EP0844175A1

EP0844175A1 - Improvements to self-contained sacking machines

Info

Publication number: EP0844175A1
Application number: EP97918163A
Authority: EP
Inventors: Manuel Payper S.A. PADULLES BAUTISTA
Original assignee: Payper SA
Current assignee: Payper SA
Priority date: 1996-05-08
Filing date: 1997-05-08
Publication date: 1998-05-27
Anticipated expiration: 2017-05-08
Also published as: WO1997042077A1; DE69701180T2; EP0844175B1; DE69701180D1

Abstract

One of the improvements lies in establishing, between the sack forming station (1) and the sack filling station (3), an intermediate station (2) whose distance from the filling station (3) is considerably less than the distance between the filling station and the sealing station (4), in order that when the sack (8) transfer carriage (9) moves, the sacks will arrive at the filling station (3) within substantially less time than that required for it to be conveyed to the other stations, allocating more time to the filling phase. Another improvement lies in providing a welding mechanism to reinforce the ends of the sack, after the sack has been filled and sealed. Another of the improvements lies in providing the sacking machine with a sack forming unit devised to fragment the continuous tubular band from which said sacks are obtained and to provide a seal by welding the bottom end of each sack, the foregoing in optimum conditions for the sacks to be capable of withstanding the next immediate sack filling phase.

Description

OBJECT OF THE INVENTION

The present invention deals with the field of autonomous sacking machines, capable of forming, filling and sealing the sacks, and the invention focuses in particular on a number of improvements with which the performance of machines of this kind is successfully enhanced, concurrently improving their functionality.

Specifically, one of the improvements consists of providing an intermediate or hold station between the sack forming station and the filling or packaging station, which requires transfer of the sack from such intermediate station to the filling station to take place within considerably less time than transfer between any of the other stations of the machine.

Another improvement lies in a welding mechanism with which both ends of the sack are considerably reinforced, in order for a greater mechanical resistance to be provided at the bases of the sack, i.e. at the weakest areas since these are the areas sealed by welding.

Another improvement consists of a studied, advantageous sack forming unit that enhances the operation of the machine and the end result of the sacking operation as such.

Machines to which the improvements of the invention apply are of the kind designed for sacking both granular and powdered products in bulk, namely for instance cattle feed, fertilisers, plastic chaff for industrial processes, ceramic enamels, etc.

BACKGROUND OF THE INVENTION

There are several known types of sacking machines in which the raw material used is a plastic heat-weldable tubular body of unlimited length, supplied in a roll, with side folds or bellows, in which three operative means are basically established, a sack forming means, which suitably fragments the continuous roll and concurrently provides a seal at the bottom end of each unit or sack, a filling mechanism which supplies each sack with the relevant quantity of the product at issue, and a sealing mechanism which suitably seals the sack, on being filled as aforesaid, ready to be shipped or stored.

Noteworthy in this sense is German patent DE-4,314,711, which discloses a filling and sealing device for sacks previously formed from a continuous roll or band, wherein each sack or unit is gripped at an area close to its mouth by means of clamps that overturn the sack 90°, open and position it beneath the filling mechanism, after which the sack is again overturned 90° and taken to a sealing station, which lies above a conveyor belt, where the sack is deposited, now sealed, standing perfectly upright, to prevent the possibility of the sack from brusquely swaying laterally, upon hitting the conveyor belt, and causing it to be opened through the recently established and still warm weld.

US patent 4,510,736 shows another machine of this kind, noteworthy therein being a first sack bottom carrying stage, in which propelling nozzles are used, a sack filling stage and a sack sealing stage, in accordance with the general basic outline referred to before. The sacks must also in this case be placed standing fully upright in order for the sealing weld not to suffer and be damaged due to the actual pressure exerted by the product.

German patent 2,614,270 discloses a sack filling machine, especially devised for a particular case in which the sacks are rather wide, the purpose being likewise for the sacks to be held upright. This case also provides for the aforesaid basic stages, namely filling the sack or bag and sealing the same, cooling the weld, and is particular also in that a mechanical pusher is positioned beneath the filling stage to compact the sack contents.

US patent 5,448,879 discloses another solution for sack forming machines.

Finally, European patent EP 0 516 979 describes a process for making, filling and sealing sacks which consequently includes the three basic functional stages which are the common denominator of most machines of this kind, referred to hereinbefore, but the working of the process according to this patent requires the use of highly complex mechanisms which adversely affect both the cost of the machine and its subsequent maintenance.

