US2373429A - Magnetic escapement for timepieces - Google Patents

Description

p 1945. R. STRAUMANN 2,373,429

MAGNETIC ESGAPEMENT FOR TIMEPIECES Fi led Feb. 4, 1943 IE2 ven zor REINHARD .STRAUMAN Attornqy Patented Apr. 10, 1945 1 MAGNETIC ESCAPEMENT FOR TIMEP IECES Reinhard Stranmann, Waldenburg; near Basel, Switzerland Application February 4, 1943, Serial No. 474,734 In'Germany December 15, 1941 1 Claim. (Cl. 58-116) It is known to control the running of watch movements and the like by means of a swinging system consisting of a spiral spring vand a flywheel, which swinging'system causes the gear work and consequently the hands to intermittently run off step by step on each swinging period.

All of the swinging systems and escapements used hitherto for this purpose possess frictional parts such as pins, anchor claws, anchor wheel impulse teeth and so on which must be lubricated, The durability of the control power of such run controllers is dependent first of all on the state of lubrication which, as is known, depreciates so quickly in little escapements that the running of the watches is soon impaired.

The main object of the present invention comprises a frictionless controlling system in which the mass of the swinging system is a constitutive part of a magnetic escapement, activating the escapement by its periodical movement.

In order that the invention may be more fully understood, there will now be described by way of example only, and with the aid of the accompanying drawing, a constructional embodiment of the invention.

Fig. 1 is a cross section through the controlling system, while Fig. 2 is a side-view of the controlling system shown in Fig. 1.

To a block a is secured a lean-spring b bearing at its free end a mass which is formed by a little magnetic bar. The spring b and the mass 9 form a swinging system designed to control the running of the watch movement in agreement with its swinging frequency. An escapement wheel d is provided with two side cheeks d arranged laterally on both sides of the magnetic bar 0, each of these side cheeks carrying an inner and outer circular row of pins e and f, respectively. The pins e and f of the side-cheeks project toward each other and on each side-cheek the inner, and outer pins are arranged in sets of live. All pins consist of a magnetically permeable material, such as for example soft-iron. The escapementwheel d is driven by the watch movement through gearing a. On rotating the escapement wheel d the magnetic bar 0 is alternately attracted.

by the inner and outer pins e and ,f of the side cheeks so that it oscillates upwardly and-downwardly. When the speed of the wheel d in the direction of the arrow shown in Fig. l is so high that the frequency of passage of the pins e and I corresponds to the swinging frequency of the swinging system b, c, the latter will come to a resonance swinging and will oscillate with a strong amplitude.

The driving or moving power transmitted to the wheel d must be so high that the wheel d tends to run somewhat faster than would be necessary for energising the swinging system b, c. The magnet c, however, acts to restrain the movement of the pins e, f in their running direction, that is to say the magnetic bar 0 tends to exert a braking action on the pins 1 until it has reached its position corresponding to the greatest amplitude, thus allowing the pins 1 to run relatively freely. After half a swinging period the same operation is repeated between th magnet c and the pins e. Accordingly, the' frequency of passage, 1. e. the rotational speed of the wheel d is adapted to the frequency of the swinging system b, 0 so that there results a constant rotational speed controlled by the swinging system.

The size and dimensions of the parts of the run controller may be chosen so that, for example, the wheel d makes one revolution per second and carries on each side cheek (1 five pins e and five pins I which are offset for "half a division relative to each other. If the swinging system is determined in such a manner that it swings with a frequency Q=5, it will maintain the wheel d at a constant rotational speed N=1 per second.

The system according to the present invention has, beside the advantage of a frictionless rimning, a further advantage in that in such a. watch movement there is no necessity for lubrication. If the pins e and f are properly disposed with respect to the magnetic bar 0, the swinging system receives a short impulse near its position of rest. as soon as a pin passes the said magnetic bar. Moreover, in the same manner, the alternate braking action of the bar 0 on the pins e and. I also takes place on its passage through the position of rest. The conditions for a constant swinging frequency of the swinging system are thus fully accomplished. The exactitucle of the controlling efiect is some few seconds within 24 hours, which is sufllcient for good watches.

2 I I momma What 1 claim is A frictionless magnetic run controller for watch movements and the like, comprising an oscillating leaf spring fixed at one end, a magnetic mass in term of a bar arranged at the free end thereof and an escapement wheel with two side-cheeks,

having each on'its inner side two similar rows oi radially displaced pins in such position relative to said magnetic mass as to cooperate there-

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