Sealing blow molded bottles

Abstract: Apparatus for sealing closed an integral neck (26) of a previously blow molded bottle (10) comprises an upper neck clamp tooling (62) and a lower neck clamp tooling (60) for engaging and supporting each end of the neck (26), and a heater (80) for raising the temperature of the neck (26) between the clamps (62,60) to permit molding and sealing by a neck sealing tool (64), having recesses (110,112,114) which define at least one cavity when closed. The clamps (62,60) and the neck sealing tool (64) each have drive means for moving them between open and closed positions, and the heater has drive means for moving it towards and away from the neck (26).

Description: The invention relates to apparatus and methods for sealing closed the open necks of blow molded plastic bottles and forming integral breakaway tops. One station blow molding, filling and sealing of plastic bottles is conventionally performed by blow molding a bottle in a closed mold using an axial blow pin and flowing liquid directly into the molded bottle while confined within the mold. Following filling, either a stopper is inserted into the open neck or supplementary tooling adjacent the neck is actuated to engage, close and seal the neck while forming a breakaway top. The mold halves and tooling are then opened and the filled, sealed bottle is ejected. Such process and apparatus are known from US-A-3,765,144. Blow molding, filling and sealing bottles within a single mold cavity is a relatively slow and expensive procedure, particularly when compared to the rates at which bottles may be molded using modern multi-station blow molding machines. One station molding, filling and sealing technology does not meet modern production requirements. The disclosed invention is an apparatus and method for rapidly sealing previously molded and filled plastic bottles. The apparatus seals the hollow neck of a preformed bottle and comprises neck sealing tooling including a mold surrounding the neck and defining at least one cavity when closed, and a first drive means for moving the mold between open and closed positions; lower neck clamp tooling located below the neck sealing tooling and including a lower clamp for engaging and supporting the bottom of the neck, and a second drive for moving the lower clamp between opened and closed positions; upper neck clamp tooling located above the neck sealing tooling and including an upper clamp for engaging and supporting the top of the neck and a third drive for moving the upper clamp means between opened and closed positions; and a heater for raising the temperature of a bottle neck held between the upper and lower clamps sufficiently high to permit molding and sealing by the neck sealing tooling, and a fourth drive for moving the heater between a position adjacent the neck and a position remote from the neck. In the accompanying drawings: Figure 1 is a side view, partially broken away, of a filled bottle with an open, unsealed neck; Figure 2 is a sectional view through the top of the bottle when sealed; Figure 3 is a side view of the seal of Figure 2; Figure 4 is a view taken along line 4--4 of Figure 3; Figure 5 is a top view of an apparatus for sealing the bottle of Figure 1; and Figures 6, 7 and 8 are partially broken away sectional views illustrating sealing the bottle. Bottles 10 are sealed by apparatus 12 shown in Figure 5. The apparatus may be part of a continuous manufacturing line including a blow molding machine 14 for blowing the bottles, a trimming machine 16 for trimming the bottles and a filling machine 18 for filling the bottles with a liquid. These machines are joined by suitable bottle conveyors. Conveyor 20 moves the filled upright bottles 10 from the filling machine 18 to the sealing apparatus 12. Figure 1 shows a filled bottle 10 before sealing. The bottle includes a generally cylindrical body 22, a conical shoulder 24 above the body and a hollow cylindrical hollow long neck 26 extending upwardly above the shoulder to a mouth 28 located at the top of the bottle. A cylindrical clamp groove 30 extends around the bottle at the top of the shoulder 24. The lower wall of the groove is located at the top of the shoulder and the upper wall of the groove is located on lower ring 32 at the bottom of neck 26. Upper ring 34 extends outwardly from the top of the neck 26. Each ring includes a narrow cylindrical portion 36, 38 and a narrow conical flange portion 40, 42 extending radially outwardly from the smaller diameter neck 26. Portions 40 and 42 also extend axially away from neck 26. Filling machine 18 flows liquid into bottle 10 through mouth 28 and neck 26 to fill the bottle to a level 44 slightly below the top of shoulder 24. The sealing apparatus 12 includes a continuously rotating table supporting thirty-six circumferentially arranged sealing