Patent Description:
Various products are distributed in plastic containers, such as containers formed from one or more polymers. Common polymers used to form containers include polyesters, such as polyethylene terephthalate (PET), high and low density polyethylenes (PE), polypropylenes (PP), and polycarbonates (PC), among others. Plastic containers can be made using various blow molding processes including injection blow molding, liquid or hydraulic blow molding, and extrusion blow molding, where such blow molding processes can employ a preform that is expanded by a fluid to form a resultant container.

Injection blow molding can be used to form certain plastic containers in one or more stages and can include use of a stretch rod. In a two-stage injection stretch blow molding process, a polymer can be first molded into a preform using an injection molding process. The preform can include the neck and finish of the container to be formed, which can include threading thereon, and a closed distal end. The preform can then be heated above the polymer glass transition temperature, optionally stretched longitudinally with a stretch rod, and blown using high-pressure gas (e.g., air) into a container conforming to a mold. As the preform is inflated, it elongates and stretches, taking on the shape of the mold cavity. The polymer solidifies upon contacting the cooler surface of the mold and the finished hollow container is subsequently ejected from the mold.

Liquid or hydraulic blow molding can form and fill a container in a single operation. A liquid product can be used to form and fill a polymeric preform within a mold into a resultant container, where the liquid product remains thereafter in the finished container. A heated preform, much like the preform used in injection blow molding, can be placed within the mold, optionally stretched, and rapidly filled using a liquid product instead of a gas to form a container therefrom. Combination of the forming and filling steps can therefore optimize packaging of a liquid product by eliminating the transport of empty containers and time demands related to subsequent filling operations.

Various types of preforms can be used in such blow molding processes. Certain embodiments of preforms include injection-molded, rotationally symmetric preforms that have an elongated, cylindrical, lateral body section, a rounded, closed bottom, and a neck section with an upper opening. Other preforms have be rotationally asymmetric with a varying thickness along an elongate axis to facilitate a material distribution that forms an asymmetric container. In either case, positioned proximate to the opening, there can be an outer threaded finish section, which can be delimited toward a bottom thereof by a collar or the like. The threaded finish section can be preserved during blow molding of the preform where the finish can form a thread for a screw cap of a finished beverage container, for example. The remaining portion of the preform, in contrast, can be deformed and stretched during the blow molding process. Preforms can be heated to predefined temperatures in order to enable blow molding in the desired manner. Heating can be performed by various means, including infrared radiation using an infrared oven, to effect defined and/or uniform temperature control of the preforms.

In particular, the polymeric material of the preform (e.g., PET) can be of such a nature that the polymer can strain harden as the polymer is stretched. Forming temperature during the blow molding process can therefore be a determinative factor in the resultant container. The strain hardening effect can be taken into consideration in the production of PET containers for the purpose of controlling and optimizing wall thickness distribution. Depending on the production process, it can be possible to apply heat via infrared radiation in such a way that the preforms are heated according to a temperature profile. In this manner, the warmer sections of the preform can be deformed with priority over other parts as long as is required for the stretching resistance resulting from strain hardening to become greater than the resistance of the adjacent cooler sections, for example. The temperature profile can be uniformly distributed around the circumference of the preforms and can vary process-dependently along the longitudinal axis of the preforms. In order to apply the desired temperature profile to the preforms, use a number of heating zones can be used, for instance up to nine or more zones. It is possible to control the plurality of different heating zones individually, whereby the selected setting is maintained constant over a longer period of operating the heating apparatus.

Preforms of different construction can require different heating regimens in preparation for blow molding into resultant containers. For example, preforms of different sizes, shapes, thicknesses, formed of or including different polymers or polymer combinations, layers, and the like can each have a predetermined temperature profile optimized for a particular blow molding process. Certain examples include different heating regimens for effecting different temperature profiles for PET preforms versus PP preforms. Other examples include different heating regimens for effecting the same temperature profile, but where the preforms have different characteristics that require different regimens to achieve the same temperature profile; e.g., preforms formed of the same material but having different thicknesses. Accordingly, various heating parameters can be tailored for particular preforms, including the number of heating zones, the temperature of certain heating zones, the exposure time to certain heating zones, and the like.

