APPARATUS AND METHOD FOR ECONOMICALLY PRODUCING BLOWMOLDED CONTAINERS HAVING OPEN NECKS ON OPPOSING FACES THEREOF

Abstract: An apparatus is provided for producing a blow-molded disposable plastic container that has open necks on two opposing faces. Two blowpin assemblies are used with one assembly being integral with the mold. In this manner, the mold may be inserted directly into conventional blow-­ molding machinery without significantly increasing align­ ment problems.

Description: The invention relates to an apparatus and a method for molding containers such as disposable containers for containing syrups and other liquids, which containers have open necks on opposing faces thereof. For many years it has been customary to utilize plastic disposable containers for storing and dispensing a wide variety of liquid materials, particularly those that are consumable. These liquids range from intravenously dispensed fluids to beverages, such as milk, to syrups such as those utilized for making sundaes and soft drinks. While many methods have been suggested for producing such containers, the process that has achieved the greatest and most economical success in producing these containers is that conventionally known as "blow-molding". In blow-molding, generally a container is produced by extruding a parison of a selected thermoplastic material in the form of a hollow tube that is then situated between two or more movable mold sections when these are in an open position. After a required length of the parison has been extruded, the mold sections for forming the container are closed together about the extruded parison so as to pinch together and close the lower end of the extruded parison and to constrict the upper end of it between the closed mold sections, which mold sections simultaneously commence the formation of a container neck portion by incompletely pinching off the top portion thereof. At substantially the same time that the mold sections are being brought together to close upon the parison, a blowpin assembly is moved into position and inserted into a neck defining opening at the top of the mold sections. Thereafter, that portion of the extruded parison situated within the mold cavity defined by the closed mold sections is inflated by a burst of gas, e.g., air or the like, and pressed against the internal walls of the mold cavity. Once the thermoplastic material has been forced by the inflating pressure against the internal walls of the mold cavity, the temperature of the thermoplastic material is lowered sufficiently so as to rigidify the thermoplastic material. Thereafter, the mold sections are opened and the blow-molded container expelled therefrom. Any flash or otherwise undesirable material that has been caught between the mold sections when they are closed is subsequently trimmed from the container and recycled for later use. This method of forming containers is of particular utility in that, inherent in the materials and temperatures used in the process, sterile containers are readily produced requiring no further action other than maintenance of a noncontaminating environment prior to the placement of the liquid materials therein. Typically, such plastic disposable containers are provided with a single opening to the outside, generally located on the surface of the container that is uppermost during use. It is also conventional to form such containers in a mold in which the neck opening is disposed at the top of the mold cavity as is shown, for example, in US-A-4,176,153 The mold apparatus is normally mounted vertically in an apparatus similar to that shown in US-A-4,147,748. Clearly, for such apparatus to operate and produce disposable plastic containers in an economical manner, the equipment must be designed for and capable of operating at a rapid rate of repetition and without a requirement for human intervention for maintenance and adjustment. One of the more critical aspects of such operation is the alignment between the blow-molding assembly and the mold sections. The blowpin assembly is usually located above the mold and adapted to be moved into communication with the mold cavity immediately after the parison has been severed from the extruder and captured between the mold sections. The registration of this blowpin assembly so as to accurately enter the mold cavity through the neck opening in the mold requires a considerable amount of care in its initial set-up and is the aspect most susceptible to breakdown during operation. While the foregoing apparatus has been found to be wholly sufficient for the manufacture of plastic disposable containers having a single neck opening therein, the disadvantage is present in that the apparatus is not readily adaptable to the situation where the disposable container is required to have more than one neck opening and where those neck openings are in opposing faces of the container, such as at the top and the bottom. Moreover, when a plurality of such neck openings are required in a container, a natural concomitant is that those neck openings be accurately positioned with respect to each other so that the equipment with which they