Apparatus for obtaining electrical signals correlated with the position of a mass of mercury in instruments and the like

Abstract: A method is disclosed for producing electrical signals indicating the position of a mercury mass in measuring instruments such as thermometers, barometers, mano­ meters, inclinometers and the like. According to the invention, the positions of mercury mass are detected and sensed by one or more electromagne­ tic proximity sensors of metals, the mercury mass being never passed through by electric current. Several applications of the above inventive concept are shown among which a compact fluid-tight vessel or capsule which a mass of mercury and a proximity sensor are included; which device, when mounted on a tiltable object, is adapted for producing a signal, or respectively no signal, when the object reaches a certain angular position with respect to the horizontal and no signal or respectively signal of another kind when the attitude of the object changes.

Description: The present invention refers to a device according to the preamble of claim 1. A device according to the preamble of claim 1 is known from US-4 129 852. In this device a mercury mass is movable with respect to a resistance coating in dependency on a movable mechanical member In a device known from FR-1 363 419, a proximity sensor is detecting the position of one end of a mercury mass, such that when its position is changing the proximity sensor is providing a signal to an amplifier which is controlling a servo motor for rising or lowering the proximity sensor by mechanical way. Furthermore the proximity sensor is coupled with a tap being in contact with a resistance. By this way the value of the resistance is changed dependent on the position of the proximity sensor. As known, an induction proximity sensor or induction proximity detector is an electric device which produces an electrical signal when approached by a metal object or when approaching a metal object. It comprises an oscillator for generating an electromagnetic field which is changed by ferrous or non-ferrous metal objects moving within said field. The sensor oscillator is contained in a compact head usually cylindrical but also of other shapes, such as forks etc. With reference to the usual cylindrical shape, the oscillator coil is located near one of the cylinder flat ends which is therefore called the actice face of the sensor and the electromagnetic field radiated thereby is symmetrical with respect to the cylinder axis. The sensor sensitivity can be defined as the distance at which the sensor emits a signal when a standard metal object moves towards or away therefrom. Such distance is measured in the direction of the axis of the sensor when this is cylindrical and the object is approached in the direction of said axis, or in a direction at righ angle to said axis when the object is approached transversely to said axis. When the object is approached diagonally the distance will be measured as the resultant of the above two movements. A relevant characteristic of the sensor is the distance from the position where the sensor emits the signal corresponding to the object presence while this approaches the sensor (operating distance) and the position where said signal stops while the object is moving away from the sensor (release distance). Several small-size proximity sensors are available on the market, the cylindrical heads of which have diameters of the order of 5 mm with sensing distance of the order of 1 mm, the interval between the operating distance and the release distance being of the order of some tenth of millimeter. It is the object of the present invention to provide a device of simple construction which is able to generate electrical signals in dependency on the movement of a mechanical member. This object is solved by the features of the characterizing portion of claim 1. Further embodiments are defined by the subclaims. In the following two embodiments of the present invention are explained by the attached drawings. In the drawing: Fig.1 shows a vertical cross section of a device according to the invention for indicating the position of a moving mechanical member. The concept of this invention is realized with the device of fig.1, which is a means for obtaining an electrical signal correlated with the movement of a mechanical member to actuate a relay or a switch, for instance a limit switch, of said moving member. The device comprises a stationary block 21 provided with two vertical bores 22, 23 which are connected together at their lower ends by a horizontal duct 25. Bores 22, 23 are partially filled with mercury M of which the meniscuses within the bores are at the same level, due to the principle of communicating vessels. A plunger 27 is inserted with large clearance into one (22) of the bores to float on the mercury mass. The mercury meniscuses will reach the same level in both the bores. A proximity sensor S is introduced into the other bore 23 with its active face FS at a level higher than the mercury meniscus in the same bore. Whenever plunger 27 is depressed in the direction of arrow F₁ by the mechanical member - not shown - and sunk further into the mercury within bore 22, the level of mercury within bore 23 will rise and approach the active face FS of proximity sensor S and cause a signal to be emitted from the latter for actuating,for instance, a relay or a switch through leads 24. The action of the above device can be delayed by a calibrated obstruction 26 of which duct 25 is provided. According to a variant of the same device, sensor S can be fitted tightly into bore 23 and plunger 27 can be made to slide fluid-tight into bore 22. In such case, a helical spring - not shown - will be provided around the plunger for restoring it to its upward position according to arrow F₂ when the depressing force by the moving mechanical member is relieved.

Claims: A device for producing an electrical signal corresponding to the movement of a movable mechanical member using the detection of the position of a movable mercury mass (M), characterised in that a plunger (27) is connected to the mechanical member and inserted with large clearance into one of the upright legs (22, 23) of an upright U-shaped tubular channel which is provided in a block (21) and partially filled with the mercury mass movable therein, the plunger (27) floating on the mercury mass (M), and that for detecting the position of the movable mercury mass (M) within the tubular channel an electromagnetic induction proximity sensor (S) is provided, which proximity sensor (S) is inserted into the other vertical leg (23) of the tubular channel and arranged at a level higher than the level of the mercury mass (M) in the same vertical leg (23). A device according to claim 1, characterized in that the proximity sensor (S) is connected to a relais or a switch. A device according to claim 2, characterized in that said tubular channel comprises a calibrated obstruction (26). A device according to one of the claims 2, or 3, characterized in that said proximity sensor (S) is tightly fitted in the corresponding vertical leg (23).

Inventors: FLORIS PIERLUIGI, O'TOOLE YVONNE, FLORIS, PIERLUIGI, O'TOOLE, YVONNE
Applicants: FLORIS PIERLUIGI, TOOLE YVONNE O, FLORIS, PIERLUIGI, O'TOOLE, YVONNE
Application year: 1983
Main classification: G01D5
IPC codes: G01B7, G08B21, G01K5, H03K17, G01F1, G01L9, G01D5