INJECTION MOLDING MACHINE

MACHINE A MOULER PAR INJECTION

English Abstract

An injection molding machine comprises a
carrier block, which contains a plasticizing cylinder
and to which hydraulic advance-retract cylinders and
hydraulic injecting cylinders are axially coupled. The
cylinder barrel of each advance-retract cylinder carries
an injecting piston for cooperating with an injecting
cylinder barrel which surrounds the advance-retract
cylinder barrel. Because each advance-retract cylinder
barrel is integrally formed with a radial flange, which
constitutes the injecting piston for cooperating with
the associated injecting cylinder barrel, the injecting
unit will be able to withstand high pressures and its
parts can yet economically be made in series.

Claims

CLAIMS
1. In an injection molding machine for processing
plastic materials, comprising
an injecting unit comprising
a carrier block,
a plasticizing cylinder having a longitudinal
center line and mounted in said carrier block so that
said longitudinal center line defines an injecting axis,
a feed screw mounted in said plasticizing
cylinder and operable to rotate about said injection
axis and axially movable along said injection axis
relative to said carrier block,
at least two advance-retract cylinder barrels
axially coupled to said carrier block and symmetrically
arranged with respect to said injection axis,
a plurality of injecting cylinder barrels,
which are axially movably mounted in said carrier block
and axially coupled to said feed screw and each of which
coaxially surrounds and is radially spaced from an
associated one of said advance-retract cylinder barrels,
and
a plurality of injecting pistons, each of which
is carried by and radially protrudes from one of said
advance-retract cylinder barrels and is axially slidably
sealed in the associated one of said injecting cylinder
barrels,
said injection molding machine also comprising
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a plurality of stationary guide rods, which axially
slidably extend through said carrier block and respective
ones of said advance-retract cylinders and each of which
carries a radially outwardly protruding advance-retract
piston, which is fixed to said guide rod and axially
slidably sealed in one of said advance-retract cylinder
barrels,
the improvement residing in that each of said
injecting pistons consists of a radial flange, which is
integral with one of said advance-retract cylinder
barrels.
2. The injection moulding machine set forth in claim 1,
wherein
each of said advance-retract cylinder barrels is
axially fixed at one end to a cylinder cover, which is
secured to said carrier block.
3. The injection moulding machine set forth in claim 2,
wherein said cylinder cover is axially fixed to said
carrier block by a plurality of fixing screws, which are
substantially parallel to said injection axis and
substantially arranged on a circular line.
4. The injection moulding machine set forth in claim 3,
wherein
an adjusting nut is connected by screw threads to
each of said advance-retract cylinder barrels and engages
said carrier block, and
said fixing screws for axially fixing each of said
cylinder covers extend through said adjusting nut
connected to the associated advance-retract cylinder.
5. The injection moulding machine set forth in claim 1,
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wherein said advance-retract cylinder barrels and said
injecting cylinder barrels are made of non-cast steel.
6. The injection moulding machine set forth in claim 1,
wherein each of said injecting cylinders and the
associated advance-retract cylinder are included in a
unit, which is detachably connected to said cylinder
block.
7. The injection moulding machine set forth in claim 1,
wherein
a radial ring is fixed to each of said guide rods
and
each of said advance-retract pistons consists of an
annular piston secured to one of said radial rings.
8. The injection moulding machine set forth in claim 1,
wherein
each of said advance-retract pistons defines in the
associated advance-retract cylinder barrel first and
second cylinder chambers and
each of said guide rods contains two substantially
parallel supply passages communicating with respective
ones of said cylinder chambers of the associated
advance-retract cylinder barrel.
9. The injection moulding machine set forth in claim 1,
wherein
said plasticizing cylinder contains a motor, which
is centered on said injecting axis and axially coupled to
and operable to rotate said feed screw about said
injection axis,
said motor is carried by an injecting bridge, which
is axially coupled to all said injecting cylinder barrels
-18-

