EP0448943A2 - Gripper bar for gripping plate-like articles in a machine for producing packages - Google Patents

Abstract

A gripper bar fitted on drive chains and destined to grip and carry plate shaped sheets of material through printing, cutting and similar machines to produce a package characterized by the bar including a hollow profile on which the grippers are fastened. Every gripper consists of a flat spring attached at one end to a leading edge wall of the bar and having the other free end taking a rest position engaging a gripper counterpart which is situated on the trailing edge of the bar. The flat spring has a length greater than the width of the bar and passes through the bar before reappearing through a window on the trailing edge of the bar.

Description

The present invention relates to gripper bars which, in a machine for working plate elements for the production of packaging, make it possible to pull and position these elements through successive printing, cutting, embossing, upsetting and / or ejecting waste.

Such bars are generally attached, at regular intervals and transversely to the direction of travel of the plate elements, to two trains of lateral chains. Inside the machine, these chains make these bars run through a circuit composed, first of all, of successive movements of horizontal translation through the various workstations, then, at the end of the machine, of a directed circular movement upwards towards an upper corridor back to the first station, and finally, in a circular movement downwards towards the starting point, that is to say at the level of the front jogging stops d 'a margin table. There, the clamps are opened by a control device which may, depending on the machine, be an integral part or not of the clamp bar.

Then, when the next plate element is pushed onto the margin table against the front tabs, and its downstream edge is brought between the lower counter clamps and the upper support fingers of the open clamps, the mechanism opening of the clamps is operated in the opposite direction, so that the new plate element is gripped by the clamp bar to be taken, during the first translation, in the first work station. Since at each workstation, the plate elements must be stopped in order to be able to execute the corresponding cutting, ejection, etc. operation, these elements must be transferred from a station to the 'other according to successive translations composed of acceleration, deceleration and stop.

The search for an increase in the production rate of the machine requires that the successive translations mentioned above be carried out at increasingly higher speeds and in an increasingly shorter cycle time. As an example, production rates of around 9,000 elements per hour are now reached, i.e. a cycle time of around 0.4 seconds, of which only around 0.3 seconds for the translation of the element in plate along a station of 1 meter in length. It is therefore easy to see the importance of the bending and torsion constraints that the accelerations in play impose on these bars of great length and connected only by their ends to the two chains of chains.

Furthermore, these clamp bars must also be sufficiently rigid so as not to deform when the axis of opening of the clamps, an axis which is an integral part or not of the bar, is driven in rotation against the action of the numerous springs ensuring the closing of the clamps. However, due to the small size of these clips mounted throughout from the upstream edge of the bar, the rear springs ensuring their closure can only be short and strong to ensure sufficient grip of the plate element. Consequently, the opening torque to be applied to the axis actuating the upper support fingers is high. In addition, as the clamps are integral with the opening axis, the latter can only be made of steel and highly dimensioned.

Given the constraints described above, the bar is currently made from a more or less rectangular tube and appreciable section. Likewise, the attachments of these bars to the chain trains must be of sufficient dimensions. Such a clamp bar is described, for example, in patent FR-A 1178295.

Such bars also have the disadvantage of acting, by their weight, on the production rate of the machine. In fact, the mobile assembly comprising the clamp bars, their associated fasteners and the two trains of lateral chains to which they are attached, constitutes a mass with a great moment of inertia whose possible accelerations are limited by the resistance capacity of the organs of gripper bars to the stresses resulting from this acceleration, as well as by the power of the main engine.

In patent FR-A 883780, it has been proposed, in order to reduce the height of a clamp bar, to machine in the bar, in full rectangular profile, housings in order to place the clamps mounted therein. elastically pivoting on the downstream edge of the bar so that, at rest, these clamps do not exceed the upper and lower faces of the bar. However, such housings or slots made perpendicular to the longitudinal direction of the bar, greatly reduce the resistance to bending and twisting of the latter.

