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Compensation Balance
A balance of a watch or chronometer which compensates the effect of variations of temperature on the vibrations of the balance. See Balance.
Mr. Richard Lange made a series of balances which are herewith illustrated, which give a clearer view of the disadvantages worked under by the pioneer experimentors. In the balance shown at A, Fig.96 the flat rim is made of brass, the arm A of aluminum, the compensating arm Z is of zinc. The balance rim is united to the arm at a either by rivets or pivots, similar rivets b b form the connection for the compensating arm; they are placed quite close to a a. In heat the zinc arm Z will expand much more than the aluminum arm A, and cause the rim to move inwardly, as indicated by the dotted line. Both arms, A and Z in this case of are equal length; the regulation of the compensation is effected by a change of position of the adjusting screws. At B, Fig. 96 the action of the compensation is increased in that the compensating arms Z Z, also of zinc are made double the length of the balance arm S. This is accomplished by attaching to the arm Z, with screws, cross-pieces, d d, of brass, to which are immovably fastened the ends of the compensating arms Z Z; a a are the pivots of the balance rim, b b the pivots to the joints to the compensating arms. The results are similar, but more effective than shown by A, as by the greater expansion of the compensating arms with an increased temperature the rim will be deflected inwardly, as shown by the dotted lines. The regulation is also effected by a change of position of the balance screws.
Experiments with this balance proved that the compensating action was still insufficient, and at A, Fig. 97 is shown a balance in which this action is further increased. This balance closely resembles the one shown at B, Fig. 96, the compensating pieces are made of zinc and rigidly connected with the balance arms and the sectional piece R. The balance rims, AA, will operate in like manner in heat and cold as those at B, Fig. 96. But the sectional pieces in this case are lengthened and composed of two metals, the inner of steel and the outer of brass, and they are also provided with tapped holes for the attachment of weights. In consequence of this form of construction of the sectional pieces R R, a compensating action will take place, inasmuch as their free ends with their screws, if such are required, will during an increase of temperature, take an inward direction, while an opposite action is produced with a fall of temperature. This style of balance can therefore be termed an auxiliary compensation balance. The compensation is effected by, 1st, a change of position of the adjusting screws, on the balance rims, A A; 2nd, by moving the auxiliary screws on R R to a different place, or making them either heavier or lighter.
B, Fig. 97, illustrates a balance with shiftable weights. Here the inner arm M, and the rims are made of brass; g g are the pivotal connections for the rims. The outer compensating arms A A, are of aluminum, and one of the ends is screwed to the arm M, the other is pivotally attached to the rim, forming a movable joint. In this style the compensating arms will tend to draw the rims inward, as steel has a greater co-efficient of expansion than aluminum, therefore the joint b, will be drawn towards the inner side of g. This balance also shows another interesting novelty. The outer ends F F, of the arm M, are made broad and thin, thus ensuring a secure movement of the slotted ends a a, of the rim.
A and B, Fig. 98, show two forms of the true auxiliary or controlling compensation. It is a well-known fact that in the usual rim compensation balance its action in the higher degrees of temperature is not sufficient, and it is necessary in particular cases to apply auxiliary means to accomplish such effects in progressive stages. This is usually done by means of small levers.
A, Fig. 98, shows the lower side of a balance so constructed. At the extreme ends of the balance rims there are small movable brass arms c c. The outer ends of these arms have cross-pieces h h, forming a continuation of the rims, and are provided with screws. The balance arm S, is made of steel; the rim is made in the customary way, steel on the inside and brass outside. On the upper and outer sides of the balance arm S, are two broad arched brass pieces m m, pivotally connected at a a, and they are also movably attached to the ends of e e by means of pivots. With a considerable increase of temperature the balance rims will have a strong inward motion, and its influence will be greater on the sectional pieces h h, therefore these latter considerably increase the effectiveness of the compensation. In the middle temperatures the movements of the sectional pieces h h, in a radial direction, cannot be very much, as the connecting pivots c and b, in the middle temperatures have the same radii.
At B, Fig. 98, the same results are obtained, but in a different way. The balance is of the usual brass-steel pattern, the rim being cut near each of the arms. At the inner end of the immovable (short) rim is screwed a rather long elastic spring F, having at its free end an auxiliary screw C. In the middle temperatures this spring is so curved as to just come in contact with the points of the balance screws. Now, if the balance rims are strongly curved inwardly in high temperatures the point of the last screw at a will move the spring F, and the auxiliary screw c, and as the screw c, whose distance from a is about three times that between a and b, it can be readily seen that the free end of the auxiliary will increase threefold any movement of the balance rims at a, in consequence of which the compensatory action is greatly increased.