stations 48. A turntable drive rotates the sealing stations 48 counterclockwise. Each station carries like heating and sealing tooling 46 as shown in Figure 5-8. Conveyor 20 delivers a filled bottle 10 to each work station 48 as the station passes a loading position 50. A suitable transfer mechanism picks up the lead bottle from the conveyor and places it on the work station with the bottom of the bottle in a support 52 on the station. The support assures initial location of the bottle in the station. Following completion of the sealing operation the turntable drive moves the work station carrying the sealed bottle to a discharge position 54 where a transfer mechanism picks up the sealed bottle and places it on discharge conveyor 56 which carries the bottle away from the apparatus. Each sealing station 48 includes a base plate 58 carrying support 52 and tooling 46 for heating and sealing the bottle neck. This tooling includes lower neck clamp tooling 60 located adjacent the lower end of the neck 26, upper neck clamp tooling 62 located adjacent the top of the neck, sealing tooling 64 located between the upper and the lower clamp neck tooling and adjacent the cylindrical portion of the neck and a neck heater 66 extending through part of the upper neck clamp tooling 62. The lower neck clamp tooling 60 includes a pair of opposed like jaws 68 each having a semi-circular recess 70 having a shape conforming to the exterior surface of the bottle groove 30 and lower ring 32. Tooling 60 includes a drive for moving the jaws 68 between an open position shown in Figure 6 where the jaws are remote from the bottle and a closed position shown in Figures 7 and 8 where the jaws are moved into engagement with the bottle and orient and support the bottle in a desired proper location for completion of the sealing operation. The upper neck clamp tooling includes a pair of exterior clamp jaws 72 having semi-circular recesses 74 at the lower ends thereof conforming to the exterior shape of the narrow conical flange 42 at the top of neck 26. Tooling 62 includes a drive for moving the clamp jaws 72 between an open position shown in Figure 6 and a closed clamp position shown in Figures 7 and 8. In the closed clamp position the semi-circular recesses 74 engage the exterior surface of flange 42 at the top of the neck. The upper neck clamp tooling 62 also includes a cylindrical interior clamp 76 having a beveled lower end 78 conforming in shape to the interior surface of the upper flange portion 42 of neck 26. The cylinder clamp 76 is located co-axially with a bottle 10 held in support 52 and is movable by a suitable drive between a lower clamp position shown in Figures 6, 7 and 8 and an elevated position above and free of the bottle. Neck heater 66 includes a cylindrical electric quartz heater 80 mounted on the end of a support rod 82 extending through a pressure seal opening in the top of the cylinder clamp 76. The cylinder and rod are located axially with respect to the cylinder clamp 76 and bottle 10. Neck heater 66 includes a drive for moving the heater and rod axially between an extended position in which the heater 80 is located within neck 26 as shown in Figure 6 and a retracted position in which the heater 80 is withdrawn above the neck and free of the bottle. A source of low pressure support air 84 is connected to the interior 86 of cylindrical clamp 76 through valve 88 and port 90 located in the upper wall of the clamp. Bottle 10 is formed from a thermoplastic resin, preferably through a parison blow molding operation, although the bottle can be formed by blow molding using an injection molded preform. The bottle may be made from low density polyethylene, high density polyethylene, polyvinyl chloride or other suitable resin. Multi-layer bottles may be used. The thickness of the neck may be 0.020 to 0.040 inch. During sealing of the bottle by apparatus 12 the open cylindrical neck 26 is closed and formed to the shape shown in Figures 2, 3 and 4. The sealed bottle includes a major cylindrical dome 92 located above conical portion 40 and a minor cylindrical dome 94 above and coaxial with dome 92. The interiors of domes 92 and 94 are connected at mouth 96. A flat, hollow U-shaped handle 98 extends across and is joined to both domes 92 and 94. The plastic joint 100 between the handle and the dome 92 is relatively weak while the plastic joint 102 between the handle and the minor dome 94 is relatively strong to permit opening of the sealed bottle 10 by twisting handle 98 and breaking the handle and the minor dome 94 away from the major dome and opening mouth 96 for discharge of the liquid sealed in the bottle. The handle and minor dome form a top which is broken away to open the bottle. When the bottle is sealed the plastic at the top of neck 26 forms waste 104 connected to handle 98 by flash 106. The waste