EP0173623A1 - Machines for packaging pulverulent materials in valve bags with the help of bag placers - Google Patents

Abstract

PCT No. PCT/FR85/00219 Sec. 371 Date Jun. 23, 1986 Sec. 102(e) Date Jun. 23, 1986 PCT Filed Aug. 13, 1985 PCT Pub. No. WO86/01486 PCT Pub. Date Mar. 13, 1986.The present invention comprises a machine having a fixed portion and fitted with a plurality of pneumatic cylinders and pistons, at least one of said cylinders and pistons is activated by a nominal-pressure supply, and which at least one cylinder and piston forms part of a subassembly which moves with respect to the fixed portion of the machine. There is a counter-pressure system for each working phase of the subassembly cylinder, including means for counteracting the nominal-pressure supply to reduce jerking movements of the subassembly during operation. Also a speed-control unit which has a variable throttling valve and an anti-return valve is affixed to the fixed portion of the machine separated from the movable subassembly. Flexible lines are connected between the subassembly cylinder and the speed-control unit so that the mass of the movable subassembly is reduced to further reduce the jerking motion of the subassembly.

Description

The present invention relates to improvements to machines for packaging powdery products in valve bags.

Generally, such bags thus equipped with valves are arranged flat in vertical or horizontal stacks.

For the automatic packaging of powdery products, it is usually necessary to open the valve of the bag located at the top of the stack, hold this bag and move it with the valve open from the store where the stack is located to a filling and weighing station comprising a distributor tube on which said valve must be threaded.

Up to now, these operations have been carried out by applying, throughout their duration, suction on the top of the battery start bag by means of suction cups.

However, experience has shown that a certain percentage of valves do not open or are incomplete, that bags are dropped, so that the operation of the packaging installation is faulty.

We realized that this sometimes high percentage of failures was largely due to the shocks generated in the bag handling head by an overly primitive design of the pneumatic control circuits, and by the phenomena of inertia of the constituent moving parts. of the gripping head of the bags.

Within the general framework of the invention, which is the reduction of the shocks to which empty bags are subjected during handling, there are thus solutions leading to the reduction of the masses in movement, either by the use of lighter constituent materials. than those employed for the construction of the heads of conventional machines, and this when the mechanical function of the substituted parts allows it, either by the distance of the moving parts from various control accessories unnecessarily weighing them down, and other solutions consisting in giving more flexibility in movement of the bag handling mechanism by the use of advanced electropneumatic systems and the creation of buffer capacities on the pneumatic control circuit.

• - réduction de la masse de sous-ensemble mobile en rotation et translation,
• - insertion de canalisations souples entre les vérins d'une part et les organes régulateurs de vitesse (étrangleurs variables et clapets anti-retour) qui sont reportés sur les parties fixes de la machine,
• - création d'une contre-pression dans chaque phase de travail (accostage exclus) dans des vérins faisant partie du sous-ensemble mobile.

The invention relates more precisely to a machine provided with a plurality of pneumatic cylinders, some forming part of a sub-assembly movable relative to the machine, characterized in that jolts are eliminated by using the at least one of the following solutions:

• - reduction of the mass of mobile sub-assembly in rotation and translation,
• - insertion of flexible pipes between the cylinders on the one hand and the speed regulating members (variable throttles and non-return valves) which are transferred to the fixed parts of the machine,
• - creation of a back pressure in each work phase (docking excluded) in jacks forming part of the mobile sub-assembly.

The invention relates more specifically to a machine as defined above, usable as a bag dispenser on a bagging machine for valve bags. In such a machine, the mobile sub-assembly consists of the bag gripping head.

The accompanying figures also show the various characteristics and advantages of the invention.

• . La figure 1 représente les six phases a, b, c, d, e, f des mouvements du mécanisme placeur de sacs.
• . La figure 2 repésente les éléments constitutifs d'une tête de placeur de sacs.
• . La figure 3 représente une partie du circuit de commande pneumatique du placeur de sacs.
• . La figure 4 représente un vérin et son système de détection de position.

In these attached figures we can see:

• . Figure 1 shows the six phases a, b, c, d, e, f of the movements of the bag placing mechanism.
• . Figure 2 shows the components of a bag placing head.
• . FIG. 3 represents a part of the pneumatic control circuit of the bag dispenser.
• . Figure 4 shows a cylinder and its position detection system.

As shown in Figure 1 (a), a supply of empty valve bags (2) is placed on the rack of the store (1). This action is the only operation performed manually, the rest of the cycle taking place automatically.

