Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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IMPROVEMENT TO LARGE PRESSES FOR THE INJECTION MOULDING OF
THERMOPLASTIC, POLYESTER AND ELASTOMER MATERIALS
SUMMARY
Improvement to large presses for the injection mould-
ing of thermoplastic materials, generally comprised of
moulds in two complementary parts; one part associated to a
fixed plate; the other associated to a mobile plate,
slidable along parallel guide columns and which can be
blocked by means of hydraulically activated, transverse
semi-collars which engage corresponding circumferential
throats of hydraulic cylinders connected to the mobile
plate.
(Figure 1)
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7 DESCRIPTION
The invention refers to structural improvements to
~r large presses for the injection moulding of plastic
,. materials in general. The aim of the invention is the im-
s~ proved operative performance of said presses, at the same
time containing manufacturing costs.
, As known, large moulding presses comprise a basic
structure which supports a fixed plate associated to a fixed
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. ~ half-mould and a mobile plate, slidable on three or more
~ support columns having parallel axes; a half-mould as-
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sociated to the mobile place; hydraulic means for moving
. said mobile plate; blocking means for said mobile plate when
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the mould is in the closed position; injecting means;
reaction means; at least one hopper with dosing means for
feeding the plasticizing cylinder having a nozzle communi-
cating with the inside of the mould through the fixed part
of same; means for extracting the moulded parts on termi-
nation of each operating cycle.
Known means are used to active the mobile plate, such
as:
- pistons and relative hydraulic cylinders, which may or
may not cooperate with mechanical means, integrated by means
for temporarily blocking the mould in the closed position;
jointed mechanisms; or other mixed devices, including
hydraulic closing means and blocking mechanisms.
Furthermore, the existance of semi-automatic or com-
pletely automatic presses is known. Said presses are pro-
vided with known automatisms which, once the operator has
fixed the operating conditions and activated the press,
allow said press to repeat the first cycle indefinitively,
including the automatic expulsion of the moulded part.
For the continuous functioning of said machines, other
than supplying the feed hopper(s), maximum precision of the
moulds and of the complex mechanisms constituting the
machine is necessary, as well as accurate and costly main-
tenance.
The improvement according to the invention, refer to
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' semi-automatic, automatic and non-automatic large presses
and is characterized by the fact that it comprises hydraulic
cylinders, cooperating with rescindable groove mechanical
means, able to guarantee blocking of the mobile plate and
A relative half-mould joined to said plate, in a perfect
closed position with respect to the half-mould coupled to
the fixed plate and with respect to the hydraulic reaction
cylinders parallel to the columns along which the mobile
~- plate is slidable.
A further characteristic of the invention is the fact
' that said hydraulic cylinders are supported by a frame which
~; replaces the counter reaction plate, thereby eliminating
, the space taken up by the plate and making more room, in
~;~ the longitudinal sense, for the expulsion mechanism of the
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~, moulded part.
~' A further characteristic of the improvement is the
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fact that the extremities of the columns, three or more,
-. make up part of the press being linked to the fixed plate by
means of corresponding piston heads, having a short run in
relative single stroke hydraulic cylinders, which can be
activated in the injection phase, thereby guaranteeing that
the position of the moulding complex, subjected to a high
level of stress generated by the inside pressure of the
mould in the operating phase, cannot be altered.
According to the improvement, the press is furthermore
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characterized by the use of a couple of hydraulic cylinders,
. whose pistons are screw adjustable with respect to the
corresponding shafts, the free end of which is fixed to
pushing means which start up on termination of the moulding
. 5 cycle so as to supply an initial unblocking and opening push
to the mould, cooperating with the reaction cylinders, the
size of which can be thus considerably reduced resulting in
economy in the volume of fluid used.