and is axially spaced from said carrier block and on its
side that faces away from said carrier block is formed
with a plurality of recesses,
a piston rod guide is secured to said injecting
bridge in each of said recesses,
each of said guide rods axially extends through one
of said piston rod guides, and
each of said advance-retract cylinder barrels
extends through and is axially slidably mounted in one of
said piston rod guides.
10. The injection moulding machine set forth in claim 9,
wherein
each of said piston rod guides is secured to said
injecting bridge by a plurality of fixing screws
extending through said piston rod guide.
11. The injection moulding machine set forth in claim 9,
wherein
each of said injecting cylinder barrels is provided
at that end which is nearer to said carrier block with a
cylinder cover, and
a plurality of clamp screws extend through each of
said cylinder covers and are screwed into said injecting
bridge and clamp said injecting cylinder barrel axially
against said injecting bridge.
12. The injection moulding machine set forth in claim 1,
wherein
each of said radial flanges defines in the
associated injecting cylinder barrel two cylinder
chambers,
each of said advance-retract cylinder barrels has
portions differing in outside diameter on opposite sides
-19-

of the associated injecting piston and defining the
inside surfaces of said cylinder chambers so that said
two cylinder chambers have different volumes.
13. The injection moulding machine set forth in claim 1,
wherein
each of said injecting pistons defines in the
associated injecting cylinder barrel two cylinder
chambers, one of which is nearer and the other remote
from said carrier block,
said plasticizing cylinder contains a motor, which
is centered on said injecting axis and axially coupled to
and operable to rotate said feed screw about said
injection axis,
said motor is carried by an injecting bridge, which
is axially coupled to all said injecting cylinder barrels
and is axially spaced from said carrier block and on its
side that faces said carrier block is formed with a
plurality of centering recesses,
each of said injecting cylinder barrels at its end
that is remote from said carrier block axially bears on
said injecting bridge in one of said centering recesses
and
each of said cylinder chambers which are remote from
said carrier block is defined by said injecting bridge.
14. The injection moulding machine set forth in claim 1,
wherein
said plasticizing cylinder contains a motor, which
is centered on said injecting axis and axially coupled to
and operable to rotate said feed screw about said
injection axis,
said motor is carried by an injecting bridge, which
is axially coupled to all said injecting cylinder barrels
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and is axially spaced from said carrier block,
each of said injecting pistons defines in the
associated injecting cylinder barrel first and second
cylinder chambers, which are nearer to and remote from
said carrier block, respectively,
first and second hydraulic line systems communicate
with said first and second cylinder chambers,
respectively, of said injecting cylinder barrels,
each of said injecting cylinder barrels is provided
with a cylinder cover at that end which is nearer to said
carrier block,
said first hydraulic line system comprises a
plurality of annular passages, each of which is formed in
one of said cylinder covers and has a port communicating
with the associated first cylinder chamber,
said second hydraulic line system comprises a
plurality of annular passages, which are formed in said
injecting bridge and each of which has a port
communicating with one of said second cylinder chambers,
and
each of said hydraulic line systems comprises a
hydraulic valve disposed under said injecting bridge.
15. The injection moulding machine set forth in claim
14, wherein each of said hydraulic line systems comprises
between the associated hydraulic valve and the associated
annular passages a plurality of rigid branch lines, which
are symmetrically arranged with respect to said injecting
axis and have equal flow areas.
16. In an injection molding machine for processing
plastic materials, comprising
an injecting unit comprising
a carrier block,
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a plasticizing cylinder having a longitudinal center
line and mounted in said carrier block so that said
longitudinal center line defines an injecting axis,
a feed screw mounted in said plasticizing cylinder
and operable to rotate about said injection axis and
axially movable along said injection axis relative to
said carrier block,
at least two advance-retract cylinder barrels
axially coupled to said carrier block and symmetrically
arranged with respect to said injection axis,
a plurality of injecting cylinder barrels, which are
axially movably mounted in said carrier block and axially
coupled to said feed screw and each of which coaxially
surrounds and is radially spaced from an associated one
of said advance-retract cylinder barrels, and
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a plurality of injecting pistons, each of which
is carried by and radially protrudes from one of said
advance-retract cylinder barrels and is axially slidably
sealed in the associated one of said injecting cylinder
barrels,
said injection molding machine also comprising
a plurality of stationary guide rods, which axially
slidably extend through said carrier block and respective
ones of said advance-retract cylinders and each of which
carries a radially outwardly protruding advance-retract
piston, which is (fixed to said guide rod and axially
slidably sealed in one of said advance-retract cylinder
barrels,
the improvement residing in that
each of said advance-retract pistons defines
in the associated advance-retract cylinder barrel first
and second cylinder chambers and
each of said guide rods contains two substan-
tially parallel supply passages communicating with
respective ones of said cylinder chambers of the
associated advance-retract cylinder barrel.
17. In an injection molding machine f or processing
plastic materials, comprising
an injecting unit comprising
a carrier block,
a plasticizing cylinder having a longitudinal
center line and mounted in said carrier block so that
-23-