In FIG. 1 (b), the first bag of the stack is gripped under the action of the bag extraction system constituted by the suction cup support rakes (3) (3 ') carrying the telescopic suction cups (4) (4 '). The telescopic suction cups are bellows suction cups made of elastomeric material which the Applicant has found more advantageous for the function of extracting bags from the store than ordinary suction cups, because they adapt better to irregularities in flatness and apparent hardness of the pile. of bags, and that during the transport of the bag their possibilities of damping reduce the releases of bags by shocks.

In FIG. 1 (c) the bag is taken over by the head. This is tilted horizontally under the action of the rotation operator. The bag holding jaws (8) are closed on the bag. They are carried by the articulated arms (7), and are constituted by solid cylinders (8) made of elastomer material embedded in supports (17). The suction cups (6) (6 ') have not yet entered into action to open the valve (2').

In FIG. 1 (d) the rotation operator has brought the entire head back to the vertical position, the jaws (8) holding the bag under the head in the vertical position, the suction cups (6) (6 ') having entered in action to open the valve (2 '). In this figure, we can see in a simplified way the construction of the gripping head consisting of two front and rear flanges (14) (14 '), two left and right arms (7) and (7') on which are fixed. the jaw supports (17) (8).

A sliding movement along the columns (18) (18 ') of the application carriage (19) causes the valve (2') of the bag to thread onto the filling spout (9) of the dosing installation not shown, as can be seen in Figure l (e).

In FIG. 1 (f), the filled bag is mechanically ejected from the spout (9) and falls on the tilting receptacle (9 ') which returns it to a conveyor belt (40), while the gripping head (19,17 ), returned to horizontal, returns to find the next empty valve bag in the stack.

Figure 2 shows in more detail the method of construction of the gripping head. We recognize on a larger scale the constituent elements already mentioned. The empty bag store is in (2).

In (5) is the rotary operator. This is a hydraulic member transforming a translational movement into a rotary movement by cooperation with a rack / pinion system.

Wedged on the rotating shaft (20) emerging from (5) is suspended the oscillating rotary assembly constituting the gripping head itself.

This assembly includes a jack (10) for advancing the bag applicator carriage and its rod (10 ').

The carriage slides on the two columns (18) (18 '). The bags are gripped by a pair of jaws (8) (8 ') controlled to close and open by the jacks (11) and (11'). These jacks are mounted on a set of flanges (14) (14 ') and spacers (15), (15'), (16) and (16 '), rigidly assembled to form a sort of cage, constituting the carcass of the applicator cart.

On this cage are articulated the arms (7) and (7 ') and their extensions (17) (17') which serve as supports for the jaws (8) and (8 ').

Suspended from the same applicator carriage, there is a bar (13) carrying suction cups (6), (6 '), (6 ") and (6") opening the valve.

These suction cups are connected to a vacuum source (not shown) and their support, namely the bar (13), rises and falls under the action of the jack (12).

It can be seen that the number of constituent elements of the head is high and that the suspended mass performing alternating rotational movements around the axis (20) and of alternating translation parallel to the columns (18) (18 ') and to the rods cylinders (11) (11 ') and (12) is relatively large.

The alternating nature of these movements leads to dead jolts caused by the inertia of the moving parts.

These jolts are detrimental on the machines of the prior art to the good grip of the bags, and also to the longevity of the material.

One of the objects of the invention resides in the systematic lightening of the mobile assemblies constituting the head, by producing in a light alloy such as AU4G the structural parts of this head, such as the flanges (14) and ( 14 '), spacers or gussets such as (15) (15 '), the applicator carriage (19), the arms (7) (7') and their extensions (17) (17 ').

The only parts remaining in steel are the axes of rotation of the arms (7), the pivot shaft of the head (20), the corresponding pins and in general the parts having to undergo high mechanical stresses.

Another characteristic of the invention, also contributing to the same aim as the above means, consists in moving the set of moving masses away from the head of the variable choke blocks / non-return valve (one block for each pipe supply of double-acting cylinders) and their transfer to the general base of the pneumatic distribution center, this in order to reduce the inertia phenomena involved. An additional advantage has been found by the applicant in the connection of said choke blocks / valve to the corresponding cylinders by long flexible pipes which introduce additional buffer capacities, giving more flexibility to the installation.