However, the height of these bars defines the minimum vertical displacement that the lower movable plate must make during the transfer of the plate elements by these bars from one work station to another. To minimize displacement in order to increase the production rate, it is advantageous to have the movable stage make the shortest possible displacement. As a result, the height of the clamp bars should be minimized, for example, to about the height of the chain trains. In addition, as the clamps are currently made entirely of metal, the clicking caused by their opening and closing creates a significant noise which must be tried to eliminate. Finally, such bars are generally connected at their two ends to the two trains of lateral chains by means of two so-called “floating” fastening devices so that, on the margin table, the plate element can be exactly positioned and oriented relative to the direction of travel and the workstation. Such "floating" devices, described for example in patent DE-C 2520231, generally comprise a connecting element engaged with one end of the clamp bar and elastically connected to the corresponding side chain train. However, this connection is thus designed that, to free the end of the bar from the corresponding connection element, each chain of chains must be spread transversely. These “floating” attachment devices of the prior art therefore have the drawback of requiring disassembly of the chains of trains with respect to the machine in the case, for example, where a clamp bar should be replaced. In addition, these fastening devices are generally heavy, difficult to execute and therefore expensive. Finally, in patent GB-A 1003838, the "floating" attachment device comprises a connecting piece connected to the bar and to a special chain train link. The connecting piece is provided with two arms engaged respectively with the outside of the lower and upper walls of the bar, and with two male and female knuckles located one towards the upstream edge and the other towards the downstream edge of the closed off. The special link has a male knuckle. The male and female knuckles are connected together by means of two rods which pass through them by corresponding bores, the male knuckle being mounted on the rods so as to allow a slight movement with elastic take-up in the running direction of the trains of chains. It should be noted that, in this attachment device, the height of the two arms is added to that of the bar.

The object of the present invention is to produce a gripper bar whose weight and height dimension are reduced to a minimum, but whose rigidity and gripping force are sufficient to withstand the stresses and forces involved during the operation of the machine. . The clamp bar must also be provided a device for attaching to the chain trains which is simple and light, while allowing easy assembly and disassembly of the bar relative to the two side chain trains.

Finally, the associated device for opening the clamps must also be lighter and require a lower opening control force while ensuring maximum simultaneous opening of all the clamps. In addition, such a clamp bar must allow a reduction in the cost of manufacture and maintenance, as well as a significant reduction in the noise level generated by it in the various workstations.

These objects are achieved by means of a gripper bar according to claim 1.

• la figure 1 est une vue en coupe transversale d'une barre à pinces selon un mode de réalisation de l'art antérieur,
• la figure 2 est une vue de dessus en coupe partielle d'un premier mode de réalisation de la barre à pinces selon l'invention,
• la figure 3 est une vue en coupe transversale selon la ligne II ÷ II de la figure 2, et
• la figure 4 est une vue en coupe transversale d'un second mode de réalisation de la barre à pinces.

The invention will be better understood using the embodiments given below by way of non-limiting examples and described with reference to the following figures:

• FIG. 1 is a cross-sectional view of a clamp bar according to an embodiment of the prior art,
• FIG. 2 is a top view in partial section of a first embodiment of the clamp bar according to the invention,
• FIG. 3 is a cross-sectional view along line II ÷ II of FIG. 2, and
• Figure 4 is a cross-sectional view of a second embodiment of the clamp bar.

In the description below of embodiments of the invention, the orders of quantified quantities of the dimensions of parts are only cited for a better understanding of the invention, it being understood that they have no limiting character, these proportions may vary within the scope of the invention to take account of the particularities of the machines or of the plate elements which are worked there.

FIG. 1 represents an embodiment of a clamp bar according to the prior art, comprising a hollow hexagonal profile 1, two elastic blades 2, 3, one of which 2 serves as a clamp and the other 3 of counter clamp, located outside and above the upper wall of the hollow section 1 at the downstream edge of which (with reference to the movement of the plate element) they are fixed by means of screws 9 and nut 10. Au upstream edge of the profile is fixed, using a screw 7, an extension bracket 4 on which the free ends of the clamp 2 and the counter clamp 3 come to bear. The clamp 2 is provided with a stud 14 extending through an opening 5 made in the bracket 4. A control member 6, in contact with the stud 14, is provided to open the clamp 2. From the Figure 1, it is clear that the clamp 2 and the clamp 3, consisting of two elastic blades located above the profile 1, necessarily lead to an increase in the overall height of the clamp bar, this with the disadvantages discussed above.

