WO2010071645A1

WO2010071645A1 - Vertical blow molding machine with parison carrier

Info

Publication number: WO2010071645A1
Application number: PCT/US2008/087313
Authority: WO
Inventors: John M. Mathy, Jr.
Original assignee: Graham Engineering Corporation
Priority date: 2008-12-18
Filing date: 2008-12-18
Publication date: 2010-06-24

Abstract

A vertical rotary blow molding machine for blow molding bottles using single or multi-cavity molds and parison carriers in gaps between molds. The amount of plastic used to mold the bottles is reduced by carrying the parison across the gaps.

Description

VERTICAL BLOW MOLDING MACHINE WITH PARISON CARRIER

The invention is an improved vertical rotary blow- molding machine for efficiently blow molding bottles using single or multi-cavity molds. The cost of blow molding the bottles is reduced by reducing the amount of plastic required and by simplifying the equipment used to extrude parisons for the machine.

The amount of plastic used to mold the bottles is reduced by reducing in mold and between mold flash. This is achieved by providing a gap between adjacent molds and a parison carrier in each gap. The wheel with attached molds and carriers rotates continuously during blow- molding. The parison carriers move newly cut parison ends across the gaps to reduce flash.

An open parison carrier is positioned on the upstream end of each mold when the open mold is rotated over a parison to close and capture the parison. The mold and parison carrier close together on the parison. The closed mold captures a portion of the parison. The parison is separated between the mold and the carrier. At the same time, the carrier captures the newly formed end of the parison. The carrier then moves upstream across the gap to carry the parison end from the newly closed mold to the next open mold as the next open mold is rotated over the supported parison. The next mold and an open parison carrier on the upstream side of the next mold then close on the parison and the cycle is repeated.

The parison is extruded at a velocity slower than the velocity at which the molds move around the wheel . Use of parison carriers reduces flash extending between adjacent mold cavities. The length of the parison extruded for each mold equals the length of the mold plus the width of one parison carrier. The parison does not extend between adjacent molds. In mold flash is reduced by positioning the mold cavities close to the mold ends.

In blow-molding machines according to the invention using multi-cavity molds, all parisons are extruded at the same rate so that identical parison portions having the same lengths are captured in each mold. A single extruder flows resin to plural, identical flow heads. A single parison controller may be used for wheels with multi cavity molds. There is no need to specially program extrusion heads to extrude parisons at different rates. This simplifies extrusion equipment, reduces cost, and reduces set up time.

Reduction in flash means less material is needed to make the bottles . Reduced material reduces the energy required for bottle manufacture. In the Drawings

Figure 1 is a representational view of an existing technology single mold vertical rotary blow-molding machine;

Figure 2 is a view like Figure 1, illustrating a vertical rotary blow-molding machine according to the present invention;

Figures 3-6 are views similar to Figure 2, showing increment positions of the rotating wheel during parison extrusion and capture;

Figure 7 is a view similar to Figure 1, illustrating an existing technology two mold vertical rotary blow- molding machine;

Figure 8 is a view like Figure 7, illustrating the present invention in a two mold vertical rotary blow- molding machine;

Figure 9 is a view like Figure 8 illustrating the present invention in a quad or four-mold vertical rotary blow-molding machine;

Figure 10 is a perspective view, partially broken away, of the parison extrusion station in the machine shown in Figure 9;

Figure 11 is a side view of the machine shown in Figure 10;

Figures 12 and 13 are views taken generally in the directions of arrows 12 and 13 shown in Figure 11;

Figure 14 is a perspective view of a parison carrier;

Figure 15 is an enlarged portion of Figure 12 illustrating a parison knife on the mold;

Figure 16 is like Figure 15 but illustrates a parison knife on the parison carrier;

Figure 17 is a partial view of two adjacent molds on the wheel of another rotary blow molding machine utilizing parison carriers which translate across the gaps between the molds;