are utilized can be constructed to receive the container and become attached to it without adjustment. Clearly, the prior art apparatus is not susceptible to easy modification to accomplish the multiple-necked container. The mere addition of a second blowpin assembly positioned so as to oppose the first blowpin assembly and on the opposite side of the mold inherently creates an exponentially more severe registration problem, which problem is compounded by the fact that accurate dimensional interrelationships between the necks are necessary. US-A 3,608,135 discloses an apparatus for blow-molding a container, having one neck, the blowpin assembly being mounted on one of the mold sections. That apparatus and method deviate from the conventional design in which the blowpin assembly is disposed outbord of the mold sections on the mold apparatus. GB-A-1,236,253 discloses a blow-molding apparatus in which the blowpin nozzle includes an annular cutting sleeve surrounding the top of the nozzle to contact the edge of the neck opening to cut the tube at that edge to remove any portion of the tube that extends beyond the edge of the neck opening. The invention as claimed in claims 1 and 7 solves the problem of how to blow mold a container including two opposing necks wherein the difficulty of achieving accurate registration between the neck openings is greatly diminished and conventional blow-molding machinery can be used. Preferred embodiments of the invention are the subject matter of the subclaims. One way of carrying out the invention is shown in the drawings, wherein: Fig. 1 is a schematic, perspective view of the blow-molding apparatus; Figure 2 is a schematic sectional view of the apparatus shown in Figure 1 taken along line 2-2 in Figure 1; and Figures 3 through 5 are schematic representations showing the apparatus according to the present invention during various phases of the performance of the method of the present invention. Turning initially to Figure 1, there is shown a perspective view of a mold assembly 10 which is comprised generally of two mating and relatively movable mold sections 12 and 14 that enclose one or more container-defining mold cavities therein. The mold assembly 10 depicted in Figure 1 has two such mold cavities therein. As noted hereinabove, the mold cavities defined by mold sections 12 and 14 have neck openings on opposing faces thereof. In the view of Figure 1, only the neck openings 26 and 28 at one end of the mold assembly are shown. The two mold sections 12 and 14 meet along a parting surface 16 that substantially bisects each of the neck openings provided in the molds, such as is shown for the neck openings 26 and 28. Preferably, the parting surface 16 is planar and also divides the internal mold cavities into substantially similar portions being in each mold section 12 and 14. One of the mold sections, in this case mold section 12, has an extension 13. Mounted on the extension 13 are a pair of air cylinders 18 and 20 that include axially movable pistons 22 and 24. The air cylinders 18 and 20 are mounted on the extension 13 through brackets 23 and 25 that are associated with cylinder 20 and brackets 27 and 29 that affix cylinder 18. The cylinders 18 and 20 are mounted on the extension 13 so as to place the movable pistons 22 and 24 in a colinear relationship with the axis of the two neck openings of the two mold cavities that are in opposition to the neck openings 26 and 28. The mold assembly 10 that is comprised of mold sections 12 and 14 and the associated apparatus mounted to mold section 12 is adapted so as to be mounted in the conventional manner into blow-molding apparatus, such as that which is shown, for example, in US-A-4,147,748 Generally speaking, as will be more fully apparent from the discussion below, the mold assembly 10 will conventionally be mounted in a blow-molding apparatus so that the axis of the neck openings 26, 28 and those with which the pistons 22 and 24 are colinear will be vertically oriented. As such, the mold sections 12 and 14 are relatively movable in a horizontal direction during the operation of the blow-molding apparatus. As can be seen, by mounting the air cylinders 18 and 20 directly to the extension 13 of one of the mold sections 12, it is possible to accurately align the pistons 22 and 24 with the neck openings associated therewith outside of the blow-molding apparatus environment and to lock those air cylinders 18 and 20 into that position such that the need for future realignment is greatly diminished. Obviously, this ability to prealign the air cylinders 18,20 outside of the apparatus environment greatly reduces the maintenance time and skills required. Turning now to Figure 2, there is shown a schematic sectional view taken along line 2-2 in Figure 1, i.e., along the parting surface 16 between the mold sections 12 and 14. Here, the two parallel container-defining mold cavities 30 and 32 are shown as having respective second neck openings 34 and 36. As denoted by the shaded portion 37, the mold section 12 is relieved slightly adjacent to the mold cavities 30 and 32 to provide venting of the cavities during the