Loehr Patent Perpetual, Switzerland 1880’s
The relationship between precision mechanics and gravity has been explored by inventors and watchmakers since ancient times, starting with the weights and pendulums of large clocks, and ending with self-winding devices and high-precision tourbillons.
In this article we will examine a very unusual pocket watch with an automatic winding mechanism from an early pendulum design, the ‘Perpetuelle’. The history of this mechanism began in 1775 – 1780, when Abraham-Louis Breguet himself refined this design, and brought it to its technically perfect form.
This version is a later copy from the 1880’s, and not from Breguet. However, the design closely overlaps with Breguet’s devices. It is labelled in the catalogues as “Loehr Patent”, after the name of its inventor.
Enamel dial with the Loehr Patent lettering.
The Von Loehr Patent
The creator of this particular watch movement design is the Austrian engineer Von Loehr, who designed a special automatic winding device in 1875, and patented it on January 10th, 1878. The patent claimed the protection of the rights to 11 schemes of mechanisms that convert the movement of an oscillating load into the tension of a wind-up spring.
The son of August von Loehr, August Ritter von Loehr, was a numismatist and money historian who was involved in the defence of the Austrian cultural collections as part of his role in the Federal Monuments Office in Austria. By all accounts it appears that he did not continue his father’s watchmaking business.
Diagrams of devices from the patent of Von Loehr, which automatically start the spring from the vibrations of the load.
The main idea is that the load is suspended in a spring-loaded state, as close as possible to the point of equilibrium. The oscillation of the load under the influence of swaying, forces the ratchet wheel to rotate, interacting with two movable teeth – pushing (fixed to the load), and fixing (fixed to the body).
The whole design, with all 11 schemes, was patented for widespread use. However, one of the devices (number 11 on the diagram) was successfully implemented for use in pocket watches, causing the production of such watches to be established in Switzerland in the 1880’s, using only one of the devices patented by Loehr.
The inner cover bears the signature Patent Perpetuelle and the serial number 3357. Note the square on the central axis, an early design for the keyless movement of the hands, performed by fixing a small handle to that square, and then turning. Also noteworthy is the shape of the hanging ring, from which the watch is held vertically in the pocket.
A large pendulum is visible through the opening…
And here it is, the Perpetuelle!
When the watch is carried vertically in the pocket, aided by the specially shaped ring, the oscillations of the weighted pendulum wind up a spring. The mechanism uses a steel ratchet wheel that interacts with two moveable teeth – pushing (fixed on a hammer) and locking. The teeth of the ratchet wheel are very small, and the mechanism reacts even to the slightest vibrations of the pendulum.
The shape of the pendulum resembles the designs of Abraham-Louis Breguet, which he used in his watchmaking from 1775 – 1778.
How the Self-Winding Function Works in a Pocket Watch
The pendulum in its two extreme positions (click to enlarge).
When you carry the watch in your pocket, the pendulum swings up and down under its own weight. Any slight movement of the pendulum will cause the steel ratchet wheel to spin by several teeth and fix with a latch. From the ratchet wheel, a spring is wound through a system of transmission wheels.
Each swing of the pendulum transmits a sufficiently large force that spins the wheel system for many tens of rotations. To see this function in real time, click the download button below.
The position of the screw and the sleeve, from which a long thin spring emerges, regulates the rigidity of the pendulum-hammer suspension. By making it softer and tougher, the mechanism can be adapted to the wearer’s gait.
Additional Features and Complications
When winding the watch with a crown or key, the wearer will feel the spring stop and thus will cease to turn it, to prevent any damage. With automatic watches, it is more difficult – they just lie in your pocket and have to take care of the safety of the winding mechanism themselves.
To remedy this, there is one more interesting design trick in the mechanism, also patented by von Loehr. This is a winding spring limiter, which protects the parts of the mechanism from damage in the event of excessive winding.
An ingenious winding limiter is mounted on the wind-up drum.
The limiter is made in a very interesting way, one cannot easily guess its purpose or principle of operation. There is a slot in the cover of the wind-up drum. A special hook is attached to the outer coil of the spring (indicated by a blue arrow). On the arbor of the drum, a gear wheel is mounted with a fixed bar and a pin at the end, which is raised up by about 1 mm (the pin is indicated by a red arrow).
The stop pin comes out from under the mechanism board and can move the locking tooth of the ratchet wheel.
The winding spring stop pin.
Until the spring is wound up to the limiter, the wheel with the stop pin dangles freely on the drum axis. When the winding spring is at its limit, its outer coil shifts to the arbor of the drum, and the tooth attached to the coil will catch on the wheel. In turn, the wheel moves the bar with the pin, and the pin lifts the locking tooth of the ratchet wheel, which is why it ceases to fix the winding spring.
Even when the spring is wound up to its limit, the pendulum will still oscillate, but the forces are not transmitted to the winding wheel system. This solution is competent as well as interesting, because if the movement of the pendulum were blocked, the limiter could simply break under the weight and movement of the pendulum.
The Keyless Hand Setting Mechanism
It would be impractical to carry around a key for setting the hands on a watch. Therefore, a toothed transfer handle is provided on the central axis, and a slot is made for it in the inner cover of the watch. With a simple movement of your finger, you can conveniently move the hands without using a key. This design has been around since the 1830’s, but it is quite rare.
The watch was made around 1880, before the mass distribution of watch crowns. This is also evidenced by the early serial number 3357, as well as the early design. Later, Loehr Patent watches were equipped with a spring winding indicator, and were predominantly made in a mainsquare shape, which gave them an additional unique quality compared to ordinary watches.
Characteristics
- Nickel case with opening front cover, signed Patent Perpetual #3357.
- Enamel dial with Roman numerals and small seconds dial, signed LOEHR PATENT.
- Steel hands, blued. Original convex mineral glass.
- Gold plated plates and bridges, simple cylinder escapement, serial number 3357 is embossed on the plate.
- Pendulum type automatic winding device.
- Additional device for the mainspring limiter.
- Keyless hand setting device.
- A specially shaped hanging ring for carrying the watch vertically in the pocket.
- In general, it is in good condition, everything works and functions accurately.
Although this watch cannot be called the perfection of workmanship, the ingenuity and applied technical solutions do make it a very interesting piece for the collection, one which can be used to study the history of the development of automatic mechanical watch winding devices.
The winding system is very similar to the later ‘bumper’ automatic machines. What is also noteworthy is that the principles applied to this movement have not undergone any drastic changes, and are still used in most automatic winding mechanisms to this day.
