Seconds Hand Reset Mechanism With Spring-Loaded Hammer Restart

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Solution Overview

Problem

Existing watch mechanisms for resetting a time-related indicator, such as the seconds hand, either rely on synchronous systems that are dexterity-dependent or suffer from friction-induced wear and timing disruptions, or they do not allow for a reliable non-synchronous reset mechanism that can instantaneously reset and restart independently of user manipulation.

Innovation Solution

A device utilizing an energy accumulator and a unidirectional hammer mechanism that stores energy from a user's action, allowing the seconds hand to reset to a predetermined position and restart instantaneously without further user input, using a frictionless design that minimizes wear and dependency on user dexterity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If a synchronous reset device is used, then the seconds hand can be reset to zero, but the resetting speed depends on user dexterity and the device complexity increases due to clutch systems

Engineering Contradiction:
Improveresetting speedVSAvoidclutch system complexity
Core Design Contradiction:
SpeedVSDevice complexity

Solution Approach 1:

The patent extracts the clutch mechanism from the reset device, replacing it with a direct-drive hammer mechanism that strikes the seconds hand directly. This eliminates the complex clutch system while maintaining the reset function, thereby reducing device complexity while preserving resetting speed.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The hammer is pre-loaded with potential energy through a spring mechanism before activation. When the user presses the button, the hammer is already positioned and ready to strike, enabling instantaneous reset without requiring the user to control the speed of engagement, thus achieving fast reset independent of user dexterity.

Inventive Principle:
Principle #10Preliminary action

2Device complexity

If friction is used to mount the seconds hand, then fewer parts are required, but friction consumes energy and risks disrupting timekeeping or causing the watch to stop

Engineering Contradiction:
Improvenumber of partsVSAvoidtimekeeping reliability
Core Design Contradiction:
Device complexityVSReliability

Solution Approach 1:

The spring-loaded hammer accumulates energy in advance and releases it instantaneously to give the seconds hand a strong initial impulse. This preliminary energy storage allows the seconds hand to overcome frictional forces without requiring continuous friction-based engagement, thereby maintaining timekeeping reliability while using fewer parts.

Inventive Principle:
Principle #10Preliminary action

3Productivity

If a non-synchronous reset device is implemented, then instantaneous reset and restart is achieved, but friction wear increases and timing may be disrupted

Engineering Contradiction:
Improvereset operation speedVSAvoidtiming accuracy
Core Design Contradiction:
ProductivityVSReliability

Solution Approach 1:

The hammer mechanism is pre-loaded with spring energy and positioned ready to strike. Upon button press, it delivers an instantaneous impulse to the seconds hand, achieving non-synchronous reset without prolonged frictional contact. This brief, controlled impulse maintains timing accuracy while enabling fast reset operation.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The reset action occurs in a single, rapid hammer strike that 'skips' over the friction problem by completing the reset in one instantaneous motion rather than through prolonged frictional engagement. This rushing through the reset action achieves instantaneous operation while minimizing friction wear and timing disruption.

Inventive Principle:
Principle #21Skipping (Rushing through)

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

Enables reliable, instantaneous resetting and restarting of the seconds hand in a single operation, independent of user actions, maintaining accurate timekeeping and reducing friction-induced wear, thus enhancing the reliability and precision of the watch movement.

Implementation Method 1

a first cam (7) rotatable about an axis (1') and a second cam (6) rotatable about the axis (1') and capable of acting on the rocker (3) to cause its rotation. The hammer (92) includes a peen (92a) designed to cooperate with the core (2a) and act thereon to cause rotation of the core until the indicator member (13) reaches the predetermined position

Methodology Applied
Scientific EffectEnergy accumulation in spring: Spring

Implementation Method 2

The indicating element (13) is mounted by friction to a drive unit (15)

Methodology Applied
Scientific EffectFriction: Friction

Data Source

PatentEP3800515B1Device for resetting a component indicating a time-related magnitude to a predetermined position
Publication Date: 2026.02.11 ROLEX SA
  • EP3800515B1 patent drawingFigure 1~2
  • EP3800515B1 patent drawingFigure 3
  • EP3800515B1 patent drawingFigure 4A~4B

AI summary

The device (100) has an energy accumulator (9) and a return element (1) for returning an indicator member i.e. seconds hand (13) indicative of the parameter connected with time to a predetermined position. The return element is powered by energy from the accumulator, where the energy is supplied to the energy accumulator by a user via a push button (4) for resetting the seconds hand to the predetermined position, and the push button is manipulatable by a user. The seconds hand is kinematically linked to a drive wheel (15) by friction or by a clutch. An independent claim is also included for a timepiece.