blow-molding operation. Adjacent to the portions of mold section 12 that include the mold cavities 30 and 32 on the extension 13 are the air cylinders 18 and 20. The air cylinders 18 and 20 have axially movable reciprocal pistons 22 and 24 to the distal ends of which are affixed blowpin nozzles 39 and 41, respectively. The reciprocal movement thereof is denoted schematically in this Figure in that blowpin nozzles 39 is shown in its retracted position whereas assembly 41 is shown in its extended position and in engagement with the mold section 12. In practice, the air cylinders 18 and 20 will operate simultaneously and will, therefore, always be in the same relative position. The blowpin nozzles 39 and 41 have tips 42 and 44, respectively, that penetrate through the neck openings 34 and 36 into the interior of the mold cavities 30 and 32. The tips 42 and 44 are sized so as to force the thermoplastic material outwardly against the neck openings 34,36 in the molds such that all desired threads or other intricacies of the neck configuration are formed. Immediately adjacent to the tips 42 and 44 are disposed annular cutting sleeves 46 and 48. The annular cutting sleeves 46 and 48 operate in cooperation with the edge defined between the neck openings 34 and 36 and external shoulders 50 and 52 on the mold cavity to substantially sever the thermoplastic material at the end of the neck so that the access material may be easily removable upon extraction of the completed containers from the mold cavity. The blowpin nozzles 39 and 41 have fittings thereon for the passage of water therethrough. Fittings 64 and 68 permit the inward flow of water to the nozzles whereas fittings 62 and 66, respectively, allow the water to flow outward from the nozzles. This fluid is utilized for cooling the nozzle which comes into contact with the semi-molten thermoplastic material such that the temperature of the material in the neck portions is lowered sufficiently to rigidify those portions of the container prior to its extraction from the mold cavities. A further set of fittings 74 and 76 are located on the respective blowpin nozzels 39 and 41 to allow a fluid pressure line to be attached to the blowpin assembly for permitting fluid to be supplied to the interior of the mold cavity under pressure so as to force the thermoplastic material against the internal walls of the mold cavities 30 and 32. This fluid, which is preferably air, is supplied through the tips 42 and 44 of the nozzles 39,41. Vents 70 and 72 are provided in the exterior of the annular cutting sleeves 46 and 48 for allowing the escape of excess pressurized fluid. The air cylinders 18 and 20 are operated in tandem by having suitable air supply lines attached thereto. The forward set of fittings 78 and 80 on air cylinders 18 and 20 communicate with the space above the pistons in the air cylinders and, when pressure is applied through fittings 78 and 80 serve to drive the pistons carrying the blowpin nozzles 39 and 41 downward and out of contact with the mold cavities 30 and 32. Conversely, the fittings 82 and 84 at the base of cylinders 18 and 20 communicate with the space in the air cylinders below the pistons and, when fluid pressure is applied through fittings 82 and 84 serve to force the pistons 22 and 24 and their blowpin nozzles 39 and 41 upward into engagement with the mold cavities. As is readily apparent, the air cylinders 18 and 20 with their respective blowpin nozzles 39 and 41 can be accurately aligned with the neck openings 34 and 36 in the mold cavities 30 and 32 prior to the insertion of the mold assembly into the blow-molding apparatus. At the opposing side of the mold cavities, conventional blowpin nozzels 38 and 40 are positioned in the mold assembly 10 so as to be capable of reciprocal movement along the axis of the respective neck openings 26 and 28. Blowpin nozzels 38 and 40 similarly have annular cutting members 57 and 59 associated therewith for cooperative engagement with external shoulders 58 and 60, respectively, at the exterior of the neck openings 26 and 28 to substantially remove excess portions of the parison of thermoplastic material at the molding stage. Also, blowpin nozzels 38 and 40 are sized to cause the proper molding of the corresponding necks on the containers. In operation, as is shown more clearly with respect to Figures 3, 4 and 5 of the drawing, initially a parison 90 is formed and directed between the mold sections 12 and 14 which, at this time, have been opened to allow the parison 90 to come between them. The opening of the mold sections 12 and 14 is indicated by the respective arrows 92 and 94. Similarly, as the blowpin nozzle 41 is, as shown in Figures 1 and 2, affixed to the extension 13 of mold section 12, blowpin nozzle 41 moves laterally together with mold section 12 as is indicated schematically by the arrow 96. Any blow-moldable thermoplastic material compatible with the fluid product to be placed therein can be utilized in the apparatus and method of the present invention. Typical illustrative thermoplastic materials suitable for the present purposes are the usual blow-molding grade materials such as