A blow molding system can often include a preform heating means in close proximity thereto, where heated preforms can be passed to a mold in short order and formed into resultant containers before a desired temperature profile of the preforms changes. A travel path of a preform through an infrared oven, for example, can be tailored to generate a predetermined temperature profile in a given preform. However, if a condition of the blow molding system and/or process is changed, it can be necessary to change the preform path or heating means to adapt to a new temperature profile for a given preform. Changes in blow molding conditions can include the use of another preform type, a change in the mold, changes in blow molding parameters, and the like. Accordingly, it can be difficult to adapt a blow molding system and/or process to changing conditions that require changes in preform temperature profiles while maintaining continuous or high throughput production of containers. Oftentimes, one or more settings may need to be changed, one or more new equilibriums reached, and one or more physical parameters may need to be adapted in the blow molding system in order to accommodate preforms having different characteristics.

Absent appropriate temperature control, a heated preform may have an improper material distribution and/or expansion during a blow molding operation and the resulting container may rupture (or "blowout") or otherwise fail an aesthetic inspection. For refined gas blow molding processes, it can be expected that from about <NUM> to about <NUM> containers per one million gas blow molded container will suffer from a blowout. The expected blowouts from a liquid blow molded container is roughly the same. In the instance of liquid blow molding, a blowout will result in more than escape of air and will result in an escape and possible waste of the liquid product to fill the container. When the blow molding liquid is water, a blowout may result in little more than wasted water and negligible down time to allow the blow molding equipment to dry. When the blow molding liquid is a petroleum product, medicine, or cosmetic, for example, a blowout can result in a significant of time due to cleaning procedures required to render the blow molding equipment once-again operational and can result in wasted and unusable product, each of which alone may create a significant economic impact on the blowing molding process and product cost but combined may render the liquid blow molding process economically unfeasible for packing the product. It would be desirable to develop a method of blow molding that would reduce the expected blowouts for a blow molding operation (liquid or gas) to about <NUM> blowouts per million containers formed.

In consideration of these issues, the present technology provides a method of determining an acceptable temperature profile of a preform prior to a blow molding operation to minimize blowouts, where the resulting blow molding operation can be maintained in a continuous or high throughput fashion.

<CIT> discloses a method for determining the temperature distribution throughout the thickness of a preform used in a container reheat stretch blow molding process.

<CIT> discloses a method for indexing a preform which has been previously heated according to a determined circumferential heating profile.

<CIT> discloses a method for heating a preform that is rotationally symmetric about its longitudinal axis, has a standard thread, and is made of a thermoplastic material.

<CIT> discloses a process for producing polypropylene bottles, wherein a polypropylene preform is formed by injection molding.

<CIT> discloses systems and methods for controlling the operation of a blow molder.

Concordant and congruous with the present invention, a method of determining an acceptable temperature profile of a preform prior to a blow molding operation to minimize blowouts has surprisingly been discovered.

In an embodiment of the invention, a method for heating a preform, the method comprises the steps of providing a plurality of preforms suitable for blow molding; inspecting each preform to identify at least a material from which the preform is formed; heating each preform; measuring the temperature of at least a portion of each preform along its longitudinal axis and around its circumference; and optimizing the heating step based on a comparison of the measuring step to the inspecting step to ensure each preform has been heated to an acceptable temperature to ensure the heating step for subsequent preforms is optimized for blow molding to militate against blowouts thereof.

In another embodiment of the invention, a method for heating a preform, the method comprises the steps of providing a plurality of preforms suitable for blow molding; inspecting each preform to identify at least a material from which the preform is formed; heating each preform; measuring the temperature of at least a portion of each preform along its longitudinal axis and around its circumference; comprising a step of compiling the measured temperatures of the at least a portion of each preform; converting the compiled measured temperatures into a three-dimensional thermal image representing the measured temperatures of the at least a portion of the preform; and optimizing the heating step based on a comparison of three-dimensional thermal image to the inspecting step to ensure each preform has been heated to an acceptable temperature to ensure the heating step for subsequent preforms is optimized for blow molding to militate against blowouts thereof.

