GB2412624A

GB2412624A - A plastic blow-moulding process

Info

Publication number: GB2412624A
Application number: GB0407022A
Authority: GB
Inventors: Seamus Oliver Madden
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-03-29
Filing date: 2004-03-29
Publication date: 2005-10-05
Anticipated expiration: 2024-03-29
Also published as: GB2412624B; GB0407022D0

Abstract

A process for manufacturing thin walled plastics containers e.g. bottles with a neck portion comprises a mould 10 wherein a parison (90 figure 6a) of plastics material is extruded about a blow pin (51 figure 4) between a pair of spaced apart mould halves (48, 49 figure 5). As the mould halves close, low pressure pre-blow air is delivered through the blow pin for partially inflating the parison in the mould. Upon closure of the mould high pressure air is delivered through the blow pin to rapidly inflate the parison against the inner wall of the mould to form the bottle. Whilst the plastics material is still malleable at the neck of the bottle the blow pin is advanced into the mould to gather and compress plastics material at the neck of the bottle which is then cut by a cutting ring (58 figure 4) on the blow pin. Upon opening the mould the bottle is removed and delivered by a conveyor 12 and a feeder 15 to a deflashing station 16 at which excess waste plastics material is removed. The bottles are then delivered by conveyors 18, 30 to a packaging station 32.

Description

A.: : A-: - 1 "A poetics bkwnlding process" This invention relates to a

plastics blamouWing process.

The invention is particularly concerned with the plastics bbw-moulding of relatively thin-walled plastics bottles of the type used for example in the dairy industry for milk packaging. In bbvmouWing such a plastics bottle a parison is extended downwardly about a blow pin and a pair of moue halves close together about the parison and blow pin. Air at a pressure in the order of 100 psi is blown through the blow pin to an interior of the parison to inflate the parison within the mould to take a bottle shape tombed by an interior of the mould against which the plastics material of the parison is brawn. A shear ring on the blow pin cooperates with a complementary shear collar at a neck opening of the Would, through which the blow pin passes, to cut a neck portion of the formed bottle away from the parison material. Usually blowing of the parison commences as the moue halves are closing together, the blowing being timed such that as the mould doses fully the bottle is fully blown and cut away from the parison at the neck portion. Particulars Beth thin- walled bottles getting the timing right presents difficulties and considerable wastage may occur in setting up the mould. Further, when the bottles are in use it is necessary to provide a good seal between the neck 2 0 portion of the bottle and an associated cap of the bottle to prevent leakage of liquid from the bottle in use. With thinualled bottles difficulties can arise due to lack of material at the bottle neck if the timing of the blowing and cuffing of the neck is not very accurate leading to a relatively high resect rate. Also the sealing surface at the neck of the bottle which cooperates with a cap has a relatively coarse finish which can give sealing problems.

The present invention is directed towards overcoming these problems.

According to the invention there is provided a plastics blab moulding process for 3 0 manufacturing a thin walled plastics container comprising a bottle with a neck portion, induding the steps: extruding a parison of plastics material downwardly about a blow pin and between a complementary pair of spaced-apart open mould : : :. :e . . . - 2 - halves, closing the mould halves together, when the mould hades are partially closed pre-bbwing the parison with bw pressure air by injecting bw pressure air through the blow pin into the parison for partially inflating the parison as the rnoub closes fully, sealingly engaging the rnould halves with the blow pin when the Would is fully closed, injecting high pressure air at full blow pressure through the blow pin into the parison within the fully closed mould for rapidity fully inflating the parison against an inner sWe wall of the mould to form the bottle in the mould, after blo Mng the parison at full blow pressure for a preset period after closing the Would advancing the blow pin into the rnould a preset distance for gathering and compressing plastics material at a neck of 2 0 the boBle, and when the blow pin is fully extended into the Would a cutting ring on the blow pin cooperating with a complementary shear steel on the mould for cutting the neck of the bottle from the parison material, 2 5 opening the mould, removing the bottle from the rnould, cooling the bottle, de-flashing the bottle, and delivering the bottle for further processing andlor packaging. a

, a e. ce* - 3 - In a preferred embodiment the time delay between closing the mould and advancing the blow pin into the mould within the range 0.4 to 0.5 seconds.

In another embodiment the process includes the step of moving the blow pin through a stroke of 1 5mm.