According to the invention, there is provided a
:, i0 press for the injection moulding of plastics material, in
~; general, comprising mutually parallel supporting and guiding
:i columns, having a first extremity linked to a fixed member
. for carrying a fixed mould part and a second extremity
: linked to a fixed support frame, a mobile member for
-~ ~15 carrying a mobile mould part complementary to the fixed
- mould part, the mobile member being slidable along the
. columns, double-stroke piston-and-cylinder devic~s, mounted
on the support frame, for moving the mobile member towards
and.away from the fixed member, mechanical locking means for
engaging the columns and locking the position of the mobile
member relative to the columns when the mould is closed, and
. a mechanism for expulsion of a moulded part, the expulsion
mechanism being mounted on the mobile member and passing
through the support frame when the mobile member is moved
away from the fixed member by the double-stroke piston-and-
cylinder devices, the said first extremities of the columns
being linked to the fixed member by hydraulic piston-and-
cylinder devices actuable to stabilize and lock the position
: of the fixed member during injection mouding.
Detailed characteristics of the invention are
illustrated by the attached, non-limitative, schematic
drawings, on a variable scale, in which:
Figure 1 is a side view showing a non-limitative,
preferred version of the press according to the invention;
Figure lA is a plane view of the press in Figure
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Figures 2, 3, 4 illustrate the press at three
different operating phases;
Figures 5 and 6, on a larger scale, highlight some
details of the machine in different operating conditions;
Figure 7 is a partial view of the transverse
section, made according to line VII-VII of Figure 5;
Figure 8, similar to Figure 7, is a partial view,
.~ in transverse section, according to line VIII-VIII of Figure
6.
With reference to Figure 1, the press comprises a
; base 1 supporting the following main organs; a hopper 2; a
f' plasticizing and feed group 3, provided with an injecting
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nozzle 4 which passes through the fixed plate 7 and enters
the fixed part 5, figures 2 to 8; columns 11, in this case
FOUR in number, symmetrically coupled, coaxial to double
stroke reaction cylinders 50; a mobile plate 9 to which the
mobile part 6 of the mould is linked; a support 12 for the
approach and return cylinders 29.
As shown in Figures 2 to 8, the half-mould 5 is fixed
to the fixed plate 7; 8 is the insert for the nozzle 4
(Figures 3, 5) which inputs into the closed mould, when the
half-mould 6, linked to the mobile plate 9, due to the
action of the pistons 43, associated to shafts 44, linked to
the plate 9, is in the position as shown in Figures 4 and 6
with respect to the fixed part 5. The mobile plate 9 is
mounted slidable on the couples of cylinders 50 with the
interposition of bushings 48. Figures 2, 7 and 8 show the
centering bushings 31 for each column 11. A known mechanism
indicated as a whole by 10, is associated to the mobile
plate 9 for the expulsion of the moulded part.
The approach and return cylinders 29, parallel to the
columns 11, pass through the fixed support 12 which can
advantageously assume the structure of a quadrangular, or
other suitable geometric shape, frame so as to eliminate any
waste of space in a longitudinal sense, so that the expul-
sion group 10, which for moulding requisites, needs to be
able to make wide longitudinal movements for stripping the
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moulded part.
Nuts 13 are protected by casings 14, Figures 7, 8, are
screwed on the columns 11 for the exact adjustment of the
, possition of the support 12.
The extremities lla of the columns 11 are linked to
the fixed plate 7 by means of single stroke pistons
~ 17 running in cylinders 18; packings 19, 20 guarantee the
;,~ sealing between piston 17, cylinder 18 and the extremity lla
, of each columns. Each cylinder 18 is associated to the
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fixed plate 7 and is fed with fluid under pressure, by means
of a suitable duct 22, Figures 5, 6. A single stroke, push
piston 23, in contact with the extremity lla of each column
11, is fed by a suitable duct 27. On each reaction cylinder
50 sleeve there is a perimetrical throat 32, Figures 2, 5,
6, 7, 8, with an edge 33 at 90 with respect to the axis of
the corresponding cylinder and the opposite edge 34 radially
diverging towards the outside. Blocking mechanisms are
fixed to the mobile plate 9, said mechanisms made up of a
couple of semi-collars 35, Figures 5 to 8, mounted slidable
on parallel rods 37, at least one of which, 37a, is as-
sociated to double strike pistons 38, running in correspond-
ing hydraulic cylinders 39, fed by suitable ducts, not
shown. The rods 37 are fixed to the plate 9; the semi-col-
lars slide along the rods 37, 37a.
