FR2459977A1 - Accelerometer for detecting rough deceleration during aircraft landing - uses spring biassed multi-directional mass making electrical contact with metal ring in response to acceleration or deceleration - Google Patents

Abstract

The accelerometer detects rough decelerations such as during aircraft landing which could damage equipment. The accelerometer comprises a cylindrical mass (21) on a rigid shaft (22) connected to a cup assembly (23). A spiral spring (24) pushes the cup onto an annular carrier (1c) with a force determined by a brass plug (33) to which an electrical connection (25) is rivetted from the inside. The plug is engaged in an electrically insulated block (31). A metal ring (27) is located adjacent to the cup assembly to permit the passage of electrical currents via the connectors (25,27a) when the mass is displaced in any direction in its cylindrical chamber (16).

Description

 The present invention relates to devices sensitive to variations in speed and which act on an electrical contact when a certain predetermined acceleration or deceleration is reached.

 In known devices of this kind a mass of inertia, which can be a ball, is kept in equilibrium in a determined position by means of a spring or a magnet.

This balance can however be upset by a more or less significant acceleration which causes a displacement of the mass of inertia compared to the case in which it is incorporated. This displacement is used to act on the state of an electrical contact secured to the housing.

 The object of the present invention is to produce an accelerometer of this type intended to detect unusual accelerations on board aircraft, such as those which may result from a hard landing.

 The device which is the subject of the invention comprises an insulating housing inside which a counterweight is made integral with a cup by means of a rod. This cup is held in abutment, by a pressure spring, on an annular and planar surface of the housing.

 The cup / spring assembly, electrically conductive and gilded for this purpose, is electrically connected to a terminal.

Near and parallel to the cup, a metal ring fixed in the housing is connected to a second terminal. When the counterweight moves following an acceleration or a deceleration, the cup comes into contact with the ring which temporarily ensures the electrical connection between the two lugs and allows the exploitation of an electrical signal.

 The appended drawing illustrates, by way of example, an embodiment of the device according to the present invention.

 As shown, it consists of a housing 1 molded in an insulating plastic material and which mainly comprises a cylindrical chamber 1b, two fixing holes 1a, 1a, an annular flat surface 1c and a recess ld in which s fits a background 31.

 The inertial assembly is constituted by a cylindrical counterweight 21 connected to a cup 23 by a rigid rod 22.

A spiral spring 24 presses the cup 23 on the bearing ic.

Its winding force can be adjusted by screwing more or less the brass plug 33 (on which a terminal 25 is riveted) in the bottom 31 of insulating material.

A metal ring 27 provided with a thimble 27a is disposed parallel to a few millimeters from the cup 23. The thimble assembly 25, plug 33, spring 24 passing through the ring 27, and the cup 23, can be gilded to facilitate the passage of weak currents, as well as the assembly 27, 27a.

For example, for the detection of an acceleration of 10 g in the axis of the rod 22 (in the direction of the arrow
F) and an acceleration of the order of 8 g in all directions of the XY plane perpendicular to this axis at the level of the span lc, the spring must have a force of 50 grams for a cup with a diameter of 16 mm and a dural weight of 4 to 5 grams, the center of gravity of which is approximately 13 mm above the XY plane.

 The device which is the subject of the invention can be used on board aircraft to detect excessively sudden decelerations liable to damage the equipment during landings.

Claims (2)

 1 - Accelerometer of the type comprising a mass of inertia whose displacement acts on an electrical contact, characterized in that the mass of inertia 21 is connected, by means of a rigid rod 22, to a metal cup 23 held in abutment on an annular bearing surface c of the housing by means of a pressure spring 24 and that, on the other hand, a metal ring 27, disposed near the cup, makes it possible to establish electrical continuity between two lugs 25 and 27a following displacement relative of the mass with respect to the housing under the action of a shock.  2 - Accelerometer, according to claim 1, characterized in that the force of the pressure spring 24 can be modified by means of a metal plug 33, on which is fixed a terminal 25, screwing into the bottom 31 of insulating material.