In another embodiment of the invention, a method for heating a preform, the method comprises the steps of providing a plurality of preforms suitable for blow molding; inspecting each preform to identify at least a material from which the preform is formed; heating each preform; measuring the temperature of at least a portion of each preform along its longitudinal axis and around its circumference; comprising a step of compiling the measured temperatures of the at least a portion of each preform; converting the compiled measured temperatures into a three-dimensional thermal image representing the measured temperatures of the at least a portion of the preform; converting the three-dimensional thermal image into a two-dimensional thermal image representing the portion of the preform measured along its longitudinal axis and around its circumference; and optimizing the heating step based on a comparison of two-dimensional thermal image to the inspecting step to ensure each preform has been heated to an acceptable temperature to ensure the heating step for subsequent preforms is optimized for blow molding to militate against blowouts thereof.

The above, as well as other advantages of the present invention, will become readily apparent to those skilled in the art from the following detailed description of a preferred embodiment when considered in the light of the accompanying drawings in which:.

The following description of technology is merely exemplary in nature of the subject matter, manufacture and use of one or more inventions, and is not intended to limit the scope, application, or uses of any specific invention claimed in this application or in such other applications as can be filed claiming priority to this application, or patents issuing therefrom. Regarding methods disclosed, the order of the steps presented is exemplary in nature, and thus, the order of the steps can be different in various embodiments, including where certain steps can be simultaneously performed. "A" and "an" as used herein indicate "at least one" of the item is present; a plurality of such items can be present, when possible. Except where otherwise expressly indicated, all numerical quantities in this description are to be understood as modified by the word "about" and all geometric and spatial descriptors are to be understood as modified by the word "substantially" in describing the broadest scope of the technology. "About" when applied to numerical values indicates that the calculation or the measurement allows some slight imprecision in the value (with some approach to exactness in the value; approximately or reasonably close to the value; nearly). If, for some reason, the imprecision provided by "about" and/or "substantially" is not otherwise understood in the art with this ordinary meaning, then "about" and/or "substantially" as used herein indicates at least variations that can arise from ordinary methods of measuring or using such parameters.

Although the open-ended term "comprising," as a synonym of non-restrictive terms such as including, containing, or having, is used herein to describe and claim embodiments of the present technology, embodiments can alternatively be described using more limiting terms such as "consisting of" or "consisting essentially of. " Thus, for any given embodiment reciting materials, components, or process steps, the present technology also specifically includes embodiments consisting of, or consisting essentially of, such materials, components, or process steps excluding additional materials, components or processes (for consisting of) and excluding additional materials, components or processes affecting the significant properties of the embodiment (for consisting essentially of), even though such additional materials, components or processes are not explicitly recited in this application. For example, recitation of a composition or process reciting elements A, B and C specifically envisions embodiments consisting of, and consisting essentially of, A, B and C, excluding an element D that can be recited in the art, even though element D is not explicitly described as being excluded herein.

As referred to herein, disclosures of ranges are, unless specified otherwise, inclusive of endpoints and include all distinct values and further divided ranges within the entire range. Thus, for example, a range of "from A to B" or "from about A to about B" is inclusive of A and of B. Disclosure of values and ranges of values for specific parameters (such as amounts, weight percentages, etc.) are not exclusive of other values and ranges of values useful herein. It is envisioned that two or more specific exemplified values for a given parameter can define endpoints for a range of values that can be claimed for the parameter. For example, if Parameter X is exemplified herein to have value A and also exemplified to have value Z, it is envisioned that Parameter X can have a range of values from about A to about Z. Similarly, it is envisioned that disclosure of two or more ranges of values for a parameter (whether such ranges are nested, overlapping or distinct) subsume all possible combination of ranges for the value that might be claimed using endpoints of the disclosed ranges. For example, if Parameter X is exemplified herein to have values in the range of <NUM>-<NUM>, or <NUM>-<NUM>, or <NUM>-<NUM>, it is also envisioned that Parameter X can have other ranges of values including <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, and so on.

