Device for braking a rotating tool in a cooking apparatus
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Solution Overview
Problem
Existing braking systems for rotating tools in cooking appliances are inadequate for rapid braking, leading to premature wear and potential safety hazards due to the inability to stop the tool within the required two seconds.
Innovation Solution
A device that underpowers the electric motor by reducing the electrical power supply, followed by connecting a single half-coil to the rotor brushes, allowing the motor to act as a direct current generator and achieve rapid braking without generating sparks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a known braking system is used to stop the rotating tool rapidly, then the braking time is reduced, but the carbon brushes and commutator experience premature wear
Solution Approach 1:
The patent replaces the traditional mechanical braking system with an electromagnetic braking mechanism. The motor is converted into a dynamo during braking, using electromagnetic induction to generate a braking torque that opposes the rotation. This substitution eliminates direct mechanical contact between brake components, thereby preventing wear on carbon brushes and commutator while achieving rapid stopping within the required two seconds.
2Speed
If the motor is converted to a dynamo by connecting both brushes to a single coil, then rapid braking is achieved, but sparks are generated on the carbon brushes
Solution Approach 1:
The patent divides the stator winding into two separate half-coils instead of using a single coil. During braking, only one half-coil is connected to the brushes at a time, which segments the electromagnetic interaction and prevents simultaneous arcing at both brush contacts. This segmentation maintains the dynamo effect for rapid braking while eliminating the harmful sparks that would otherwise be generated.
3Reliability
If the motor is underpowered gradually to reduce speed, then component wear is reduced, but the braking time exceeds the required two seconds
Solution Approach 1:
The patent implements a two-phase braking sequence: first, the motor is underpowered or freewheeled to reduce speed from high velocity to a lower threshold, then the dynamo braking mode is activated for final rapid stopping. This periodic switching between gentle deceleration and aggressive braking allows the system to achieve the required two-second stopping time while minimizing wear during the initial deceleration phase.
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 solution enables rapid braking of the rotating tool within the required time frame, reduces wear on components, and minimizes the risk of sparks, thereby enhancing safety and efficiency.
Implementation Method 1
During active braking, the rotor is therefore a direct current generator. This current generated by the rotor is injected into the half-coil that is connected in series, which causes rapid braking of the rotor
Implementation Method 2
The underpowering phase, or 'passive' braking, makes it possible to reduce the rotational speed of the motor thanks to the friction of the motor, shaft and the tool mounted on the shaft
Data Source
AI summary
The device for braking an electric motor comprises a rotor provided with two brushes and a stator comprising at least two half-coils connected in series to the brushes while the motor is nominally activated.Said device comprises a means for underpowering, the motor, a means for connecting in series a single half-coil to the rotor brushes and a means for controlling the braking by underpowering the motor until at least one value of a physical quantity reaches a predetermined value and the single half-coil is connected in series to the rotor brushes when the value of a physical quantity reaches the predetermined value.