Manually operated work device
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Hand-held blower impellers are difficult to dismantle due to their secure attachment, which complicates maintenance and assembly.
Innovation Solution
The impeller is secured to the shaft using a nut with a frictional engagement system, featuring a first frictional contact surface that allows for automatic tightening during operation, reducing the required assembly torque and preventing over-tightening, while a second conical frictional contact surface provides high friction torque without slippage, enabling easy removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the impeller is securely attached to the shaft using a nut, then the impeller remains firmly fixed during operation, but the impeller becomes difficult to dismantle for maintenance
Solution Approach 1:
The nut is designed to transition from a static fastening component to a dynamic self-tightening component during operation. The first friction contact surface enables the nut to automatically post-tension the impeller against the shaft when relative movement occurs between the impeller and shaft, transforming the attachment system from purely mechanical to dynamically adaptive, thereby maintaining secure attachment while enabling easy disassembly when needed.
Solution Approach 2:
The nut performs self-tightening through the frictional engagement mechanism. During operation, when the impeller moves relative to the shaft, the first friction contact surface generates friction torque that automatically post-tensions the nut without external intervention. This self-service mechanism ensures reliable attachment during operation while allowing simple disassembly by overcoming the friction torque.
2Reliability
If a high tightening torque is applied to the nut during assembly, then the impeller is securely fastened, but the risk of over-tightening and damage increases
Solution Approach 1:
The system performs self-tightening during operation through the frictional engagement between the nut and impeller. The first friction contact surface generates friction torque that automatically post-tensions the nut to the required level during operation, eliminating the need for high initial tightening torque and preventing over-tightening damage during assembly.
Solution Approach 2:
The friction torque characteristics of the first friction contact surface are designed to provide automatic post-tensioning at operating conditions. By selecting appropriate friction coefficients and contact surface parameters, the system achieves secure fastening during operation without requiring excessive initial tightening torque, thus avoiding over-tightening damage.
3Length of moving object
If the shaft diameter is reduced for compact design, then the device becomes more compact, but the friction torque capacity decreases
Solution Approach 1:
The solution transitions from relying solely on radial friction contact (single dimension) to incorporating axial friction contact through the conical second friction contact surface. The wedge effect of the conical surface converts axial forces into radial clamping forces, enabling sufficient friction torque capacity on a reduced-diameter shaft by utilizing the third dimension (axial direction) for force generation.
Solution Approach 2:
The conical geometry of the second friction contact surface changes the force distribution parameters. The wedge effect increases the contact pressure and frictional engagement between the shaft and impeller hub, compensating for the reduced shaft diameter and maintaining adequate friction torque capacity despite the smaller dimensions.
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
This design allows for simple disassembly and reassembly of the impeller, reducing the risk of over-tightening and facilitating maintenance, while maintaining secure attachment during operation, and allows for a compact shaft design.
Implementation Method 1
A first friction torque acting about the axis of rotation can be transmitted between the nut and the impeller via a first friction contact surface
Implementation Method 2
In the second, conical frictional contact surface, a conical frictional force acts at a distance from the axis of rotation
Implementation Method 3
A wedge effect results from the conicity of the second friction contact surface. This wedge effect causes an increase in the frictional contact forces
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The invention relates to a hand-held tool with a fan wheel (7). The fan wheel (7) is held against rotation on the shaft (3) by means of a nut (6) by frictional engagement. A threaded friction torque (MA) can be transmitted via a threaded section (11) between the nut (6) and the shaft (3). A first friction torque (M1) can be transmitted via a first friction contact surface (12) between the nut (6) and the fan wheel (7). The first friction contact surface (12) is designed such that, at a minimum tightening torque of the nut (6), the first friction torque (M1) is greater than the threaded friction torque (MA). As a result, during operation of the tool (1), the relative movement between the fan wheel (7) and the shaft (3) causes the nut (6) to move along with it. The nut (6) tightens the fan wheel (7) against the shaft (3). The second friction contact surface (13) is conical towards the axis of rotation (4).