On the other hand, sacks of the kind referred to before obtained from a continuous tubular band with side bellows or folds, pose a sealing problem at both their bottom and top ends, namely that the respective cross-welds, which affect only the two walls of the sack at an intermediate, larger sector of the sack, then brusquely affect, at its ends, the four walls that provide the folds or bellows of the side walls, three stretches being thus established over each weld line aforesaid, namely an intermediate and two end stretches, the thickness of the end stretches being twice that of the intermediate one, thereby providing weak points for such weld, at the points at which said three sectors are interconnected. Furthermore, these side bellows of the sack, designed to open up when the sack is being filled, cannot do so at their end portions, for this is prevented by the sealing cross-welds, permanent folds being defined at such end portions which should desirably not be accessible for the material to be sacked, for the sack to have a better overall configuration after being definitely filled and sealed.

In order to solve these drawbacks, the two halves of each bellows are known to be fixed to the respective side walls of the sacks, at its end areas, by means of welds affecting small triangular areas. The solutions used to date for obtaining such welds are however either structurally very complex or adversely affect machine productivity, increasing the time of each of its operative cycles.

These machines are in any event fitted with continuous tubular band entraining means, welding means to establish the seal at the bottom of each sack, and cutting means to shear off the next sacks, the above-mentioned machines providing different solutions therefor, although the common denominator is always an extremely complex construction which adversely affects both the manufacturing costs of such machines and the subsequent maintenance costs. Moreover, in sacking machines of this kind, filling of the sacks is made immediately after forming the sacks, and the weld constituting the bottom seal of the bag is not able at times to stand the load the product exerts within the sack, because it has not cooled down sufficiently.

DESCRIPTION OF THE INVENTION

The improvements subject of the invention fully solve the above-mentioned drawbacks, affording high productive rates with a simple and consequently inexpensive structure for the sacking machines.

Accordingly, in order to attain a high production, of some 1200 sacks/hour, the machine has up to 3 seconds available for each of its different operative phases.

At the sack forming station, considering a perfectly reasonable welding time of 1.5 seconds plus a further 1.2 seconds to measure the length of each sack, the required time is 2.7 seconds, which is clearly less than the available time.

That is not the case of the sack filling station, for it is well-known that there is an increasing use of sacks having side folds or bellows which should not be opened during manipulation, for they would otherwise be difficult to recover whilst maintaining a good sack presentation, in addition to which there is an increasing demand for corner welds at the sack corners, which requires maintaining the said folds throughout the sack making, filling and sealing process. This means notably reducing the section available as the product "input mouth" into the sack, which entails a greater filling time and moreover, due to requirements such as package material savings, correct sack presentation and good sack stability on the pallets, the product must be properly settled within the sack, to which end the use of a tamping or compacting mechanism has been provided which in turn also "takes up" extra time.

It follows from the above that in order to maximise packaging quality, clearly at the expense of the time allocated to this operation, the time lag entailed by the transfer of the sack from the forming station to the filling station must be reduced to a minimum.

Now then, in accordance with one of the improvements of the invention, this is achieved using an intermediate or hold station, lying very close to the packaging station, and thus instead of passing straight from the forming station to the packaging station, each sack first passes to such an intermediate station, the transfer from such intermediate station to the filling station thus requiring considerably less time.

In accordance with another characteristic of the invention, a pre-opening operation of the sack takes place at this intermediate station with the assistance of a clamp having suction pads, thereby for the potential initial opening difficulty the sack may pose due to the residual effects of the cutting operation, to be overridden at this intermediate station, the sack being opened at the subsequent filling station almost instantaneously, a crosswise displacement of the clamps holding the sack towards each other expediting such operation, together with the set of suction pads provided at such filling station.

In accordance with another of the improvements subject hereof, the carriage transferring the sacks between the various stations making up the machine is U-shape in plan, with side branches pointing towards the machine outlet, thereby to provide a fully diaphanous space throughout the sack transfer area, for the side clamps fixing the sacks only project into the side branches of the carriage when they clamp down on the sacks.

In accordance with another improvement of the invention, the said carriage has three sets of clamps, the two end sets of which are rigidly connected to said carriage, whereas the intermediate set is mounted through guides and with a floating type motion specifically by means of two side pneumatic cylinders, that work as mere resilient elements assisted by a stop locked to the machine bed, advantageously facing the filling station, and therefore as opposed to the fixed run of the carriage, which defines a similarly fixed run for the end clamps, between the forming station and the intermediate station, on the one hand, and between the filling station and the sealing station, on the other, the run between the intermediate station and the filling station is much shorter in order that the filling operation may begin beforehand, i.e. making a better use of the space available in each cycle.

In accordance with another characteristic of the invention, a compacting element is established beneath the filling station, associated to the frame supporting the ejection conveyor belt, tamping the base of the sack to improve its filling conditions.

