Читать книгу Rules and Practice for Adjusting Watches - Walter J. Kleinlein - Страница 18

A very practical arrangement for testing a few watches at a time in the higher temperature is shown in Fig. 1. This is electrically equipped and will maintain an even temperature at all times.

The outside of the box is constructed of about one-half inch lumber and the inside is lined with asbestos. It is about fourteen inches high by ten inches wide and eight inches deep.

"A". Is an incandescent lamp set in a porcelain base.

"B". Is a porcelain plug through which the wires "C" enter the box.

"D" and "E". Are metal uprights with a thumbscrew on the top, under each of which a wire terminates.

"F". Is the compensating bar, one end of which is fastened solidly to "D" with rivets.

The opposite end is free and rests against the end of a thumbscrew which passes through "E."

The thumbscrew is to be adjusted so that the free end of "F" will rest against it in a temperature of 70° Fahr. or any lower temperature. As the temperature rises the free end of the bar moves away from the end of thumbscrew, breaking the circuit and extinguishing the light, which cuts off the source of heat. As the temperature decreases the bar again comes into contact and creates the circuit.

This bar can be made of various compensating metals, one combination of which is a strip of zinc about six inches long by three eighths of an inch wide and one thirty-second of an inch thick. On the outside of this soft solder a strip of tin six inches or a trifle less in length, by one fourth inch wide and one thirty-second of an inch thick. Both metals should be bent to a curved form before they are soldered together as shown in the cut.

Fig. 1

It is generally preferable to have the bar taper to a slightly narrower width at its free end, and near this free end it is necessary to solder a small strip of platinum at the point where the end of thumbscrew comes in contact.

"G", "H", "I" and "J" are ventilating holes one inch in diameter and covered by a swinging slide so that the holes can be opened or closed as desired for regulating the ventilation. "K". Is a shelf of brass screen located about five inches from the top and on which the watches and a thermometer are placed in testing.

"L". Is a handle for the purpose of convenience in carrying the box. The front is to be enclosed by a door made in two parts, the upper section of which is glass which will admit of observing the thermometer. Proper adjustment of the thumbscrew and bar makes the box ready for use.