Richard's Registering Apparatus
From Scientific American Supplement, April 7, 1883
Messrs. Richard Bros., manufacturers of instruments of precision at Paris-Belleville, have devised a series of apparatus comprising thermometers, barometers, and hydrometers, which present the one character in common of inscribing their indications in ink, in a continuous manner, upon a sheet of paper ruled in squares and carried along by a clockwork movement. These instruments are arranged so that they can be easily moved about from place to place. Their mechanical arrangements are so simple that any experienced person can use them, and their price is so low as to bring them within reach of all.
Arrangement of the Registering Mechanism
All the apparatus under consideration are arranged according to one type. All their parts are supported on a base surmounted by a glass case which allows the tracing pen and paper to be seen. In the apparatus for use in apartments, the mounting of the cases is of wood, but in those designed to be placed in the open air it is of metal, as is also the base that supports the whole. The part designed to receive the registerings, including the clockwork movement, is identical in all the instruments, and thus explains the moderate price at which they can be manufactured.
The registering device consists of a vertical drum, movable around an axis, and in the interior of which is placed a clockwork movement. The upper end of this drum is provided with two apertures (closed by disks pivoted at one side) for the passage of the winding and regulating keys. The lower end is traversed by one of the axes of the wheelwork, upon which is mounted externally a pinion. This latter gears with a fixed wheel keyed upon a rod which is mounted on the base of the apparatus, and which serves as the axis upon which the drum revolves. It results from this arrangement that the movement of the wheelwork revolves the toothed pinion which performs the role of a planet wheel and brings about a general rotary motion of the drum containing the motor. It results also that the drum and its clockwork movement may be easily separated from the rest of the system, it being only necessary for this purpose to unscrew a nut so as to disengage the drum.
One of the most striking peculiarities of these instruments lies in the construction of the tracing pen. This consists simply of a small reservoir of thin metal in the form of a reversed triangular pyramid. One of the surfaces of the latter is affixed to the style, and its apex, which grazes the surface of the paper, is slit on one side, like the point of a pen, in order to cause a flow of the ink with which the reservoir is filled. The ink used is a mixture of aniline black and glycerine.
Registering Barometers
The barometers to which the Messrs. Richard apply the registering device just mentioned are aneroid instruments of special construction. The aneroid chamber or shell of these instruments is formed of two thin metallic valves soldered together at their edges. After a vacuum has been created in the chamber, the two valves, which then tend to approach each other, are kept apart by the action of a spring in the interior formed of two curved pieces of steel which bear against each other at their extremities. Each valve slightly flattens when the external pressure increases, and expands when it diminishes. One of them carries at its center a screw, and the other a nut, so that a series of similar chambers may be superposed in a vertical column by screwing one on top of the other. Under these circumstances, if the base of the column is resting upon a fixed plane, the top will rise or fall at each variation in the pressure of the atmosphere to a degree which is the sum of the displacements of each chamber. By varying the number of chambers composing the column, then, different displacements may be obtained for the same atmospheric variations, according to the degree of sensitiveness required in the apparatus.
In barometers designed for meteorological observations the Messrs. Richard employ eight chambers for each column. Under such circumstances, and with the amplification given by the style, the pen traverses the total height of the registering drum for a variation in atmospheric pressure equivalent to a height of eight centimeters of mercury.
The movements of the top of the column of chambers are made to move the extremity of the short arm of a lever, whose longer arm forms the registering style. This lever amplifies the movements of the top of the column about forty times. The barometer, when once regulated, undergoes no apparent variations as regards the amplitude of its oscillations, and the only change that can be observed with time is a general movement due to a slow variation in the state of equilibrium of the metal composing the chambers, and which is equivalent to a displacement of the zero of the scale. To correct this effect, the entire column is mounted upon a solid base that may be raised or lowered by a regulating device actuated by a screw that is maneuvered by a special key. A concordance may thus be established at any moment between the indications of the instrument and those of a mercurial barometer. To prevent the temperature from exerting a disturbing influence on the indications of the barometer, a small quantity of air is left in one of the chambers.