Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to an apparatus or the
manufacture of a blown plastics hollow article with a closed
bottom.
In a device of this kind ~German Patent Specification
No. 1,062,002) the bottom sections of the closed blow mold parts
do not come into contact with each other, but surround a tubular
preform produced by extrusion. The inside piece is an extension
of a blow needle which is guided into the draw-off device and
which reciprocates with the blow needle, but has a fixed position
relative to the recess in the off-take device.
The blow-needle is also fixed in position and serves as
a slide track for a shut-off part which is reciprocable as an
interior part of the tubular die to adjust the width of the
nozzle opening. In order to produce a bottom, the blow mold ;~
parts are slightly separated from each other, i.e., sufficiently
so that the resuIting yap can accept a loop or the like which
pulls the preform concentrically together at the lower end so as
to produce a tube with a closed bottom. However, this device
cannot be used if it is desired to produce an extruded tubular
preform in the recess with an end wall transverse to the long-
itudinal axis at its open end. Moreover, the production of the
bottom is obviously expensive.
Also known (Kautex Information 1, Reprint "Maschinen-
markt", 75th year, Issue 8, 22, 66/1969) is the extrusion of a
tubular pre~orm from an apparatus into the open without a draw-
off device, and then introducing this preform into a blow mold
the bottom pieces of which have extensions which meet when parts
of the blow mold are brought together and thus produce a base.
Since the tube here is extruded into the open it is generally
too long. The excessive length is taken off when the blow mold
is closed. However, the excessive length constitutes an excess-
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ive consumption o~ material.
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The present in~ention provides an apparatus of thefirst kind with which a mouthpiece with an end wall can be pro-
duced in the recess of the draw-off device, where a reduced
consumption o~ the material is assured although a base can be
produced.
An apparatus of the kind initially menti~ned is dis-
closed in German Utility Model 1,980,402, in which, however, no
separatlng device is shown which cuts off material extruded from
the tubular die and not accommodated by the blow mold~ i.e.,
residual waste from the tubular die. However, a shearing blade
can be proviaed as shown in (German Patent Specification l,111,810)
as a separating apparatus which slides along the front of the
tubular die and separates the residual waste. If the blow mold -
is immovable in the axial direction, i~e., cannot move away from
the tubular die, then sufficient space must be left between the
blow mold and the tubular die so that the knife can slide along
the front of the tubular die when the blow mold is closed, or
else the knife can only operate when the blow mold is open, `
resulting in an enlargement of the residual waste or an increase ~;
in the time required to produce the tube blank.
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The present invention provides an apparatus of the
first kind in which not only can the waste be kept as small as
possible, but can also be separated with the blow mold closed.
~ ccording to the present invention there is provided,
an apparatus for producing a blown plastics hollow article having
a closed end and comprising an extrusion die having a nozzle
piece and a die nozzle concentrically surrounding the nozzle
piece to define an annular gap therebetween terminating in a die
aperture for extruding plastics material, a draw-off device
mounted ~or reciprocating movement between an in-contact position
and a withdrawn position with respect to the die nozzle to form a -~
column of extruded material extending from the die nozzle, said
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draw-o~f device also havin~ a recess for moulding a top portion
of the article, a reciprocably mounted mandrel arrangement for
movement within said nozzle piece, an end portion of the mandrel
being arranged to project into said recess when the draw-off
device is in the in-contact position, and a blow mold extending
around the path of movement of the draw-off device so that said
column of extruded material is formed in said mold said blow
- mold comprising a plurality of mold members mounted for movement ;~
between open and closed posi~ions, each member being ~rovided with
bottom lateral projections adjacent said die aperture which are
shaped to cooperatively abut one another in the closed position
when said draw-off device is withdrawn to close the end of said
column of extruded material and thereby form the closed end of
the hollow article, and a blow needle located in the draw-off
device for blowing the extruded material into the closed mold
when the draw-off device is in the withdrawn position.
In particular the present invention provides for the
axial reciprocating motion of thenozzle cone and mandrel.
The present invention further provides that surface
,1~ 2~ portions of the bottom projec~ions, in the closed position of the
i~ blow mold sections rest on the tubular die.
It is particularly expedient and advantageous if
during the closing projections coming together act as knife
edges. The knife edges cut awa~ the excess plastic as close as
possible to the bottom.
In particular, the invention further provides that the
nozzle piece and a die nozzle accommodating same form an
annular gàp, the blow mold is axially immovable, each bottom
projection has an extension furnished with a knife edge which,
when the blow mold sections are closed, in situated just down-
stream o~ the tubular die, while the extensions separated from
the tubular die come together and a separa~ing apparatus is pro-
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vided that acts on the ~ront of the tubular die. The separating
apparatus comprises the nozzle piece which is axially movable to ~ .
close the die aperture.
