The machine according to the present invention may be for being advantageously employed for production processes of electric accumulators wherein a continuous grid is obtained starting from a continuous lead ribbon or tape, which continuous grid is cut into pieces of predetermined length to obtain single plates to be inserted into electric accumulators.

Background of the invention Nowadays, according to the known art, the machines for forming lead tapes operate in a generally intermittent fashion.

For that purpose, such machines are traditionally provided with a feeding system that is capable of advancing the lead tape stepwise through a die by means of which the tape is expanded and consequently the grid mesh is formed.

As known, in such machines the tape stops in correspondence of the expansion area in order to be formed and expanded by the teeth of the die, which is generally actuated by movement means also coupled with the feeding system. Once the expansion has taken place, the tape advances by a predetermined length in order to make it possible for a subsequent portion of tape to be formed.

In practice, these known machines have proven to be affected by a number of drawbacks. As known in fact the discontinuous feeding system of these machines does not make it possible to achieve high productivity levels and this because the stepwise advancement speed of the lead tape is inevitably limited by the mechanical resistance of the lead.

A further shortcoming stems from the fact that these machines do not allow production of grids having very high quality level. This is particularly due to the stepwise advancement of the lead tape that is imparted by the discontinuous feeding system. In fact such a system brings about several inaccuracies in the correct positioning of the tape in the expansion area because of the repeated stop-and-go phases. The thus obtained grid production characterised by an uneven distribution of mesh that cause the grids to acquire a rather irregular aspect.

In order to overcome the above mentioned drawbacks, a machine for formation of electric accumulators grid has been recently proposed which accomplishes the lead tape expansion on a continuous basis by means of a suitable mechanism that allows the expander die to follow the tape with a substantially equal advancement speed along the whole formatioh length.

This machine, described and claimed in the Italian patent application IT-A- VR980000056 comprises movement means for the advancement of a continuous tape across a formation area associated with die means moved by actuating means according to a motion law having a component oriented along the tape advancement direction and another component oriented along a direction that is substantially normal to the tape advancement direction. The first component allows the die teeth to advance substantially in synchronously way with respect to the tape, whereas the second component allows the die teeth to indent and expand the tape during a pressing phase of the machine.

In practice, though this machine enables to achieve improved productivity and quality with respect to the prior known machine, it entails a remarkable operative limitation due to the fact that the die is actually provided with substantially the same advancement speed of the tape only along the forming tract, whilst at the end of such tract it is subject to a remarkable deceleration along the tape advancement direction and to an acceleration along the detachment direction of the die.

The motion law of the die does not practically allow to achieve large expansions of the tape, i. e. expansions involving deep indentations with teeth of remarkable length. As a matter of fact, a sudden slowing down of the die accompanied by expansions of remarkable extent prevents the lead to detach from the teeth of the die, and in practice gives raise to an incompatible interference between the advancing tape and the teeth of the die.

Such circumstance practically limits the operation of said known type of machine to expansions of reduced entity.

A further drawback of this known machine resides in that it does not allow to vary in a cost effective and simple way the type of expansion to be carried out on the lead tape, and consequently to change the final shape of the continuous grid to be obtained. Such shape variation is ever rhore felt within the field of electric accumulator production as it is in this field there is an increasing tendency to differentiate the shape of the positive grid with respect to that of the negative grid because of their different electrochemical behaviour.

At the present time, in order to change the expansion of the tape in this known type of machine, it is necessary to replace the eccentric shafts that are present in the mechanism of the die. Such operation is slow an cumbersome and negatively affects the machine productivity.

A further shortcoming of this known type of machines is related to the variations of the operating speed that occur for example during the start-up or stopping phase of the machine. In fact, due to the remarkable weight of the movable members present in die moving mechanism, the machine components are subjected to mechanical deformations that vary according to the number of revolution and that finally induce indentations in the tape.

The above circumstance gives rise to an undesired modification of the grid conformation as a function of the machine operating speed and, therefore, in particular, of the speed of the machine at the start-up and stopping phases.

Summary of the Invention A primary object of the present invention is therefore to overcome the drawbacks affecting the machines of the known types by providing a machine for the production of electric accumulators grids, which enables to continuously form lead. tapes with expansions having the desired extent, and in particular having remarkable sizes.

A further object of the present invention is to provide a machine that allows to vary the forming of the tape, hence the shape of the grid product by means of simple adjustment operations.

Another object of the present invention is to provide a machine with an optimum operating rate that allows to maintain the extent of the tape expansions constant at any operating speed and in particular during the start-up and stopping phases.

A further object of the present invention is to provide a machine that is structurally simple and operatingly fully reliable in use.

