Thermoplastic Container Bottom with Curved Shoulder
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Solution Overview
Problem
The manufacturing of thermoplastic containers, particularly the bottom, faces challenges in achieving sufficient mechanical strength and stability due to complex shapes and high material thickness, which requires precise control of blowing conditions and increased energy costs, and current methods struggle to produce containers with reinforced radial rigidity without material accumulation and blockages.
Innovation Solution
A container design with a shoulder connecting the seat and annular zone, featuring non-zero curvature and varying radii, and a corresponding mold cavity with similar features, allowing for improved radial rigidity and flow of material during blow molding, reducing the need for high blowing pressures and enhancing production efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the bottom of the container has a complex shape with many recessed and projecting reliefs to improve mechanical strength, then the radial rigidity and resistance to vertical loads are improved, but the manufacturing precision and control of blowing conditions become more difficult
Solution Approach 1:
The patent applies curvature to the bottom profile by defining a convex portion with a specific radius of curvature (R1) that is greater than the radius of curvature (R2) of the seat portion. This continuous curved design eliminates sharp angles and complex reliefs, allowing the thermoplastic material to flow more uniformly during blow molding while still providing the necessary radial rigidity and mechanical strength to support vertical loads.
2Strength
If high pressure blowing is used to achieve correct deformation and shaping of material in the bottom region, then the mechanical strength and shape taking are improved, but the energy consumption and equipment costs increase
Solution Approach 1:
The continuous curved bottom profile with optimized radius of curvature reduces flow resistance and eliminates dead zones where material could accumulate. This allows the blowing process to proceed more efficiently with lower pressures, as the material naturally follows the curved path from the preform to the mold cavity without requiring excessive force to overcome sharp transitions or complex geometries.
Solution Approach 2:
The patent changes the geometric parameters of the bottom profile by specifying a radius of curvature (R1) for the convex portion that is greater than the radius of curvature (R2) of the seat portion. This parameter optimization creates a more favorable flow path for the thermoplastic material, reducing the blowing pressure required to achieve proper forming while maintaining the necessary mechanical strength.
3Shape
If the material path from preform to mold wall includes changes in direction or points of inflection, then the container shape is achieved, but the material distribution and cooling at the bottom become insufficient
Solution Approach 1:
The patent eliminates points of inflection and sharp direction changes by defining a continuous curved bottom profile. The convex portion with radius of curvature (R1) smoothly transitions to the seat portion with radius of curvature (R2), ensuring uniform material flow and consistent contact with the mold wall for effective cooling, while still achieving the required container shape.
4Strength
If the thickness of material thermoplastic in the bottom of the preform is substantially greater than elsewhere, then the mechanical strength is improved, but the stretching and shape taking become slower and more difficult
Solution Approach 1:
The continuous curved design with optimized radius of curvature reduces flow resistance during stretching, allowing the thicker material in the bottom region to be formed more quickly and efficiently. The smooth curvature prevents material accumulation and facilitates uniform deformation, maintaining productivity despite the increased material thickness required for strength.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design achieves reinforced radial rigidity and improved resistance to vertical loads while facilitating the molding process with reduced energy consumption and increased production rates, ensuring stable container positioning and handling.
Implementation Method 1
The deformation and shaping of the material in the bottom region are currently obtained by implementing high pressure blowing (typically of the order of 40x10^5 Pa)
Implementation Method 2
The deformation and shaping of the material in the bottom region are currently obtained by implementing high pressure blowing
Implementation Method 3
poor cooling of the material against the mould
Data Source
Figure 1
Figure 2~4
AI summary
The invention relates to a bottom of a mould for producing thermoplastic containers, and to a container thus produced. The container (1) produced comprises: a base (4) having a concave peripheral wall (6) extending essentially coaxially to the X-X' axis, this concavity defining a non null curvature all along the wall (6); an annular region (7) forming a tubular peripheral wall (8) extending essentially coaxially to the X-X' axis, the transversal radial distance between the X-X' axis and said wall (8) being longer than the transversal radial distance between the X-X' axis and any point along the concave peripheral wall (6) of said base (4); and a shoulder (9) forming a connecting region between the base (4) and the annular region (7). The depth of said annular region is between 0.5 and 2 %, preferably between 1 and 1.5 %, especially 1.2 % of the diameter of the annular region (7), and the height of the base (4) is between 5 and 15 mm.