By application of these measures as an arrangement for
removing the waste in an apparatus of the first kind, the
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extensions with knife edges can be disposed as closely as desired
¦ to the die nozzle, and the residual waste can still be separated
from the die nozzle when the blow mold is closed. By combining
the extensions furnished with knife edges with the movability of
the nozzle piece and with small residual waste, the time requir-
ed for the production of a tube blank is reduced, since the
~ residual waste does not have to be subsequently removed either
; from the tube blank or from the die nozzle. "Close" as used
~ herein means that no other apparatus parts are present between
¦ 10 the die nozzle and the closed extensions.
i The end face of the nozzle piece which reciprocates
I for the purpose of chanying the size of the die aperture is
situated e.g., at the front end surface of the die nozzle when
I the annular gap is closed, and inside the die nozzle when the
J annular gap is wide open. However, it is particularly expedient
and advantageous if the front end of the nozzle piece which
¦ reciprocates for the purpose of changing the size of the die
aperture projects beyond the nozzle wall when the die aperture
is closed and is situated at the end face of the die nozzle when
the die aperture is wide open. This configuration renders the
special measures at the nozzle piece and/or die nozzle unnecess-
ary, so that even with the die aperture wide open the gap
terminates precisely at the end face of the die nozzle, per-
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mitting the draw-off device for forming the mouthpiece of the
container, to come to rest tightly against the die nozzle. This~
is possible because the extensions and knife edges of the closed
blow mold are a sufficient distance away from the die nozzle.
Closing off the die aperture with the nozzle piece projecting
permits tight sealing of the die aperture despite wear after
prolonged use of the apparatus.
It is possible to make the generating surfaces of the
die nozzle and the nozzle piece boundiny the annular gap, start-
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ing from the front end and going backwards, first cylindrical, -
and only thereafter conical. However, it is particularly
expedient and advantageous when the surface of the die nozzle
and that of the nozzle piece arrangement bounding the annular
gap are both flared conically from the ~ront to the rear. In
this way the annular gap can be closed very quickly. The ter-
minating edge of the no~zle mouth piece is situated at the end
face of the die nozzle, and the end piece of the nozzle piece
projecting from the die nozzle when the aperture is closed is
1~ kept s~all.
A waste separating arrangement is usually provided in
conjunction with the following measures: the bottom segments of
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the closed blow mold parts rest on the nozzle mouthpiece, re-
ducing the length of the residual clot. The separation of the
tube extruded from the ring nozzle from the material inside the ~ ;
die nozzle takes place precisely at the end face of the die
nozzle. The nozzle piece bounding the annular yap accommodates t~`'~,' .''
an inside reciprocable mandrel the front end portion of which
projects forward into the recess of the draw-off device so as to
form a container mouthpiece and is retracted into the die nozzle j;
when the blow mold parts close. The nozzle piece is reciprocable
during the extrusion of the tube from which a container is blown,
in order to vary the annular gap and hence the thickness of the
tube wall.
The present invention will be further illustrated by
way of the accompanying drawings in which:
Figure 1 is a vertical section through an apparatus for
producing a hollow article in accordance with one e~bodiment of
the present invention with a blow mold and waste cutting device, ,
the essential parts of the apparatus being shown with the blow
mold open.
Figure 2 is vertical section of the apparatus according -
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to Figure 1 with the blow mold c~osed and the waste cutting de- --
vice in operation.
Referring to the accompanying drawings the apparatus
comprises a tubular die 30 consisting of a nozzle cone 1 and a
die nozzle 2. The nozzle cone 1 and the die nozzle 2 form an
annular die aperture 3 which is supplied with molten plastic 4
through an annular space between the nozzle cone 1 and the die '~
nozzle 2.
The die no~izle 2 is stationary hut the nozzle cone 1
can reciprocate in the direction of arrow 5.
A vertically reciprocable draw-off device 6 is provided
in an opposed upper position with respect to the tubular die, the
draw-off device also being referred to as a top mold and its
direction of reciprocation being indicated by the arrow 7. A
mandrel 8 a portion of which is vertically projectable from the
die nozzle 2, as indicated by arrow 26, is centrally situated in
the nozzle cone 1, and the projecting portion 29 extends into a
recess 9 of the draw-off device 6 when this is in a lowered posi-
tion. A blow needle 10, disposed centrally in the draw-off
device 6, extends lnto the recess 9. The mandrel 8 and the
nozzle cone 1 form a mandrel device 34.
A blow mold is arranged to be closed or opened when the
halves 11 of the blow mold are reciprocably moved horizontally
as indicated by the arrow 12. ~he blow mold has internal contours
13. At the side of the off-take device 6 there is a trip dog 14 ~ -
which during the vertical motions of the off-take device 6 slides
past two spaced proximity switches 15 and 16. The proximity
switches control the retraction motion of the draw-off device 6
and the width of the die aperture 3 in a manner not shown. ;
Initially the draw-off device 6 is lowered and its
recess 9 bears upon the member 29, while a neck 17 or tubular
head of plastic is forced intothe space between end piece 29 and
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the recess 9. When the draw-off device 6 moves upwardly while
plastic con-tinues to be extruded through nozzle opening 3, a
preform 18 is produced. The start 19 of this preform production
i occurs when the draw-off device 6 bears at the bottom on the
member 29 in the position shown as 19 in Fig. 1. The end 20 of
¦ preform production occurs when the draw-off device 6 assumes the
position shown at 20 in Fiy. 1.