When an element or layer is referred to as being "on," "engaged to," "connected to," or "coupled to" another element or layer, it can be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers can be present. In contrast, when an element is referred to as being "directly on," "directly engaged to," "directly connected to" or "directly coupled to" another element or layer, there can be no intervening elements or layers present.

Although the terms first, second, third, etc. can be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms can be only used to distinguish one element, component, region, layer or section from another region, layer or section.

Spatially relative terms, such as "inner," "outer," "beneath," "below," "lower," "above," "upper," and the like, can be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms can be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device can be otherwise oriented (rotated <NUM> degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

As shown in <FIG>, the present technology is drawn to method of thermal imaging using a heating system <NUM> and method for optimizing preform temperature profiles and ways of using such systems, especially in blow molding a container (not shown) from a thermoplastic preform <NUM>. The system <NUM>, explained in more detail hereinbelow, generally includes a first camera <NUM>, a second camera <NUM>, and a heating means <NUM>.

With respect to the preform <NUM>, <FIG> shows an exemplary preform <NUM> having an elongate axis O having an overall shape resembling a test tube. The preform <NUM> has a neck <NUM>, a shoulder <NUM>, a body <NUM>, and a rounded, closed bottom <NUM>. Typically, the neck <NUM> and the shoulder <NUM> is each formed and in its definitive shape as it enters the system <NUM> and does not need to be heated or thermally imaged as contemplated herein. Accordingly, typically only the body <NUM> and the bottom <NUM> are heat treated and thermally imaged by the system <NUM>, though the entire preform <NUM> may be heated, as desired. The tubular body <NUM> of the preform <NUM> is closed at an upper end by the hemispherical bottom <NUM> and at its lower end comprises the neck <NUM> which is already in the definitive shape of the neck <NUM> of the container, the annular shoulder <NUM> which extends radially outwards roughly delineates the unheated portion of the preform <NUM> from the heated portion thereof. The preform <NUM> may be formed of a polyester material, such as polyethylene terephthalate (PET) and other polyesters, polypropylene, acrylonitrile acid esters, vinyl chlorides, polyolefins, polyamides, and the like, as well as derivatives, blends, and copolymers thereof. As shown, the preform <NUM> has a shape well known to those skilled in the art similar to a test-tube with a generally cylindrical cross section and a length typically approximately fifty percent (<NUM>%) that of the resultant container height, or the preform <NUM> may have any shape, length, and formed from any material, as desired. As explained hereinabove, the heat treatment preformed in the system <NUM> is intended at preparing the preform <NUM> for conversion, by blow molding with a gas or a liquid, so as to shape each preform <NUM> into the container.

In the system <NUM>, each preform <NUM> is provided at an entrance E of an infeed station by way of a mag-lev track, rail, or other transport mechanism (not shown). The preforms <NUM> are then individually placed onto a conveyor <NUM>, which transports the preforms <NUM> through the system <NUM>, as detailed hereinbelow, and ultimately to an exit S of the system <NUM> for further processing steps <NUM>. The further processing steps <NUM> may include transporting the preform <NUM> for one of re-entry into the entrance E for additional heating, rejection and recycling, or to a blow mold loading station (not shown) for forming the preform <NUM> into the container.

Each preform <NUM> enters the system <NUM> (at ambient temperature) disposed on a spindle <NUM> (as shown in <FIG>) which allows for the <NUM>° rotation thereof as the preform <NUM> traverses therethrough. At the entry E, each preform <NUM> is inspected and measured by a first camera <NUM>. The camera <NUM> is a visual-inspection camera but the camera <NUM> may be an infrared camera or any other camera capable of measuring the desired characteristics noted herein of each preform <NUM>. For example, the camera <NUM> is adapted to inspect, measure, transmit, and/or collect data concerning the preform <NUM> including, but not limited to, a starting (often times ambient) temperature of the preform <NUM>, the material from which the preform <NUM> is formed, the material state (i.e., amorphous v. crystalline) of the preform <NUM>, any inclusions (i.e., foreign materials) in the preform <NUM>, an image of the preform <NUM> with a desired resolution, and the physical dimensions (e.g., height, width, diameter) of the preform <NUM>. The camera is in electronic communication with a computer <NUM>, and/or a process controller (not shown), and/ or other data processor (not shown) capable of processing and/or tabulating the images and date from the first camera <NUM>.