In accordance with another characteristic of the invention, at the sack sealing station, specifically the mobile arm of the welding clamp, an approach sensor is provided for such welding clamp to allow the absence of a sack, the existence of a crease at the mouth of the sack, the existence of product waste at said mouth impairing sealing, or any other fault whatsoever which may be detected by an unusual dimension of the thickness of the mouth of the sack, to be detected.

In accordance with another aspect of the invention, the machine to which the improvements apply also has a sack reinforcement welding mechanism which is precisely aimed at providing the triangular welds at the ends of the bellows of each sack rapidly, simply and efficiently.

More specifically and in order to achieve the above, the welding mechanism subject hereof, in accordance with another characteristic of the invention, is designed to be established between the feed station and the sack forming station of the machine, thereby for the sack reinforcement welds to be provided before the sacks are formed, specifically on the continuous band, before it is fragmented. A cooling device centring the continuous band is arranged at the outlet from this corner welding mechanism.

Specifically, the welding mechanism is structured with two heads capable of adjusting their distance from each other in order to suit it to different sack widths, each of the heads having a dolly-like weld guide plate designed to be housed in the respective fold or bellows of the continuous tubular band, reaching up to the bottom of such bellows, in order to duly free all its sectors, whilst the clamps of the welding grip are established on either side of this guide plate, to be clamped down after each unit displacement of the continuous tubular band against the intermediate guide plate, causing the marginal areas of the bottom end of a sack and the top end of the next immediate sack to be welded simultaneously, specifically by means of a single trapezoidal weld, which will be fragmented along its middle line at the subsequent sack forming station, one of its halves becoming part of one sack and the other half part of the next sack, as aforesaid. On either side of this dolly-like part or guide plate, which must stand the high temperatures upon the heads being heated, two similar guide plates are provided with the sack being formed passing through them, which plates have holes crossed by the welding parts, thereby, upon the welding parts being removed when the corner welding operation is over, for the sack material to be retained without being entrained if they stick to the welding parts.

The clamp-down of these welding clamps, at each welding stage as such, can be effected by any suitable conventional means, such as pneumatic pistons for instance, to which end the arms of each clamp will be mounted to move crosswise on the respective head, moving in synchrony towards or away from the intermediate guide plate.

The machine also provides, as another improvement, a forming means or unit which resolves a number of problems resulting from conventional machines of this kind referred to in the prior art section.

More specifically, and in order to achieve the above, the forming unit subject hereof is structured with a pair of tangent rollers, one being an entraining roller and the other a press roller, the first of which is driven by a gearmotor and through an encoder which allows its turning movement to be controlled at will, to define a dimensionally accurate entrainment of the continuous tubular band in accordance with the size of the sack to be obtained, whereas the press roller is pivotally mounted on end arms and is manually separable from the entraining roller with the assistance of an eccentric that may in turn be driven by a lever.

The chassis supporting these entraining and press rollers is at the same time the supporting means for a pair of pivoting bracings, each supporting the respective welding and cutting mechanisms, both bracings being driven in synchrony and in opposition to each other by means of respective connecting rods, through an eccentric that is in turn driven by means of a pneumatic cylinder, thereby for driving of the piston of said cylinder in a particular direction to cause the welding and cutting grips to move towards each other, whereas movement in the opposite direction causing them to be separated.

In order to supplement the above-mentioned structure and ensure an optimum security of the weld defining the bottom of each sack, beneath said cutting and welding mechanism, at the lower level of the machine a deflector plate is established directing the bottom sealed end of the sack towards a pair of blowing nozzles, extending to match the height of the sack, one being fixed, although it may be positionally adjusted, and the other being pivotable to approach the first nozzle, upon being driven by a pneumatic cylinder, and therefore once the weld at the bottom end of a sack has been established level with the blowing nozzles, the latter approach each other exercising their cooling action on both faces of the sack, rendering its weld rapidly consistent upon being cooled.

Because machines of this kind are able to form and fill sacks of different dimensions, the length of said blowing nozzles has been provided to be suitable to the maximum expected width of said sacks, and for the blowing mechanism in turn to be altogether adjustable in height, in order to suit the position of such blowing nozzles to the height of each type of sack. In this sense, the support of said blowing nozzles is mounted on the machine chassis through vertical guides, and has a spindle or similar transmission means to be lifted/lowered, driven from a wheel, through a belt or other suitable driving means, and thus upon said wheel being hand-driven, the working level of the blowing nozzles may be established, as aforesaid, to suit any sack size.

