Watch

Summary

A watch is a portable timepiece intended to be carried or worn by a person. It is designed to keep a consistent movement despite the motions caused by the person's activities. A wristwatch is designed to be worn around the wrist, attached by a watch strap or other type of bracelet, including metal bands, leather straps, or any other kind of bracelet. A pocket watch is designed for a person to carry in a pocket, often attached to a chain. Watches were developed in the 17th century from spring-powered clocks, which appeared as early as the 14th century. During most of its history the watch was a mechanical device, driven by clockwork, powered by winding a mainspring, and keeping time with an oscillating balance wheel. These are called mechanical watches. In the 1960s the electronic quartz watch was invented, which was powered by a battery and kept time with a vibrating quartz crystal. By the 1980s the quartz watch had taken over most of the market from the mechanical watch. Histo

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https://en.wikipedia.org/wiki/Watch

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Tribological Approach to the Watch Movements

Valentine Agnès Madeleine Magnin

Mechanical watches are complex and sensitive systems that have to maintain a faultless precision over their lifetime. However, this precision can be altered by disturbances occurring during the functioning time, such as friction, lubricant drying, or wear, leading to surface modification. Due to the significant number of contacts, and diversity of materials, geometries, motions, and lubricants, these disturbances and their consequences over time are difficult to control. To deeply understand these phenomena and limit their effect on watches precision over time, a tribological study of watch movements is necessary. The goal of this Ph.D. research is to contribute to the development of a scientific methodology to appraise friction and wear evolution over time in watch movements. To achieve this, a system approach combined with a modelling of the phenomena was used to anticipate the evolution of two critical watch components: the barrel and the escapement. Based on existing theories of lubrication, the performance of the Swiss lever escapement was appraised as a function of well defined geometrical, kinematic, and dynamic parameters. The developed formalism allowed to highlight the relevance of the radii of curvature of the escapement tooth and the anchor pallet on the effectiveness of the fluid lubrication of the Swiss lever escapement. The tribology of the barrel, a brass piece coated with a nickel sublayer and a flash of gold, was then investigated. Wear characterization of real pieces allowed to identify the relevant wear mechanisms at the barrel drum/spring contact. Friction tests were performed to reproduce the observed phenomena in controlled conditions. A predictive law was proposed to estimate the loss of power at the escapement wheel and showed that the wear of the barrel drum can significantly affect the energy efficiency of the watch. Model surfaces composed of a nickel substrate of a specific waviness profile coated with different gold thicknesses were used for further investigation on the wear mechanisms of the gold coating. A simple mechanistic model considering contact pressure, geometrical, and frictional properties was developed to predict the minimum gold thickness necessary to lubricate the system. Two different relations were proposed according to the sliding direction. These relations were used to evaluate possible improvement strategies in terms of materials properties and surface finishing. With the intention to perform further tribological studies of any contacts of a mechanical watch, a methodology was proposed. This methodology stands on three phases: analysis, modelling and application to the watch. This thesis emphasizes the need of a tribological study to better understand the tribological response of a mechanical watch. By combining reviews of literature, experimental observations, and theoretical laws, analytical models were developed to identify critical parameters, materials and design strategies for improving the tribological response of watch components.

EPFL2020

Impeccable appearance of surfaces is a key constraint in high-end jewelry and watch manufacturing. Based on long tradition in the industry, appearance of products is assessed by trained individuals through visual inspection in designated intervals on the production line. Despite the high efficiency of the visual quality control in detecting aesthetic defects, it suffers from a major shortcoming. In many cases when the expert declares the appearance of an artifact to be unsatisfactory, she/he is unable to specify the surface defect that has caused the aesthetic imperfection. In other words, the visual control cannot provide a correlation between actual properties of the surfaces and the responsible manufacturing process to their aesthetic consequences. Addressing this industrial problem requires developing a methodology for assessing aesthetic defects on the polished surfaces based on an understanding of the surface phenomena. This research work builds its approach towards the study of aesthetics of surfaces around an existing framework that proposes four parameters of color, gloss, translucency and texture as measurable surface properties, which can be linked to appearance. The current study allowed implementation of this general framework to the case study of polished gold surfaces by developing necessary application-related definitions and measurement techniques. Measurement techniques that were employed here granted the possibility for quantitative assessment of surface and near surface properties of ternary gold-silver-copper alloys in terms of topography, chemical composition, microstructure, mechanical properties and optical properties. Based on findings of those measurements, two leading surface properties that could cause a defect in aesthetic appearance of polished gold surfaces were recognized to be roughness and chemical composition. Quantitative correlations could be drawn for 18 karat gold alloy between the magnitude of two well defined physical and chemical properties of the surface (surface roughness and near surface chemical composition) with color characteristics of the surface (through CIELAB

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values) and reflection properties (through calculation of total integrated scattered light). Finally, this work highlighted the significance of roughness evaluation at different length scales and also the importance of considering the chemical composition at the surface and near the surface. It was also shown that both of these parameters are modified during the common fabrication process of a watch or jewelry piece.

EPFL2019

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This paper describes the development of a voice data recording watch and the accompanying software and hardware needed to build an integrated solution for medical data capture and automatic codification. The developed system is used to capture on the stand-alone watch, either by voice recording or by form-filling, the relevant information on the healthcare service being provided. The captured information is stored locally and then downloaded to a PC, via a USB connection. In the PC, speech is translated first into text and then into medical codification, with minimum userintervention. The resulting information is stored into local or centralized patient databases, to be sent later to 3rd-party SW for billing, reporting and statistics. The user controls the watch either via a touch-screen based interface or via a voice-driven interface for hands-free operation. Although this work is multidisciplinary, in this paper the emphasis is put on the description of the DSP implementation.

EURASIP2008

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EPFL2019

Tribological Approach to the Watch Movements

Valentine Agnès Madeleine Magnin

EPFL2020