said longitudinal center line defines an injecting axis,
a feed screw mounted in said plasticizing
cylinder and operable to rotate about said injection
axis and axially movable along said injection axis
relative to said carrier block,
at least two advance-retract cylinder barrels
axially coupled to said carrier block and symmetrically
arranged with respect to said injection axis,
a plurality of injecting cylinder barrels,
which are axially movably mounted in said carrier block
and axially coupled to said feed screw and each of which
coaxially surrounds and is radially spaced from an
associated one of said advance-retract cylinder barrels,
and
a plurality of injecting pistons, each of which
is carried by and radially protrudes from one of said
advance-retract cylinder barrels and is axially slidably
sealed in the associated one of said injecting cylinder
barrels,
said injection molding machine also comprising
a plurality of stationary guide rods, which axially
slidably extend through said carrier block and respective
ones of said advance-retract cylinders and each of which
carries a radially outwardly protruding advance-retract
piston, which is fixed to said guide rod and axially
slidably sealed in one of said advance-retract cylinder
barrels,
-24-

the improvement residing in that
said advance-retract cylinder barrels and said
injecting cylinder barrels are made of non-cast steel,
each of said radial flanges defines in the
associated injecting cylinder barrel two cylinder
chambers,
each of said advance-retract cylinder barrels
has portions differing in outside diameter on opposite
sides of the associated injecting piston and defining
the inside surfaces of s aid cylinder chambers so that
said two cylinder chambers have different volumes.
18. In an injection molding machine for processing
plastic materials, comprising
an injecting unit comprising
a carrier block,
a plasticizing cylinder having a longitudinal
center line and mounted in said carrier block so that
said longitudinal center line defines an injecting axis
a feed screw mounted in said plasticizing
cylinder and operable to rotate about said injection
axis and axially movable along said injection axis
relative to said carrier block,
at least two advance-retract cylinder barrels
axially coupled to said carrier block and symmetrically
arranged with respect to said injection axis,
a plurality of injecting cylinder barrels,
which are axially movably mounted in said carrier block
-25-

and axially coupled to said feed screw and each of which
coaxially surrounds and is radially spaced from an
associated one of said advance-retract cylinder barrels,
and
a plurality of injecting pistons, each of which
is carried by and radially protrudes from one of said
advance-retract cylinder barrels arid is axially slidably
sealed in the associated one of said injecting cylinder
barrels,
said injection molding machine also comprising
a plurality of stationary guide rods, which axially
slidably extend through said carrier block and respective
ones of said advance-retract cylinders and each of which
carries a radially outwardly protruding advance-retract
piston, which is fixed to said guide rod and axially
slidably sealed in one of said advance-retract cylinder
barrels,
the improvement residing in that
each of said injecting pistons defines in the
associated injecting cylinder barrel first and second
cylinder chambers, which are nearer to and remote from
said carrier block, respectively,
first and second hydraulic line systems
communicate with said first and second cylinder chambers,
respectively, of said injecting cylinder barrels,
each of said injecting cylinder barrels is
provided with a cylinder cover at that end which is
nearer to said carrier block,
-26-

said first hydraulic line system comprises a
plurality of annul ax passages, each of which is formed
in one of said cylinder covers and has a port communi-
cating with the associated first cylinder chamber,
said second hydraulic line system comprises a
plurality of annular passages, which are formed in said
injecting bridge and each of which has a port communi-
cating with one of said second cylinder chambers,
each of said hydraulic line systems comprises
a hydraulic valve disposed under said injecting bridge,
and
each of said hydraulic line systems comprises
between the associated hydraulic valve and the associated
annular passages a plurality of rigid branch lines, which
are symmetrically arranged with respect to said injecting
axis and have equal flow areas.
-27-

