Plastic Belt Pulley Rib Layout for Reduced Radial Deformation
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Solution Overview
Problem
Belt pulleys made of plastic materials for washing machines face challenges in achieving low weight while maintaining mechanical properties to prevent deformation under radial and axial loads, leading to issues like bending and increased material usage.
Innovation Solution
A belt pulley design featuring a central hub, a concentrically arranged circular dividing rib that divides the pulley into inner and outer sections with radially arranged reinforcing ribs forming a honeycomb pattern, and arc-shaped ribs in the outer section to enhance stiffness and reduce deformations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If belt pulleys are made of plastic material to reduce weight, then weight is reduced, but mechanical strength and stiffness deteriorate causing deformation under load
Solution Approach 1:
The belt pulley is divided into multiple sections separated by radially arranged dividing ribs. These ribs segment the pulley structure into distinct zones that can independently manage stress distribution, preventing overall deformation while maintaining lightweight plastic construction.
Solution Approach 2:
The invention uses a composite plastic material containing mineral or synthetic filler (such as calcium carbonate, glass fibers, or talc) mixed with a thermoplastic base material. This composite structure provides enhanced mechanical strength and stiffness comparable to metal while retaining the weight advantages of plastic materials.
2Strength
If large cross-section ribs are used to ensure mechanical properties, then strength is improved, but weight and material consumption increase
Solution Approach 1:
The reinforcing ribs are strategically positioned only where stress concentration occurs, such as between the hub and belt contact surface, and along the dividing ribs. This localized reinforcement provides necessary strength without adding material throughout the entire pulley structure.
Solution Approach 2:
The reinforcing ribs are designed with curved or arc-shaped configurations rather than straight lines. This curvature allows the ribs to better distribute radial forces and resist deformation more efficiently, reducing the need for excessive rib thickness while maintaining structural integrity.
3Strength
If mineral or synthetic filler is added to increase elastic modulus, then stiffness is improved, but manufacturing defects occur due to filler precipitation
Solution Approach 1:
The invention optimizes the filler content within specific ranges (5-40 wt% mineral filler, or 10-30 wt% synthetic filler) and adjusts processing parameters such as injection molding temperature and pressure to prevent filler precipitation. The melt temperature is controlled to ensure uniform filler distribution without aggregation during solidification.
4Reliability
If belt preload force is applied to ensure stable belt position, then operational stability is improved, but radial deformation increases causing belt shift
Solution Approach 1:
The dividing ribs segment the belt contact surface into multiple zones, allowing the belt preload force to be distributed across several smaller contact areas rather than one large continuous surface. This segmentation reduces the cumulative radial deformation while maintaining stable belt positioning.
Solution Approach 2:
The invention addresses radial deformation by introducing structural elements (dividing ribs and reinforcing ribs) that provide stiffness in the radial dimension without compromising the overall lightweight design. These ribs create a three-dimensional stress distribution network that resists radial forces more effectively.
Data Source
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AI summary
A belt pulley (6) of a washing machine drum (3) made of a plastic material, comprising a hub, a circumference of the belt pulley to receive a belt (8), a substantially circular dividing rib (14) dividing the belt pulley to the inner and outer concentric section with a plurality of reinforcing ribs (15, 16, 16'), wherein the dividing rib is arranged on a line of a polygon having the centre in the belt pulley axis and exhibiting corners, into which, from a side facing the hub, a portion of the outermost ribs lead, said ribs being part of a plurality of reinforcing ribs of the inner section, wherein at least a portion of these ribs leading into the corners of the dividing rib run, extend along a line of polygons, preferably hexagons, which are radially arranged in the inner section and in contact with each other along one of their sides, wherein, from at least one said corner of the dividing rib on the side facing the outer circumference, at least one arc-shaped rib of the outer section originates, and its free end contacts the outer circumference of the belt pulley.