We can see in Figure 3 the choke / valve blocks in (41), (41 '), (42), (42'), (43), (43 '), (44) and (44'). These choke / valve blocks are grouped together with the pneumatic unit represented by the distributors with drawers not identified and it is understandable the reduction thus brought to the moving element of the head by noting that each member is usually made of a block of machined cast iron. The hose connections are made downstream of points A to K to the corresponding cylinders operating on the head (11, 11 ', 12 and 46) and the rotary operator (5).

Finally, the main characteristic of the invention resides in the establishment, in opposition with the supply network at nominal pressure, of a back-pressure network, the latter being at most 3 bars lower than the pressure. nominal and which, thanks to interventions judiciously triggered over time, allows damping at the end of the movement of the masses in movement of the translation and rotation cylinders of the components of the head of the bagger. At the usual rates of work of modern baggers, which reach values between 800 and 1200 bags / hour, the corresponding cycle times are very short, between 4.5 sec and 3 sec and no longer accommodate the response times of oleopneumatic accumulators, imposed by the viscosity of the oil.

These then become practically ineffective in their role as shock absorbers.

We had the idea of supplying the double-acting cylinders, at precise moments in their outward and return travel determined by inductive sensors with compressed air at these two pressures of 5 bar and 3 bar (nominal pressure, back pressure ), alternately on the full section of the cylinder and on the differential section of these cylinders. It should be understood that these values are given for information only and that it would not go beyond the scope of the invention to choose other values.

In the present description, the full section (SI) corresponds to the bore of the cylinder and the differential section (S2) is the previous section, minus the section of the cylinder rod.

The description of the movements of the cylinder (10) for translating the head clearly illustrates the new principle implemented in the invention. We will rely on Figure 4 to describe these movements.

This figure shows the translation cylinder, excluding the head and its annexes. The jack (10, 10 ') is provided on its rod with a metal ring intended to act by influence, passing successively in front of the four detectors (51 to 54).

• . par l'intermédiaire du distributeur (26) elle attaque l'arrière du vérin (10) et agit sur la pleine section (SI) de son piston, non sans avoir traversé le bloc régulateur de vitesse (45'). Ce bloc comprend classiquement un clapet anti-retour et un étrangleur variable montés en parallèle. Ici, suivant la représentation conventionnelle, le clapet: fonctionne à l'état ouvert.
• . par l'intermédiaire du distributeur (27) à travers l'économiseur (22) qui est constitué d'un limiteur de pression (23) monté en parallèle avec un clapet anti-retour (24). Cet économiseur règle à la fois la pression et la quantité de l'air admis sur la face arrière du vérin (10) et règle la puissance du freinage exercé sur le vérin en agissant sur le temps de réponse affecté au freinage. Plus la quantité d'air admise est forte, plus court est le temps de freinage, plus intense est celui-ci. On freine à l'aplomb du détecteur (53) et le mouvement se termine à petite vitesse de (53) à (54) où le vérin atteint la position de blocage avant.

Suppose we start from the stop, the ring (30) being opposite the detector (51). A time delay, adjustable from zero to one second gives the order to the head to transport a bag on the filling spout already encountered -9, in Figure 1 (d) -, deactivates the detector (52) and activates (53) . The distributors (25) - pilot distributor - and (26, 27), - working distributors - are in the "working" position (energized electromagnets). The nominal air pressure emanating from the source (21) manifests itself in two parallel circuits:

• . through the distributor (26) it attacks the rear of the jack (10) and acts on the full section (SI) of its piston, not without having passed through the speed regulator block (45 '). This block conventionally comprises a non-return valve and a variable throttle mounted in parallel. Here, according to the conventional representation, the valve: operates in the open state.
• . through the distributor (27) through the economizer (22) which consists of a pressure limiter (23) mounted in parallel with a non-return valve (24). This economizer regulates both the pressure and the quantity of air admitted to the rear face of the jack (10) and adjusts the braking power exerted on the jack by acting on the response time assigned to braking. The greater the quantity of air admitted, the shorter the braking time, the more intense it is. The brake is plumb with the detector (53) and the movement ends at low speed from (53) to (54) where the jack reaches the front locking position.

The cylinder (10) being of the damping type has on its rod a shoulder which closes the normal outlet of the compressed air from the front chamber to divert the outlet flow to a smaller orifice and provided with a needle allowing adjust the exit section and hence the smooth landing on the last two cm of the stroke. The ring is then plumb with the detector (54) which switches the pressures by resting the distributors (27) and (25) and thus sends the back pressure to the rear, the front chamber being in exhaust at the open air.