Figure 18 is a view taken along line 18-18 of Figure 17, illustrating a parison carrier closed; and Figure 19 is a view similar to Figure 18 showing the parison carrier open. Description of the Preferred Embodiments

The existing technology single mold blow-molding machine 10 shown in Figure 1 uses eighteen closely spaced trapezoidal molds 12 with single cavities located on pitch circle 14. The wheel is continuously rotated in the direction of arrow 8. Parison 18 is continuously extruded from flow head 16 on pitch circle 14 at the circumferential speed of the mold cavities so that the total length of parison extruded during one revolution of the wheel is equal to the circumferential length of the pitch circle. Parison programmer 20 varies the thickness of the parison as desired in order to obtain desired bottle weight.

As illustrated in Figure 1, the parison length 22 for each mold is equal to the chord length of the mold at mold cavity 24. The parison length 22 is considerably longer than the length of mold cavity 24 so that a substantial portion of the captured parison is waste, forms flash and must be trimmed away and disposed of.

Figure 2 illustrates a single cavity vertical rotary blow-molding machine 30 according to invention, including eighteen circumferentially spaced rectangular molds 32 and eighteen parison carriers 34. Parison knives are mounted on the upstream ends of the molds and sever captured parisons when the molds close. Each parison carrier is located in a V-shaped gap 36 with angled sides between two adjacent molds and includes a clamp for engaging the parison. Carriers 34 may be like the parison carriers 106 illustrated in Figures 10-14 of the drawings, and described herein. The parison carriers 36 are rotatably mounted on the wheel at pivot connections 38 and are rotated back and forth across gaps 36 in the directions of arrows 44 and 48 by drives as the wheel rotates. The parison is extruded at a rate slower than the rotational speed of the molds 32.

The number of molds spaced around the wheel is not critical to the invention. The wheel may have a desired number of molds which may be greater than or less than eighteen.

Figure 3 illustrates the position of the wheel of machine 30 after rotating mold 32' has closed on and captured parison 40 extruded up from flow head 42. The parison lead end is clamped in closed carrier 34' positioned on the downstream or lead end of mold 32'. Parison carrier 34' holds the parison vertically between the open halves of mold 32' during vertical growth of the parison, rotation of open mold 32' over the parison and closure of the mold on the parison. When mold 32' closed the knife on the mold cut the parison at carrier 34' '. At this time parison carrier 34'' was against the upstream or trailing end of mold 32' as shown in Figure 2. The carrier closed on the parison to hold or clamp the new lead end of the cut parison when the mold closed.

After capture of the parison in closed mold 32 ' , cutting of the parison and capture of the new end of the parison by carrier 34'', the closed parison carrier 34'' continues to rotate with the rotating wheel and is also rotated upstream around pivot 38 in the direction of arrow 44 as illustrated in Figures 2-6. As the mold and the carrier continue to rotate with the wheel, carrier 34'' is rotated away from mold 32', across gap 36 and against mold 32''.

Parison carrier 34'' moves or carries the clamped end of the parison essentially vertically above extrusion head 42 at the extrusion rate, a rate which is slower than the circumferential rate of rotation of mold 32' around the wheel . This movement provides separation between the carrier 34'' and mold 32' as the carrier moves across the gap 36 and against open mold 32''. The clamped end of the parison is moved from mold 32' to mold 32'' to reduce flash between the molds. The ends of the bottle molding cavities in the molds are located adjacent the ends of the molds to reduce in-mold flash.

Continued rotation of the wheel moves open mold 32'' past head 42 so that the mold catches up with closed parison carrier 34' '. The mold 32' ' then closes to capture and cut the parison as described. At the same time, open parison carrier 34' ' ' on the trailing end of mold 32'' closes on and captures the new cut end of the parison.

Following closing of mold 32'', cutting of the parison and capture of the new end of parison 40 by closed parison carrier 34''', mold 32'' continues rotation around the wheel and closed parison carrier 34''' moves essentially vertically above head 42 at a rate slower than the rate of movement of mold 32' ' around the wheel and moves across gap 36 to engage the leading end of mold 32'''. The described cycle is repeated for successive molds and parison carriers.

