BACKGROUND OF THE INVENTION
The present invention relates to an improved press for
extruding non-ferrous metal section members.
More specifically, the field of the invention is that of
pressing apparatus using for extruding section members or profiled elements (such
as door profiled elements, motor vehicle profiled elements and son on), starting
from non-ferrous metals (such as aluminium, bronze, copper, brass and the like.
The above mentioned presses conventionally use variable
displacement pumps, coupled to servo-valves and electric motors.
In such constructions, the press cylinder fluid (usually
oil) is circulated by the pump, in turn driven at constant R.P.M.'s by the electric
The displacement or flow-rate of the pump is changed depending
on the press cylinder movement requirements (in particular during the filling of
the material to be extruded), while holding the motor R.P.M.'s constant, and by
changing the inclination of the pump plate, by means of a specifically designed
The above disclosed construction has the drawback that
it requires that a servo-valve be used, which, in addition to being a separated
component, susceptible to failure and requiring frequent servicing operations, also
requires a dedicated driving system.
A further drawback of the above mentioned construction
is the requirement of holding the electric motor in a rated operation range, even
in periods in which the pump is in a rest condition, which negatively affects the
overall system managing cost.
SUMMARY OF THE INVENTION
Accordingly, the main object of the present invention is
to provide a novel extruding press for extruding non-ferrous metal section members,
which is much more simple than conventional extruding presses and, moreover, comprises
a small number of press components.
Another object of the present invention is to provide such
an extruding press which, differently from prior like extruding presses, allows
to achieve a very high power saving, in particular in driving the pump controlling
The above objects, as well as yet other objects, are achieved
by the extruding press according to claim 1.
Preferred embodiments of the invention are defined in the
With respect to prior non-ferrous metal section member
extruding presses, the inventive extruding press provides the advantage of eliminating
the requirement to include therein a plurality of servo-valves, and the related
driving pump, as well as that to precisely control the cylinder driving pump flow-rate.
Yet another advantage of the inventive extruding press
is that the cylinder driving pump operating motor is driven only as it is effectively
required, while leaving said motor in a rest condition, or at low R.P.M.'s, as the
press cylinder is a rest condition, while discriminating the number of driving motors
to be used, depending on the contingent operating requirements.
BRIEF DESCRIPTION OF THE DRAWINGS
The above objects, as well as yet other objects, advantages
and features of the present invention will become more apparent hereinafter from
the following detailed disclosure of a preferred embodiment of the invention, which
is illustrated, by way of a non limitative example, in the accompanying drawings,
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Figure 1 is an operating diagram of a conventional
extruding press for extruding non-ferrous material section members;
Figure 2 shows a schematic diagram of an
inventive extruding press;
Figure 3 shows an operating diagram and
principle of a low inertia motor used in the extruding press shown in
The extruding press 1 of figure
1, which is a conventional type of extruding press, comprises a pressing
punch 2 for extruding a non-ferrous metal section member, made, for example, of
an aluminium material (not shown).
The pressing or extruding punch 2 is in turn driven by
oil-dynamic or hydraulic driving cylinders 3 and 4, therethrough the operating or
driving fluid is conveyed, inside a respective driving circuit 5, by a variable
displacement pump 6.
In particular, said variable displacement pump 6 comprises
a pump plate 7, the inclination of which is controlled by a respective servo-valve
8, in turn controlled by a driving pump 9, controlled by a dedicated motor 10. The
rotary movement of the pump 6 plate 7 is controlled with constant R.P.M.'s, by a
driving motor 11, coupled to the electric mains 13, through a switching assembly
In this prior embodiment, the electric motor 11 is a conventional
asynchronous motor, rotatively driving the plate 7 of the pump 6 at a constant revolution
number, and accordingly independently from the operating status of the cylinders
3 and 4 of the extruding press 1.
This is provided to overcome the drawbacks related to a
slow response of the electric motor 11 to the operation of the pump 6, the flow-rate
or displacement of which is controlled by the inclination of its plate 7.
The extruding press according to the invention, indicated
by the reference number 14 in figure 2,
comprises a pressing or extruding punch 2, in which the hydraulic cylinders 3 and
4 are driven by a fluid conveyed, inside the respective hydraulic circuit 5, by
a piston pump 15.
Said piston pump 15 is in turn controlled by a low inertia
electric motor 16, in particular a converter three-phase asynchronous motor, having
a forced ventilating system and a square motor casing.
As is clearly shown in the diagram of figure
3, said electric motor 16 is a four-pole three-phase asynchronous motor,
comprising a square casing 18, an independent radial electro-fan 19, a double-output
shaft 26 for coupling an encoder assuring a high operating precision, connectors
20 for the motor brake 25 and for the encoder, insulating elements 21, strengthened
by vacuum resins, a low inertia rotor 22, thermal probes 23, having a non-linear
variable resistance, arranged in the motor windings, and a low leak magnetic sheet
element 24, designed for providing a high electromagnetic efficiency.
The electric motor 16, in particular, is so designed to
be coupled by frequency converters (either of a V/f or of a vectorial type) and
is adapted to operate like a D.C. motor and brushless servo-motors, so as to provide
a greatly improved performance with respect to a conventional asynchronous type
of electric motor. The number of revolutions of the motor 16 is in turn controlled
by an inverter 17 coupled to the mains 13.
According to the present invention, the flow-rate of the
operating fluid to the cylinders 3 and 4 is herein controlled not by the pump 15
which, in this case, has a constant delivery flow-rate, but by the revolution number
of the motor 16 driving said pump 15.
In fact, said motor 16, which, as stated, is a three-phase
asynchronous motor of a type suitable for converters, has a very small inertia,
thereby allowing to provide a quick response for quickly changing, if required,
the displacement speed of the extruding punch 2, for example in feeding the metal
material to be extruded, to properly distinguish this feeding step from the extruding
step of the section member, performed with a constant extruding speed.
For further clarifying the advantages of the invention
with respect to the above disclosed prior art, a Table is herein enclosed, showing
the power drain of a conventional motor 11 and of a low inertia motor 16, as the
flow-rate and pressure of the pumps 6 and 15 change depending on the fluid delivery
required by the press oil-dynamic cylinders 3 and 4.
In the herein considered example, the pumps 11 and 16 of
the extruding systems 1 and 2 respectively operate at 690 operating cycles/day,
for a period of time of 15 sec during the extruding material loading step, 105 sec
in the extruding step proper, and with 1 h of machine rest time. The motor 10 of
the pump 9 of the servo-valve 8 of the system of figure
1, on the contrary, operates for 24 h/day.
The motors 11 and respectively 16 are herein provided in
a number of three, each having a power of 135 kW, for controlling each respectively
a respective pump 6 and 15.
The motor 10 has a power of about 25 kW.
PERIOD OFREST OF THE PRESS
TOTAL CONSUMED POWER/DAY (kWh)
I X 70
I X 130
I X 25
II X 70
II X 130
II X 25
III X 70
III X 25
III X 25
Total consumed power (kW) by the motors 11
Power consume/day (kWh)
I X 70
I X 130
Consumed Power (kW) by the motors 16
II X 70
II X 130
III X 70
Total Consumed Power (kW) for the motors 16
Consumed power/day (kWh)
As shown in the above Table, the power saving achieved
by the system of figure 2 (due to the reduction
of the number of the operating motors) corresponds to about 14%/day.
This power saving is obviously multiplied as a greater
number of motors 16 and corresponding pumps 15 are used.