Description

BACKGROUND OF THE INVEIfTION
1. Field of the Invention
This invention relates to an injection molding
machine for processing synthetic resins and other plastic
materials, comprising in an injecting unit a plasticizing
cylinder, which is mounted in a carrier block, th at is
axially coupled to at least two hydraulic advance-retract
cylinders, which are symmetrically disposed with respect
to the injection axis and serve to axially displace the
injecting unit on stationary guide rods, on which
advance-retract pistons are fixedly mounted, and
at least two injecting cylinders, which are supported
by and axially movable relative to the carrier block
and are symmetrically disposed with respect to the
injection axis and serve to axially drive a rotatable
feed screw, which is pro~,rided in the plasticizing
cylinder. Each of the advance-retract cylinders is
coaxially surrounded by one of said injecting cylinders
and carries an injecting piston for cooperating with said
injecting cylinder.
Description of the Prior Art
German Utility :yodel 70 46 62~ discloses an
injecting unit of that kind, in which each actuating
cylinder and the associated injecting cylinder are
hydraulically connected in series in such a manner
th at the two associated cylinders constitute a unit
but are separately supplied with liquid under pressure.
_ 2 -

The cylinders of each pair are nested one in the other
and the injecting cylinder is mounted on the advance-
retract cylinder in such a manner that the actuating
cylinder carries the injecting piston cooperating with
the associated injecting cylinder; th at injecting piston
is secured in recesses of the advance-retract cylinder.
The advance-retract cylinder is indirectly secured to the
carrier block and cannot be removed unless screws have
been loosened and the advance-retract cylinder has been
displaced to release an axial lock. For this reason a
quick exchange of the advance-retract cylinders is
prevented by the means by which they are fixed. The
injecting cylinders are constituted by a casting,
which also constitutes an injecting bridge.
U.S. Patent 4,668,178 discloses another
injecting unit of that kind, in which the advance-retract
cylinder barrels consist of non-cast steel barrels, which
at one end are supported in corresponding annular
shoulders of the carrier block. The associated sleevelike
cylinder covers tightly enclose the guide rods and extend
almost throughout the axial length of the bores of the
carrier block and fit said bores without a play. For
this reason the advance-retract cylinders cannot be
operated until the injecting unit h as completely been
mounted.
U.S. Patent 4,850,841 discloses another
injecting unit, in which each advance-retract cylinder

~~~z~9 ~r~
and the associated injecting cylinder are separate from
each other and separately mounted in the carrier block.
In that case the cylinders screw-connected to the carrier
block can easily be replaced and their operativeness can
be tested before they are installed. But the carrier
block casting must be sufficiently large for accommo-
dating a,11 cylinders. An increase of the size of the
casting will give rise to increasingly stringent
problems which are due to the formation of pipes
during the casting process. Besides, such a carrying
block will render an injection into the parting line
of the mold more difficult in an upright injecting
unit.
Finally, it is known from U.S. Patent 5,129,816
that the coaxial arrangement of th a cylinders can be
improved in that they are adjustably mounted on the
carrier block by means of a plurality of screws, which
are parallel to the injection axis and arranged approx-
imately on a circular line.
SUMMARY OF THE INVENT ION
In view of the x~rior art discussed hereinbefore
it is an object of the invention to provide an injecting
molding machine which is of the kind described first
hereinbefore and in which the injecting unit meets the
increasing requirements, particularly as regards the
transmission of strong forces, whereas the requirements
for an economical series manufacture are also met.

That object is accomplished in accordance with
the inventien in that each advance-retract cylinder
barrel is integrally formed with a radial flange,
which constitutes an injecting piston for cooperating
with an associated injecting cylinder.
Each advance-retract cylinder barrel is formed
during its manufacture with the injecting piston for
cooperation with an associated injecting cylinder.
Because that injecting piston is integral with the
cylinder barrel it can take up even high pressures
without an arising of problems and without a risk
of leakage. Machining can be effected in a simple
manner because any dimensional tolerances, particularly
of the outside surfaces of the cylinder barrel, are less
significant than, e.g., dimensional tolerances of the
recesses provided in the prior art for receiving the
injecting piston. Besides, the much lower structural
expenditure and space requirement of the means f or
fixing the cylinder barrels and the much smaller
space required for such means permit an injection
through an axial sprue and into the parting line.
According to a preferred feature each advance-
retract cylinder barrel and the associated injecting
cylinder barrel constitute a unit, which is adapted
to be fixed in the carrier block by a cylinder cover
provided on the advance-retract cylinder barrel and
consist of respective non-cast steel barrels. In that
5

~~a~a ~
case the unit comprising the two nested cylinders pref-
erably includes also the injecting bridge and can be
fitted into the bores of the carrier block with a
relatively small amount of work. Besides, it is possible
before the assembling to test the operativeness of each
advance-retract cylinder and the associated injecting
cylinder because in that case it will be sufficient to
close the advance-retract cylinder with the cylinder
cover. In the premises of the user it will then be
possible in case of a shutdown to effect a replacement
even by moderately skilled staff because it is again
sufficient to remove only the forward cylinder cover
in order to detach the advance-retract cylinders from
the carrier block. The cyl nder barrels consist of
non-cast steel because it h as been found in practice
that the use of castings will give rise to difficulties
particularly under high pressures as pipes are formed
during the casting operation and, by experience, rendex
almost 25% of the castings inoperative. The use of
non-cast steel barrels will also facilitate the manu-
facture of the advance-retract cylinder barrel which
is integrally formed with an injecting piston because
that piston can simply be formed out of the wall of
the cylinder.
According to a preferred feature the cylinder
cover of each advance-retract cylinder is fixed to the
carrier block by a plurality of fixing screws, which are
- 6 _