Rotation of the wheel of machine 30 moves each mold 32 continuously around the circumference of the wheel. A parison segment 46 captured in each mold 32 is blown and solidifies in the mold prior to opening of the mold and associated carrier 34 when at the bottom of the wheel for ejection of the blow-molded bottle and to position the open mold and carrier in position for rotation past head 42. Each carrier 34 is rotated back across its gap 36 before returning to the extrusion head. Rotation of the carriers across the gaps may occur at the bottom of the wheel, as shown in Figure 2.

Parison 40 is extruded at a rate slower than the rotational speed of molds 32. During each revolution of wheel 30, the total length of parison extruded is less than the circumference of the pitch circle 50 for the molds. Parison segments 46 are captured in the molds with each segment having a length equal to the length of the mold plus the width of a parison carrier 34. Between cavity flash is reduced. The amount of resin required to make the finished bottle is reduced. The amount of energy required for extruding the parison is reduced.

Use of parison carriers 34 permits the parison to be extruded in a straight line up from head 38. There is no need to extrude around the pitch circle, as required in the machine shown in Figure 1. Figure 7 illustrates an existing technology rotary blow-molding machine 52 with dual cavity molds for blow molding like bottles in identical inner and outer cavities. The molds are trapezoidal in shape. In each mold the outside parison segment length 54 is greater than the inside parison segment length 56. Inner and outer flow heads 58 and 60 extrude different length inner and outer parisons 62 and 64 for capture in inner and outer mold cavities 66 and 68. Parison 64 must be extruded at a faster rate than parison 62 is extruded because the circumference of the pitch circle for cavities 68 is longer than the circumference of the pitch circle for cavities 66. The parisons are extruded continuously. Waste tail flash extends from the ends of the cavities in adjacent molds. Separate parison programmers are required for each extrusion head 58, 60 in order to mold identical bottles having desired thickness and strength characteristics in the inner and outer molds .

The tail flash for bottles molded in outer cavities 58 is longer than the tail flash for the bottles molded in inner cavities 56 because the cavities are the same length and the circumferential distance between the outer cavities is greater than the circumferential distance between the inner cavities.

Heads 58 and 60 may be co-extrusion heads. Because different parisons must be extruded by the heads 58, 60 it is necessary to provide separate parison extruders for each layer extruded by each head. The provision of a large number of extruders is expensive and complicates construction, setup and operation of the wheel.

Figure 8 illustrates a two-mold vertical rotary blow-molding machine 70 according to the invention. Machine 70 is like machine 30 except that each rectangular mold 72 has identical inner and outer mold cavities 74 and 76 and two parison knives. The ends of the cavities are near the ends of the molds to reduce tail flash.

Parison carriers 78, similar to parison carriers 34 but with two clamps on each carrier, are located in V- shaped gaps 80 with angled sides between adjacent rectangular molds 72. The parison carriers 78 are connected to the wheel at pivots 82 for rotation across gaps 80 between the leading and trailing ends of adjacent molds 72.

The flow heads 84 and 86 continuously extrude identical parisons 88 and 90 vertically upwardly at the same speed for capture between closing molds 72 as the molds are rotated over the flow heads and the molds and parison carriers are closed on the parisons as described in connection with the operation of machine 30.

A single parison controller 92 is provided for both flow heads. This is possible because both parisons 88 and 90 are identical and are extruded at the same rate. Additionally, single extruders can provide resin to both flow heads. Parison segments captured in each mold 72 and associated parison carrier 78 have an equal length Blow molding bottles using wheel 70 reduces the flash inherent in conventional wheel 52 shown in Figure 7. In wheel 70, the inner and outer mold cavities have the same length. Inner mold cavities 74 are positioned as close together circumferentially as possible. The cavities are positioned close to the ends of the molds to reduce in-mold flash. In the existing technology machine, with continuous parison extrusion, the greater spacing between outer cavities results in more flash extending between the outer cavities than in the inner cavities. This type of flash is greatly reduced in wheel 70.