After inspection and measuring by the camera <NUM>, each preform <NUM> is transported via the conveyor <NUM> through the system <NUM> and past a series of heating means <NUM>. The heating means <NUM> may be an infrared oven, for example, or any suitable heating means as known by one of ordinary skill in the blow molding art. Direct and/or indirect (e.g., reflected) thermal energy can be applied by the heating means <NUM>. Multidirectional application of thermal energy can be used as well as where preforms <NUM> themselves are moved, spun, or rotated about various thermal radiation sources in the various heating means <NUM>. Any number of heating means <NUM> may be utilized, as desired, but, as shown in <FIG>, the system <NUM> includes three (<NUM>) heating means <NUM>. As best shown in <FIG>, each heating means <NUM> comprises five (<NUM>) heating elements <NUM> to facilitate heating of each preform <NUM> at different heights thereof along the longitudinal axis O. It is understood that the number of heating means <NUM> and the heating elements <NUM> present in the heating means <NUM>, or operation thereof during a given process, may vary based on the size or specifications of each preform <NUM>, material properties of each preform <NUM>, and the like. The heating means <NUM> are spaced longitudinally along the conveyor <NUM> through the system <NUM> so as to introduce into the preforms <NUM> a desired temperature profile that will allow for optimization of the distribution of the plastic material during the remaining steps in a pre-stretch and blow molding process. The temperature profile may vary or define a gradient along the longitudinal axis O of each preform <NUM>. Alternatively, the temperature profile may be constant over the length of the preforms <NUM>. Additionally, the temperature profile may vary across the thickness of the preforms <NUM> with, for example, the material on the exterior of the preform <NUM> being at a higher temperature than the material on the interior of the preform <NUM>. The actual temperature profile will depend on the specific design of the preform <NUM>, including its shape and material composition, material distribution, and the design of the resulting container to be formed. As each preform <NUM> passes the heating means <NUM>, each preform <NUM> is rotated on its spindle <NUM> thus being heated by the heating means <NUM> until each preform <NUM> reaches a second camera <NUM>.

As shown in <FIG>, the camera <NUM> is an infrared camera adapted to inspect and measure the temperature of each preform <NUM> along the longitudinal axis O thereof and around an entire circumference thereof. The camera <NUM> measures a temperature of the preform <NUM> along its axis O and circumference at a defined and desired number of data points and/or at a desired resolution (as constrained by the camera <NUM>). For example, data points may correspond to a height of each of the heating elements <NUM> and/or portions of the preform <NUM> therebetween along each degree of the circumference of the preform <NUM> and/or areas therebetween. The camera <NUM> is in electronic communication with a computer <NUM> and/ or a process controller and/or other data processor (not shown) capable of processing and/or tabulating the thermal characteristics data measured by the camera <NUM>. For example, the computer <NUM> converts the thermal characteristics data of the preform <NUM> into a three-dimensional thermal image <NUM> of each preform <NUM>, as best shown in <FIG>. The computer <NUM> may then convert the three-dimensional thermal image <NUM> into a two-dimensional thermal image <NUM> (also known as a heat map). Alternatively, the computer <NUM> may convert the thermal characteristics data directly into the two-dimensional thermal image <NUM>. The image <NUM>, when viewed left to right, is a representation of a temperature measurement of the preform <NUM> from about <NUM>° to about <NUM>° taken as the preform <NUM> rotates on the spindle <NUM>. Thus, the temperature profile of the three-dimensional preform <NUM> may be viewed in two dimensions. Furthermore, the temperature profile of the preform <NUM> may be viewed as a whole or at desired discreet pixel or areas, for example, along a longitudinal area <NUM>, as shown in <FIG>. As an example and as best shown in <FIG>, the three-dimensional thermal image <NUM> can be divided into a desired number of longitudinal areas such as, for example, three-hundred fifty-nine (<NUM>) longitudinal areas corresponding to each degree of the preform <NUM> as rotated about its axis O from about <NUM>° to about <NUM>°. In this way, a particular longitudinal area <NUM> of the three-dimensional thermal image <NUM> and of the preform <NUM> itself can be more easily and readily observed on the two-dimensional thermal image <NUM> without the requirement to access and/or rotate the three-dimensional thermal image <NUM>.

