Page:EB1911 - Volume 18.djvu/589

 of many foreign coins, are put on by the marking machine, and a plain collar is used in striking.

The coining presses now used are all modifications of the lever press invented by Uhlhorn of Grevenbroich near Cologne in 1839. The press in use at the Royal Mint since 1882 is shown in figs. 6 and 7. The lever M worked from the front of the machine causes the fly-wheel to be connected with the driving-wheel and the machine starts. The blanks are placed in the slide J and the lowest one is carried forward to the die in two successive movements of the “layer-on” K, a rod working backwards and forwards on a horizontal plate and actuating the finger L, fig. 8. The lower die is firmly fixed to the bed of the machine, and the blank is placed exactly upon it. The collar A′ is then raised by the lever G so as to encircle the blank, and the upper die which is held at A is brought down. This is done by the little crank B on the axle of the fly-wheel, acting through the rod C, and the bent lever D, which forms a toggle-joint at E with the vertical piece of metal below it. The straightening of the toggle-joint when C is pushed forward forces A down to strike the coin. The reverse movement of D lifts up the upper die and the collar drops simultaneously so that its upper surface is level with the face of the lower die on which the finished coin lies. Another blank moved on by the finger L pushes off the finished coin which falls down the tube N. The diagram, fig. 9, shows the relative position of the dies and levers more clearly. The dies and collar are shaded. The presses at the Mint strike from 90 to 125 coins per minute, most of them working at the rate of 110 coins per minute. There are 19 presses and it is possible with these to strike between 700,000 and 800,000 pieces in an ordinary working day.

. 6.. 7.

. 8.

Weighing the Coins.—Gold and silver coins are examined and tested by ringing, and each coin is then weighed separately by being passed over delicate automatic balances. The first automatic balance for weighing single coins was introduced at the Bank of England in 1843 and was designed by William Cotton the deputy governor of the Bank. In 1851 these balances, improved by Richard Pilcher were introduced at the Royal Mint, and modifications of them are now used at most foreign mints. For mint use it is necessary that they shall distinguish between “light,” “heavy” and “good” coins which do not differ from standard by more than the small weight known as the “remedy” (see above). The balances used in the Royal Mint were further improved by J. T. Butler in the year 1889. The balance consists essentially of a beam with two scale pans, one for the coin and the other for the counterpoise. The beam is released and in the course of a second or so takes up a certain position dependent on the relative weights of the coin and counterpoise. Its position is then fixed by an automatic grip, and the coin falling down a shoot enters one of three compartments of a box, according to the position of the beam when it is arrested. The chief working parts are shown in fig. 10. The beam A is of steel made in one piece, about 11 in. long. . 10.

Its centre and end knife edges are shown in fig. 11. The scale pan for the coin is shown in fig. 12. B is the pan on which the coin rests, at a point above the beam. The coins are placed in a rouleau in the hopper C and the lowest one is pushed on to the pan B by a slide not shown in the figure. While the coin is being moved the hanger D is held firmly by the forceps E to prevent the pan from being pushed sideways. The forceps are then opened and the beam released, but at this moment the levelling bar F is allowed to drop momentarily by a bent lever G acting on the pin G′, until the ends of F press down on a stirrup in each hanger at H, H. This brings the beam to a horizontal position. The lever G at once