Machine 70 operates similarly to machine 30 with the exception that two parisons 88 and 90 are extruded up between successive open two-cavity molds 72. The molds close and capture the parison segments as the parisons are cut and new ends of the parisons are gripped by the closed parison clamps. The carrier then rotates about pivot 82 to carry the parison ends across gap 80 as the wheel rotates and as the parisons grow vertically above heads 84 and 86. The next open upstream mold 72 and open clamps on the carrier on the next mold are moved over the parisons, close on the parisons to capture parison segments in the mold, sever the parisons and clamp the new ends of the parisons. The closed parison carrier then moves upwardly above the extruders as it moves across the gap to support the growing parisons and carry the parison ends across the gap. The wheel moves the closed mold away from the carrier and the cycle is repeated.

Figure 9 illustrates vertical rotary blow molding machine 100, like machines 30 and 70, but with eighteen four-cavity molds 102. Molds 102 are rectangular. Each mold includes four identical mold cavities 104 spaced radially outwardly along the mold. Parison carriers 106, similar to carriers 34 and 78, are mounted on the wheel at pivots 108 and rotate between the leading and trailing ends of adjacent molds in V-shaped gaps 110 with angled sides between the molds. Each carrier has a parison clamp for each parison.

Four like flow heads 112 are spaced radially along the pitch circles for the mold cavities. A single parison controller 118 controls all heads 112. Single extruders may provide individual types of resin flowed to heads 112, which may be co-extrusion heads.

The four heads 112 extrude four like parisons 114 upwardly along the pitch circles of the four mold cavities at the same rate, which is slower than the rotational speeds of the molds around the pitch circles. The molds close on and cut the parisons and the parison carriers capture the ends of the parisons and move across the gaps 110 between adjacent molds as previously described. The captured parison sections have an identical lengths 116.

In rotary blow molding machines with molds having a number of radially spaced cavities of the same length there are wide circumferential spaces between the outermost cavities in adjacent molds. These wide spaces prevent the use of multi-cavity molds in conventional rotary blow molding machines because of the large amount of flash extending between adjacent bottles molded in the outermost cavities and resultant waste. The present invention eliminates flash between adjacent molds and permits efficient and rapid blow molding of bottles using multi-cavity molds, and permits use of simplified extrusion equipment.

Figures 10-15 illustrate components of the rotary blow-molding machine 100 of Figure 9. The machine includes two spaced radial wheel plates 120 mounted on a horizontal main shaft (not illustrated) . A drive mechanism (not illustrated) continuously rotates the shaft and plates in the direction of arrow 121. The machine 100 operates similarly to machines 30 and 70.

Four cavity molds 102 are spaced around the wheel defined by plates 120. Each mold includes two mold halves 122. The mold halves are mounted on bearings moveable along tracks 124 mounted on the plates and extending parallel to the axis of rotation of the wheel. Mold clamp drives for moving the mold halves along the tracks between opened and closed positions are not illustrated. When closed, parison knives 137 mounted on one mold half 122 sever the parisons, as previously described. Knives 137 are shown in Figure 15.

Each parison carrier 106 includes a rod 126 extending between plates 120 and rotatably mounted in bearings on the plates. Arms 128 are mounted on the ends of rods 126 extending outwardly from one plate 120. Rotary cam followers 130 extend upwardly from the free ends of arms 128. During rotation of the wheel, cam followers 130 engage a fixed cam 132 mounted on the frame of the machine to rotate or pivot the parison carriers 106 in the direction of arrow 134 shown in Figure 11 and rotate the carriers from downstream molds, across tapered or V-shaped gaps 110 and to upstream molds. A spring or pressure cylinder may hold the followers 130 against cams 132 during engagement as the followers move along the cams as shown in Figure 11. Detents, latches or cylinders may hold the carriers against either adjacent mold.