Pistons 43, with shafts 44, connected, in 45, to the
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mobile plate 9, are mounted in the double stroke approach
and return cylinders 29, connected in 46, 47 to intake and
discharge dùcts for the fluid under pressure.
A couple of cylinders 51, having an axis parallel to
the longitudinal axis of the press are fixed to the plate 7,
only one of which can be seen in Figure 6. A piston 52 is
mounted in each cylinder 51, said piston having a run
limited by the height of the cylinder. The free end of the
shaft 53 is provided w~th pushers which act against the
mobile plate 9.
The use and working of the machine as described below:
- in an initial phase the mobile plate 9 is moved away
from the fixed plate 7, Figure 2. The pistons 43, in the
corresponding cylinders 29, are in an end of run position,
Figure 2.
- At the second stage, after input of fluid under pres-
sure into the circuit of the machine, the pistons 43 move
the mobile plate 9 towards the fixed plate 7 and the parts
6, 5 of the mould gradually come together, Figures 3, 5,
until the frontal contact of the plates 9 and 7 is obtained
Figures 4, 6. The sliding of the plate 9 with respect to
the sleeve of the cylinders 50, is facilitated by the
presence of bushings 48 fixed to the plate 9; said bushings
are, obviously, longer than the width of the throats 32, so
as to avoid jamming. At the same 'ime the piston 23,
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~, activated, rests on the bottom of the cylinder 18 keeping
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the piston 17 in the end of run position with the respect to
said cylinder.
- At the third stage, the mobile plate 9 is blocked by
means of the closure of the semi-collars 35 caused by the
activation of the hydraulic cylinders 39. Said semi-collars
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:; penetrate the throats 32, borne by the reaction cylinder
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50 sleeve.
- At the fourth stage, fluid under pressure is added
through the duct 22, due to the activation of the piston 17
which stabilizes the relative positions of the fixed plate
7 and the columns 11, avoiding any, minimal, movement of the
parts 5 and 6 of the mould.
- The injection phase follows, for example, of part "A",
Figure 6, and, finally, the stage at which the mould opens
and part "A" is expelled, Figure 2. Once the part is expel-
led, the machines returns to the starting condition, ready
for another operating cycle.
On termination of the injection cycle, the initial
push for detaching the parts 5, 6 of the mould is supplied
by the couple of short run pistons 52 running in the
cylinders 51. The consequent opening of the mould and the
initial position of the machine is obtained due to the
action of the double stroke hydraulic approach and return
cylinders 29, fed by ducts 46, 47 activating the pistons 4-,
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the shafts 44 of which are fixed to the mobile plate 9.
The initial detachment of the parts 5, 6 of the mould,
operated by the pistons 52, allow for power to be contained
consequently the size of the hydraulic cylinders 29, result-
ing in considerable economy of fluid, oil and optimal
sequence of the phases of the operating cycle of the machine.
Obviously the press is furnished with a plurality of
known mechanisms, such as end of run switches, thermostats
and safety devices to interrupt the operating cycle, at any
phase, in case of any unforeseen faults that may arise when
the machine is running.
The advantages deriving from the above described im-
provement can be summarized as follows:
- ~limination of the reaction plate and consequently
wider longitudinal movement of the expulsion means;
- Improved accessibility to said expulsion mechanism;
- Terminal bearing of the support columns with respect
to the fixed plate, with the intermediary of a fluid
bearing, under pressure, so as to prevent any deformation of
the fixed plate.
- Considerable reduction in the overall length of the
machine due to the frame shape of the support 12, replacing
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- - the reaction plate, and which can be crossed by the expul-
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sion means.
- ~upport means for the support columns not subject to
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any bending stress.
`.` - Possibility of choosing the most suitable
- materials to build the organs of the machine, according
-~- to the reduced stress to which some organs are subjected
due to the particular architecture of the press. An
- example of this are the double stroke cylinders 29 which,
according to the improvement, are subject to compression
rather than to traction which necessitates the use of
materials having a high resistance to stress.
Although the description and the drawings
refer to examples of horizontal presses, the patent is
not limited to such structure and does not exclude
vertical presses having the characteristics described and
any other si~ilar or equivalent solution to the solution
described, as long the aims of the invention are
satisfied.
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