DESCRIPTION OF THE DRAWINGS

In order to provide a fuller description and contribute to the complete understanding of the characteristics of this invention, a set of drawings is attached to the specification as an integral part thereof which, while purely illustrative and not fully comprehensive, shows the following:

Figure 1.- Is a schematic side elevation representation of an autonomous sacking machine made in accordance with the improvements subject of the invention, shown with the carriage in the limiting retreated position.

Figure 2.- Is a schematic plan representation of the unit shown in the preceding figure.

Figure 3.- Is a representation similar to that of figure 1, at an initial forward phase of the sack transfer carriage.

Figure 4.- Is a plan view of the unit shown in the preceding figure.

Figure 5.- Is a representation similar to that of figure 1, yet again of the same unit of said figure in the limiting forward position of the transfer carriage.

Figure 6.- Is a plan view of the unit shown in the preceding figure.

Figure 7.- Is a view similar to that of figure 1 with the carriage retreated, i.e. in a phase returning to the position of said figure 1 to complete the operative cycle of the machine.

Figure 8.- Is a plan view of the unit shown in the preceding figure.

Figure 9.- Is a schematic sectional representation of the machine, at the filling station level.

Figures 10 and 11.- Are two perspective close-views of the machine, facilitating the understanding of the general construction of the machine.

Figure 12.- Is a schematic side elevation representation of the same autonomous sacking machine fitted with the sack reinforcement welding mechanism subject of another improvement of the present invention.

Figure 13.- Is a partial schematic plan representation of the continuous tubular band constituting the sack forming raw material, with the tubular band leaving the welding mechanism shown in the preceding figure.

Figure 14.- Is a front elevation close-view of the said welding mechanism.

Figure 15.- Is a plan view thereof.

Figure 16.- Is a perspective view of the same welding mechanism, duly coupled to a sacking machine, represented only partially.

Figure 17.- Is a schematic side elevation representation of a sack forming unit for sacking machines, made in accordance with another improvement of the invention.

Figure 18.- Is a plan view of the unit shown in the preceding figure.

Figure 19.- Is a perspective close-view of the same unit shown in the preceding two figures.

Figure 20.- Is a side elevation view of the cooler assisting the former as such shown in the preceding three figures.

Figure 21.- Is a front elevation and sectional view of the unit of the preceding figure.

Figure 22.- Is finally a perspective view of the unit shown in the preceding two figures.

PREFERRED EMBODIMENT OF THE INVENTION

With reference to these figures, an autonomous sacking machine made in accordance with the improvements of the invention can be seen to be based upon a sack forming station (1), an intermediate or hold station (2), a filling station (3) and a sealing station (4).

At the sack forming station (1), as is conventionally the case, the continuous tubular band (5) is fragmented at regular intervals, in accordance with the expected height of the sacks, and welded to seal the bottom of such sacks, by means of a pair of welding and cutting heads (6) beneath which lie a first pair of support clamps (7) for the already formed sack (8), which pair of clamps (7) is mounted fixed on a carriage (9) responsible for transferring the sacks (8) from the forming station (1) to the intermediate (2), filling (3) and sealing (4) stations.

This carriage (9), which figure 2 clearly shows is U-shaped, with a fully diaphanous sack transfer space (8), is driven by a gearmotor (10) acting on an eccentric (11) and a connecting rod (12) to transmit a longitudinal reciprocating motion to said carriage (9), the extent of the forward and consequently backward movement accurately matching the distance between the sack forming station (1) and the intermediate station (2), and the distance between the filling station (3) and the sealing station (4), whereas the distance between the intermediate station (2) and the filling station (3) is considerably smaller.

In order to offset this dimensional difference, whereas the pair of clamps (7) with which transfer is effected from the sack forming station (1) to the intermediate station (2), just as the pair of grips (13) with which the sacks are transferred from the filling station (3) to the sealing station (4) are fixed, the pair of clamps (14) with which transfer is effected from the intermediate station (2) to the filling station (3) is mounted to slide on guides along the carriage (9) with a floating nature, particularly associated to the rod (15) of a pneumatic cylinder (16), which acts as a spring or resilient element to enable free displacement of the carriage (9) once the pair of clamps (14) has come to face the filling station (13), in a limiting position defined by a stop (17) upon which each pair of clamps (14) abuts in their travel, and which consequently lies operatively facing the filling station (3), as shown particularly in figure 3.

The intermediate or hold station (2) is not only designed to substantially shorten the run the sack (8) must complete in each operative cycle, in moving forward to the filling station (3), but farther facilitates opening of the mouth of the sack (8), to which end said intermediate or hold station (2) is not only assisted by a pair of floating grips (14), but has a clamp (18) drivable by a pneumatic cylinder (19) and provided with suction pads (20) that act on the sack walls, at its mouth level, to open it before it is definitely opened at the filling station (3) by the suction pads (21) present at such station.

