DE1943197A1 - Balance for clocks - Google Patents

Description

PATEPiTANWALT · ■ or "

Dr, ERNST STURM 2S.-

MUNICH 23
LEOPOLDSTR. 20 / IV

Les Fabricates d'Assortiments Reunies, Le Locle (Switzerland)

Balance for clocks

The energy consumed by the balance spring increases with the oscillation range (amplitude) and by and large also with the moment of inertia. This is a fact known to those skilled in the art and if the designer of a caliber (clockwork) determines that the oscillation amplitude is too small / then tries he either after increasing the spring force or he chooses a smaller balance wheel with a smaller moment of inertia, which is the same available energy with a larger amplitude swings.

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A / gb / 16 936
Case 38

· Ϊ \

ν '' * ^::: 1943137

On the contrary, if you want the stability and precision properties In a watch, the moment of inertia of the balance is increased as much as possible, which enables the quality factor Q of the oscillator to be increased. It is Q = ~ N, in which N = number of periods of a damped, not driven oscillator until its amplitude drops to - ^ - its original value (e = base of natural logarithms). at Marine chronometers, for example, are used to have a balance with a large moment of inertia, which is therefore used to maintain the Ganges require considerable force.

In a watch, especially in a small caliber, e.g. In women's watches, the available energy is limited. If one therefore wants to increase the moment of inertia and the quality factor, so with this intention one is very soon limited by the Amplitude that becomes too weak. This limitation is particularly noticeable in the current trend, in the interests of the Improving the quality factor to increase the vibration frequency. A high frequency oscillator consumes more energy and you have to decrease the moment of inertia of the balance when you you want to ensure a sufficient amplitude, what then to The result is that the quality factor is not improved to the extent hoped for.

In short, the technical problem that arises is the following

How can the energy consumption of a balance wheel with a given moment of inertia be reduced as far as possible? Because any reduction of energy consumption at a given moment of inertia would in egg: ER ner available 'property power and at given frequencies *

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hlen what the

Permit to choose disturbances with a larger moment of inertia Quality factor Q would favor.

How can one reduce the energy loss during the vibration of a Reduce balance?

You first have to know where energy is going, through which physical process it is lost. These energy losses ^! are caused:

a) Due to the friction between the balance and the air

b) By the friction of the pegs.

c) Due to the internal friction of the spiral spring. t

The aim of the present invention is to reduce the factor mentioned under a), i.e. the friction between balance wheel and air.

In the classic, uncut, circular balance Kranz, this friction only acts laterally for the wreath, because the wreath always occupies the same position when the balance wheel vibrates Part of the room. Forehead resistance (penetration resistance) is only available for the edges of the arms or spokes of the balance wheel. It is the one It is obvious that this friction is proportional to the surface area of the balance wheel, and also to that at a given angular velocity depends on the circumferential speed proportional to the radius. So one understands why unrest with a large moment of inertia consume more energy. To increase the moment of inertia one must either increase the mass, which is a constant The density of the wreath surface is increased, or it is necessary to increase the radius that increases the circumferential speed Consequence. There are also other factors, but the

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The amount of energy consumed against the air increases as a whole with the moment of inertia.

There is therefore a tendency to assume that an increase in the density of the material used would be beneficial rather than a prescribed one Mass then decreases the friction surface. There is also a radical remedy to switch off air friction by turning the balance wheel can vibrate in a vacuum.

In doing so, however, one encounters another difficulty: the air friction has a stabilizing effect on the amplitude of the balance wheel when the force supplied is reduced ( the spring's moment falls when it unrolls). The balances made of very dense material or oscillating in a vacuum consume little energy, but their amplitude decreases considerably between the highest degree of tension of the spring and the spring tension after 24 hours, which results in rate changes when the period changes with the amplitude changes only to a certain extent (isochronism error).

It is therefore a matter of creating an oscillator whose energy consumption is as small as possible, but not too large Has a decrease in amplitude when the available force decreases by a given percentage.

One is therefore compelled to study the curve that represents the Represents power consumption as a function of amplitude. The inventor wrote in the Journal, suisse d'horlogerie, Schweiser edition, No. 9/10, 1967, pages 339-345 shown that when the total frictional torque

F as a function of the angular velocity 6 by the formula?