Each parison carrier 106 includes a parison clamp having a pair of parison clamp members 136 slidably mounted on a track 138 extending along a rod 126. Pressure cylinders 140 are mounted between brackets 142 on the rod 126 and the adjacent clamp members 136 to move the members between open and closed positions to engage and release parisons extruded between the clamp members.

Clamp members 136 are located in gaps 110. Rotation of rods 126 rotates the clamp members between the upstream and downstream ends of adjacent molds 102. Grooves 144 are provided in the clamp faces of members 136 to grip and securely hold the severed parison ends when the cylinders 140 are extended. See Figure 14.

The parison carriers rotate across gaps 110 from an upstream mold 102 to a downstream mold 102 when the molds are at the bottom of the wheel and the molds are opened to eject the blow molded bottles. This rotation of the parison carriers may be made by engagement between cam followers 130 and a second cam, similar to cam 132, which rotates the clamp members about rod 126 in the direction of arrow 146 shown in Figure 9. The parison carriers preferably move from the closed, clamped position to the open position when molds 102 open to eject the bottles.

In wheel 100, the parison carrier is moved between molds by a mechanical drive. A pressure cylinder drive may be used if desired. In wheel 100, the parison clamps are open and closed by pressure cylinder drives. Mechanical drives may be used if desired.

In blow molding machines 30, 70 and 100, the parison knives are mounted on the upstream ends of mold halves and are extended and retracted across the meeting face of the mold with closing and opening of the molds. In rotary blow molding machine 149 illustrated in Figure 16, parison knives 139 are mounted on the downstream sides of one clamp member and are moveable with the clamp members to cut the captured portions of the parisons in the mold from the new parison ends captured by the clamps. Machine 149 is like machine 100 with the exception of knives 139. Machine 149 operates like machine 100.

If desired, the parison knife may be mounted on a separate, thin drive located at the upstream end of the molds, between the molds and the parison clamps. In this case, each parison knife would have a separate drive to extend the knife to sever a parison captured by the mold and the mold clamp and to withdraw the knife. The parison carriers of wheels of rotary blow molding machine 100 are rotated across gaps between adjacent molds on the wheel. Rotary movement of the parison carriers move the clamped parison along arcs and maintains the ends of the parisons in close alignment above the flow heads so that the parisons are in proper alignment with the molds during mold closing and parison capture .

However, it is not necessary for the parison carriers to be rotated across gaps between adjacent molds. In some applications, particularly in wheels with single cavity molds, the parison carriers may be translated across gaps between adjacent molds.

Figure 17 illustrates two adjacent trapezoidal molds 150 mounted on the wheel of vertical rotary blow molding machine 148 with rectangular gaps 152 with parallel sides between adjacent molds. The gaps are defined by parallel mold ends 154 and 156. A parison carrier 158 is located in each gap 152.

Each carrier 158 includes a pair of clamp members 160 mounted on the piston rods of clamp pressure cylinders 162. The clamp members may have grooves like grooves 144 on members 136. The pressure cylinders 162 are connected to the end of the piston rod of a shift pressure cylinder 164 by frame 166. Extension and retraction of cylinder 164 translates the parison carrier back and forth across gap 152 in the directions of arrow 166, between mold ends 154 and 156. Extension and retraction of cylinders 162 move the parison clamp members 60 between a closed, parison clamp position shown in Figure 16 and an open position free of the parison shown in Figure 17. As shown in Figure 16, the closed parison clamps engage and hold collapsed parison 168. The pressure cylinder 164 and frame 166 are suitably mounted on the rotary wheel to permit translation of the parison carriers 158 back and forth across gap 152. Parison knives (not illustrated) may be mounted on the moulds, on the carriers or between the molds and carriers, as previously described. In wheel 148, pressure cylinder drives translate the carrier across the gaps. Pressure cylinder drives open and closes the clamp members 160. Mechanical drives may be used for both purposes, if desired.

