DE102009044651B4 - Clock with magnetic shield - Google Patents

Abstract

Clock (1) with magnetic shielding (2; 2 '), characterized in that the magnetic shielding (2; 2') consists of an alloy which consists in weight percent of 3% <Co <20%, 6% <Cr <15 %, 0% ≤ S ≤ 0.5%, 0% ≤ Mo ≤ 3%, 0% ≤ Si ≤ 3.5%, 0.2% ≤ Al ≤ 2.0%, 0% ≤ Mn ≤ 4.5 %, 0% ≤ Me ≤ 6%, where Me is one or more of the elements Sn, Zn, W, Ta, Nb, Zr and Ti, 0% ≤ V ≤ 4.5%, 0% ≤ Ni ≤ 5%, 0% ≤ C <0.05%, 0% ≤ Cu <1%, 0% ≤ P <0.1%, 0% ≤ N <0.5%, 0% ≤ O <0.05%, 0% ≤ B <0.01%, 0% ≤ S <0.5%, balance iron and usual impurities.

Description

The invention relates to a clock, in particular a mechanical clock with magnetic shield.

A watch, especially a watch with shielding against external magnetic fields is in the DE 1 146 454 as well as in the CH 516 835 disclosed. This shield makes the watch less susceptible to external magnetic fields which, without shielding, can affect the accuracy of the clock. It is desirable to protect the movement against external magnetic fields of up to 1000 Gauss.

The shield may be in the form of a closed capsule encasing the movement to protect the clock or gear from the influence of external magnetic fields. Alternatively, the shield may include a plurality of separate parts disposed about the movement. In both cases, the shield is made of a material of high permeability, high saturation polarization and low hysteresis.

When designing a timepiece, the workability of the shielding material is important, as the shielding should be made accurately to keep the size of the watch as small as possible. Furthermore, in the case of a capsule, the mechanical properties of the shield should also be such that the capsule can be constructed so that it can be closed again if a repair of the movement should be necessary.

Pure iron could be used as the material for the capsule since it has a very high permeability and a large saturation polarization and hence a good shielding effect. However, iron has the disadvantage that it can also corrode in closed watches due to the humidity.

A nickel-iron alloy, such as mumetal, may be used for the capsule. A nickel-iron alloy has improved corrosion resistance but less saturation polarization than pure iron.

The GB 1 299 390 discloses a watch made of a hardened stainless steel.

However, further improvements are desirable to simplify the manufacture of the shield members and extend the life of the parts.

The object is therefore to provide a clock with magnetic shield, which better meets these requirements.

This is solved by the subject of the independent claim. Further advantageous developments are the subject of the dependent claims.

According to the invention, a magnetic shield is provided, the magnetic shield consisting of an alloy consisting, by weight, of 3% <Co <20%, 5% <Cr <15%, 0% ≤ S ≤ 0.5%, 0% ≦ Mo ≦ 3%, 0% ≦ Si ≦ 3.5%, 0.2% ≦ Al ≦ 2.0%, 0% ≦ Mn ≦ 4.5%, 0% ≦ Me ≦ 6%, wherein Me is one or more more than one of Sn, Zn, W, Ta, Nb, Zr and Ti, 0% ≦ V ≦ 4.5%, 0% Ni ≦ 5%, 0% ≦ C <0.05%, 0% ≦ Cu < 1%, 0% ≤ P <0.1%, 0% ≤ N <0.5%, 0% ≤ O <0.05%, 0% <B <0.01%, balance iron and common impurities.

The magnetic shield of the clock according to the invention thus consists of a chromium-cobalt-iron alloy. This alloy can be machined well without cutting or by turning. Consequently, the shape of the shield can be made in various ways to accurately control the shape and dimensional accuracy of the shield. This alloy also has good corrosion resistance so that the shield in the watch shows little or no corrosion.

Further, this alloy has a high saturation polarization (J _s ), a low coercive force (H _c ) suitable for use as a magnetic shield.