high- and low-density polyethylene, polypropylene, polycarbonate acetate, acrylonitrile-butadiene-styrene (ABS), and the like. As is well known, the parison 90 at this point is in a semi-molten state and is incapable of self-support. Therefore, the mold assembly is oriented vertically so as to accommodate the gravity feed of the parison 90 into the mold. After the parison 90 has entered the mold, the mold sections 12 and 14 are closed about the parison such that the openings at the respective ends of the parison 90 are captured between the neck openings 28 and 36 at the ends of the mold cavity 32, as indicated by arrows 98, 100 and 102 in Figure 4. At this time, the two blowpin nozzels 40 and 41, are advanced into engagement with the mold such that the tips 42,44 thereof pass through the neck openings 34,36 and into the interior of the mold cavity 32 simultaneously molding the respective necks on the container. This is schematically illustrated in Figure 4 by the arrows 104 and 106 that are associated with the respective blowpin nozzles 41 and 40. After the blowpin nozzles 40 and 41 have come into engagement with the mold, the pressurized fluid is then passed through the two blowpin nozzels 40,41 the interior of the mold cavity 32 to force under fluid pressure the parison 90 outward against the internal walls of the container-defining mold cavity 32. At this time, the air remaining in the mold cavity and external to the parison 90 is forced from the mold cavity at the parting line venting provided at 37 as shown in Figure 2. When the parison 90 comes into contact with the cooled blowpin nozzles 40 and 41 and the mold sections 12 and 14 all of which are maintained at temperatures well below that at which the selected thermoplastic material becomes rigid, the thermoplastic material is cooled relatively rapidly to a temperature at which it has rigidified. Generally, the mass of the mold sections 12,14 and the exposure of the outer surfaces to the ambient enfironment is sufficient to supply adequate cooling. It is, however, within the purview of the invention to cool the mold sections 12 and 14, such as by circulating a coolant therethrough. At this time, the blowpin nozzels 40 and 41 are retracted from engagement with the mold cavity as indicated by arrows 108 and 110, respectively. Substantially concurrently, mold sections 12 and 14 are retracted from contact with the parison 90 which has now been formed into the desired container, as indicated by arrows 112 and 144, respectively. Lower blowpin nozzle 41, being affixed to mold sections 12, also moves laterally as indicated by arrow 116. A molded container 90 having open necks 118 and 120 on its opposing upper and lower faces is now permitted to drop free from the mold for further processing and filling. At this time, the substantially severed remaining portions of the parison indicated schematically at 122 and 124 are retained with the container upon extraction from the mold cavity. This moil is later removed in a separate operation.

Claims: Apparatus (10) for molding a container from a semi-molten, hollow tube (90) of thermoplastic material, the apparatus comprising a split type mold assembly having a container-defining mold cavity (30, 32) therein that is formed to a configuration substantially identical to the exterior of the container and having a first neck opening (26, 28) corresponding to a first neck (118) on the container, the mold assembly including two relatively horizontally movable mold sections (12, 14) each having a portion of the cavity therein, the mold sections meeting along a parting surface (16) that substantially bisects the first neck opening (26, 28), and the mold assembly being adapted to enclose a length of the tube (90) of thermoplastic material therein with one end of the tube (90) passing at least partially through the first neck opening (26, 28), a first vertically movable blowpin assembly disposed so that its line of movement is substantially colinear with the axis of the first neck opening (26, 28) in the mold assembly, the first blowpin assembly comprising blowpin nozzles (38, 40) adapted to move into engagement with the end of the tube (90) passing through the first neck opening (26, 28) so as to cause the molding of the tube end against the mold assembly to form the first neck on the container and being adapted to supply a fluid under pressure to the interior of the tube (90) to force the tube to expand and come into contact with the interior of the cavity characterized for molding a container including two necks (118, 120), one on each of its opposing upper and lower faces by the split type mold assembly having a second neck opening (34, 36) corresponding to the second neck on the container, the parting surface (16) substantially also bisecting the second neck opening (34, 36) and the other end of the tube (90) passing at least partially through the second neck opening (34, 36), a second blowpin assembly mounted on one (12) of the mold sections, the second blowpin assembly comprising means mounted on the one mold section (12) and having a support (18, 22; 20, 24) for reciprocally moving the support