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ATO Mantel Clock
(Impulsed; moving magnet; mechanically switched)

ATO mantel clock

This attractive Mantel clock, standing 7 inches high, was made by Leon Hatot's company in France in the mid 1920s. The name 'Galibert' and the name 'Le Havre' have both been added after the dial was made and represent the retailer who originally sold the clock. The case is veneered in Mahogany with Sandalwood stringing. There is a cut-out in the centre of the dial through which the 1/4 second pendulum can be seen swinging.



ATO Mantel clock

View from the rear. The 1/4 second pendulum rod is of invar with  a bob in the form of a curved magnet passing through a coil assembly on the right and a copper hoop on the left. The coil carries a current (controlled by a switch mounted on the pendulum) for a short period once per complete swing. This gives impulse to the pendulum on each left-to-right swing as viewed from the back of the clock. The copper hoop is effectively a single turn damping coil to limit excessive swings of the pendulum. There is a rating nut at the bottom of the pendulum. The pendulum carries a pawl which moves an index wheel by one tooth each complete swing thus driving the hands. The movement is a typical ATO design of small round plates about an inch and a half in diameter.

ATO pendulum magnet and coil

Detail of the pendulum magnet and coil.



ATO Mantel clock - indexing pawl & wheel

Detail of the index pawl and wheel. 


ATO Mantel clock - pendulum switch action
The action of the pendulum switch viewed from the rear of the clock.

Mounted towards the top of the pendulum there is a rocking cage (connected to one pole of the battery) which embraces two fixed pins. The left pin (shown solid black) is connected via the coil (bottom right) to the other pole of the battery. The right-hand pin is insulated. On each left-to-right swing of the pendulum the rocking cage makes contact with the 'live' pin and the circuit is completed giving impulse to the pendulum. On the right-to-left swing of the pendulum, the rocking cage meets with the insulated pin and no current flows. 

(This drawing is not to scale)

The rocking contact cage on the pendulum. The vertical silver pin is the electrical contact pin.

The pendulum suspension is by 2 pairs of wire hoops and is very rugged.

ATO Mantel clock
Voltage: 1.5v
Battery type: Originally specially made, but use
one LR14/MN1400/C size cell
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Copyright  Text & Pictures - Martin Ridout.   Last updated Jan 2005.