Just before the terminal posltion 20, a second proximity
switch 21 is provided in the path of motion of trip dog 14, which
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switch only acts on the drive equipment of the draw-off device 6
when this is in its terminal position 20.
The die nozzle 2 is provided with an inclined portion
~ 22 which cooperates with a corresponding inclined portion 23 of
,~ the blow mold halves 11 when the blow mold halves are closed.
The inclined portion 23 is provided on a member 24, the interior
of which has a projection 25. When the blow mold is closed, the
, projections 25 of the two bottom members 24 slide into the region
7 previously occupied by the portion 29 which has now been retracted
into the die nozzle 2 by means of a piston-and-cylinder arrange-
ment (not shown~. The projections 25 therefore compress a bottom
end zone 27 of the preform 18 together when the blow mold closes
¦ and cause the cutting edg~s28 of the projections 25 to come into
action.
The portion 29, like the mandrel 8 is solid and is pro-
vided with a plane end face. ~t its bottom end the blow needle
10 is substantially closed by an end wall on which it supports
only a small projecting stud 31 through which air can be blown
into the preform 18. The cutting edges 28 are straight, because
only two blow mold halves 11 are provided so that the resulting
,i 30 bottom has a pressure seam that runs diagonally.
Referring particularly to Fig. 2, when the blow mold
halves 11 are closed bottom members 24 bear on the die nozzle 2,
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namely on the end face 22 which in this case extends at an angle
to the axis 32. The projections 25 abut each other by means of
their cutting edges and cut off residual waste 33 from the tube
disposed in the blow mold. The mandrel device 34, comprising the ;~
nozzle cone 1 and mandrel 8, can be reciprocated in the direction
indicated by the arxow 5. In its forward position, shown in Fig.
2, it cuts the residual waste 33 from the material 4 disposed in
the tubular die.
' The cuttiny edges 28 are spaced from the front of the
die nozzle 2. The projections 25 define with the die 30 a cavity
35 that accommodates the residual waste 33 and just spans the
exit aperture of the die nozzle 2. The portion 29 of the mandrel
8 extends into this space 35 when it is pushed forward to close
the die aperture 3 in accordance with Figure 2.
The die aperture 3 delimits an annular space or gap
defined by an internal surface 36 of the die nozzle 2 and by an ;
external surface 37 of the mandxel device 34, and having a conical
shape in which at least one of the surfaces 36 and 37 extends at
an angle relative to axis 32. The diameter o~ the annular gap
converges in the direction from annular duct 38 towards the die
aperture 3. The cross-section of the annular gap 3 also conver- . .
ges to the front of the tubular die when the die aperture 3 opened ; .
in accordance with Figure 1, the angle between surface 37 and ; :
axis 32 being less than the angle between surface 36 and axis 32. `,.
. The internal surface 36 and the end face 22 of the die nozzle 2
form an acute angle with respect to each other. When the die ~ ;~
aperture is closed, the mandrel device 3~ and the die nozzle are
in contact at the end face of the die nozzle 2. The residual : :
waste 33 is cut off from the material disposed in the tubular die .
on the front thereof and not within it.
According to Figure 2, each half blow mold half 11 is :
slidable on a h~orizontal rail 39 which is mounted on a strand 40.
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The stand 40 also suppo~ts as blow mold operating device 41 com-
prising two double-action piston-and~cylinder arrangements, each
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of which acts on one of the blow mold halves 11. Pressure fluid,
; compressed gas or hydraulic ~luid can be fed to the piston-and-
cylinder arrangements of the blow mold operating equipmen-t 41
through pipes 42.
Referring to Figure 1, a platform 43, which also supports
stand 40, carries a rod 44 on which a projection 45 of the draw-
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off device 6 is slidable. A driving unit 46 which acts on the
projection 45 in order to move the draw-off device 6 is also
mounted on the platform. The driving device is also constructed
as a piston-and-cylinder arrangement to which pressure fluid can
be fed via pipes 42.
The platform 43 further supports an adjusting device 47
~, which comprising two piston-and-cylinder arrangements and being
adapted to act on the nozzle cone 1, and a mandrel operating
device 48 which is constructed as a piston-and-cylinder arrange-
ment and is adapted to act on the mandrel 8. These piston-and-
cylinder arrangements can also be fed pressure fluid through
pipes 42. In each instance pipes 42 open into a valve arrange-
ment 49, S0, 51, 52, 53 by which it is possible not only to turn
the flow of pressure fluid on and off, ~ut also to adjust or
control the quantity of pressure fluid passing through per unit
time. Each of the valve arran~ements is connected to main lines ~ ~`
, 54 through which pressure fluid is furnished to the apparatus.
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