Furthermore, and with reference specifically to figure 9, the grips (14) which transfer the sack to the filling station (3) are complemented at the height of the filling stage with further grips (29) associated to the filling mouth and capable of moving crosswise, driven by respective pneumatic cylinders, thereby to move towards each other and together with the suction pads (21) effect an optimum opening of the mouth of the sack (8) and consequently provide optimum sack filling conditions.

Improvement of the sack (8) filling conditions is also expedited by a compacting element (22) lying beneath the sack (8) in the vertical position of the filling station (3), which tamps the base of the sack to achieve the repeatedly mentioned compacting effect. As shown in phantom in figure 1, the compacting element (22) is positionally adjustable for its height to be suited to the dimensions of each type of sack (8), which adjustment is made simultaneously in regard to the ejection belt (23), to which end both elements are mounted on a common chassis.

Finally, and with reference to the sealing station (4), the mobile arm (24) of the welding clamp (25), driven by the respective, classic cylinder (26), has a rear extension (27) designed to act on an approach sensor (28), as shown specifically in figure 5, thereby for said sensor (28) to precisely detect the distance of the welding clamp (25), which must match the thickness of the mouth of the sack and which, as aforesaid, allows a faulty feeding of sacks to be detected, due to the absence of a sack, a crease at the mouth of the sack resulting in a faulty sealing thereof, or any other fault whatsoever which may be detected by reason of a different thickness of the mouth of the sack with respect to the respective pre-set dimension.

In accordance with the construction described, operation of the machine is obvious with reference to figures 1 to 8.

Specifically, figures 1 and 2 show the zero point, from which each operative cycle of the machine begins, in which a sack (8) lies at the sack forming station (1), a second sack (8) lies at the intermediate station (2), a third sack (8) lies at the filling station (3) and a fourth sack lies at the sealing station (4), whereas other sacks are already fully sealed on the ejection conveyor belt (23). Upon the operative cycle beginning, specifically upon the gearmotor (10) being started, the carriage (9) moves forward entraining the first of the above-mentioned sacks towards the intermediate or hold station (1), whereas a new sack is formed at the forming station (1), the second sack being directed towards the filling station (3), its bottom or lower end impinging upon the compacting element (22), the bottom being bent inwards to prevent the product from accessing the bottom corners of the sack, improving its conformation at the filling stage, whereas the third sack, which was already fall, passes on to the sealing station (4), and the fourth and last sack, located at said sealing station, is entrained by the conveyor belt (23). At the end of the forward phase of the carriage (9), the intermediate station (2) is at a pre-opening phase of the mouth of the respective sack, the filling station (3) fills the sack, which shall have begun beforehand due to the shorter run required for such sack between the intermediate station (2) and the filling station (3), and the last sack (8) is sealed at the last station (4). The clamps (7), (13) and (14) are then all opened simultaneously and the carriage (9) returns to the initial position, shown in figure 1, to begin a new operative cycle.

In accordance with another improvement, the machine also includes a sack reinforcement welding mechanism, which mechanism is shown in figures 12 and 16 both as a whole and in close view, the reference numeral of the welding mechanism being generally (30), the mechanism being applicable as aforesaid to an autonomous sacking machine using a continuous tubular band in the form of a roll (31) as the raw material, supplied by a feeder comprising a pair of supporting arms (32), pivoting with the assistance of cylinders (4), to expedite the roll (31) loading and lifting operation, a drive roller (34) being established above the roll, assisted by a respective gearmotor (35), to unroll said continuous tubular band, to which end the roller (34) is also mounted on a pivoting arm (36) assisted by another cylinder (37).

The roll (31) supplies the continuous band to a feed station (38) from which said band passes to the welding mechanism (30), and from there on to a station (39) at which the weld is cooled and the sack forming sheet is centred, said station (39) comprising a number of rollers which establish a winding path to facilitate the two functions aforesaid, namely on the one hand cooling of the weld and on the other centring of the sheet, the band then passing to the sack forming station (1) at which the continuous band fragmentation and bottom end sack sealing operations are effected, a carriage (9) being located under this forming station (1) to sequentially transfer the sacks (8) to the sack filling station (2) and finally a sack sealing station, from which the sacks are ejected, as explained above.

Now then, with reference specifically to figures 14 and 15, the welding mechanism (30) comprises a chassis (40) designed to be locked to the machine frame, the chassis (40) having a double spindle (41) locked to it, i.e. the spindle having two counter-threaded sectors, on which respective nuts (42) are mounted which, upon acting manually on a wheel (43) lying at one of the ends of the double spindle (41), move towards or away from each other, depending on the direction in which said wheel (43) is turned.

