Mandrel Design for Stone Polishing with Balanced Belt Drive
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Solution Overview
Problem
Existing mandrel systems for abrasive tool heads suffer from vibration sensitivity due to off-center mass distribution, complex assembly processes, and high maintenance costs, particularly due to the need for balanced gear transmissions and pneumatic/hydraulic actuating cylinders, which complicate adjustments and increase inertia during operation.
Innovation Solution
The mandrel design features a balanced arrangement with electric motors and a belt drive system where the mass center coincides with the rotation axis, incorporating a tongue with an inclined end to minimize vibrations and allow for easy adjustment and rapid transmission ratio changes, using a telescopic sleeve and spherical contacts for precise alignment, and a disjointable coupling for efficient maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the electric motor is positioned off-axis to use standard motors and pass cooling water through the mandrel shaft, then the assembly is simpler and more practical, but the center of gravity moves far from the mandrel axis causing vibrations
Solution Approach 1:
The patent introduces a counterweight element (element 7) that is adjustable along the mandrel axis to compensate for the off-axis position of the electric motor. This counterweight creates a balancing moment that offsets the centrifugal forces generated by the motor's eccentric position, thereby reducing vibrations while maintaining the practical benefits of off-axis motor placement for cooling water passage and standard motor usage.
2Manufacturing precision
If shims are used to adjust the mandrel position on the supporting structure, then assembly errors are compensated, but the assembly process becomes uncomfortable and requires considerable testing work
Solution Approach 1:
The patent incorporates adjustment elements (elements 4 and 5) that allow for preliminary adjustment of the mandrel position relative to the supporting structure before final assembly. This enables the operator to pre-position the mandrel at the correct angle and location, eliminating the need for time-consuming shim adjustments and repeated testing during assembly.
3Adaptability or versatility
If pneumatic or hydraulic actuating cylinders are positioned outside the mandrel body for axial adjustment, then the tools can be adjusted for sizing, smoothing and polishing, but greater stress is created on the supporting structure and mandrel body
Solution Approach 1:
The patent positions the actuating cylinders (elements 13 and 14) inside the mandrel body, nesting them within the existing structure. This internal positioning allows the cylinders to adjust the abrasive tools for sizing, smoothing, and polishing operations while the mandrel body itself absorbs and distributes the mechanical stress, reducing the load on the external supporting structure compared to external cylinder placement.
4Stability of the object's composition
If a coaxial pneumatic piston is used for vertical motion, then the mandrel is balanced, but the construction and maintenance costs increase
Solution Approach 1:
The patent uses a belt drive system with counterweights (element 7) to achieve vertical motion and balancing of the mandrel, replacing the need for a complex coaxial pneumatic piston assembly. This approach maintains the balancing benefits while using simpler, more cost-effective mechanical components that are easier to manufacture and maintain.
Data Source
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AI summary
An improved mandrel for sizing, smoothing or polishing stone materials with rotating abrasive heads, comprising: a sleeve within which a body (12) of the mandrel is sliding, which in its turn is provided with a shaft (22) at whose end a rotating head with abrasive tools is applied; a pair of actuating cylinders (13) for the positioning of said mandrel (1), that is to say, of the head connected to it, on the supporting metal structure (2); a pair of electric motors for the activation in rotation of the mandrel and a drive from said motors to the shaft (22) of the mandrel; wherein said motors are coupled in rotation with the shaft of the mandrel with a belt drive; wherein, finally, the coupling between a supporting plate (15) of the belt drive (16) connected to the body (12) of the mandrel sliding within said adjustable sleeve (3) is realized by a disjointable coupling (37) in which screws (38) clamp radial lobes (39) of the body of the mandrel to lugs (40), which are made in the centre of the supporting plate (15); the radial lobes (39) are alternated with ports (41) to allow the passage with clearance of the lugs (40) during the disjointing of the coupling with the rotation of the supporting plate (15).