CA1062416A

CA1062416A - Apparatus for the manufacture of a blown plastic tube blank with closed bottom

Info

Publication number: CA1062416A
Application number: CA228,144A
Authority: CA
Inventors: Gerhard Linss; Karl Ossberger
Original assignee: OSSBERGER-TURBINENFABRIK Firma
Current assignee: OSSBERGER-TURBINENFABRIK Firma
Priority date: 1974-06-01
Filing date: 1975-05-30
Publication date: 1979-09-18
Also published as: DE2426735B2; JPS5932297B2; ES438074A1; DD118014A5; CH585618A5; SE411109B; GB1502338A; DE2426735A1; ATA410275A; CA1070074A; JPS515368A; JPS6110294B2; FR2275299B1; SE7506187L; JPS59207217A; DE2426735C3; SU584747A3; BR7503433A; AT359281B; FR2275299A1

Abstract

ABSTRACT OF THE DISCLOSURE
The present invention provides an apparatus for pro-ducing 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in a die aperture for extruding plastics material, a draw-off device mounted for reciprocating movement between a withdrawn position and an in-contact position with respect to the die nozzle and having a recess for moulding a top portion of the article, a reciprocably mounted mandrel arrangement for movement within said nozzle cone, 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 having a plurality of mold members mounted for movement between open and closed positions of the blow mold, each member being provided with bottom projections which are shaped to cooperatively abut one another in a closed position of the blow mold, 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in the draw-off device for blowing the extruded material into the closed mold when the draw-off device is in the withdrawn position.

Description

~ - 10624~6 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-. .
ive consumption o~ material.

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)624~6 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.
~. 1 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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`~- 10624~6 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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06Z4~6 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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6Z~16 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-:. .
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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~, -,` 106Z4~6 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 . ~ .
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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6Z4~6 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 ':::
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, t ." :
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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 , ~ - . . .
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-;j .
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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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. 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 for 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 draw-off device also having 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 positions, each member being provided with bottom lateral projections adjacant said die aper-ture 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.

2. An apparatus according to Claim 1, in which surface portions of the projections of the blow mold members, in the closed position of the blow mold, bear on the die nozzle so that the blow mold is clamped between the die nozzle and the draw-off device in its withdrawn position.

3. Apparatus according to Claim 1 or 2, in which the projections of the blow mold members act as cutting edges when they meet on closing to cut off waste material.

4. Apparatus according to Claim 1, wherein the nozzle piece is reciprocably movable with respect to the die nozzle from a normal position to an advanced position, the nozzle piece, in the advanced position, closing the die aperture and thereby separating waste material from material in said annular gap.

5. Apparatus according to Claim 4, wherein the blow mold is fixed in the axial direction, each bottom projection includes a cutting edge which, in the closed position of the blow mold members is disposed immediately downstream of the die nozzle, and a cavity bridging the die aperture is formed between the die aperture and the closed cutting edges, the end of nozzle piece projecting into said cavity in the advanced position when the die aperture is closed, and lying in the end plane of the nozzle die when the die aperture is open.

6. An apparatus according to Claim 4 or 5, in which inner surface of the die nozzle is conically flared, the outer surface of the nozzle piece is conically flared, and the annular gap is defined between said inner surface and said outer surface.

7. Apparatus according to Claim 4, in which surface portions of the bottom projections of the blow mold members are arranged to bear on the die nozzle in the closed position.

8. Apparatus according to Claim 7, in which the pro-jections, when surface portions thereof bear on the die nozzle, define a vacant space spanning the die aperture.

9. Apparatus according to Claim 4 or 5, in which when the die aperture is open, the cross-section of the annular gap decreases in the direction towards the die aperture.

10. Apparatus according to Claim 4 or 5, in which the internal surface and the end face of the die nozzle are at an acute angle to each other.