The polarization J of the shield at a magnetic field H of 160 A / cm may be greater than 1.6 T or greater than 1.7 T. The saturation polarization J _{s of} the magnetic component at a magnetic field H of 600 A / cm may be greater than 1.75 T or greater than 1.8 T. A high value of the saturation polarization J _s enables the size and weight of the shield to be reduced.

The shield may have a resistivity (ρ) greater than 0.4 μΩm or greater than 0.5 μΩm or greater than 0.58 μΩm.

The magnetic shield can be designed differently. In a first embodiment, the magnetic shield consists of a pot and a lid, which are interconnected. This shield provides a capsule that completely or almost completely envelops the movement.

The pot and the lid can be connected to one another by a spring or by a thread. A thread has the advantage that no air gap is created between the parts, so that the protection against moisture and the shield against external magnetic fields are improved. Due to the good machinability of the alloy described above, a thread can be faithfully placed in the pot and lid, so that the air gap is kept as small as possible.

In a further embodiment, the magnetic shield consists of one or more separate parts. The movement is thus not necessarily completely enveloped by the shield. While not as effective as a capsule, this shield is simpler and less expensive to manufacture, and is more suitable for less expensive watches or watches exposed to smaller magnetic fields. One or more of these parts may be plate-shaped.

In this description, all compositions are given in weight percent.

In one embodiment, the Co content of the shield is in the ranges 6% <Co <16%. For applications where high J _{s is} desired, higher Co content can be provided. Since cobalt is a relatively expensive element, it may be desirable to use a lower cobalt content for applications where it is desirable to reduce material costs.

The alloy may contain 0.01% ≦ Mn ≦ 1% and 0.005% ≦ S ≦ 0.5% or 0.01% ≦ Mn ≦ 0.1% and 0.005% ≦ S ≦ 0.05%. In another embodiment, the ratio of manganese to sulfur is Mn / S, ≥ 1.7. The provision of manganese and sulfur additives within these ranges further improves the degrees of freedom of the machining properties of the alloy.

The alloy may have titanium in place of the manganese and may therefore contain 0.01% ≦ Ti ≦ 1% by weight. Ti also improves the degrees of freedom of the machining properties of the alloy and has the added advantage of improving the magnetic properties and corrosion resistance of the alloy.

In one embodiment, the alloy has 9% <Co <20%, 5% <Cr <15%, 0% ≦ S ≦ 0.5%, 0% ≦ Mn ≦ 4.5%, 0% ≦ Al ≦ 2.5%, 0% ≦ V ≤ 2.0%, 0% ≤ Ti ≤ 2.0%, 0% ≤ Mo ≤ 2.0%, 0% ≤ Si ≤ 3.5%, 0% ≤ C <0.05%, 0% ≤ P <0.1%, 0% ≤ N <0.5 %, 0% ≤ O <0.05%, 0% ≤ B <0.01%, and at least one of Al, V, Ti and Mo.

This alloy thus consists of 9% <Co <20%, 6% <Cr <15%, 0% ≤ S ≤ 0.5%, 0% ≤ Mn ≤ 4.5%, 0% ≤ Al ≤ 2.5%, 0% ≤ V ≤ 2.0%, 0% ≦ Ti ≦ 2.0%, 0% ≦ Mo ≦ 2.0%, 0% ≦ Si ≦ 3.5%, 0% ≦ C <0.05%, 0% ≦ P <0.1%, 0% ≦ N <0.5% , 0% ≦ O <0.05%, 0% ≦ B <0.01%, as well as at least one of the elements Al, V, Ti and Mo, the remainder iron and common impurities.

This alloy represents a sub-selection of the general formula mentioned above. This alloy has at least one of Al, V, Ti and Mo and an improved corrosion resistance. Furthermore, the manufacture of the shield can be simplified, since this alloy can be produced with annealing temperatures in a wider temperature range with a low H _c .

In one embodiment, the alloy comprises aluminum, wherein 0.2% ≦ Al ≦ 2.0%, V = 0%, Ti = 0%, and Mo = 0%.

