Torque Shut-Off Clutch With Cam Ring for Reliable Opening
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Solution Overview
Problem
Existing shut-off clutches in electric hand-held power tools, such as screwdrivers, fail to reliably and efficiently transition to an open state when the specified torque is reached, leading to potential damage from excessive torque application.
Innovation Solution
A torque-dependently releasable shut-off clutch with a cam ring and guide rings that axially preload switching elements, ensuring controlled movement and reliable transition to an open state when the triggering torque is exceeded, using a design that allows for positive guidance of switching elements in all directions and includes a freewheel mechanism for direction reversal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing shut-off clutch designs are used with balls climbing cam elements at inclines less than 90 degrees, then the clutch can be constructed simply, but the transition to the open state is not reliable and excessive torque may be applied
Solution Approach 1:
The patent inverts the traditional cam element approach by using a cam ring with a cam track that guides the ball along a predetermined path including a vertical section. Instead of the ball climbing a cam element at an incline, the ball is guided through a cam track that provides a 90-degree vertical section, ensuring reliable clutch opening while maintaining simple construction.
Solution Approach 2:
The patent introduces a cam ring as an intermediary component between the ball and the cam element. The cam ring with its cam track acts as a mediator that guides the ball through a controlled path, ensuring the ball reaches the vertical section and reliably opens the clutch, while the spring element serves as an intermediary to provide axial preload on the ball.
2Reliability
If switching elements are not axially preloaded, then the construction is simpler, but the switching elements cannot be positively guided in all directions and may lose their function
Solution Approach 1:
The patent applies preliminary action by preloading the ball axially against the cam ring using a spring element before the clutch needs to switch. This preload ensures the ball is positioned correctly and can be positively guided in all directions when torque is applied, preventing the ball from losing its function while keeping the construction relatively simple.
Solution Approach 2:
The patent changes the parameter of axial force by introducing a spring element that applies a predetermined axial preload on the ball. This parameter change ensures the ball remains in contact with the cam ring and can be properly guided, while the spring constant and preload force can be adjusted to optimize performance without excessive complexity.
3Reliability
If the clutch remains closed beyond the nominal torque, then continuous operation is maintained, but the screw connection may be damaged from excessive tension
Solution Approach 1:
The patent applies preliminary anti-action by designing the clutch to automatically open when the nominal torque is reached, preventing excessive tension on the screw connection before damage can occur. The cam track with its vertical section ensures the clutch opens reliably at the predetermined torque, and the spring element ensures the ball is ready to follow the cam track path, providing protective action in advance.
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 clutch effectively protects screw connections from excessive tension and motor overload by reliably opening when the nominal or maximum torque is reached, reducing wear, vibration, and noise while maintaining a robust and simple construction.
Implementation Method 1
a cam ring (7) which is rotatably connected to the drive shaft (2) or to the output shaft (3), and an axially non-displaceable first guide ring (8) which is rotatably connected to the other of the drive shaft (2) and the output shaft (3)... the cam ring (7) and the second guide ring (9) are axially prestressed against one another and receive the at least one switching element (11) axially between them
Data Source
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AI summary
The invention relates to a torque-dependently releasable shut-off clutch for an electric hand-held power tool, in particular for a screwdriver, for selectively transmitting torque from a drive shaft to an output shaft coaxial with the drive shaft. The shut-off clutch comprises a cam ring, an axially immovable first guide ring, which guides a switching element, in particular a ball, and a second guide ring. The cam ring and the second guide ring are axially preloaded against one another and axially accommodate the switching element between them. The shut-off clutch can be moved from a first, non-torque-transmitting switching position to a second, torque-transmitting switching position.If a first trigger torque is exceeded in the first switching position, the switching element is deflected relative to the cam ring in the axial direction against the effect of the preload, thereby moving the shut-off clutch to the second switching position. This provides a robust and simply constructed shut-off clutch that opens reliably when the first trigger torque is exceeded.