is easily broken away at the flash. The neck sealing tooling 64 includes a pair of like mold halves 108 each having recesses 110, 112 and 114 for molding the neck 26 to form major cylindrical dome 92, the minor cylindrical dome 94 and break away handle 98 when the mold halves are closed on the heated neck. The meeting faces in the mold halves between the recesses are shaped to form joints 100 and 102 and 106. Vacuum manifolds 116 in the mold halves are communicated to the recesses 110, 112 and 114 by small diameter vacuum lines 118. Manifolds 116 are connected to a vacuum source (not illustrated). The operation of sealing apparatus will now be described by following the path of one sealing station 48 from the loading position 50 around the turntable and back to the loading position. As station 48 is moved past loading position 50 jaws 68, jaws 72 and mold halves 108 are on the open position shown in Figure 6. The cylindrical clamp 76 is withdrawn directly above the bottle support a distance greater than the height of bottle 10 and rod 82 is vertically withdrawn so that the bottom of the heater is further away from the support than the height of the bottle 10. With the tooling in the described position the transfer mechanism positions the lead bottle 10 on conveyor 20 in the recess of bottle support 52 with neck 26 located between the open jaws 68 and 72 and open mold halves 108. As the station and bottle are rotated through angle 120 the jaws 68 are moved together, close on the bottom of the neck and extend into clamp groove 30 and around lower ring 32 to hold the bottle in proper orientation for the subsequent sealing operation. Jaws 68 also form a pressure seal with the neck. Clamp jaws 72 are moved from the position of Figure 6 to that of Figure 8 to engage the outer surface of conical flange 42 and cylindrical clamp 76 is lowered to engage the inner surface of flange 42 so that the top of the neck is held in place between the jaws and clamp and supported. The clamp 76 forms a seal enclosing the space 86 inside the clamp cylinder and neck. With the neck clamped at both ends rod 82 is lowered to position the quartz heater 80 within the supported neck 26 as shown in Figure 6. Following insertion of the heater the tooling is maintained as described during movement of the work station through arc 122. Radiant quartz heater 80 is preferably tuned to emit infrared radiation in the absorption band of the plastic resin forming neck 26 and thereby to increase the rate at which the emitted energy heats the supported neck. During heating of the neck valve 88 is actuated to connect the low pressure air source 84 to the interior space 86 inside the clamp 76 and neck 26 and above the liquid in the bottle. The positive pressure of the air in this space prevents the softened neck plastic from sagging inwardly and undesirably contacting the heater 80. The relatively cool top of the neck is maintained clamped between jaws 72 and clamp 76 during heating in order to prevent vertical collapse of the neck as it is heated and softened. At the end of heating cycle as measured by arc 122 the neck has been heated to a temperature sufficiently high to permit molding to seal the bottle and form the top structure of the finished bottle. The amount of positive pressure within the neck during heating is dependent upon the properties of the plastic resin in the neck and the temperature to which the plastic is heated for sealing and may vary from one- half pounds per square inch to as much as two pounds per square inch. In most applications a pressure of one pound per square inch is sufficient to prevent inward sagging of the heated neck. The positive pressure maintained in the neck is not sufficient to blow the neck outwardly into the mold halves 108. Following heating of the neck the station rotates through arc 124 and the rod 82 is withdrawn to raise heater 80 above the supported neck 26. Figure 7 illustrates rod 82 in the withdrawn position. Following withdrawal of the heater the mold halves 108 are closed on the heated and softened neck 26 as station 48 rotates through arc 126. At this time the vacuum manifolds 116 are connected to a vacuum source. The lands at the top of recesses 114 form a seal with the neck plastic and the bottoms of the mold halves form a seal with clamp jaws 68 so that withdrawal of the confined air within the recesses 110, 112 and 114 through lines 118 and manifolds 116 reduces the pressure in the recesses and draws the softened plastic into the recesses to form a seal closing the top of the bottle and forming the domes 92 and 94, handle 98, joints 100 and 102 and waste 104 above the handle. The molded plastic resin cools and sets as the station continues to rotate through relatively large arc 128. The molds halves 108, and jaws 68 and 72 open as the station is rotated through relatively