In further embodiments, the alloy comprises aluminum and one of the elements Ti, V and Mo such that 0.2% ≦ Al ≦ 2.0%, 0.2% ≦ Ti ≦ 2.0%, V = 0% and Mo = 0% or 0.2% ≦ Al ≦ 2.0%, 0.2% ≦ V ≦ 2.0%, Ti = 0% and Mo = 0% or 0.2% ≦ Al ≦ 2.0%, 0.2% ≦ Mo ≦ 2.0%, V = 0% and Ti = 0%.

A combination of aluminum and one of the elements Ti, V and Mo leads to a further improvement in corrosion resistance.

Embodiments will now be explained in more detail with reference to the drawings.

1 shows a mechanical watch with magnetic shield according to a first embodiment,

2 shows a mechanical watch with magnetic shield according to a second embodiment, and

3 shows the dependence of the coercive force on the annealing temperature.

1 shows a schematic partial cross section of a mechanical wristwatch 1 with magnetic shielding 2 in the form of a capsule 3 that the gear, not shown 4 the watch almost completely wrapped.

The clock 1 includes an outer housing 5 with a transparent top 6 , under which the clock hand and the dial are arranged. Of Furthermore, it comprises a pot-shaped lower part 7 and an annular center part 8th , The lower part 7 is above the middle part 8th with the shell 6 attached. The outer case 5 encloses the shield 2 as well as the movement 4 ,

The capsule 3 consists of a lid 9 and a pot 10 that have a thread 11 connected to each other. A threaded connection has the advantage that the air gap between the two parts 9 . 10 the capsule 3 can be kept as small as possible, so the shielding 2 the movement 4 can shield against larger external magnetic fields well.

The shield 2 however, closes the movement 4 not completely, as in a not shown area of the pot 10 at least one opening is provided, so that the movement 4 outside the shield 2 or the outer housing 5 can be adjusted for example with the regulating pin.

The lid 9 and pot 10 the shield 2 each consist of the same material, namely an iron-chromium-Colbalt alloy, which is described by the following formula:
3 wt% <Co <20 wt%, 5 wt% <Cr <15 wt%, 0 wt% ≤ S ≤ 0.5 wt%, 0 wt% ≤ Mo ≦ 3% by weight, 0% by weight ≦ Si ≦ 3.5% by weight, 0% by weight ≦ Al ≦ 4.5% by weight, 0% by weight ≦ Mn ≦ 4, 5 wt%, 0 wt% ≤ Me ≤ 6 wt%, wherein Me is one or more of Sn, Zn, W, Ta, Nb, Zr and Ti, 0 wt% ≤ V ≤ 4.5 wt%, 0 wt% Ni ≤ 5 wt%, 0 wt% ≤ C <0.05 wt%, 0 wt% ≤ Cu <1 wt% , 0 wt .-% ≤ P <0.1 wt .-%, 0 wt .-% ≤ N <0.5 wt .-%, 0 wt .-% ≤ O <0.05 wt .-%, 0 Wt .-% <B <0.01 wt .-%, balance iron and common impurities.

In one embodiment, the alloy may be described by the following formula:
9% <Co <20%, 6% <Cr <15%, 0% ≤ S ≤ 0.5%, 0% ≤ Mn ≤ 4.5%, 0% ≤ Al ≤ 2.5%, 0% ≤ V ≤ 2.0%, 0% ≦ Ti ≦ 2.0%, 0% ≦ Mo ≦ 2.0%, 0% ≦ Si ≦ 3.5%, 0% ≦ C <0.05%, 0% ≦ P <0.1%, 0% ≦ N <0.5%, 0% ≦ O <0.05%, 0% ≤ B <0.01%, as well as at least one of the elements Al, V, Ti and Mo, balance iron and common impurities.

In a further embodiment, the lid 9 as well as the pot 10 the shield 3 from 9.96% by weight Cr, 9.2% by weight Co, 0.01% by weight Mn, 1.7% by weight Mo, 1.2% by weight Al, balance iron, the alloy 93 / 7971 corresponds to Tables 1 to 3.