~~~~~ i'~
parallel to the injection axis and arranged approximately
on a circular line. In that case each advance-retract
cylinder barrel is larger in diameter adjacent to the
injecting bridge so that the cylinder space available
for retracting the feed screw is decreased. This affords
the advantage that the feed screw can be retracted at a
higher speed which is higher than the speed of the
advancing movement which is imp arted to the feed
screw during the injecting operation and is effected
by the fluid in the other space of the cylinder.
Besides, the use of cylinder spaces which differ
in size i.s an essential requirement for the control
of the movements, particularly if the holding pressure
is to be controlled.
According to a preferred feature each cylinder
chamber of each injecting cylinder is supplied with
liquid under pressure through a supply passage and a
succeeding annular passage, which is provided adjacent
to the associated cylinder cover and terminates in an
outlet, and hydraulic valves are provided adjacent to
the injecting bridge and are connected to said cylinder
chambers by rigid lines, which have identical cross-
sections and are symmetrically arranged with respect
to the injection axis. Owing to the supply of the
liquid under pressure through an annular passage
the hydraulic liquid flows uniformly into said cylinder
chambers. If the outlet is provided at the top end of
_ 7 _

the annular passage, it will be possible to effectively
suppress undesired accompanying phenomena, such as an
occurrence of air bubbles. An exact control of the
pressure in associated cylinder chambers can be effected
because rigid lines rather than elastic lines are
provided so that the pressure in the cylinder chambers
will not be influenced by an elasticity of the material
of the lines. The symmetrical arrangement of all lines
and their identical cross-sections also will contribute
to an avoiding of problems in the control or automatic
control of pressure.
BRIEF DESCRIPTTON OF THE DRAWING
Figure 1 is a top plan view showing an
injecting unit.
Figure 2 is a side elevation showing the
injecting unit of Figure 1.
Figure 3 is a horizontal sectional view
taken on a plane on the level of the guide rods and
showing the injecting unit on a larger scale.
Figure 4 is a vertical sectional view showing
a guide rod of Figure 3.
Figures 5, 6, 7 are sectional views showing
the injecting unit of Figure 1 and taken on lines V-V,
VI-VI, and VII-VII, respectively, in Figure 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIT~IENT
An illustrative embodiment of the invention
will now be described with reference to the drawings,
_ g _

