Alarm Clock Mechanism Backlash Compensation Cam

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Solution Overview

Problem

Existing mechanical timepiece alarm mechanisms suffer from inaccuracies in triggering the alarm due to cumulative transmission play, which can cause the alarm to sound prematurely or be delayed, especially when adjusting the alarm time forward, leading to inconsistent wake-up times.

Innovation Solution

Incorporating a backlash cam with a spring-biased roller or sloping wheel that generates a torque to counteract the cumulative transmission play, ensuring the gears remain in functional contact and maintaining the programmed wake-up time accuracy by orienting the torque opposite to the given direction when the angular distance is within the cumulative transmission clearance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the alarm time is adjusted forward by rotating the trigger cam in the given direction, then the alarm time can be set more quickly, but the cumulative transmission play causes the alarm to trigger prematurely or with inconsistent timing

Engineering Contradiction:

Improvealarm setting speedVSAvoidalarm trigger timing accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The spring-loaded roller applies a preliminary counteracting force to the cumulative transmission play in the gear train. By pre-loading the roller against the trigger cam, the system compensates for the backlash that would otherwise cause timing inaccuracies when adjusting the alarm forward, ensuring accurate trigger timing while maintaining quick adjustment capability

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The spring-loaded roller acts as an intermediary element between the trigger cam and the gear train. It mediates the transmission of motion by maintaining constant contact and eliminating gaps caused by cumulative transmission play, thereby ensuring precise timing without restricting the user's ability to quickly adjust the alarm time

Inventive Principle:

Principle #24Intermediary (Mediator)

2Speed

If the gear train is designed with multiple stages to achieve the required speed reduction, then the trigger cam can be driven at the correct rate, but cumulative transmission play accumulates across stages causing timing errors

Engineering Contradiction:

Improvetrigger cam rotation rateVSAvoidangular position accuracy

Core Design Contradiction:

SpeedVSMeasurement precision

Solution Approach 1:

The invention converts the harmful effect of cumulative transmission play into a beneficial pre-loaded contact system. The spring-loaded roller is deliberately designed to apply force against the trigger cam, transforming the potential for timing errors into a mechanism that ensures constant, precise contact throughout the gear train stages, thereby maintaining both correct rotation rate and high angular position accuracy

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Reliability

If the trigger cam has angular play to accommodate transmission clearance, then the mechanism can function reliably, but the displayed wake-up time diverges from the actual trigger time

Engineering Contradiction:

Improvemechanical function stabilityVSAvoidtiming information accuracy

Core Design Contradiction:

ReliabilityVSLoss of information

Solution Approach 1:

The invention changes the parameter of contact force by introducing a spring-loaded roller that dynamically applies force to the trigger cam. This ensures that the angular play necessary for reliable mechanical function is eliminated during operation, as the spring maintains constant contact pressure, thereby ensuring that the displayed wake-up time accurately reflects the actual trigger time while preserving mechanical reliability

Inventive Principle:

Principle #35Parameter changes

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 solution ensures that the alarm is triggered at the correct programmed time, even when adjusting the alarm time forward, by maintaining gear contact and reducing the lag between the displayed wake-up time and the actual trigger cam position, thus providing reliable and accurate timing.

Implementation Method 1

a roller (27) or a sloping wheel biased against the profile of the cam of backlash by the force of a spring (23)

Methodology Applied

Scientific EffectSpring force: Spring

Implementation Method 2

the force exerted by the roller (27) or the incline on the cam of backlash generates a torque likely to rotate the latter

Methodology Applied

Scientific EffectTorque: Torque

Data Source

PatentEP3686694B1Alarm clock mechanism and timepiece comprising such a mechanism

Publication Date: 2021.08.18 PATEK PHILIPPE SA

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AI summary

The mechanism includes a triggering cam (11) driven in a given direction by a first gear train actuated by the hour wheel (25) of the movement and arranged to trigger the striking mechanism when it reaches a predetermined angular position. The mechanism also includes a backlash compensation cam (21) fixed coaxially to the triggering cam (11), and a roller or inclined wheel (27) held against the profile of the backlash compensation cam by the restoring force of a spring (23). The backlash compensation cam, on the one hand, and the roller or inclined wheel, on the other hand, are arranged to cooperate so that the force exerted by the roller or inclined wheel on the backlash compensation cam generates a torque capable of rotating the latter in order to tension the gears of the common part of the first and second gear trains.