Note: Descriptions are shown in the official language in which they were submitted.
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MACHINE FOR MAKING CONTINUOUS GRIDS FOR ELECTRIC
ACCUMULATOR PLATES
Field of the invention
's
The present invention relates to a machine for the formation of grids for
electric
accumulator plates.
The machine according to the present invention may be for being
to 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.
is Background of the invention
Nowadays, according to the known art, the machines for forming lead tapes
operate in a generally intermittent fashion.
2o 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.
2s 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
3o tape to be formed.
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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
to 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
2o 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 corriponent 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
3o teeth to indent and expand the tape during a pressing phase of the machine.
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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
1o 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.
is
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
2o 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 chore 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
2s 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
3o negatively affects the machine productivity.
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A further shortcoming of this known type of machines is related to the
variations of the operating speed that occur for exemple 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
s 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
1o 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
15 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.
2o 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
2s optimum operating rate that allows to maintairi 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
3o structurally simple and operatingly fully reliable in use.
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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
s 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
1o 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
is 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 coriiponent oriented along the
translation direction and in opposite sense with respect thereto.
2o 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
25 simple and operatively fully reliable.
Short Description of the Drawin s
The technical features of the present inventiort according to the above
3o mentioned objects and aims are clearly defined by the annexed claims, and
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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
1o machine according to the invention with some parts thereof removed, said
cross section being taken along the line III-III 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;
is 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.
2o Detailed Description of a preferred Form of Embodiment
With reference to the attached drawings, the m~ichine 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
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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
to 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 anal 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
2o 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
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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 1
1.
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 1 1 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.
1o 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 1 1 and
13 are interconnected and synchronised in such a way that, when the die
1s 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
maximuri~~ 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.
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Advantageously, the movement transmission unit 12 comprises connection
means 14 having a first end 15 coupled with the first eccentric shaft 1 1 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
1o 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
2o bearings 24 which allow free rotation thereof about the axis R of shaft 22.
The above mentioned die means 9 are provided ~Jvith 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 rov~is that are symmetrically
positioned with respect to a middle plane P on a plate 26 that is integral
with
3o frame 23.
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A detaching member 27 is advantageously located between teeth 25, which
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.
1s 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-
2o 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
25 vertical position of counter-knife 28 with respect tb die means 9 according
to
their angular position. Third eccentric shafts 33 ark brought into rotation by
a
motor 34 through reduction gears 35.
During operation of machine 1 the relative position of die means 9 with
3o respect to counter-knife 28 is prone to change as 'a function of the
operating
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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
s 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.
1o According to a further aspect of the present invention, the machine further
comprises adjustment means 37 for changing the phase between first
eccentric shaft 1 1 and second eccentric shaft 13.
Advantageously, said adjustment means 37 comprise a graduated scale 36
is positioned in correspondence of second eccentric shaft 13, which makes it
possible to controllingly rotate the second eccentric shaft 13 when this
fatter
is uncoupled from first eccentric shaft 11. Once the adjustment has been
completed, the coupling with first eccentric shaft X11 is re-established with
a
phase changed by a predetermined amount. In such a way, it is possible to
2o 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.
25 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 technically equivalent elements
3o and any sizes, shapes and materials may be used according to the specific
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needs and requirements.
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