A support (44) is locked to each nut (42) with a head (45) in turn locked to such support, the mechanism thereby having two heads (45) duly opposing one another, each having a fixed dolly-like guide plate (46) at a middle level, both guide plates being coplanar as shown in figure 15, the plates being designed to be respectively housed in the side bellows of the continuous tubular band from which the sacks are to be obtained, acting as separators during the bellows welding phase, which is carried out with the assistance, at each head (45), of a clamp (47) provided with electric heating resistors (48) shaped as an isosceles trapezium, which are mounted to slide crosswise on the respective head (45) and may choke the marginal area of the continuous tubular band against the intermediate guide plate (46) during the welding phase, or be separated to allow the free passage of said band up to a new working area thereon. Two slotted plates (49) are provided as side guide plates for the welding heads to cross, used as guide elements and to prevent the actual welding heads from entraining the formed sack material.

Specifically, with reference to the close-view of figure 13, in which the reference numeral of the continuous tubular band is (5), it may be seen that level with what is subsequently to become the cut line (50) rendering adjacent sacks independent, welding areas (51) are established at each of the ends of this imaginary line (50), with the same trapezoidal configuration as the electric heating resistors (48), and therefore each of these welding areas (51) will be split into two once the sacks have been rendered independent and formed, one of the two halves belonging to the bottom of a sack, whereas the other half will be the mouth of the other.

This partial choking of the mouth of the sack by no means hinders the subsequent filling of the sack at station (3), but however provides a perfect symmetry between the base of the sack and its mouth, thereby for the sack to have formally and structurally identical ends when closed.

The machine also includes as an improvement a sack forming mechanism or unit, comprising an entraining roller (52) assisted by a press roller (53), the drive roller (52) receiving through a drive belt (54) or other similar element a motion generated by a motor (55), with the respective reducer, the motor being controlled by an encoder which allows the turning movement of the entraining roller (52) to be adjusted and consequently the quantity of continuous tubular band constituting the raw material for obtaining the sacks at will and fall accurately, the latter being entrained at each respective operative sack forming cycle. The press roller (53) is established between a pair of pivoting arms (56) mounted upon a pivoting axis (57), the arms (56) being laterally displaceable to separate the press roller (53) as required from the drive roller (52) at the first continuous tubular band coupling operation, by means of an eccentric (59) that may in turn be manually driven by a small lever (59) located at the front of the machine.

The chassis (60) supporting the rollers (52) and (53) in turn acts as a support (61) for a funnel (62) suitably channelling the continuous tubular band towards the band cutting and welding area, the funnel (62) being obviously located in the vertical position of the tangent plane between both rollers (52) and (53).

Pivotally connected to the chassis (60) through top axes (63) are a pair of bracings (64) enclosing the rollers (52) and (53) and the funnel (62), each of the bracings (64) being fitted at its lower end with a tamper (65) acting on the respective side of the sack, an electrowelding head which had reference numeral (6) in figure 1, one being fitted with a cutter (66) and the other with a dolly (67), and therefore when the bracings (64) close upon each other, the first to act are the tampers (65), suitably fixing the continuous tubular band, and then the cutter (66) acts to render independent the bag sealed in the preceding operative cycle of the mechanism, the electrowelding heads (6) then acting to seal the next immediate bag or sack.

The pivoting movement of the bracings (64) is achieved with a preferably pneumatic cylinder (68) acting on an eccentric (69) having two radial appendices (70) and (71) to which two connecting rods (72) and (73) are articulated to act simultaneously and in opposition to each other on said pivoting bracings (64), to provide the movements to or away from each other.

Whilst a sack is being rendered independent and the bottom of the next one sealed by welding in the welding and cutting mechanism described and shown in figures 17 to 20, the sealing weld of the immediately preceding sack, i.e. the sack that is being cut off, is being consolidated at a lower level, to which end the lower area is provided with the mechanism shown in figures 20 to 22, comprising a deflector plate (74) directing a pair of blowing nozzles (75-75'), both of which are positionally adjustable, towards the bottom end of each sack, the first lying fixed at the bottom end of the deflector plate (75) whereas the second one (75') lies at a substantial distance from the first one, mounted on an arm (76) which pivots about its midpoint (67) and receives at its end opposite the actual nozzle (75') the drive of a pneumatic cylinder (78) with which the nozzle (75') is drawn close to the nozzle (75), once the bottom of the sack has reached the blowing area.

With reference specifically to figure 20, these nozzles (75-75') are provided with a longitudinal groove (79) for the passage of air, from which a number of outlets (80) project which are duly directed towards the sack weld.