small arc 128. At the same time cylinder 76 is raised above the bottle thereby releasing the waste plastic 104. The sealed bottle 10 rests freely on the support 52. Rotation of the turntable moves the station 48 and sealed bottle to the discharge station 54 where a discharge transfer device picks up the bottle and places it on discharge conveyor 56. Continued rotation of the turntable brings the sealing station back to the loading position 50 for receipt of a further filled bottle 10 and initiation of another sealing cycle. Sealing apparatus 12 uses a cylindrical quartz heater to heat and soften the plastic in the bottle neck. Alternatively, it is contemplated that the neck may be heated and softened using an external heater which essentially surrounds the supported neck and radiates energy into the neck. In some cases an external heater and a rod heater may be used together where relatively high energies are required to heat and soften the neck resin. Apparatus 12 as described is used to seal a bottle filled with liquid. The apparatus 12 may also be used to seal empty bottles as required. For instance, it may be desirable to seal empty blow molded bottles where the bottles are stored for a period of time and must be sealed closed in order to maintain their shape prior to filling. Apparatus 12 includes a number of stations 48 which move around a continuous circular path. It is contemplated that the stations may move around paths of different geometries. For instance, stations may move along a linear path extending between the loading and discharge stations. After discharge the sealed bottle the station would return rapidly to the upstream loading station. Other shaped paths may be used as required.

Claims: Apparatus for sealing the hollow neck of a preformed plastic bottle, the apparatus comprising a. neck sealing tooling (64) including a mold surrounding the neck and defining at least one cavity when closed, and a first drive for moving the mold between open and closed positions; b. lower neck clamp tooling (60) located below the neck sealing tooling and including a lower clamp for engaging and supporting the bottom of the neck, and a second drive for moving the lower clamp between opened and closed positions; c. upper neck clamp tooling (62) located above the neck sealing tooling and including an upper clamp for engaging and supporting the top of the neck and a third drive for moving the upper clamp between opened and closed positions; and d. a heater (80) for raising the temperature of a bottle neck held between the upper and lower clamps sufficiently high to permit molding and sealing by the neck sealing tooling, and a fourth drive for moving the heater between a position adjacent the neck and a position remote from the neck. Apparatus as in claim 1 including a closing member (76) engagable with the top of the neck for closing the interior of the neck, a source of pressure (84), a port (90) opening into the interior of the neck and a pressurisation line connecting the source of pressure and the port. Apparatus as in claim 2 wherein the pressurisation from the source of pressure has a pressure sufficient to prevent inward sag of the middle of the neck when heated. Apparatus as in claim 2 or 3 wherein the closing member extends inside the neck. Apparatus as in claim 2, 3 or 4 wherein the closing member includes a circular end (78) engagable with an interior surface of the neck and the port extends through the member. Apparatus as in claim 5 including a rod (82) extending through the interior of the closing member, said heater (80) being attached to the end of the rod adjacent the neck and the fourth drive is attached to the rod. Apparatus as in claim 1, 2, 3, 4 or 5 wherein said heater is located within the interior of the neck. The method of sealing closed the neck (26) of a preformed plastic bottle (10) having an elongate neck including the steps of: a. securing the top and the bottom of the neck in clamps to support the middle of the neck when heated; b. heating the middle of the secured neck to a molding temperature; c. molding the heated neck to form a seal extending across the neck and closing the interior of the bottle; d. cooling the molded neck; and e. releasing the clamps to free the top and bottom of the cooled and sealed neck. The method of claim 8 including the step of increasing the pressure within the interior of the neck during heating to prevent inward deformation of the heated neck. The method of claim 8 or 9 including the steps of inserting a heater into the neck to heat the middle of the neck and removing the heater after heating and prior to molding.

Inventors: DUNDAS DENNIS L, DUNDAS, DENNIS L.
Applicants: GRAHAM ENG CORP, GRAHAM ENGINEERING CORPORATION
Application year: 1991
Main classification: B29C49
IPC codes: B29C49, B29C65, B29L22, B65B51, B29C57