(~ C~ F rv r
and further advantages afforded by the invention ~~1~' ~ ~ ~
become apparent from said description.
The illustrated injecting unit comprises a
carrier blocx 10, in which a plasticizing cylinder 17
is mounted by means of a nut 34. The plasticizing
cylinder 17 is a component of a plasticizing sub-unit,
which is provided with heating means. The plasticizing
cylinder 17 has a longitudinal center line and is so
mounted in the carrier block 10 that said longitudinal
center line constitutes an injection axis s-s. The
carrier block 10 h as two wing portions 10a, which
are formed with respective bores 10b, which axe sym-
metrical to the injection axis s-s and contain respective
hydraulic advance-retract cylinders A for axially
displacing the injecting unit on guide rods 19 of
the injection molding machine. Said guide rods 19
are provided with fixed annular advance-retract pis-
tons 32, which are axially slidably sealed in the
advance-retract cylinders. The guide rods 19 are
axially fixed to a stationary mold carrier of the
injection molding machine, which is intended to process
synthetic resins or other plastic materials, such as
ceramic compositions. Each advance-retract cylinder A
comprises two cylinder covers 13, 14, a barrel 18,
which is made of non-cast steel, and an advance-retract
piston 22, which is provided on a guide rod 19.
Two hydraulic injection cylinders E are t
- 9 -

provided, which are also symmetrical with respect to the
injection axis s-s and serve for axially displacing a
feed screw 35, which is contained in the plasticizing
cylinder 17. The cylinder barrel 18 of each advance-
retract cylinder A carries an injecting piston 18b,
which is axially slidably sealed in the cylinder
barrel 11 of an associated injecting cylinder E.
The steel barrel 11 of each injecting cylinder E
coaxially surrounds and is radially spaced from the
steel barrel 18 of an associated advance-retract
cylinder A. More than two sets of advance-retract
and injecting cylinders may be provided around the
injection axis s-s.
The injecting piston for cooperating with
each injection cylinder consists of a radial flange 18b,
which is provided on the cylinder barrel 18 of the
associated advance-.retract cylinder and is integrally
formed with the barrel 18 that is made of non-cast
steel; but a different arrangement is also possible.
As is apparent from Figure 2 the advance-
retract cylinders A are freely carried by the carrier
block 10 in such a manner that two-thirds of the length
of the advance-retract cylinders A protrude rearwardly
out of the wings 10a. On the other hand, the injecting
cylinders project rearwardly out of the advance-retract
cylinders and are fixed in an injecting bridge 25, which
carries a motor 26 for rotating the feed screw and
- 10 -