To complement the structure described and allow an adjustment of its height, enabling it to be suited to various sack sizes, the support (81) of the structure is mounted to move vertically on guides (82) duly locked to a chassis (83), which could be the actual chassis (60) of the machine, the support (81) being further assisted by a spindle (84) the free end of which receives, through a pulley (85) or the like, with the assistance of the respective belt (86), the movement of the pulley (87) of a wheel (88) also established on the actual chassis (83), thereby upon actuating the wheel (88) in either direction, for the spindle (84) to lift or lower the support (81) and consequently suit the deflector plate (74) and the blowing nozzles (75-75') to the level at which the bottom end of the sack is arranged, at which it is welded, depending on the intended length of the sack.

Claims

Improvements introduced in autonomous sacking machines, of the kind which use a continuous tubular band having side folds or bellows as the raw material for making the sacks, and which are provided with a first sack forming station, at which said continuous band is fragmented and the bottom of each of the sacks is welded, a sack filling station and a sealing station, after which the fall and sealed sacks are ejected by means of a conveyor belt, these stations being assisted by a bottom reciprocating carriage which intermittently transfers the sacks from one station to another, characterised in that between the sack forming station (1) and the sack filling station (3) an intermediate hold station (2) is provided, being particular in that said intermediate station (2), which lies at exactly the same distance from the sack forming station (1) as the sack filling station (3) lies from the sealing station (4), is considerably closer to said filling station (3) in order to limit the sack transfer time towards said filling station, at the expense of the machine devoting more time in each cycle to the actual filling operation; a sack reinforcement welding mechanism is moreover provided, located before the sack forming station (1), the actual sack forming station including a special forming unit designed to fragment the continuous tubular band from which the sacks are obtained and provide a weld sealing the bottom end of each sack.
Improvements introduced in autonomous sacking machines, as in claim 1, characterised in that the carriage (9) transferring the sacks (8) between the various stations (1), (2), (3) and (4), has a pair of fixed grips (7) to transfer each sack (8) from the sack forming station (1) to the intermediate station (2), and another pair of fixed grips (13) to transfer the sacks (8) from the filling station (3) to the sealing station (4), and a pair of floating and guided grips (14) to transfer the sacks (8) from the intermediate or hold station (2) to the filling station (3), these clamps or grips (14) being associated to a pneumatic cylinder (16), acting as a resilient element supporting said clamps, which are assisted by a stop (17) that is operatively located at the vertical position of the filling station (3), thereby for said grips to stop, in the forward movement of the carriage (9) at an intermediate phase, before the carriage ends its run and when the mobile grips (14) face the filling station (3), against the spring tension of the cylinder (16), allowing the filling phase to begin immediately.
Improvements introduced in autonomous sacking machines, as in claim 1, characterised in that a clamp (18) is established at the intermediate or hold station (2) provided with suction pads (20) which carry out at said intermediate station (2) a pre-opening phase of the mouth of the sack (8), prior to its being definitely opened at the filling station (3) by the suction pads (21) of such station, provision having moreover been made for the filling station to have two associated clamps (29) capable of moving crosswise towards each other, to expedite the sack (8) opening operation.
Improvements introduced in autonomous sacking machines, as in preceding claims, characterised in that the transfer carriage (9) is U-shaped, with its side branches pointing towards the machine outlet, i.e. towards the ejection conveyor belt (23), said carriage therefore providing a fully diaphanous space for locating and transferring the sacks (8) from the forming station (1) to the sealing station (4).
Improvements introduced in autonomous sacking machines, as in preceding claims, characterised in that in the vertical position of the filling station (3), and on a lower level, a compacting element (22) is established upon which the lower end of the sack (8) is seated before and whilst it is filled, tamping the base of such sack (8) to improve the filling conditions.
Improvements introduced in autonomous sacking machines, as in claim 1, characterised in that the sealing station (4) is provided, specifically on the pivoting arm (24) of its welding clamp (25), with a rear extension (27) designed to act on an approach sensor (28) which allows the detection of any fault at the station due to a level of approach between the welding heads (25) differing from the pre-set approach, either because of the absence of a sack, or because of an unwanted crease at its mouth or any other cause whatsoever.