Table 1 summarizes the compositions of seven other example alloys which are also for shielding 3 can be used.

Alloys 93/7964, 93/7965 and 93/7966 have aluminum and no vanadium. The aluminum content is increasingly increased. Alloy 93/7964 consists of 13.25% by weight Cr, 10.25% by weight Co, 0.02% by weight Mn, 0.02% by weight Si, 0.34% by weight Al, Rest iron. Alloy 93/7965 consists of 13.30 wt% Cr, 10.25 wt% Co, 0.01 wt% Mn, 0.01 wt% Si, 0.84 wt% Al, Rest iron. Alloy 93/7966 consists of 13.30% by weight Cr, 10.25% by weight Co, 0.02% by weight Mn, 0.02% by weight Si, 1.40% by weight Al, Rest iron.

As with alloy 93/7971, alloy 93/7972 has no silicon, but molybdenum. It consists of 8.90 wt .-% Cr, 13.45 wt .-% Co, 0.01 wt .-% Mn, 1.94 wt .-% Mo, 1.15 wt .-% Al, balance iron.

Four other alloys have aluminum as well as vanadium. The cobalt content is increasingly increased. Alloy 93/7967 consists of 13.00% by weight of Cr, 10.30% by weight of Co, 0.01% by weight of Mn, 0.04% by weight of Si, 1.39% by weight of Al, 1 wt .-% V, balance iron. The alloy 93/7968 consists of 13.20 wt .-% Cr, 13.40 wt .-% Co, 0.01 wt .-% Mn, 0.07 wt .-% Si, 1.36 wt .-% Al, 0.99 wt.% V, balance iron. Alloy 93/7969 consists of 13.25% by weight of Cr, 16.50% by weight of Co, 0.01% by weight of Mn, 0.03% by weight of Si, 1.32% by weight of Al, 0.99 wt .-% V rest iron.

Alloy 93/7970 is not part of the present invention due to the high cobalt content and consists of 13.15 wt.% Cr, 20.70 wt.% Co, 0.01 wt.% Mn, 0.02 wt. % Si, 1.27 wt.% Al, 0.99 wt.% V, remainder iron.

The coercive force H _c and polarization J of the alloys of Table 1 are summarized in Table 2. The alloys summarized by the above formula are suitable for a magnetic shield for a watch since its polarization J (H) is greater than 1.6T or 1.8T with a magnetic field H of up to 560 A / cm and a lower coercivity of less than 1 A / cm or 0.6 A / cm.

3 1 shows a diagram with regard to the dependence of the measured coercive field strength H _c on the annealing temperature for the alloys of Table 1. The lower coercive force H _c of less than 5 A / cm or 1 A / cm can be used for the alloys 93/7965, 93/7966, 93/7967, 93/7968, 93/7971 and 93/7972 are achieved at annealing temperatures of 800 ° C up to 1150 ° C, as in 3 shown. Consequently, the production process of these alloys is very reliable, since large differences in coercive force due to deviating temperatures in the furnace are avoided.

The electrical resistance as well as the mechanical values of the elastic modulus (modulus of elasticity), the yield strength (Rp 0,1 and Rp 0,2), tensile strength (Rm), expansion (A), hardness (Vickers) (HV), fracture constriction (Z) are summarized in Table 3.

2 shows a schematic view of a mechanical wristwatch 1' with magnetic shielding 2 ' according to a second embodiment. In the second embodiment, the shield consists of three separate parts 12 . 13 . 14 spaced apart within the outer housing 5 are arranged.

The first part 12 is plate-shaped and at the bottom of the case below the movement 4 arranged. The second part 13 is also plate-shaped and is above the movement 4 arranged below the dial. The third part 14 is ring-shaped and envelops the margins of the gangs 4 , However, there is an air gap between the annular third part 14 and the plate-shaped first part 12 and the plate-shaped second part 13 ,

The shield 2 ' against external magnetic fields is not as good as in the first embodiment, in which the movement 4 almost completely with the shield 2 is wrapped. However, this embodiment can be used in applications where lower shielding is acceptable. The individual parts 12 . 13 . 14 Compared to the first embodiment, they are easier to manufacture because they do not have to be exactly matched.