comprises a bearing block, in which means are movably
mounted which serve to transmit torque from the drive
motor 26 to the feed screw 35.
The advance-retract cylinders A, the injecting
cylinders E, and the injecting bridge 25 constitute a
sub-unit, which is anchored in the carrier block 10.
For that purpose a cylinder cover 13 of each advance-
retract cylinder A is fixed to the carrier block by a
plurality of fixing screws 21, which are approximately
parallel and are approximately arranged on a circular
line. Said fixing screv~is are screwed into an adjusting
nut 30, which is screwed on the forward end portion 18e
of the steel barrel 18 of an associated advance-retract
cylinder A and constitutes the means with which the
sub-unit A, E, 25 engages the carrier block 10. Each
guide rod 19 is provided with a radial ring 19c, to
which an annul ar piston 22 is ffixed. Each guide rod 19
is formed with two axial bores, which constitute
passages 19a, 19b for supplying liquid under pressure
to the cylinder chambers 15 and 16 contained in each
advance-retract cylinder A on both sides of the annular
piston 22. The cylinder chambers 15, 16 are defined by
the guide rod 19, which serves as a piston rod, by the
annular piston 19, and by the steel barrel 18. The
cylinder chamber 16 is axially defined by the piston 22
and the cylinder cover 14, which has been screwed into
internal screw threads 18d formed in the adjacent end
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~~~;~'~ ~~~
portion of the steel barrel 18. The cylinder chamber 16
is supplied with liquid under pressure when it is desired
to retract the injecting unit from the mold plate. The
other cylinder ch amber 15 of each advance--retract
cylinder is disposed in front of the cylinder chamber 16
and serves to advance the injecting unit toward the mold
plate. The cylinder chamber 15 is axially defined by the
annular piston 22 and the cylinder cover 13, which may be
mounted on the cylinder barrel 18 before the final
assembly so that the cylinder can be tested for op-
erativeness. liquid under pressure can be supplied
to the annular piston 22 from both sides.
Each steel barrel 18 is integral with an
injecting piston for cooperating with an associated
injecting cylinder E and constitutes also a piston
rod for the associated injecting cylinder E. Each
steel barrel 18 is axially movably mounted in an
annular piston rod guide 31, which is secured in
a recess 25b of the injecting bridge 25. A plurality
of screws 32 extend through the piston rod guide 31
and are screwed into the injecting bridge 25. The
radial flange 18b provided on the steel barrel 18
axially defines two cylinder chambers 28, 29, which
are supplied with liquid under pressure on either
side of the flange 18b in order to axially move the
feed screw 35. By a supply of liquid under pressure
to the cylinder ch amber 28 the feed screw 35 is moved
-- 12 -

~~~a~z~ ~~~
toward the mold plate. The cylinder chamber 28 is axially
defined also by the cylinder cover 12, which is connected
to the injecting bridge 25 by clamp screws 23 (Fig-
ures 1, 2). >i'or that purpose the steel barrels 11 are
also held in centering recesses 25a formed in the
injecting bridge 25. The cylinder barrels 11 comprise
end portions 11a, which are smaller in diameter and
fit into mating portions of the cylinder cover 12 and
the injecting bridge 25. hiquid under pressure is
supplied to the rear cylinder chamber 29 of each
injecting cylinder E when it is desired to retract
the feed screw. The cylinder chamber 29 is defined
by the steel barrel 11 and by the injecting bridge 25,
which serves as a cylinder cover. The steel barrel 18
h as adjacent to the injecting bridge 25 an end por-
tion 18a which is larger in diameter than the remaining
portion of the steel barrel 18 so that the cylinder
eh amber 29 is smaller in cross-section than the cylinder
eh amber 28 and the feed screw can be retracted at a
velocity which is higher than the velocity at which
it is advanced for injecting under the same boundary
conditions.
The hydraulic control system is disposed
below the injecting bridge 25 so that only short
lines for the hydraulic liquid are required between
the hydraulic valves 27 and the cylinder chambers.
The liquid supply lines are symmetrical with respect
- 13 -

r V
to the injection axis s-s and are rigid and have
identical cross-sections sa that the stresses will
be uniform and the movements will be as symmetrical
as possible. Each supply line comprises an annular
passage 33a or 37a, which has a, port 33b or 37b for
supplying hydraulic liquid to an associated cylinder
chamber. Each annular passage 37a is formed in th a
injecting bridge 25 and its port 37b merges at the
bottom of the centering recess 25a into the associated
cylinder chamber 29. Liquid under pressure is supplied
to each cylinder chamber 28 through a supply line 33
and an annular passage 33a, which communicates with
the cylinder ch amber 28 through a port 33b. The annular
passage 33a and the ports 33b are formed in the cylinder
cover 12. It is also apparent from Figure 4 that a
section of the supply line 33 is disposed between
the injecting bridge arid the cylinder cover and will
be clamped in position as the clamp screws 23 are
tightened.
To assemble the injecting unit, the steel
barrels 11 axe fitted over the steel barrels 18 arid
the sets of steel barrels 11, 18 are secured to the
injecting bridge 25 by means of the clamp screws 23.
The piston rod guides 31 are secured to the injecting
bridge 25 by the screws 32. The cylinder barrel 18 is
provided at its rear end with the cylinder cover 14
and the sub-unit which has now been assembled is
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~~~~4a~) ~'~
pushed onto the guide rods 19 and the advance-retract
pistons 22 provided thereon and is also pushed through
the bore 10b of the carrier block 10. Thereafter an
adjusting nut 30 is screwed onto screw threads on the
end portion 18c of each cylinder barrel 18 so th at the
sub-unit is engaged with the carrier block 10. The
cylinder chamber 15 is then closed by the insertion
of the cylinder cover 13 and the cover 13 is secured
to the carrier block 10 by the screws 21. When the
hydraulic lines have been connected to the hydraulic
control system of the injection molding machine, liquid
under pressure can be supplied to the rotary motor 26
through supply lines 26a, 26b.
It must be possible to transport the entire
injecting unit as such. For that purpose the unit is
provided with a carrier 20 for supporting the injecting
unit at its forward end. The movements of the advance-
retract and injecting cylinders are measured by linear
potentiometers 36.
_ 15 _

Representative Drawing