According to a first embodiment of the invention shown in FIGS. 2 and 3, the clamp bar essentially consists of a bar 100 proper, clamps each comprising an upper finger 110 and a counter clamp 125, of an opening axis of clamps 140 and two attachment devices 165, 169 located at each end of the bar 100 to connect the latter to the side chain trains (not shown).

The bar 100 is made from a hollow profile made of aluminum, magnesium or composite material. Seen in cross section, the profile of this bar 100 is trapezoidal with an upper wall 100a, a lower wall 100b and two upstream side edges 100c and downstream 100d converging at 45 ° upwards. The thickness of this bar 100 is approximately 3 mm, except for two inwardly oriented thicknesses, one on the bottom wall 100b close to the center line, the other in the bottom corner of the upstream edge 100c. These extra thicknesses will be used thereafter to accommodate element fixing screws. This profile also has a short horizontal extension 100e extending the bottom wall 100b on the upstream side. In other words, this horizontal extension 100e constitutes a tongue extending over the entire length of the bar 100. Finally, the upstream edge 100c of the bar 100 is pierced, at regular intervals, with windows 112, and the end downstream of the bottom wall 100b is pierced with circular access orifices 116 in correspondence with the windows 112.

Below each of these windows 112 are fixed counter-clamps 125 by means of screws 129 passing through the through orifices 128 of the counter-clamp 125 and of the threads made in the extra thickness appearing at the upstream lower corner 100c. Each counter-clamp 125, in the form of a plate, is composed of two wings inclined relative to one another.

A first wing extends horizontally upstream by resting on the upper face of the longitudinal tongue 100e. The other wing, inclined at 45 ° relative to the horizontal, comes to rest against the outside face of the upstream edge 100c. The particular fork shape of these counter-clamps 125 is produced by stamping or by molding. This shape is such that, once in place, each counter-clamp 125 is thus supported by the longitudinal tongue 100e. The horizontal flat spout of these counter-clamps 125 has a width of approximately 20 mm and its extreme edge is covered by a strip of vulcanized or glued elastomer 127. It should also be noted that the active surface 127 of the counter-clamp 125 is located in the horizontal extension of the lower wall 100b of the bar 100. For the skilled person, it is easy to understand that, in the case where it is advantageous to work without gripping pliers on the front edge of a sheet, the pliers and the counter-pliers can be easily and quickly removed from the pliers bar.

Each clamp is a steel leaf spring 110, the length, width and thickness of which are approximately 120 mm, 20 mm and 1.2 mm respectively. This same blade 110 is curved at about 60 ° at its first end 110a called the attachment. At its other end 110b, called the support end, the blade 110 is bent at 30 ° approximately, then straightened horizontally to be bent again at its end 126 roughly perpendicular to the active surface 127 of the counter-clamp 125. This leaf spring 110 is fixed at its attachment end 110a, slightly bent towards the bottom, on the internal face of the downstream edge 100d of the bar 100 by means of a screw 115 and a nut 120 internal to the bar 100, the latter fixing elements being put in place through circular access orifices 116. Thus , the leaf spring 110 passes through the entire interior of the profiled bar 100 in order to emerge from the window 112 and to bear at its support end 126 on the active surface 127 of the counter-clamp 125. The end of support 126 of the leaf spring 110 is rectified to reveal a succession of teeth 126. Taking into account the particular shape given by folding the leaf spring 110, the teeth 126 press with a certain force on the active surface 127 of the counter clamp 125 l when the screw 115 and nut 120 assembly is tightened to fix the leaf spring 110 in place. It turns out here that the assembly formed by the teeth 126 and the elastomer layer 127 greatly increases the gripping force of the plate element by the clamp bar.

According to the first embodiment shown in Figures 2 and 3, the clamp bar 100 is provided with a device for simultaneously opening all the clamps. This opening device comprises an opening axis 140 extending along the axis of the bar 100 and maintained above the internal face of the lower wall 100b of the bar 100 by bearings 142. View in cross section , this opening axis 140 is located about a quarter of the bottom wall 100b of the bar 100 on the upstream side. Preferably, this opening axis 140 is a hollow tube with thin walls of anodized aluminum and a diameter equal to about 10 mm. The bearings 142 are made from synthetic resin and held in place by screws 146, the head of which penetrates into a housing specially drilled in the excess thickness of the bottom wall 100b. The coefficient of friction between the opening axis 140 and the bearings 142 in synthetic resin being very low, this axis 140 can easily rotate inside the bearings 142. This solution eliminates the use of rolling bearings expensive, as well as their lubrication, thereby reducing manufacturing and maintenance costs.