These and other objects are all accomplished by the machine for making accumulator grids according to the present invention, that comprises a supporting structure lying on the ground, die means mounted on the supporting structure and operatively acting upon a continuous lead tape that moves at a substantially constant advancement speed along an advancement direction, moving means for moving the die means with a ! speed component oriented along the advancement direction, to allow the die means to advance in a substantially synchronous manner with respect to the continuous tape and with an expansion speed component which is oriented along a direction that is normal to the advancement direction in order to accomplish the expansion of the continuous tape, the moving means comprising at least one first motorised eccentric shaft mechanically coupled to the die means through a movement transmission unit. According to the present invention, the machine is characterised in that the movement means further comprise a second eccentric shaft driven in phase from the first eccentric shaft, which second eccentric shaft being also mechanically coupled with the movement transmission unit for imparting to the die means a speed correcting component oriented along the translation direction and in opposite sense with respect thereto.

With this machine it is possible to continuously expand lead tapes with indentations of any depths, within predetermined limits, for producing electric accumulator grids having a desired conformation.

Furthermore, the machine according to the present invention is constructively simple and operatively fully reliable.

Short Description of the Drawings The technical features of the present invention according to the above mentioned objects and aims are clearly defined by the annexed claims, and

the advantages of the invention will appear more clearly by the following detailed description, furnished with reference to the attached tables of drawings that illustrate a preferred embodiment of the invention by way of not limiting example, wherein: FIG. 1 schematically illustrates a production line of electric accumulator plates incorporating the forming machine according to the present invention; FIG. 2 schematically illustrates a side view of the machine with some parts sectioned and removed to better show the structure of other parts; FIG. 3 schematically illustrates a first cross sectional view of the machine according to the invention with some parts thereof removed, said cross section being taken along the line lil-lll of Fig. 2; FIG. 4 schematically illustrates a second cross sectional view of the machine according to the invention with some parts thereof removed, said cross section being taken removed along line IV-IV'of Fig. 2; FIG. 5 illustrates a magnified detail of the machine according to the invention and relating to a carriage engaged onto a guide; FIG. 6 illustrates a schematic view of the movement means of the die for the indentation and expansion of the continuous tape.

Detailed Description of a preferred Form of Embodiment With reference to the attached drawings, the machine for the formation of grids according to the present invention is overall indicated with the reference numeral 1.

The machine is operatively interposed between a feeding unit 2 for feeding a continuous lead tape (not illustrated in the drawings as being of a well known type) arranged upstream of a traction unit 3. Advantageously, along the same lead plate production line, at the outlet of traction unit 3, a grid flattering unit 4 and a lug cutting unit 5 may also be provided. In such a way, the

production of lead grids may be accomplished by means of a single and very compact production plant 6 depicted in Fig. 1.

Hereinafter reference will be made to an embodiment of machine 1 for forming a continuous lead tape for the production of electric accumulators plates, considering that the material making up the tape may be any alloy suitable for the production of electric accumulators.

With particular reference to the attached Figures 2,3 and 4, the machine according to the invention comprises a supporting structure 7 lying on the ground, die means 9 mounted on the supporting structure in correspondence of an expansion zone 8, the die means 8 being operatively acting on a continuous tape 10 in order to cause expansion and formation thereof.

In operation, the tape moves across the expansion zone 8 along an advancement direction A with a substantially constant advancement speed imparted by feeding unit 2 and by a traction unit 3 mentioned above.

Die means 9 are actuated by movement means 10 to cyclically exert pressing and expanding action onto the tape passing through the expansion zone 8. By means of a mechanism that will be described in detail hereinafter, these movement means drive die means 9 according to a motion law providing an advancement speed component oriented along the advancement direction A, to enable the die means to advance in substantially synchronous way with the tape, and an expansion speed component oriented along a direction B that is normal to the advancement direction A to accorhplish the expansion of the tape.

The movement means 10 are driven by means of two first eccentric shafts 11 (see fig. 2) which are brought into rotation by a motor (not shown) and

they are mechanically coupled with die means 9 through a movement motion transmission unit 12. This latter also fulfills the function of supporting the die means 9, while discharging their weight onto the first eccentric shafts 11.

According to the invention, movement means 10'further comprise a second eccentric shaft 13 which is rotary driven in phase with the first eccentric shafts 11 and is also mechanically coupled with the movement transmission unit 13 to thereby impart to die means 9 a correcting component speed oriented along the advancement direction A and in opposition thereto.

Thus, a compensation effect of the advancement speed held by die means 9 takes place both during the tape expansion phase and during the subsequent phase of detachment from the tape surface. In other words, with particular reference to the schematic drawing of Fig. 6, the two eccentric shafts 11 and 13 are interconnected and synchronised in such a way that, when the die means 9 start to perform the tape following it at a predetermined advancement speed, the speed compensation due to the action of second eccentric shaft 13 attains the minimum value. The compensation reaches its maximum amount in correspondence of the highest value of the advancement speed of die means 9.

