Cutting Crown Attachment With Threaded Insert to Reduce Fracture
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Solution Overview
Problem
Conventional cutting crown attachments for comminution devices suffer from increased fracture sensitivity due to the notch effect caused by fastening threads, which reduces their load-bearing capacity and leads to premature failure.
Innovation Solution
A cutting crown attachment design featuring a threaded insert with a rotationally symmetrical head section for axial form fit and a non-rotationally symmetrical shank section for rotational form fit, minimizing notch forces and distributing tangential forces effectively, thereby enhancing the load-bearing capacity and service life of the cutting crown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a threaded insert with fastening threads is used to attach the cutting crown to the holder, then the cutting crown can be securely fastened, but the notch effect increases fracture sensitivity and reduces load-bearing capacity
Solution Approach 1:
The invention extracts the fastening threads from the cutting crown material itself and relocates them to a separate threaded insert component. This separation removes the source of notch effects from the cutting crown, eliminating the fracture sensitivity caused by threaded holes while maintaining secure fastening capability through the insert's external threads engaging with the holder.
Solution Approach 2:
The threaded insert acts as an intermediary component between the cutting crown and the holder. It provides the fastening function through its internal threads engaging with the holder's external threads, while its head section with form-fit surfaces transfers loads to the cutting crown without creating notch effects. This mediator approach allows secure attachment while protecting the cutting crown from fracture-sensitive features.
2Stability of the object's composition
If the cutting crown is made of brittle material to increase stability, then stability improves, but fracture sensitivity increases due to notch effects from fastening threads
Solution Approach 1:
By extracting the fastening threads from the cutting crown and placing them in a separate insert, the invention eliminates the notch effects that would compromise brittle materials. The cutting crown can now be made from optimally stable brittle materials without the compromising influence of threaded holes, which are the primary source of fracture initiation in such materials.
Solution Approach 2:
The invention applies different structural qualities to different components: the cutting crown is optimized for stability using brittle materials without threads, while the threaded insert absorbs the mechanical fastening function. This local differentiation allows each component to have the optimal properties for its specific function, with the cutting crown having high stability and the insert handling the stress concentration from threading.
3Device complexity
If fastening threads are directly incorporated into the cutting crown, then the attachment is simple, but the notch effect reduces the service life of the cutting crown
Solution Approach 1:
The invention segments the attachment system into three distinct components: the cutting crown, the threaded insert, and the holder. This segmentation isolates the notch-effect-prone threading to the insert component, allowing the cutting crown to remain free of threads and thus free from associated fracture sensitivity. The modular design maintains simplicity while extending service life by protecting the critical cutting crown from damaging stress concentrations.
4Stability of the object's composition
If a rotationally symmetrical head section is used for axial form fit, then axial stability is improved, but tangential force distribution is insufficient
Solution Approach 1:
The invention combines symmetrical and asymmetrical features in the threaded insert: the head section is rotationally symmetrical to provide uniform axial form fit and stability, while the shank section incorporates non-rotationally symmetrical form-fit surfaces that specifically address tangential force distribution. This asymmetric design in the shank creates complementary mating surfaces that effectively transfer tangential loads between the cutting crown and holder without concentrating stresses.
Data Source
Figure 1~2
Figure 3a~3b
Figure 3c~3d
AI summary
The invention relates to a cutting crown fastening for the positive locking and rotationally secure fastening of a cutting crown to a holder associated with it of a shredding device, in particular to a rotor of a shredding device, comprising a cutting crown, a cutting crown holder associated with the cutting crown, a screw bolt and a threaded insert with a head section and a shank section, wherein the threaded insert has an internal thread complementary to the external thread of the screw bolt and the cutting crown holder has a passage for receiving the screw bolt, and in the installed position the threaded insert is arranged in a positive locking manner in an axial and tangential direction in a retaining recess of the cutting crown associated with it.The cutting crown holder according to the invention is characterized in that the positive locking design of a cylindrical surface of the threaded insert for the holding recess of the associated cutting crown extends over the entire longitudinal extent of the threaded insert, wherein the threaded insert is rotationally symmetrical over the longitudinal extent of the head section to provide an axial positive locking to the holding recess, and has at least over a longitudinal section a conical cylindrical surface which, in the installed position, corresponds to a complementarily designed conical receiving section of the holding recess, and the threaded insert is non-rotationally symmetrical in the area of the longitudinal extent of the shank section to provide a rotational positive locking to the holding recess.