of claims 1 to 3, characterized in that:
- the blocking pad (71) is fixed to two parallel lever arms (28) extending laterally and horizontally upstream of the installation, keyed onto a pivot shaft (29) mounted on the chassis (1) and biased downwards by tension springs, drives the upper jaw (9) with interposition of a return spring (85) and carries said knife (56),
- the knife drive device (10) comprises an angle gear (32) fixed to one of said lever arms (28) of the blocking shoe (71), said angle gear (32) having a drive shaft (33) whose axis coincides with said pivot shaft (29) of said blocking shoe (71) and an output shaft (34) whose axis is perpendicular to the plane of the drive pulley the belt (61) supporting the knife (56), and
- the disassembly of said tension springs makes it possible to rock as a block upwards and upstream of the installation, the blocking pad (71), the upper jaw (9) and the cutting device (10). 5.- Installation according to one of claims 1 to 4, characterized in that:
- The first control member (24) and the second control member (31) are cams keyed onto the carrier shaft (14) of the lower transport roller (6) which cooperate with rollers (23, 30) mounted respectively on the support lever arms (18) of the upper transport roller (7) and the support lever arms (28) of the locking pad (71) said rollers (23, 30) being held against their respective cam (24 , 31) by elastic forces. 6.- Installation according to one of claims 1 to 5, characterized in that the upper transport roller (7) is continuously rotated by the lower transport roller (6), during operation of the installation, by through at least one pair of pulleys (22a, 22b) cooperating by friction fixed laterally on at least one side of the transport rollers (6, 7), at least one of which is covered with a strap of material elastic with a diameter slightly greater than the diameter of the transport roller, ensuring the elasticity required when the sheath (2) is passed by the transport rollers (6, 7) and the drive of the upper roller (7 ) during the intermittent stop of the sheath (2). 7.- Installation according to one of the preceding claims, characterized in that the stacking table (67) is slightly lowered by the blocking pad (71) before cutting said sheath (2) so as to sufficiently tension the part of sheath included between the welding jaws (8, 9) and the blocking pad 71 and to facilitate cutting of said sheath by the knife 56.

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