In a further embodiment the shear steel on the mould defines a tapered hole having a side wall which tapers outwardly at an angle of 15 to a central axis of the hole and the cutting ring on the blow pin has a right angle cuffing edge for engagement with said side wall above the inner narrowest part of the hole.

In another embodiment the process includes engaging an exterior of a cylindrical cap part of the blow pin with an air seal tombed in two associated seal parts mounted on the mould halves said seal parts engaging and forming an air seal with the cap part, the cap part slidably engaging the air seal parts for moving between a raised prep blowing position and a lowered mairblowing position.

In another embodiment the process includes starting injecting the bw pressure prebbw air into the parison as the closing mould halves are coming into contact with the parison.

In another embodiment the full blow pressure air is at about 100psi (6.89 bar).

In a further embodiment the preblow air pressure is in the range 20-25psi (1.38 bar 1.72 bar).

In a further embodiment the process includes the step of pressure testing the bottles 3 0 downstream of the de-flashing station.

In another embodiment the process includes aligning a set of upstanding bottles in a number of rows and columns, pulling an outer plastics envelope about the set of bottles and sealing the envelope encasing the set of bottles.

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. - 4 - The invention will be more clearly understood by the following description of some enbodiments thereof, given by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a schematic plan view of a plastics bottle bbw-moulding production line according to the invention; Fig. 2 is a detail perspective view of a mould portion of the production line; Fig. 3 is an enlarged detail perspective view of portion of the mould; Fig. 4 is an exploded perspective view of a blow pin assembly for the mould; Fig. 5 is a perspective view of portion of the blow pin and mould; Fig. 6 is a detail diagrammatic illustration of the mould with the blow pin shown in a raised position; 2 0 Fig. 7 is a view similar to hg. 6 with the blow pin shown in a lowered neck cutting position; and Fig. 8 is an elevational view of a plastics bottle formed by the process.

Referring to the drawings a process and apparatus for carrying out a plastics bbw moulding process for manufacturing a thin walled plastics bottle according to the invention will be described.

Referring initially to Fig. 1 a production line for the production of plastics bottles 3 0 according to the invention is shown schematically. At a mould 10 plastics bottles are prepared by a blow-moulding process which will be described in more detail later. A plurality of bottles are blown together in a row. Formed bottles are Imed onto an inclined cooling conveyor 12 on which the bottles are allowed cool in air for a preset period.

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Immediately downstream of the cooling conveyor 12 a row of bottles 14 is transferred onto a feeder 15 for delivery to a deflashing station 16. At the deflashing station 16 excess plastics material at the top and bottom of each bottle are removed.

Cleaned bottles are delivered by a conveyor 18 to a selector 20 which directs the bottles as required and as preset to either a raw bottle delivery line 22 or a bottle labelling line 24.

1 0 Referring first to the raw bottle delivery line 22 bottles are conveyed to a testing station 26 at which the neck of each bottle is sealed and air at pressure SO millibars is injected into the bottle for a period of two seconds. If there is greater than 8% drop in air pressure then the bottle is rejected into a reject bin 28.

Acceptable bottles are delivered by conveyor 30 to a packaging station 32. At the packaging station 32 a plurality of upstanding bottles are arranged in a number of rows and columns in a rectangular array 34. An envelope of plastics material is then pulled over the array 34 of bottles and sealed to fomm an envelope 36 containing the array 34 of bottles. This envelope 36 of bottles is then lifted onto a pallet 40.

Referring now to the labelling line 24, this is essentially similar to the raw bottle delivery line 22 except that a labelling station 42 is inserted between the testing station 26 and the packing station 32. At the labelling elation 42 a label band is pulled down over an exterior of the bottle, said label referring to the produce which is to be filled into the 2 5 bottle subsequently.

Referring now in particular to Figs. 2 and 3 the moulding machine 10 and cooling conveyor 12 are shown. Robot transfer amps 45 are mounted at their inner ends on a rotatable spindle 46 having an associated drive motor 47. The amps 45 are mounted directly beneath associated pairs of mould halves 48, 49 in which the bottles are tromped. Ram means (not shown) is provided in conventional fashion for moving the rnouW halves 48, 49 together and apart during the mousing process. After forming bottles within bottle shaped recesses in the rnould 10 the mould halves 48, 49 open and the arms 45 grab a flashing tail at a bottom of each bottle and swing the bottles . : :-:. . ala. ..e ale. - 6

onlo the looming conveyor 12 when the spindle 46 is rotated by the motor 47. The bottles are released onto the cooling conveyor 12 and the arms 45 swing bade beneath the moue halves 48, 49 for engagement with the next set of bottles prepared in the mould 10. The bottles cod in air in traveling along the conveyor 12 between an inlet 43 and an outlet 44 of the conveyor 12.