F ~ a + bÖ + cß- ²

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is given, the consumed force P as a function of the amplitude φ is given by the formula

2, ". 1, 2 * - ^ 2 3 3 P = - = - aw * + rb ω f + - = r- cw a> «I 2 I» ι Τ

co = s 2 τ / y s oscillation frequency

The curve for P as a function of the amplitude ep shows the in Fig. 1 of the drawing illustrated course. In this figure the letters have the following meanings:

P = Available force at the highest degree of tension

cf = corresponding amplitude

P _OA = power available after running for 24 hours

= corresponding amplitude

'= Difference in amplitude

It can be seen at once that the amplitude difference AcP depends on the mean slope of the curve in the area of use. The greater this inclination, the smaller is Αφ. This slope is given by the equation:

dP _ _2__ _{aaJ + b ω} 2 _6_ 3 2

dcp 7f "ι JT * ι *

The problem therefore lies in reducing P while maintaining a sufficient slope between q> and But P depends on the slope according to the formula

ffo

dP ,

—Z - · aas together. a <3> j

Adds to the curve of the ifcLöituag "^ fr * ift function of ψ

OC5314 / -j 328 "^<P

the curve Z according to FIG. 2 is obtained. In this illustration, P is the area below the curve Z up to the abscissa cs>. The problem is therefore to reduce the area under curve Z, while at the same time maintaining the ordinate in the abscissa point <$.

dP The ordinate at the abscissa point G _Q can be divided into three

Split segments, namely:

^p a ^β ir

b ~ - ~ To

P · / =: b tu " Φ

= -4- ciO ³ 9 ² c TT

Pi = -ψ- c £ 0 "α>

Likewise, the area P _{Q can be divided} into three parts, ttämlieh t

P - -2-

a u

^P o -

The _{quantities P ft} , P _{^ and P c} are connected to ^ and P ¹ in the following simple way:. "

^P aj ο

P = ■ = cp ρ ¹ ^ b 2 lo ^p b

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^{ρ (}

One wants to ^{keep P 1} (4 ') = P' + Ρ £ + P ¹ constant. One can therefore only make changes between P ¹ , P 'and P ¹ (e.g. subtract a certain value Ap ¹ from P' and subtract it between P 'and P ¹

a b c

to distribute).

Because the goal is to reduce the area below curve Z, i.e. P, you can see in which sense these changes have to be made: You have to e.g.

Grosse / P * (which you have to multiply by <t to obtain the corresp ίο

to get the corresponding area part) and the quantities P 'and P' (which one only has to multiply by - ~ r- or ---tr- to get the corresponding areas) increase. One must therefore favor those greats whose multiplication factor is small at the expense of those whose multiplication factor is large, i.e. favor ^{P ^ and P £ at the expense of P 1,}

and P ¹ at the expense of P '.
cb

On which geometrical and physical characteristics of the balance do these quantities P _a , P ^ and P _c , P ^, P £ and P ^ depend? They are proportional to a or b or c.

a = so-called dry friction coefficient, proportional to the Weight of the balance and the radius of the pivot.

b = so-called viscous coefficient of friction, the what the the part attributable to the friction of the air on the wreath

is proportional to S and R.

c = quadratic coefficient of friction, proportional to S and 3

^R m

¹ J 3 OH / ■ ύ £. '

There is therefore a simple means of increasing P ^ and P ¹ at the expense of P ¹ without reducing the moment of inertia: One has to increase R _m , which results in the same moment of inertia.

2 ment the reduction in mass (moment of inertia = mR _m ), therefore

the reduction of P ¹ allowed. Since P 'and P' are proportional to R _m and R, respectively, they increase with the radius and you get what you want, namely a decrease in P without changing P ¹ to <P. The reduction of the mass causes a reduction in the area of the ring with the same density and the same radius, / but since the radius is increased when the mass is reduced, one obtains a finer ring and of larger size, i.e. a less compact one, so that the reduction the mass does not result in a reduction in the area.

One must also try to reduce the masses that are close to the center and therefore neither contribute to increasing the moment of inertia nor to stabilizing the amplitude, that is, the masses of the shaft, the roller and also the arms or spokes. This allows the reduction of P 'and all the more the enlargement of P / and / or P ¹ .

The increase in the radius also allows P ^ to be favored at the expense of P £, because P _c is proportional to

3 2

R _m , while Ρ £ is proportional to R »

In summary, it should be said that a decrease in mass with an increase in radius ^{enables P 1} to be reduced at the expense of P £ and P ^; it also allows P * to be increased more than P £ “but does not allow £ to be reduced . A reduction of P £ at the expense of P ^ would therefore make it

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* »· Ft

ben, to reduce P even more without influencing P ¹ <Φ _Ο ).

Decrease in b. To do this, one has to reduce the area of the ring without reducing the moment of inertia.

A first means of doing this is that in German patent no

(Registration P 17 73 523.8) proposed: increasing the density of the material used for the wreath. This reduces the area, which makes P 'and P * smaller. It is then sufficient to increase the radius to restore P * ( a> ). Since P * increases more rapidly with the radius than P /, a reduction in P 'is achieved on the whole at the expense of P'.

But here, too, there is still a limit: since the volume of the wreath decreases and the radius increases with it, one arrives at very less compact forms, where the area becomes significant in relation to the volume, so that one quickly arrives at an optimal radius which the energy consumption because of P, and P is too great. The obstacle is therefore the lack of compactness. If you want to overcome this, you have to try to use more compact forms.

