There are actually four basic design classifications:
▪ Electromechanical clocks that use mechanics to rewind the mainspring (via attachment of a motor or an electromagnet)
▪ Electromechanical clocks that use mechanics to operate the pendulum or oscillator
▪ Electromagnetic clocks that use electromagnetic impulses to operate the pendulum or oscillator
▪ Synchronous clocks that rely on the the 50 or 60 Hz utility frequency of the AC power line as a timing source, by driving the clock gears with a synchronous motor.
In 1814, Sir Francis Ronalds (1788) of London invented the forerunner of an electric clock, the electrostatic clock. His prototype was powered with a dry pile battery. It proved unreliable in timekeeping, however, because of a strong dependence on a stable room temperature and 'weather conditions'.
In 1815, Giuseppe Zamboni (1776-1846) of Verona invented and showed another electrostatic clock run with dry pile battery and an oscillating orb. Over the test of time Zamboni's clock was praised "the most elegant and at the same time the most simple movement yet produced by the electric column". Zamboni's clock had a vertical needle supported by a pivot and was so energy efficient that it could operate on one battery for over 50 years.
Numerous people were intent on inventing the electric clock with electromechanical and electromagnetic designs around the year 1840, such as Wheatstone, Steinheil, Hipp, Breguet, and Garnier, both in Europe and America.
In 1840, Alexander Bain (1811-1877), a Scottish clock and instrument maker is the first to invent and patent the electric clock. His original electric clock patent is dated October 10, 1840. On January 11, 1841, Alexander Bain along with John Barwise, a chronometer maker, took out another important patent describing a clock in which an electromagnetic pendulum and an electric current is employed to keep the clock going instead of springs or weights. Later patents expanded on his original ideas.
Matthias Hipp (1815-1893), clockmaker born in Germany, is credited with establishing the production series, mass marketable electric clock. Hipp opened a workshop in Reutlingen, Switzerland, where he developed an electric clock to have the Hipp-Toggle, presented in Berlin at an exhibition in 1843. The Hipp-Toggle is a device attached to a pendulum or balance wheel that electromechanically allows occasional impulse or drive to the pendulum or wheel as its amplitude of swing drops below a certain level, and is so efficient that it was subsequently used in electric clocks for over a hundred years. Hipp also invented a small motor and built the chronoscope and the registering chronograph for time measurement.
The first electric clocks had prominent pendulums because this was a familiar shape and design. Smaller clocks and watches with a spiral-balance are made on the same principles as pendulum clocks.
The configuration of this device is comparatively very simple and reliable. The typical deviation of the electromechanical clock is about 10 seconds per hour and it usually can run for about a year using the energy of the single battery. The electrical current powers either a pendulum or an electromechanical oscillator.
The electromechanical oscillator component has an attached magnet that passes two inductors. When the magnet passes the first inductor or sensor, the simple amplifier opens the current across the second inductor, and the second inductor works as electromagnet, providing an energy pulse to the moving oscillator. This oscillator is responsible for the accuracy of the clock. The electronic part would not generate electrical pulses if the oscillator is absent or does not move. The resonance frequency of the mechanical oscillator should be about several times per second.
In the presented diagram of the 1968 year electromechanical clock, the resistor R1 can be about 27 kΩ, the capacitor C1 about 25 μF and capacitor C2 about 0,033 μF. Both inductors have about 2300 windings. The device is a common collector amplifier, opening current across the inductor Lu only when the oscillator magnet passes the sensor inductor L0, causing the base current and opening the transistor. This clock uses the 1.5 V battery (the most of devices used 1.5 - 4.5 V power source).
By the mid 19th century, ideas had already germinated for the first electrical clocks. The foreground was occupied less by the electrical drive of the clock itself, and much more by the control of several secondary clocks by a central timepiece. The section on "Electrical horology systems" provides more on this.
The decorative, electrically driven clocks to be shown in this section appeared at the start of the 20th century. The first, really popular clock to be manufactured in large numbers and different versions was the English "Eureka" with its impressive, large balance wheel. The system rests on the principle of a moving-coil instrument. The large balance wheel is also on ball bearings. It is the first known application of ball bearings in clocks.
Around 1910 the French "Brillié" wall clock became common. This is actually a central timepiece which generates switching pulses for secondary clocks. The drive principle, however, has persisted almost to the present day, which is why this type of clock is also mentioned here. Unfortunately, little has been passed down of the history of Brillié clocks. The drive consists of a fixed electrical coil, inside which is a polarized magnet attached to the pendulum. A contact system controls the current in the coil in such a way that the pendulum receives a drive pulse in the right momentum. The motion work and other mechanisms are driven via a ratchet wheel.
The most common electrical Einzeluhr is the "Bulle clock". Despite its English name, this is a French make founded by Mr Favre-Bulle, watch and clock engineer from Besançon, in the years 1915 to 1920. The Bulle clock was manufactured and sold in many versions as a table or wall clock up to around 1970. The principle of the Bulle clock is similar to the Brillié, with the essential difference that the magnet is fixed and the coil is mounted on the pendulum. This arrangement is more complicated than the Brillié, but proved itself for more than 5 decades. Whether this arrangement was dictated by patent claims is beyond my knowledge. However, a Bulle clock runs for about 3 years with a modern 1.5V batterie (UM1)!
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