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Glossary

Glossary - R

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RATCHET WHEEL

Toothed wheel prevented from moving by a click pressed down by a spring.

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REGULATING UNIT

Made up by balance and balance spring, governing the division of time within the mechanical movement, assuring its regular running and accuracy. As the balance works like a pendulum, the balance spring's function consists of its elastic return and starting of a new oscillation. This combined action determines the frequency, i.e. the number of vibrations per hour, and affects the rotation speed of the different wheels. In fact the balance, by its oscillations, at every vibration (through the action of the pallets), frees a tooth of the escape wheel (see escapement). From this, motion is transmitted to the fourth wheel, which makes a revolution in one minute, to the third and then the center wheel, the latter making a full rotation in one hour. However, everything is determined by the correct time interval of the oscillations of the balance.

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REGULATOR

Regulating the functioning of a movement by lengthening and shortening the active section of the balance spring. It is positioned on the balance-bridge and encompasses the balance spring with its two pins near its fixing point on the bridge itself. By shifting the index, the pins also are moved and, by consequence, the portion of the balance spring capable of bringing the balance back is lengthened or shortened by its elastic force. The shorter it is, the more reactive it tends to be and the more rapidly it brings the balance back and makes the movement run faster. The contrary happens when the active portion of the balance spring is lengthened. Given today's high frequencies of functioning, even slight index shifts entail daily variations of minutes. Recently, even more refined index-regulation systems were adopted (from eccentric to micrometer screws) to limit error margins to very few seconds per day.

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REMONTOIR or CONSTANT-FORCE

Old term used to denote any mechanism assuring a constant transmission of the driving power to the escape wheel.

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REPEATER

Mechanism indicating time by acoustic sounds. Contrary to the watches provided with en-passant sonnerie devices, that strike the number of hours automatically, repeaters work on demand by actuating a slide or pusher positioned on the case side. Repeaters are normally provided with two hammers and two gongs: one gong for the minutes and one for the hours. The quarters are obtained by the almost simultaneous strike of both hammers. The mechanism of the striking work is among the most complex complications.

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RETROGRADE

Said of a hand that, instead of making a revolution of 360? before starting a new measurement, moves on an arc scale (generally of 90? to 180? and at the end of its trip comes back instantaneously. Normally, retrograde hands are used to indicate date, day or month in perpetual calendars, but there are also cases of retrograde hours, minutes or seconds. Unlike the case of the classical indication over 360? the retrograde system requires a special mechanism to be inserted into the basic movement.

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ROLLER TABLE or ROLLER

Part of the escapement in the shape of a disc fitted to the balance staff and carrying the impulse pin that transmits the impulses given by the pallets to the balance.

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ROTATING BEZEL

Part of the escapement in the shape of a disc fitted to the balance staff and carrying the impulse pin that transmits the impulses given by the pallets to the balance.

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ROTOR

In automatic-winding mechanical movements the rotor is the part that, by its complete or partial revolutions and the movements of human arm, allows winding of the mainspring.

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