vertically so that its line of movement is substantially colinear with the axis of the second neck opening (34, 36) in the mold assembly, and a second blowpin nozzle (39, 41) mounted on the support and being adapted to move into engagement with the end of the tube (90) passing through the second neck opening (34, 36) so as to cause the molding of the tube end against the mold assembly to form the second neck (120) on the container, the second blowpin nozzle (39, 41) being adapted to supply the fluid under pressure to the interior of the tube (90) generally concurrently with the application of fluid pressure by the first blowpin assembly to force the tube to expand and come into contact with the interior of the cavity to form the container and means for cooling the container (90) to rigidify the container prior to removing the container from the mold. Apparatus according to Claim 1 for molding a container including two necks (118, 120) of different size, wherein the first blowpin assembly is associated to the larger neck opening (26, 28) and the second blowpin assembly is associated to the smaller neck opening (34, 36). An apparatus according to Claim 1, wherein the means for reciprocally moving the second blowpin nozzle (37,41) comprises an air cylinder (18, 20) having an axially movable piston to the distal end of which is affixed the blowpin nozzle (39, 41). An apparatus according to Claim 1, wherein the second blowpin nozzle (39, 41) includes an annular cutting sleeve (46, 48) surrounding the top of the nozzle to contact the edge of the neck opening (34, 36) in the mold assembly to limit the travel of the nozzle and to cut the tube (90) at that edge to remove any portion of the tube that extends beyond the edge of the neck opening (34, 36). An apparatus according to Claim 1, wherein a plurality of mold assemblies and associated first and second blowpin assemblies are mounted in parallel to produce a like plurality of containers simultaneously. An apparatus according to Claim 1, wherein the container-defining cavity (30, 32) is substantially bisected by a planar parting surface (16). A method for forming a plastic container, the method comprising the following steps forming a semi-molten, hollow tube (90) of thermoplastic material, providing an open assembly of mold parts having, when in its closed configuration, a container-defining mold cavity (30, 32) therein that is of a configuration substantially identical to the exterior of the container, the assembly including two relatively, horizontally movable mold sections (12, 14) each having a portion of the mold cavity therein, the mold sections meeting along a parting surface (16) that substantially bisects a first neck opening (26, 28) that the container-defining mold cavity (30, 32) has, which first neck opening (26, 28) corresponds to the first neck (118) on the container and the assembly comprising first blowpin nozzles (38, 40), closing the mold assembly about the tube of thermoplastic material so as to confine a length thereof between the mold sections (12, 14) and within the cavity (30, 32) with an access opening at the end of the tube (90) remaining open being defined by the first neck opening (26, 28), positioning the first blowpin assembly (38, 40) into the access opening in the end of the tube confined in the first neck opening (26, 28), supplying fluid under pressure through the first blowpin assembly to the interior of the tube (90) to blowform the tube into the container by forcing the thermoplastic material against the mold cavity (30, 32), cooling the thermoplastic material in the container-defining configuration to set the material, withdrawing the blowpin assembly from contact with the container, and opening the mold assembly to remove the completed container from the mold cavity, characterized for molding a container having two necks (118, 120), one of which is on each of the opposing upper and lower faces of the container by the mold cavity (30, 32) having a second neck opening (34, 36) corresponding to the second neck (120) on the container and the parting surface (16) also bisecting the second neck opening when the mold assembly is closed, an acces opening at the other end of the tube (90) remaining open being defined by the second neck opening (34,36), mounting and permanently aligning a second blowpin assembly on one (12) of the mold sections so that a blowpin nozzle (39, 41) is reciprocally movable along a vertical line colinear with the axis of the second neck opening (34, 36), positioning the second blowpin assembly into the access opening in the second end of the tube confined in the second neck opening (34, 36) and fluid also being supplied under pressure through the second blowpin assembly. A method according to Claim 7, wherein all excess material is removed from the container. A method according to Claim 8, wherein the excess material is substantially cut from the container prior to the blowpin assemblies being withdrawn from contact with the molded container.

Inventors: HOHMANN, FRANK G.
Applicants: THE COCA-COLA COMPANY
Application year: 1985
Main classification: B29C49
IPC codes: B29C49, B29L22, B65D1