What Is a Pendulum Clock?

The pendulum clock is a kind of clock. It was invented by Dutch physicist Christiaan Huygens in 1656 ^[1] . It is manufactured according to the law of single pendulum. The pendulum is used to control other parts to make the clock go faster In general, it can report points. It is necessary to use a clockwork to provide energy to make it oscillate.

The swinging pendulum is oscillated by the transformation of gravity potential energy and kinetic energy. Simply put, if you pull the pendulum high, it will go down due to the influence of gravity. After reaching the lowest position, it has a speed and cannot stop directly (It's like the brake can't stop immediately.) Because of the inertia, it will continue to rush through the lowest position, and swing back to the highest position because gravity slows it down to 0, and the clock pendulum has a downward acceleration. So reciprocating, it kept swinging.

According to the above description, the pendulum can swing forever, but due to the existence of resistance, it will gradually decrease and finally stop. So use the clockwork to provide energy to make it oscillate.

According to the formula, the pendulum length L is proportional to the square of the period T, so the longer the pendulum length, the longer the period (the pendulum is a type of single pendulum) The single pendulum period formula is only applicable to mechanical vibration with a swing amplitude less than 5 degrees.

The structure of the pendulum clock can be roughly divided into the travel time part, the dot part, the pointer part and the dot control part.

1. Travel time

It consists of a head wheel (ie a box wheel with a built-in spring), a second wheel, a three wheel (center wheel), a four wheel, an escape wheel, a pallet fork, a pendulum, etc.

The barrel wheel is the largest wheel in the movement. The mainspring is housed in a box under the wheel (the majority of pendulum clocks produced before do not have a barrel). The second, third, and fourth wheels are all transmission wheels, and the structure is composed of wheel axles, wheels, pin wheels, and so on. The structure of the escapement wheel is the same as that of the above-mentioned wheels, but its tooth profile of the wheel is an oblique triangle. The escapement fork is also called a clip, and its function is to take over the escapement gear teeth and send it out.

The pendulum assembly includes a pendulum, a pendulum and a pendant device. There is a through hole in the middle of the pendulum, the pendulum rod passes through it, and the lower part is screwed to fix it. This device can raise or lower the pendulum to adjust the speed of the clock.

2. RBI

It consists of a round box, a round two, a round three, a round four, a round five and a wind wheel. There is a star angle wheel on the RBI three wheels. When the wheel train rotates, it continuously raises and lowers the lifting lever on the RBI shaft. Two ends of the RBI shaft are fixed with two hammers. Two short gongs make a pleasant sound. The wind wheel is mainly used to adjust the rotation speed of the gear train, so that the clicking sound has a suitable time interval.

3. Pointer section

It consists of a split wheel, a cross wheel and a time wheel. The structure principle is basically the same as the alarm clock.

4. RBI control section

The pendulum clock ticks every half an hour, and the number of full-time taps must be the same as the time indicated by the hour hand. Therefore, its tick must be controlled by the travel time. There is a mechanism for controlling the number of punctuations between the travel time and the puncture. It is composed of a two-cornered cam, a twelve-cornered cam, a sector tooth, a brake lever, a switch lever, and a gear shift cam.

The two-corner cam is tightly fixed on the central wheel shaft of the travel part, and it makes one revolution with the central wheel every hour. The radius of the two-point cam tooth tip is one long and one short. The long hits the whole point and the short hits the half point. The twelve angle cam is sleeved on the hour wheel tube, and it makes one revolution every twelve hours, and one corner of the twelve angle cam is rotated every hour. The lifting lever usually blocks the nails on the five-wheel of the RBI, making the RBI mechanism inoperable. When the two-corner cam rotates clockwise, slowly lift the brake lift lever, and the upper end of the brake lift lever finally releases the nail (this process is also called lift brake), but after turning the five-round stop nail through an angle, It was blocked by the turning angle of the switch lever again, and the dot mechanism stopped running. As the lifting lever was lifted, the switch lever was jacked up. The original end of the switch lever supported the fan-shaped toothed plate and now released, the fan-shaped toothed plate fell, and the middle folded corner of the toothed plate was in the middle of one corner of the twelve-point cam. When the two-angle cam pushes the lift lever to the highest point and falls, the nail stop position of the switch lever blocking the five-wheel drive is also disengaged at the same time, and the trigger mechanism starts to rotate. Click the star angle wheel on the three wheels to turn the lift lever to drive the hammer to hit the gong. The gear-shifting cam fastened on the four-wheel axle also rotates. The gear-pin on the cam moves the fan-shaped tooth plate upwards until the end of the switch lever supports the fan-shaped halogen plate again, and the lifting lever blocks the nails on the fifth wheel. , RBI work is complete.

A clock with a pendulum as a vibration system. It usually has the function of telling the time, so it is also called self-clocking. 1582 ~ 1583, Italian physicist and astronomer

The pendulum clock uses the periodic vibration (oscillation) process of the pendulum to measure time. Time = vibration period of the pendulum × number of vibrations. And the period of vibration of the pendulum T = 2 (l / g) ^ 0.5

Generally, the weight of the pendulum is determined, and the vibration period of the pendulum can be adjusted by adjusting the reference length (l) of the pendulum. The shorter the pendulum reference length is, the faster the clock becomes; otherwise it becomes slower. For precision pendulum clocks, an additional weight method is also used to fine-tune the period of the pendulum vibration. The pendulum clock is placed in different geographical locations (different earth latitudes and altitudes), and the gravitational acceleration of the pendulum will change to affect its vibration cycle. Placing the pendulum clock in a different temperature and pressure environment can also cause changes in the vibration cycle. Changes in temperature will cause changes in the size of each part of the pendulum, including the reference length of the pendulum. Generally, the temperature increases, the pendulum swells and the clock becomes slower; otherwise, the pendulum shortens and the clock becomes faster. Therefore, precision pendulum clocks are often made of materials with different coefficients of linear expansion to make temperature compensation tubes to compensate for temperature effects. Changes in air pressure cause changes in air resistance and air density, which in turn cause changes in the vibration cycle. Therefore, precision pendulum clocks are often installed in a constant-pressure housing to eliminate the effects of air pressure.

The vibration amplitude of the pendulum affects the isochronism of the clock. The smaller the amplitude, the smaller the variation of the day difference caused by the amplitude change (see the time difference of the clock), that is, the better the isochronism, so the precision pendulum clock often uses a small pendulum swing. However, small swings are sensitive to external shocks and impacts, so they have high requirements on the installation environment. The time difference of pendulum clock can generally reach within 20 seconds / day, and precision pendulum clock can reach several thousandths of a second.

The pendulum clock is a mechanical clock. Although some quartz electronic clocks are also equipped with a pendulum or twisted pendulum, they only play a decorative role. ^[2]