As can best be seen in FIG. 3, this opening axis 140 passes under each leaf spring 110. A cam 144 is attached by gluing or pinning on the upstream side of the opening axis 140, and this, under each leaf spring 110 respectively. These cams 144 have a length substantially equal to the width of the spring blades 110, ie 20 mm, and a generally square cross section with rounded edges except the left side which, as seen in FIG. 3, has a concave circular line corresponding to the perimeter of the opening axis 140. Since the contact surface between the cam 144 and the opening axis 140 is large, the cam 144 can be simply attached to this axis 140 by gluing or pinning. In addition, the length, shape and arrangement of the cam 144 relative to the blade 110 are chosen so as to minimize the torque throughout the opening of the clamp. This limitation is obtained, as can be seen in FIG. 3, by the fact that, during the rotation of the cam 144, the length L₁ of the lever arm of the opening torque gradually decreases to compensate for the increase in the force of blade reaction 110.

As shown in Figure 2, the opening axis 140 emerges from the hollow bar 100. At each end of the axis 140 is mounted a lever 147. Thus, when the clamp bar 100 arrives at the stops for jogging the margin table, means (not shown) raise the upstream end of the levers 147 to turn the axis 140 anticlockwise by an angle equal to about 33 °, so to cause the lifting end of the spring blades 110 to be lifted to a height of 6 mm by the respective underlying cams 144. This lifting of the spring blades 110 by the cams 144 over such a height is sufficient for the insertion of elements in standard plate in the clamps. Consequently, the limitation of the opening torque of the clamps described above makes it possible to reduce the dimensions of the opening axis 140. In addition, the cams 144 are not attached along the upstream side of the axis d opening 140 according to a rectilinear generator, but according to a slightly helical generator, so that the clamps located on the ends of the bar 100 are opened first. This arrangement makes it possible to take account of the twist of the opening axis 140, which is only a hollow aluminum tube, during its rotation against the effect of the spring blades 110. The part of the lower face lever 147 coming into contact with control means (not shown) is protected by a layer of elastomer, vulcanized or bonded in order to eliminate noise and reduce wear on the surfaces in contact.

Wedges 150 of hardened and hardened steel are fixed by screws inside the bar 100 along the center line of the bottom wall 100b. These shims 150 take up the bending forces acting on the clamp bar 100.

The clip bar 100 is connected at each of its ends to a chain of chains (not shown) by a so-called "floating" fastening device shown on the left part of FIG. 2. This device comprises a fastening piece 165 provided with an upstream arm 170a and a downstream arm 170b, both engaged with the corresponding end of the bar 100. The attachment arms 170a, 170b have a shape which exactly matches the outside face of the upstream edges 100c and downstream 100d from the bar 100 to which they are attached using screws 162 placed from inside the bar 100 through the access orifices 116. The size and arrangement of the attachment arms 170a, 170b are chosen so that they do not increase the height of the clamp bar in any way. The attachment piece 165 is also provided with an upstream female knuckle 167a and a downstream 167b.

The "floating" device further comprises a male knuckle 169 forming part of a special link 174 of the chain train (not shown). The male 169 and female 167 knuckles 167a, 167b are connected to each other by means of an axis 172 in the form of a rod which passes through them by corresponding bores.

In the bore of the male knuckle 169, the rod 172 is surrounded by two sockets 171a, 171b of synthetic resin separated from each other by a spring 180. A first socket 171b, located downstream, is bonded to the internal surface of the 'the bore, while the other sleeve 171a, located upstream, can freely slide in its bore. In the bore of the downstream female knuckle 167b, the rod 172 is surrounded by a stop sleeve 173 acting in relation to a nut 160 engaged with a thread of the downstream end of the rod 172. The upstream end of the rod 172 is provided with a head 172a so that, when the nut 160 is screwed, the rod 172 is fixed longitudinally relative to the female knuckles 167a, 167b. On the other hand, it is planned to leave a certain clearance H for the male knuckle 169 so that the latter can slide along the rod 172 against the force of the spring 180. From FIG. 2, it is clear that on the downstream side, the male knuckle 169 can slide via the synthetic bushing 17a bonded to the rod 172, while, on the upstream side, this same knuckle slides directly on the upstream bushing 171a. Such a fastening device allows the locking of the clamp bar 100.