As noted above, the temperatures of the preform <NUM> are tabulated by the computer <NUM>. The temperatures measured are then plotted against the position of the measurement on the preform <NUM>, as shown in a graph <NUM> in <FIG>. As shown on the graph <NUM>, the temperature of the preform <NUM> at each temperature measurement taken by the camera <NUM> (x-axis) is plotted against the position of such measurement on the preform <NUM> (x-axis). In this way, the graph <NUM>, a numerical/ graphical representation of the temperature measurements, can be readily compared and directly correlates to the two-dimensional thermal image <NUM>, a color-based heat map.

By creating the two-dimensional thermal image <NUM>, temperature measurements of each heated preform <NUM> may be readily and easily ascertained before the preform <NUM> is transferred to the blow molding station and molded into the final container. In some instances, the thermal images <NUM>, <NUM>, and/or the graph <NUM> may indicate that a preform <NUM> has "cool regions" <NUM> or "warm regions" <NUM>. Such regions <NUM>, <NUM> may result in blowouts during blow molding, thus requiring remedial action during the heating of the preform <NUM>. Because the exact location of such regions <NUM>, <NUM> can be pinpointed by observance and analysis of the thermal images <NUM>, <NUM>, and/or the graph <NUM>, remedial action can be taken to ensure proper heating of the preform <NUM> to minimize blowouts during blow molding thereof into the container. The remedial action may include adjustment of one or more of process parameters and settings of the system <NUM>, including adjustment of the heating means <NUM> or specific heating elements <NUM>, to increase or decrease the temperature of any portion of the preform <NUM> (e.g., the regions <NUM>, <NUM>), as desired, so that subsequent preforms have a different and acceptable temperature profile to minimize blowouts during blow molding. Additional remedial actions include, for example, upwardly or downwardly adjusting the spin rate of the spindle <NUM> upon which each preform <NUM> is disposed, or increasing or decreasing the residence time of the preform <NUM> (or speed of the conveyor <NUM>) within the system <NUM>, and/or cooling airflow within the system <NUM> may be increased or decreased.

In use, the images and/or information obtained from the first camera <NUM> are processed by the computer <NUM> to determine the thermal treatment appropriate for each preform <NUM> is to receive from the heating means <NUM>. For example, the first camera <NUM> may identify individual preforms formed from different materials or having different sizes corresponding to resulting containers having different volumes. Accordingly, each preform <NUM> may require its own specific thermal treatment from the heating means <NUM>, and/or the first camera <NUM> may detect an unacceptable number of inclusions or other unacceptable issues with a particular preform and signal the system <NUM> via the computer <NUM> or the process controller to reject that preform and remove it for recycling or destruction. Once each preform <NUM> receives its thermal treatment from the heating means <NUM>, data is gathered for each preform <NUM> by the second camera <NUM>. The computer <NUM> compares the data for each preform <NUM> as received from the first camera <NUM> and to data received from the second camera <NUM> to ensure that the thermal treatment was appropriate and acceptable for the given specifications (e.g., dimensions and/or material) of the preforms <NUM>.

Claim 1:
A method for heating a preform (<NUM>), the method comprising the steps of:
providing a plurality of preforms (<NUM>) suitable for blow molding;
heating each preform (<NUM>); and
measuring the temperature of at least a portion of each preform (<NUM>) along its longitudinal axis (O) and around its circumference;
the method characterized by the following steps:
inspecting each preform (<NUM>) to identify at least a material from which the preform (<NUM>) is formed; and
optimizing the heating step based on a comparison of the measuring step to the inspecting step to ensure each preform (<NUM>) has been heated to an acceptable temperature to ensure the heating step for subsequent preforms (<NUM>) is optimized for blow molding to militate against blowouts thereof.