The parts 12 . 13 . 14 the shield 2 ' of the second embodiment also consist of one of the alloys described above. In one embodiment, these three parts are the shield 2 ' from alloy 97/7971, ie from 8.90% by weight Cr, 13.45% by weight Co, 0.01% by weight Mn, 1.94% by weight Mo, 1.15% by weight Al, rest of iron.

LIST OF REFERENCE NUMBERS

1

Wristwatch according to a first embodiment

1'

Wristwatch according to a second embodiment

2

magnetic shield according to a first embodiment

2 '

magnetic shield according to a second embodiment

3

capsule

4

gait

5

casing

6

top

7

lower part

8th

midsection

9

cover

10

pot

11

thread

12

first part of the magnetic shield 2 '

13

second part of the magnetic shield 2 '

14

third part of the magnetic shield 2 '

Claims (14)

Clock ( 1 ) with magnetic shielding ( 2 ; 2 ' ), characterized in that the magnetic shield ( 2 ; 2 ' ) consists of an alloy, in weight percent, of 3% <Co <20%, 6% <Cr <15%, 0% ≤ S ≤ 0.5%, 0% ≤ Mo ≤ 3%, 0% ≤ Si ≤ 3 , 5%, 0.2% ≤ Al ≤ 2.0%, 0% ≤ Mn ≤ 4.5%, 0% ≤ Me ≤ 6%, wherein Me is one or more of Sn, Zn, W, Ta, Nb , Zr and Ti, 0% ≦ V ≦ 4.5%, 0% ≦ Ni ≦ 5%, 0% ≦ C <0.05%, 0% ≦ Cu <1%, 0% ≦ P <0.1 %, 0% ≤ N <0.5%, 0% ≤ O <0.05%, 0% ≤ B <0.01%, 0% ≤ S <0.5%, balance iron and common impurities. Clock ( 1 ) according to claim 1, characterized in that the magnetic shield ( 2 ; 2 ' ) from a pot ( 9 ) and a lid ( 10 ), which are interconnected. Clock ( 1 ) according to claim 2, characterized in that the pot ( 9 ) and the lid ( 10 ) are connected together by a spring. Clock ( 1 ) according to claim 2, characterized in that the pot ( 9 ) and the lid ( 10 ) by a thread ( 11 ) are interconnected. Clock ( 1 ) according to claim 1, characterized in that the magnetic shield ( 2 ' ) from one or more separate parts ( 12 . 13 . 14 ) consists. Clock ( 1 ) according to claim 5, characterized in that the part ( 12 . 13 ) is plate-shaped. Clock ( 1 ) according to one of the preceding claims, characterized in that the alloy has 0.01% ≤ Mn ≤ 1% and 0.005% ≤ S ≤ 0.5%. Clock ( 1 ) according to claim 7, characterized in that the alloy has 0.01% ≤ Mn ≤ 0.1% and 0.005% ≤ S ≤ 0.05%. Clock according to one of the preceding claims, characterized in that the ratio Mn / S ≥ 1.7. Clock ( 1 ) according to one of the preceding claims, characterized in that the alloy has 6% <Co <16%. Clock ( 1 ) according to one of the preceding claims, characterized in that 0.2% ≤ Al ≤ 2.0%, V = 0%, Ti = 0% and Mo = 0%. Clock ( 1 ) according to one of claims 1 to 10, characterized in that 0.2% ≤ Al ≤ 2.0%, 0.2% ≤ Ti <2.0%, V = 0% and Mo = 0%. Clock ( 1 ) according to one of claims 1 to 10, characterized in that 0.2% ≤ Al ≤ 2.0%, 0.2% ≤ V ≤ 2.0%, Ti = 0% and Mo = 0%. Clock ( 1 ) according to one of claims 1 to 10, characterized in that 0.2% ≤ Al ≤ 2.0%, 0.2% ≤ Mo ≤ 2.0%, V = 0% and Ti = 0%.

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