Referring now in particular to Figs. 4 and 5 a blow pin assembly for each bottle forming recess in the mould 10 is shown and indicated generally by the reference numeral 50.

The assembly 50 indudes a tubular blow pin 51 connected to a pressurized air supply (not shown). A blow pin cap element 52 is mounted on the blow pin 51, a central bore 53 of the cap 52 receiving the blow pin 51. Four radial air passages 54 are provided in a bottom face 55 of the cap 52.

A cutting ring 58 engages the bottom face 55 of the cap 52 and has a central through hole 59 for reception of the blow pin 51. A circular array of spaced-apart axially extending cooling air holes 60 pass through the cutting ring 58. A knifer circular peripheral cutting edge 61 of the cutting ring 58 tomes a right angle cutting edge, that is a side 63 and a bottom face 64 of the cuffing ring 58 are substantially perpendicular.

Engaged against a bottom face of the cutting king 58 is a neck bore calibration ring 62.

The neck ring 62 sits in an associated rebate 65 at an upper end of a body element 66. The body element 66 has a central air passage 67 surrounded by a ring of cooling air holes 68 corresponding to the air holes 60 in the cutting ring 58.

2 5 A blow pin tip 70 has a stepped inner end 72 which engages and seats within a socket 73 tombed at a bottom end of the body 66. The blow pin tip 70 has a central air through passage 75 with a number of radial air outlet slots 76 for directing air laterally and upwardly within the mould during the blowing process.

Mounted on the rnould halves 48, 49 for cooperation with the brow pin 50 is an air seal and a shear steel 81. Each of these 80, 81 are generally disc shaped and are in two halves as shown in the drawing. Each overlying pair of halves 80, 81 is bolted to the top of an associated moue part 48, 49 with central openings 83, 84 in the air seal and shear steel 81 aligning with a neck opening 85 at a top of the moue part 48, 49 . : '. #. :e e' :, ' - 7 - as shown in Fig. 5.

An inside face 87 of the opening 84 in the shear steel 81 cooperates with the cuffing edge 61 of the cuffing ring 58 on the blow pin 50 for cutting the neck of the bottle from the parison material. The opening 84 in the shear steel 81 is a tapered hole having a side wad 87 which tapers outwardly from bottom to top at an angle of 15 to a central axis of the hole 84. The cuffing ring 58 on the blow pin 51 has a right angle cuffing edge 61 for engagement with said side wall 87 above the inner narrowest point of the hole 84.

In use, and referring in particular to Figs. 6 and 7, a parison 90 is extruded downwardly about the blow pin 50 between the two rnould halves 48, 49. The mould halves 48, 49 start closing inwardly together. As the moue halves 48, 49 are closing prbbwing takes place with air at a pressure in the order of 20 psi being injected through the blow 1 5 pin 50 into the parison 90. The bw pressure prebbwing air is switched on when the mould halves are about 50% closed and coming into contact with the parison. When the mould halves 48, 49 are fully closed the air seal 80 forms an airtight seal with the cap 52 on the blow pin 51, engaging an exterior of the cap 52. The pressure of air being delivered through the blow pin 50 is then increased to a main blow pressure of 2 0 approximately 100 psi to rapidly fully inflate the parison 90 thus forming a battle 91 in the mould cavity 92. After at lest 0.4 seconds, and typically at about 0.5 seconds after closure of the rnould and injection of high pressure air, the blow pin 51 is moved downwardly 15mm by means of a ram (not shown) the blow pin 51 gathering and compressing plastics material at the neck of the bottle 91 between the cutting ring 58 2 5 and the inside face 87 of the hole 84 in the shear steel 81 until the cutting edge 61 on the blow pin 50 cooperates with the face 87 on the shear steel 81 on the mould halves 48, 49 to cut through the parison material at the neck of the bottle 91 (Fig. 7). This is typically about 1mm above the bottom of the hole 84.

