CYLINDER ESCAPEMENT
Cylinder escapement (2.5 Hz)
Speed 1:4
Cylinder escapement (2.5 Hz)
Normal speed
The cylinder escapement was invented in 1725 by George Graham, who drew inspiration from the “hog’s trough” escapement of his mentor, Thomas Tompion, and significantly improved its performance. By 1750, the cylinder escapement had become the most widely used, replacing verge escapements thanks to its superior timekeeping precision.
Despite its advantages, the cylinder escapement suffered from low efficiency and underwent continuous refinement for over 150 years. Abraham-Louis Breguet achieved its highest performance by combining a hardened steel escape wheel with ruby cylinder lips. From the mid-19th century onwards, the cylinder escapement was gradually phased out, ultimately replaced by the more efficient Swiss lever escapement.
This is a frictional rest escapement. The numerous frictions generated by its operation result in low efficiency (high energy losses). Nevertheless, when manufactured with precision and properly finished, it can achieve good chronometric performance. The amplitude of the balance wheel oscillations can reach around 150°, allowing for better regulation than a verge escapement and making it possible to dispense with the fusee.
The escapement consists of two elements: the escape wheel and the cylinder. The cylinder is an integral part of the balance wheel staff, forming its central section. It is hollowed with a slot whose two vertical edges, called the lips, successively receive the impulses from the teeth of the escape wheel.
The impulse is transmitted directly to the cylinder by the escape wheel, whose outer tooth surfaces form the impulse planes. The teeth of the escape wheel are positioned above the plane of the wheel body. The escape wheel most often has 15 teeth, and only very rarely 13.
Figure 1
The operation of the cylinder escapement can be divided into five phases, which occur in a fixed cycle at each oscillation of the regulating organ. These five phases are:
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External rest
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External impulse
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Internal drop and rest
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Internal impulse
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External drop and rest
Below is a detailed description of the action of each component during these five phases:
1. External rest:
During this phase, the tip of the tooth rests against and rubs on the outside of the cylinder while the balance performs its supplementary arc (Figure 2).
Figure 2
2. External impulse:
The tip of the tooth comes into contact with the impulse plane of the cylinder’s entry lip. This marks the beginning of the external impulse (Figure 3).
Figure 3
The tip of the entry lip comes into contact with the impulse plane of the tooth (Figure 4).
Figure 4
3. Internal drop and rest:
Once the external impulse is completed, the tooth leaves the impulse plane of the entry lip (Figure 5) and drops against the inner wall of the cylinder in its rest position. The balance then performs its supplementary arc (Figure 6).
Figure 5
Figure 6
4. Internal impulse:
The tip of the tooth comes into contact with the impulse plane of the cylinder’s exit lip. This marks the beginning of the internal impulse (Figure 7).
Figure 7
The tip of the exit lip comes into contact with the impulse plane of the tooth (Figure 8).
Figure 8
5. External drop and rest:
The tooth leaves the impulse plane of the exit lip (Figure 9) and drops onto the outer wall of the cylinder in its rest position (Figure 10).
Figure 9
Figure 10
Note:
For a complete understanding of the operation of the cylinder escapement, please refer to the two animations shown at the top of this page.
Advantages:
The cylinder escapement achieves an amplitude of around 150°, which is greater than that of the verge escapement, allowing for improved timekeeping performance.
Although still relatively inefficient, the cylinder escapement offers better efficiency than verge escapements.
Disadvantages:
The escape wheel teeth remain in constant contact with the cylinder, generating significant friction. This affects efficiency and demands exceptional cleanliness, precise lubrication, and consequently, frequent maintenance.
The cylinder escapement requires high manufacturing precision, careful material selection, and finely finished surfaces to function correctly.