After an adjustable time delay, which is in practice on the order of half a second, the distributor (27) changes to the working position and sends the nominal pressure to the front of the jack (10). We then play on the difference of sections S 1 and S2 and the piston (10 ′) quickly backs up until the ring passes in front of the detector (52) which then puts the distributor (26) in the working position and sends the counter pressure on the rear panel SI.

After blocking in the rear position and a delay similar to the delay in the rear blocking position, the movement can repeat itself.

The same principle of using a braking back pressure can be used when other translation or even rotary actuators are operated, such as the actuator (5).

This body is also called "rotation operator". It is conventionally made up of two cylinders connected by a common rod, and operates in opposition by admission of working fluid on the two end faces of its cylinders. The common rod is arranged in its part central rack and the latter meshes with a pinion, thereby delivering on the output shaft (20) of the latter a rotational movement.

It is this rotational movement which is printed on the gripping head of the bags.

Referring to Figures 1 (a) to 1 (f). we see that the alternating rotational movement is broken down into two parts: an ascending part 1 (d) and a descending part 1 (f).

The suspended masses have been reduced as much as possible, as described above. On the other hand, efforts have also been made to balance these masses as much as possible around the axis (20). However, it will be understood that, given the essentially different functions and natures of the organs constituting the gripping head of the bags (jacks, structural parts, arms, clamps) it has not been possible to push the balance of all. These masses therefore cause a non-negligible unbalance effect, and it is therefore understandable that we were led to extend the invention to this jack (5) rotation operator by making it operate as a motor in its upward rotation phase. 1 (d) and in brake in its downward rotation phase FIG. I (f). This is achieved by applying to the cylinder (5) what has been said for the translation cylinder (10), with regard to the judicious use, mutatis mutandis, of the nominal pressure / back pressure system.

This leads to a smooth operation of the head, which is a key element in the operation of the bagger.

To make the reliability of the head in question total, it has been found desirable to add a function fulfilled by the jack (47), moreover supplied in a conventional manner. Figure 2

This jack (47), mounted on the movable arm (17 '), actuates a profile (48) which cooperates with a fixed profile (49) mounted on the movable arm (17) to guarantee that the plane of the valve before opening by the suction cups (6) to (6 '' ') is perpendicular to the plane of the bag.

Claims (7)

1. Machine provided with a plurality of pneumatic cylinders, some forming part of a movable subassembly with respect to the machine, characterized in that the jolts of operation are eliminated by resorting to the combination of the following means : - use of a back pressure network for each working phase of the cylinders of the mobile sub-assembly, in opposition to the supply network at nominal pressure, and reduction of the masses of the mobile sub-assembly in rotation and in translation, and / or - insertion of flexible pipes between the cylinders on the one hand and the speed regulating organs (variable throttles and non-return valves) which are transferred to the fixed parts of the machine. 2. Machine according to claim 1, such as a bag dispenser on a bagging machine for valve bags, characterized in that the movable sub-assembly is constituted by the bag gripping head. 3. Machine according to any one of claims 1 or 2 such that the reduction of the moving masses is obtained by the production of structural parts in light alloy such as AU4G with the exception of the axes, trunnions and other parts undergoing high stresses. 4. Machine according to any one of claims 1 to 3 characterized in that flexible pipes are inserted between the speed regulating members carried on the fixed part of the machine and the energy user jacks constituting the moving head, with production a buffer capacity effect. 5. Machine according to any one of claims 1 to 4 characterized in that the damping of the movements of the cylinders at the end of the race at the two extreme dead centers is obtained by the creation of a back pressure on the face opposite to the face of the piston of the jack subjected to the nominal driving pressure, the two pressures being switched by inductive detectors activated by a ring secured to the rod of the jack concerned, the detectors being adjustable in distance between them and acting by means of time delays and of electromagnet distributors. 6. Machine according to any one of claims 1 to 5 characterized in that the rotational movement of the bag gripping head is obtained by a rotary operator playing the role of motor in the ascending phase of the cycle and brake in the descending phase. 7. Machine such as a bag dispenser on a bagging machine for valve bags characterized in that it comprises a jack (47) mounted on one of the arms (17 ') and actuating a profile (48) which cooperates with a profile (49) mounted on the other arm (17) and fixed relative to the latter to maintain the plane of the valve before it opens perpendicular to the plane of the empty bag held by the arms (17, 17 ').

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