High pressure air is injected for about another 4 seconds for cooling the plastics material within the mould. The grooves 54 in the blow pin cap 52 allow air into the hole 83 in the air seal 80 to cool the plastics material immediately above the neck portion of the bottle so that it can be readily easily and quicidy deflashed later. The mould is then vented and an amn 45 Grips a flashing flange 93 at a bottom of each baffle, the :, cle t. ;# tat - 8 - flashing flange 93 projecting dowrnNardly from the mould. When the mould opens the arm 45 pulls the bottle away from the parison material above the neck and deposits the bottle on the cooling conveyor 12.

A fresh parison is then extruded downwardly between the open mould halves and the cycle repeated.

Fig. 8 shows a plastics home moulded by the process of the invention.

It will be appreciated that using the process of the present invention additional material is built up at the neck of the home 91. Also with the two step blowing the plastics material is partially solidified but still malleable so that it can be shaped and cut more accurately as the blow pin 30 moves downwardly. There is a dense compaction of material at the neck of the bottle to provide a smooth sealing surface.

The invention is not limited to the embodiments hereinbefore described which may be varied in both construction and detail within the scope of the appended claims.

Claims

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1. A plastics bbvrnouWing process for manufacturing a thin walled plastics container comprising a home with a neck portion, including the steps: extruding a parison of plastics material downwardly about a blow pin and between a complementary pair of spaced-apart open mould halves, closing the mould halves together, when the rnould halves are partially closed prmbbwing the parison wffl low pressure air by injecting bw pressure air through the blow pin into the parison for partially inflating the parison as the rnould closes fully, sealingly engaging the mould halves with the blow pin when the rnould is fully closed, iniecting high pressure air at full blow pressure through the blow pin into the parison within the fully closed rnould for rapidly fully inflating the parison against an inner side wall of the rnould to form the bottle in the mould, after blowing the parison at full blow pressure for a preset period after closing the rnould advancing the blow pin into the mould a preset distance for gathering and compressing plastics material at a neck of the bottle, and when the blow pin is fully extended into the moue a cutting ring on the blow pin cooperating with a complementary shear steel on the rnould for cutting the neck of the bottle from the parison 3 0 material, opening the rnould, removing the bottle from the rnould, ë:. ë.e :e eee.

- 10 - cooling the bottle, de-flashing the bottle, and delivering the bottle for further processing and/or packaging.

2. A process as claimed in claim 1 wherein the time delay between closing the moue and advancing the blow pin into the moue within the range 0.4 to 0.5 1 0 seconds.

3. A process as claimed in claim 1 or claim 2 including the step of moving the blow pin through a stroke of 15mm.

4. A process as claimed in any preceding claim wherein the shear steel on the moue defines a tapered hole having a side wall which tapers outwardly at an angle of 15 to a central axis of the hole and the cuffing ring on the blow pin has a right angle cutting edge for engagement with said side wall above the inner narrowest part of the hole.

5. A process as claimed in any preceding claim including engaging an exterior of a cylindrical cap part of the blow pin with an air seal formed in two associated seal parts mounted on the mould halves said seal parts engaging and faming an air seal with the cap part, the cap part slidably engaging the air seal parts 2 5 for moving between a raised position and a lowered position.

6. A process as claimed in any preceding claim which indudes starting injecting the low pressure prebbw air into the pafison as the closing mould halves are coming into contact with the pardon.

7. A process as claimed in any preceding claim wherein the full blow pressure air is at about 1 OOpsi (6.89 bar).

8. A process as claimed in any preceding claim wherein the preblow air pressure e e e e e e ese e e e e e e e e e e e e e see ace e e ece e e e e e e see ece e - 11 is in the range 225psi (1.38 bar- 1.72 bar).

9. A process as claimed in any preceding claim including the step of pressure testing the bottles downstream of the de-flashing station.

10. A process as claimed in any preceding claim including aligning a set of upstanding bottles in a number of rows and columns, pulling an outer plastics envelope about the set of bottles and sealing the envelope encasing the set of bottles.

11. A plastics bbw-rnoulding process substantially as hereinbefore described wffl reference to the accompanying drawings.

12. Plastics containers whenever produced by the process as claimed in any preceding claim.