Wheel 148 with parison carriers 158 operates as previously described. The molds on rotary wheels using translating parison carriers are preferably trapezoidal in shape to facilitate mold ends making flush engagement with the parison carriers. In order to reduce in-mold flash, molds 150 preferably have single bottle cavities.

Claims

1. A rotary blow molding machine for reducing flash, the machine including, a rotary wheel, a plurality of molds spaced around the wheel, a flow head positioned to extrude a parison between open molds on the wheel for capture by the molds, said molds including a downstream mold and an upstream mold, a gap between the downstream and upstream molds, a parison carrier in the gap, the parison carrier having a first location on one side of the gap adjacent the downstream mold and a second location on an opposite side of the gap adjacent the upstream mold, a parison carrier drive including a drive member and a drive connection between the drive member and the parison carrier so that the parison carrier drive moves the parison carrier from the first position across the gap to the second position, and a parison knife for severing the parison, the knife between the mold and the parison carrier, wherein when the parison carrier is in the first location closing of downstream mold captures a portion of the parison in the mold for blow molding, the parison knife severs the parison to create a new end of the parison, and the parison carrier drive moves the parison carrier to the second location to carry the new end of the parison across the gap.

2. The rotary blow molding machine as in Claim 1, wherein said wheel rotates around a horizontal axis.

3. The rotary blow molding machine as in Claim 1, wherein the gap has angled sides.

4. The rotary blow molding machine as in Claim 3 , wherein the parison carrier drive rotates the parison carrier across the gap.

5. The rotary blow molding machine as in Claim 1, wherein the gap has parallel sides.

6. The rotary blow molding machine as in Claim 5, wherein the parison carrier drive translates the parison carrier across the gap.

7. The rotary blow molding machine as in Claim 1, wherein the parison carrier includes a first parison clamp .

8. The rotary blow molding machine as in Claim 7, including a plurality of flow heads, each mold including a plurality of cavities, and the parison carrier includes a second parison clamp, each parison clamp associated with a parison extruded from one flow head and with one cavity in each mold.

9. The rotary blow molding machine as in Claim 8, including an extruder for flowing resin to each flow head.

10. The rotary blow molding machine as in Claim 1, including a plurality of gaps, each gap between two adjacent molds, a parison carrier in each gap, and a parison carrier drive for each parison carrier.

11. The rotary blow molding machine as in Claim 1, wherein the parison carrier includes two clamp members and a clamp member drive to open and close the clamp members, wherein said members close to capture the parison therebetween during movement of the parison carrier across the gap.

12. The rotary blow molding machine as in Claim 11, wherein the clamp member drive is mechanical .

13. The rotary blow molding machine as in Claim 11, wherein the clamp member drive includes a pressure cylinder .

14. The rotary blow molding machine as in Claim 1, wherein the parison carrier drive includes cam and a cam follower .

15. The rotary blow molding machine as in claim 1 wherein the parison knife is mounted on the downstream mold.

16. The rotary blow molding machine as in claim 1 wherein the parison knife is mounted on the parison carrier .

17. The method of reducing flash during blow molding containers using a rotary blow molding machine having a rotary wheel, a plurality of molds spaced around the rotary wheel, gaps between the molds and a flow head for extruding a parison for capture by the molds, comprising the steps of: a) extruding a parison between an open downstream mold and closing the downstream mold to capture the parison; b) separating the parison to form a segment of the parison in the mold and a new parison end; c) moving the new parison end from the downstream mold across the gap to an adjacent open upstream mold; and d) closing the adjacent upstream mold on the parison.

18. The method of Claim 17, including the step of: e) holding the new end of the parison in a carrier and moving the carrier and the new end of the parison across the gap.

19. The method of Claim 17, including the step of: f) clamping the new end of the parison in a clamp and moving the clamp across the gap to the upstream mold.

20. The method of Claim 17, including the step of: g) rotating the new end of the parison across the gap.

21. The method of Claim 17, including the step of: h) translating the new end of the parison across the gap .

22. The method of claim 17, including the step of: i) cutting the parison.