Chronograph Reset Mechanism with Segmented Hammers
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Solution Overview
Problem
Conventional chronograph reset devices are bulky, lack precision in resetting minute and hour hands to zero due to manufacturing tolerances, and can damage the needle axes with excessive pressure from hammers.
Innovation Solution
A reset device featuring a push button, lever, sliding control member, and pivoting hammers with elastic arms, allowing for precise rotation of heart-shaped reset cams and reducing overall size and stress on the needle axes, utilizing a sliding control member to rotate hammers around their pivots and incorporating a reset jumper for precise zero resetting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a single piece comprising hammers is used to strike the cams for resetting, then the reset function is achieved, but the device becomes bulky and exerts excessive pressure on the needle axes
Solution Approach 1:
The single piece hammer mechanism is segmented into separate hammer elements (first hammer for seconds counter, second hammer for minutes counter, third hammer for hours counter) that can be independently controlled. This segmentation allows for a more compact arrangement and reduces the overall stroke required, thereby reducing device bulk while maintaining the reset function.
Solution Approach 2:
The hammers are made movable and controllable through a sliding member that can be positioned at different locations. The sliding member dynamically selects which hammer(s) are actuated based on the reset position, allowing for precise control and reduced stroke requirements compared to a fixed single-piece mechanism.
2Ease of operation
If a single piece hammer mechanism is used, then the reset function is achieved, but manufacturing tolerances cause imprecise resetting of minute and hour hands to zero
Solution Approach 1:
By segmenting the reset mechanism into separate hammers for different counters (seconds, minutes, hours), each hammer can be independently adjusted and positioned. This allows for higher precision in each individual hammer-cam interaction, compensating for manufacturing tolerances and ensuring accurate resetting to zero for each counter.
Solution Approach 2:
The sliding member acts as an intermediary that precisely controls the positioning and actuation of each hammer. It mediates between the user's reset input and the individual hammer mechanisms, ensuring that each hammer strikes its corresponding cam at the correct position for precise zero resetting.
3Ease of operation
If hammers are used to strike the reset cams, then the hands are reset to zero, but the hammers exert strong pressure that can damage or break the needle axes
Solution Approach 1:
The hammer mechanism is made dynamic with the sliding member allowing selective positioning. The hammers can be positioned to engage the cams only when needed, and the elastic arms provide a cushioning effect that reduces impact pressure. The system transitions from a static single-piece hammer to a dynamic multi-hammer system with controlled engagement.
Solution Approach 2:
The hammers are equipped with elastic arms that act as cushioning elements before the actual striking occurs. These elastic arms deform during the striking process, absorbing and distributing the impact force, thereby reducing the peak pressure transmitted to the needle axes and preventing damage.
4Ease of operation
If the stroke of the single piece is made large enough to allow hammers outside the cam path in rest position, then the reset function works, but the device becomes even bulkier
Solution Approach 1:
Instead of using a single large stroke in one dimension, the invention distributes the reset action across multiple smaller strokes in different dimensions. The sliding member moves in one dimension to select hammers, while each hammer strikes in another dimension. This multi-dimensional approach reduces the overall device length while maintaining functionality.
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 provides a compact, precise, and stress-reducing mechanism for resetting chronograph hands to zero, preventing damage to the needle axes and ensuring accurate restarting of chronograph hands while minimizing bulk and manufacturing inaccuracies.
Implementation Method 1
The lever 3 is subjected to the action of a return spring 7 which opposes the action of the push button 2
Implementation Method 2
The sliding member 4 is subjected to the action of an all or nothing spring 13, called a reset jumper
Implementation Method 3
Each hammer 5 comprises, on one side of its pivot 17, a first arm 18, and on the other side of its pivot 17, second and third arms 19, 20. The first and third arms 18, 20 are rigid. The second arm 19 is elastic.
Data Source
Figure 1
AI summary
The device (1) has a sliding control unit (4) movable in translation and actuated by a manual control unit (2) i.e. push button, and hammers (5) actuated by the unit (4) to co-operate with respective resetting cams (6) e.g. second meter hand resetting cams, in the form of core. The hammers are pivoted around pivots (17) independent of the unit (4) and are articulated to the unit (4) for being pivoted around the pivots by a translation movement of the unit (4). Each hammer has an elastic arm (19) whose rigid end defines a percussion surface (22) that co-operates with the corresponding cam. An independent claim is also included for a device for starting, stopping and resetting a chronograph comprising a clutch.