The invention therefore follows the consideration of whether it is not advantageous would be to leave the continuous ring and divide the inertial mass into separate parts, what it brings with it frontal friction, but which can be reduced by using aerodynamic shapes, what subdivision but greater © compactness, that is to say, for a given volume, results in a smaller area. Account and experience have that Inventor confirmed the correctness of this assumption. The introduction of a stimulation is compensated in liohsra mass by the

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reduction in lateral friction as a result of the reduction in surface area. This forms the subject of the invention. She strikes a balance before, which has separate, preferably aerodynamically profiled, arms-borne masses. For the sake of At least two symmetrical masses are necessary in equilibrium. Might also help to facilitate the achievement of equilibrium more, e.g. three masses should be provided, provided that this does not affect compactness, in the interests of compactness one is preferred keep the number of crowds to the strict minimum.

With regard to the back and forth movement of the balance wheel, the aerodynamic profile must be symmetrical and there the rear one If the profile is more important than the front one, it is often better to have the profile end in points rather than round ones.

Definition of compactness.

One takes as a measure of compactnessζ
3

V s or »if there are several bodies:

Y-

IZS ₁

V = volume of the body S = area of the body

This dimension has the advantage that it only depends on the shape and not on the size. V is immutable when all linear dimensions of a body are multiplied by one and the same factor »

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Examples

Compactness of a sphere (maximum ' compactness)

Compactness of a cube

ή * R '
3

S m 4 ~ R

³ rr = r

4 t «

0.455

V = a *

S = 6a

0.408

Global compactness of two spheres with the same radius

2. 4T

= 0.405

Compactness of an ordinary continuous ring of rectangular cross-section

V ■ 2 S β 2 TT R _m . 2 (h + s)

V 2ΤΓ ^R m • hs hs If "πι (H + β) (h + s) VlT V ^R m hs 2 V "Π" - \ / ^R m 0.52054

R «* mean radius

in ,

of the wreath

h = height of the wreath s - width of the wreath

fsT ^

+ S)

The range of compactness of the wreath of ordinary unrest (according to the norms of the Swiss watch industry) extends approximately from 0.248 to 0.264.

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The balance wheel according to the invention has at least two arms carried inertia bodies or weights that are spread over the whole extend less than half of the rest circumference during the The rest of the scope is free from material. The balance wheel is characterized by the fact that the inertia bodies are more compact is than 0.310 and preferably greater than 0.320. This compactness is the compactness of the inertial mass alone (body and any balance screws); the arms carrying the mass are not "included" in the above value. Are the bodies of inertia Pieces made separately from the arms are made outside the inner radius of the body parts of the arms are considered to be part of the inertial mass.

Figures 3 and 4 of the drawings show an example Embodiment of the balance wheel according to the invention.

Fig. 3 is a section along the line III - III of Fig. 4, and

Fig. 4 is a plan view.

The balance wheel shown in Figs. 3 and 4 has two identical ones Inertia bodies or weights 1 and 2 carried by arms 3 and 4. Each of the bodies has two pyramidal ends 5, in order to reduce the forehead friction when the balance wheel oscillates. The ■ Width (Fig. 4) of the arms 3 and 4 is quite larger than theirs Thickness (Fig. 3), The two bodies or weights 1 and 2 extend / in total for less than half of the rest scopej the rest of the perimeter is devoid of material. In the example shown the compactness of the bodies 1 and 2 is approximately 0.35. The density of the bodies 1 and 2 is advantageously quite large. she

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can, for example, exceed ^{9 g / cm 3.} The * number of bodies 1 and 2 could be greater than two. The pyramids 5 that form the ends of bodies 1 and 2 can be more or less blunt and could also be replaced by hemispheres.

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Claims (5)

1) JUnruh for watches, with at least two inertia bodies or weights carried by arms, which as a whole extend over less than half the circumference of the balance wheel, while the rest of the circumference is free of material, characterized in that the compactness of the inertia bodies (1 , 2) is greater than 0.310. 2) balance according to claim 1, characterized in that the compactness of the inertia bodies (1, 2) is greater than 0.320. 3) balance wheel according to one of claims 1 and 2, characterized in that the inertia bodies (1, 2) are aerodynamically profiled »d« s means »more or less stepped or hemispherical _K. Have ends in order to facilitate the penetration of the bodies (1, 2) into the air and thus to reduce the face friction when the balance wheel vibrates. 4) balance wheel according to one of claims 1 to 3, characterized in that two inertia bodies (1 # 2) are provided * 5) balance according to one of claims 1 to 3, characterized in that three support bodies are provided ι 6) balance according to one of the claims X to 5, characterized labeled in _t records "that the Trlgheitskörper from a 'material! stand"", whose density is greater than 9 gr / e * ³ . = ■ '·' V · - '>, --S. BAD ORIOJNAL 0098U / 1328