Improvements introduced in autonomous sacking machines, as in claim 1, characterised in that the sack reinforcement welding mechanism comprises a chassis (40) designed to be locked to the frame of the machine, which chassis (40) has a double spindle (41) locked to it, the spindle having two coaxial counter-threaded sectors on which respective nuts (42) are mounted and drawn towards or away from each other depending on the direction of rotation supplied to the spindle (41) by a hand-driven wheel (43) or any other suitable driving means, the nuts (42) having locked to them respective supports (44) for two facing heads (45), each of which is provided with a guide plate (46) acting as an intermediate dolly for the welding mechanism, designed to be coupled in the respective side fold or bellows of the continuous tubular band constituting the sack, each dolly guide plate (46) being enclosed by the arms of a welding clamp, which may be displaced in synchrony and by any suitable means towards or away from the fixed intermediate guide plate, preferably constituted by two side guide plates (49) having a hole through which the welding clamps are introduced.
Improvements introduced in autonomous sacking machines, as in claim 7, characterised in that the sack reinforcement welding mechanism (30) is located at the sack forming station (1), the mechanism thus acting on the continuous tubular band (5) before the band is fragmented into respective sack segments, constituting a stage subsequent to the welding equipment and before entering the sack forming stage following by a stage (39) at which the weld produced is cooled down and the sheet is centred as it moves along, the stage being formed by a winding path achieved upon said sheet passing through rollers.
Improvements introduced in autonomous sacking machines, as in claims 7 and 8, characterised in that the welding clamps (48) are trapezoidal in shape and act on the continuous tubular band (5) at the imaginary transverse lines (50) through which said band is to be fragmented upon being cut, the welds (51) being located on the ends of said lines (50), each weld being trapezoidal in shape and resulting in two triangular welds upon the continuous tubular band (5) passing the sack forming station (1), one for the mouth of a sack and another one for the bottom of the next immediate sack.
Improvements introduced in autonomous sacking machines, as in claims 7, 8 and 9, characterised in that the sack reinforcement weld mechanism is of little length, which means that input and output of the sheet of that stage can be made by simple manual insertion.
Improvements introduced in autonomous sacking machines, as in claim 1, characterised in that the sack forming unit comprises an entraining roller (52) and a press roller (53), the first of which receives movement from a gearmotor (55) through a suitable transmission, controlled by an encoder which allows the quantity of each movement to be suited to the specific length of each type of sack, whereas the press roller is suspended from a pair of pivoting arms (56) and may be separated from the entraining roller (52) to initially couple the continuous tubular band (5), by means of an eccentric (58) which acts directly on at least one of said arms (56) and to which a manual drive lever (59) is locked.
Improvements introduced in autonomous sacking machines, as in claim 11, characterised in that the chassis supporting the entraining (52) and press (53) rollers have two bracings (64) articulated to them which enclose both said rollers and a funnel (62), downwardly channelling the continuous tubular band (5), said pivoting bracings constituting through their bottom end a mobile support means for the cutter for cutting the continuous tubular band, provided at the welding heads (6) thereof, and for a pair of tampers (65) which suitably stabilise said continuous tubular band (5) during the cutting and welding phase.
Improvements introduced in autonomous sacking machines, as in claims 11 and 12, characterised in that the pivoting bracings (64) supporting the cutting and welding mechanisms are driven simultaneously and in opposition to each other by a preferably pneumatic cylinder (68), which acts on an eccentric (69) provided with a pair of radial extensions (70) and (71) lying opposite each other, to which two connecting rods (72) and (73) are articulated which relate said eccentric and the pivoting bracings (64) in such a way that pivoting in the direction of the eccentric (69) causes the bracings (64) to approach each other, and pivoting in the opposite direction causes the same to be separated.
Improvements introduced in autonomous sacking machines, as in claim 11, characterised in that in the vertical position of the funnel (62) guiding the continuous tubular band (5) and on a lower level of the machine, a deflector plate (74) is established which leads the bottom end of the sack towards a pair of blowing nozzles (75-75'), one being fixed and the other pivotable, which may be positioned at a considerable distance for the free passage of the bottom end of the sack, and be subsequently positioned in proximity during the blowing phase of its weld.
Improvements introduced in autonomous sacking machines, as in claim 14, characterised in that said blowing nozzles (75-75') are positionally adjustable, and the pivoting nozzle (75') may be driven by a pneumatic cylinder (78).
Improvements introduced in autonomous sacking machines, as in claim 14, characterised in that each blowing nozzle (75-75') has a longitudinal duct (79) for air to be drawn in, from which a number of outlets or nozzles (80) as such project, directed towards the weld line sealing the bottom of each sack.
Improvements introduced in autonomous sacking machines, as in claims 14 to 16, characterised in that the blowing unit is established on a support (81), capable of moving vertically on similarly vertical guides (82) which relate the support (81) to a chassis (83), at the same time as a spindle (84) which, with a suitable transmission (86), is related to a hand-driven wheel (8), the height of the support (81) being adjustable through such wheel (88) in order to suit the level of the blowing nozzles (75-75') to different sack sizes.