The use of two eccentric shafts 11 and 13 to control the motion law affecting the movement transmission unit 12 enables the die means 9 to follow the tape at an advancement speed that is substantially proximal to the constant advancement speed of the tape for the whole pressing-expanding tract.

This makes it possible to accomplish an optimal expansion of the tape, particularly without any jerks caused by sudden changes of speed of the die means 9.

Advantageously, the movement transmission unit 12 comprises connection means 14 having a first end 15 coupled with the first eccentric shaft 11 and a second end 16 coupled with the eccentric shaft 13.

More precisely, connection means 14 comprise one first pair of a arms 17 and one second pair of arms 18 that are mutually interconnected at one end thereof by hinges 19.

The first pair of arms 17 is further fixed with its other end 15 to a first trunnion 20 mounted on the first eccentric shaft 1 1, whereas the second pair of arms 18 is fixed with its other end 16 to a second trunnion 21 mounted around a second eccentric shaft 13.

In accordance with the embodiment illustrated in the attached drawings, and with particular reference to Fig. 3, the first pair of arms 17 horizontally supports the ends of a supporting shaft 22 which in turn supports a frame 23 carrying die means 9.

Frame 23 is mechanically coupled to supporting shaft 22 by means of bearings 24 which allow free rotation thereof about the axis R of shaft 22.

The above mentioned die means 9 are provided with a plurality of teeth 25 that are caused to interact with the continuous tape to indent and expand it along a normal direction B with respect to its horizontal advancement direction A. In such a way, a well known continuous lead grid type is obtained in which the mesh amplitude depends both on teeth 25 size and on depth of the indentation, hence on the movement of die means 9. Teeth 25 are arranged along a plurality of parallel rows that are symmetrically positioned with respect to a middle plane P on a plate 26 that is integral with frame 23.

A detaching member 27 is advantageously located between teeth 25, which <BR> <BR> <BR> <BR> member is intearal with the su<BR> member is integral with the supporting structure 7 of machine 1 and serves to detach the grid edges formed by teeth 25 of die means 9.

The expansion exerted onto the tape is accomplished by the combined action of die means 9 and of a counter-knife 28 that is mechanically connected to the movement transmission unit 12 through transmission means 29 which drive the counter-knife 28 along the advancement direction A having the same speed component held by die means 9.

To this end, counter-knife 28 is rigidly secured to a slide 30 that is slidingly mounted on guides 31 mechanically fixed to supporting structure 7 in order to guidingly support counter-knife 28 along the advancement direction A.

According to a preferred embodiment of the present invention illustrated in Fig. 5, transmission means 29 comprise pairs of vertical columns 29'that are integral with the movement transmission unit 12 (and are particularly fixed in proximity of plate 26 bearing teeth 25), which columns are free to vertically slide inside second guides 32 integral with slide 30 in order to move counter- knife 28 along the advancement direction A.

Advantageously, guides 31 supporting counter-knife 28 by means of slide 30 are mechanically coupled with a pair of third eccentric shafts 33 which are provided on the supporting structure 7 and that are capable of adjusting the vertical position of counter-knife 28 with respect to die means 9 according to their angular position. Third eccentric shafts 33 are brought into rotation by a motor 34 through reduction gears 35.

During operation of machine 1 the relative position of die means 9 with respect to counter-knife 28 is prone to change as'a function of the operating

speed of machine 1 because of the structural deformations taking place internally thereof. By means of the pair of eccentric shafts 33, it is possible to maintain a constant relative distance between die means 9 and counter- knife 28 by simply changing the angular position of the pair of eccentric shafts 33 according to the speed of machine 1.

This allows to produce a continuous grid having a mesh size that is constant and continuous, even during start-up and stopping phases of machine 1.

According to a further aspect of the present invention, the machine further comprises adjustment means 37 for changing the phase between first eccentric shaft 11 and second eccentric shaft 13.

Advantageously, said adjustment means 37 comprise a graduated scale 36 positioned in correspondence of second eccentric shaft 13, which makes it possible to controllingly rotate the second eccentric shaft 13 when this latter is uncoupled from first eccentric shaft 11. Once the adjustment has been completed, the coupling with first eccentric shaft 111 is re-established with a phase changed by a predetermined amount. In such a way, it is possible to change the motion law followed by the die means 9 and counter-knife 28 in order to produce grids with meshes having different conformations.

The thus conceived invention achieves its intended objects and aims.

Obviously, the invention may assume in practice other shapes and configurations different from that illustrated above without departing from the scope of protection.

Moreover, all details may be substituted by techhically equivalent elements and any sizes, shapes and materials may be used according to the specific needs and requirements.