The male knuckle 169 is also provided with a support arm 176 extending in the direction of the hollow bar 100 and the end of which penetrates inside the latter and engages in free sliding, in the direction of running of the chain of chains, in a hook 178 fixed on the internal face of the lower wall 100b of the bar 100. The arm 176 prevents the rotation of the clamp bar around the rod 172.

In FIG. 4, a second embodiment of a clamp bar according to the invention is illustrated. As before, the upper finger of the clamp consists of a spring leaf 310 of length greater than the width of the profiled bar 300. However, in this embodiment, the profile of the bar 300 is essentially rectangular. Two languages, one upstream 302, the other downstream 303, extend respectively on each side the upper wall 300a of this bar 300. As before, the rectangular windows 312 are drilled at regular intervals along the upstream vertical edge 300c of the bar 300. In addition, rectangular windows 311 are also cut in correspondence with the windows 312 along the downstream vertical edge 300d of the bar 300.

The attachment end 310a of the spring blade 310 is folded up on itself, so that once engaged through the bar 300 by the windows 311 and 312, it can be fixed to the face bottom of the downstream tongue 303, by means of a screw 315, a washer 318 and a nut 320. The counter-clamp 325 is fixed under the upstream tongue 302 in correspondence with the window 312. The support end of the blade spring 310 has the shape of a pointed tongue 326 curved downwards. The end in correspondence of the counter-clamp 325 has two longitudinal projections.

To limit the travel of the bearing end 310b of the blade 310, as well as the wear and the noise which results from the contact of the tongue 326 with the active surface 327 of the counter-clamp 325, provision is made, Between the bearing end 310b of the blade 310 and the counter-clamp 325, a damping element 371 which, when the clamp is closed, prevents the tongue 326 from coming into contact with the counter-clamp 325.

In the second embodiment of the clamp bar, the clamp opening device is completely external to the bar itself. In the counter-clamp 325, a large opening 330 is arranged under the blade 310, opening through which a roller 345 can pass which controls the opening of the clamps when it is moved upwards using means (not shown). ) controlled by the machine. To limit noise during the opening of these clamps, an elastomer layer 370 is vulcanized under the leaf spring 310 at the place where the roller 345 pushes.

Claims (18)

Gripper bar for gripping plate elements for a printing, cutting, embossing and / or upsetting machine for the production of packaging, comprising a hollow profiled bar (100) having at least one upper wall ( 100a) and lower (100b) and an upstream (100c) and downstream (100d) edge, pliers distributed at regular intervals along the bar (100) and each consisting of an upper finger (110) in the form of a blade elastic attached by one end (110a) to the downstream edge (100d) of the bar (100), the other end (110b) bearing on a counter-clamp (125) located on the upstream side (100c), the bar (100 ) being connected at each of its ends to two trains of lateral transport chains, characterized in that each elastic blade (110), the length of which is greater than the width of the bar (100), passes through the interior of said bar (100) to emerge from a window (112) provided in the upstream edge (100 c) of the bar (100). Clamp bar according to claim 1, characterized in that the attachment end (110a) of the elastic blade (110) is bent so as to be able to be fixed against the internal face of the downstream edge (100d). Gripper bar according to one of the preceding claims, characterized in that the bearing end (110b) of the elastic blade (110) is bent downwards towards the wall bottom (100b) of the bar (100), the active face (127) of the counter-clamp (125) extending upstream at the level of the bottom wall (100b), and the bearing end (126 ) of the blade (110) being curved downwards essentially perpendicular to the active surface (127) of the counter-clamp (125). Gripper bar according to one of the preceding claims, comprising a gripper opening control member, in the form of a rotary axis (140) extending in the longitudinal direction of the gripper bar (100), this axis (140) being intended to be rotated by means of a clamp opening control lever (147) located at each end of the clamp bar (100) and controlled by the machine, characterized in that the opening axis (140), rotatably mounted on bearings (142) fixed to the bottom wall (100b) of the bar (100), extends throughout the interior of the hollow bar (100) below the blades (110) and near the upstream edge (100c), opening elements (144) integral with the axis (140) acting on the underside of each blade (110) in an area between the quarter and a third of the length of the leaf spring (110) from the support end (126). Clamp bar according to claim 4, characterized in that the opening elements (144), in the form of a cam, are fixed on the opening axis (140) so that the respective fixing points form a line slightly helical to compensate for the deformation in torsion of this axis (140) during its rotation of opening of grippers. Gripper bar according to claim 5, characterized in that the shape, size and arrangement of each cam (144) relative to the leaf spring (110) are chosen so that, when the cam (144) rotates ), the length (L₁) of the lever arm of the opening torque of the clamp decreases progressively so as to compensate for the increase in the reaction force of the leaf spring (110) and thus limit the opening torque. Clamp bar according to one of claims 4 and 6, characterized in that the opening axis (140) is a hollow tube of anodized aluminum. Clamp bar according to one of claims 4 to 7, characterized in that the bearings (142) and the opening cams (144) are made of synthetic resin, the cams (144) being fixed by gluing or pinning on the opening axis (140). Clamp bar according to claim 1, the upper wall (300a) of which has a tongue (303) extending downstream of the hollow bar (300), characterized in that the attachment end (310a) of the elastic blade (310) emerges through a window (311) made in the downstream edge (300d) of the bar (300) and is bent about 180 ° upwards so that it can be fixed against the underside of the downstream language (303). Gripper bar according to one of claims 1, 2, 3 or 9, the opening of each gripper is carried out individually from a control member (345) integral with the machine, characterized in that the counter pliers (325) is provided with an opening (330) situated between the upstream edge (300c) of the bar (300) and the active surface (327) of the counter-pliers (325), opening through which each individual clip opening member (345). Clamp bar according to one of the preceding claims, connected at each of its ends to a special link (174) of two trains of lateral chains by a fastening device, characterized in that each fastening device comprises at least one attachment piece (165) provided with two attachment arms (170a, 170b) detachably connected respectively to the upstream (100c) and downstream (100d) edges of the bar (100), these two arms (107a, 170b) being designed so that each one exactly matches the external shape of the edge, without increasing the height of the clamp bar (100). Gripper bar according to one of the preceding claims, characterized in that a noise, stroke and wear damping element (371) is interposed between the bearing end (310b) of the blade (310 ) and the counter clamp (325). Gripper bar according to one of the preceding claims, characterized in that the bearing end (126) of the leaf spring (110) is curved approximately perpendicular to the active surface (127) of the flat-nosed hard pliers (125). Gripper bar according to one of claims 1 to 13, characterized in that the bearing end (126) of the blade (110) is in the form of teeth. Gripper bar according to one of the preceding claims, characterized in that the active surface of the counter gripper (325) is provided with at least one tooth (327). Gripper bar according to one of claims 1 to 12, characterized in that an elastomer layer (127) is vulcanized on the active face of the counter gripper (125). Clamp bar according to one of claims 10 to 16, characterized in that the attachment piece (165) is provided with two female knuckles (167a, 167b) located respectively on the side of the upstream and downstream edge of the bar (100 ) and the special link (174) is provided with a male knuckle (169), the three knuckles (169, 167a, 167b) being connected to each other by means of an axis (172) in the form of a rod which cross member inside corresponding bores, the male knuckle (169) being mounted on the rod (172) with an axial clearance, intended for locking the gripper bar in a work station, and provided with a support arm (176) one end of which can freely slide in a corresponding element (178) fixed on an internal face of a wall (100b) of the bar (100). Clamp bar according to claim 1, characterized in that, in the bore of the male knuckle (169), the rod (172) is surrounded by two plastic bushings (171a, 171b) longitudinally spaced apart and separated from one another by a spring (180), a first socket (171b) located on the side of the downstream female knuckle (167b) is glued to the walls of the corresponding bore, the other socket (171a) abutting, under the effect of the spring (180,) towards the upstream female knuckle (167a), and the length of the male knuckle (169) is less than the distance separating the two female knuckles (167a, 167b) so as to allow said axial play.

Images