GB2084330A

GB2084330A - Protection of Accelerometers Against Impact

Info

Publication number: GB2084330A
Application number: GB8128444A
Authority: GB
Original assignee: Sundstrand Data Control Inc
Current assignee: Sundstrand Data Control Inc
Priority date: 1980-09-22
Filing date: 1981-09-21
Publication date: 1982-04-07
Also published as: NL8104355A; JPS5784361A; DK417781A; AU522709B2; GB2084330B; IT8149330A0; DE3129697A1; FR2490828A1; AU7338581A; CA1163833A; SE8104814L

Abstract

An assembly T comprises a housing 10 containing an accelerometer. An elastomeric potting compound, e.g. silicone rubber, encapsulates and protects the accelerometer against impact. A connector 35 is secured by means of a bracket 37 having tabs 38, 39 screwed to the housing 10. The housing 10 has faces 27, 28 carrying electronic component boards 68, 69, longitudinal passages 70, 71 for fastening screws 72, 73, and longitudinal passages for wires from connecting pins 60 on the accelerometer. <IMAGE>

Description

SPECIFICATION Transducer Assemblies The invention relates to assemblies containing accelerometers protected against impact and suitable for use in aircraft. Our UK Patent Application 2065308A describes such use of our Q-FLEX accelerometer which has a quartz flexure and servo electronics all in one miniature package. The basic structure of this accelerometer is disclosed in U.S. Patent 3,702,073.

The invention provides a transducer assembly comprising a housing having a central chamber containing an accelerometer, an electrical connector for the accelerometer extending from an end of the housing, and an elastomeric potting compound encapsulating the housing and part of the connector for protecting the accelerometer against impact.

Drawing: Fig. 1 is a perspective front view of the encapsulated transducer assembly according to the invention; Fig. 2 is a perspective rear view of the transducer assembly of Fig. 1 prior to encapsulation; Fig. 3 is a vertical section through an adapter housing, showing an accelerometer positioned therein and a gluing fixture, in broken line, during mounting; Fig. 4 is an exploded front perspective view of the adapter housing in Fig. 2 and certain parts associated therewith; Fig. 5 is a central, vertical section of the encapsulated transducer shown in Fig. 1 with certain interior components shown in elevation; Fig. 6 is a transverse sectional view of an aircraft centerline gear axle having a pair of encapsulated transducer assemblies according to Fig. 1; and Fig. 7 is a transverse sectional view of an aircraft nose gear axle having a pair of encapsulated transducer assemblies according to Fig. 1.

A transducer assembly T includes an adapter housing 10 having a central chamber 11 (Fig. 3) which mounts an accelerometer A having one cylinder casing 1 2 and an accelerometer header 1 5 at one end. The accelerometer A is cantilevermounted in the chamber 11 for reduced thermal conductivity, by being glued along a glue line 1 6 to a wall of an inner section 1 7 of the chamber 11 and with an outer section of the chamber having a greater diameter to be spaced further from the casing 1 2 of the accelerometer. A tapered gluing fixture 20, indicated by broken line in Fig. 3, is used to position the accelerometer within the chamber 11 during the assembly operation.

The adapter housing 10 is generally elliptical in cross-section and has one side 25 which is arcuately curved and with the opppsite side being made up of several planarfaces including a central face 26 and a pair of inclined faces 27 and 28 which provide mounting faces for a number of components. An end 29 of the adapter housing provides a mounting face for the transducer assembly and with the central chamber 11 opening to the opposite face 30 of the adapter housing and with the accelerometer header 1 5 extending therebeyond.

An electrical connector 35 has an exposed, threaded end 36 and is mounted to the adapter housing 10 by means of a connector bracket 37.

The connector bracket 37 has a relatively thin annular body with a pair of bent tabs 38 and 39, each of which has an aperture and as shown at 40 for the tab 38. The annular body of the connector bracket abuts against an annular base flange 45 of the electrical connector 36 and surrounds a reduced diameter section 46 of the electrical connector which fits into the central opening of the connector bracket, and with these parts being soldered together. The connector bracket tabs 38 and 39 engage cut-back surfaces 48 and 49 on the adapter housing faces 27 and 28, with the apertures in the tabs aligned with threaded openings which extend into the adapter housing.The electrical connector bracket tabs 38 and 39 are secured to the adapter housing by respective screws 50 and 51 which pass through openings in a pair of safety wire brackets 52 and 53 which are superimposed upon the respective tabs 38 and 39 and with the parts shown in assembled relation in Figs. 2 and 5.

Each of the safety wire brackets 52 and 53 have an L-shaped leg 54 and 55, respectively, extending therefrom having an aperture in the free end thereof for connection of a safety wire thereto during mounting of the transducer assembly.

As shown particularly in Fig. 2, the accelerometer header has a number of pins 60 which have the ends of wires soldered thereto and with their being four groups of wires extending from the accelerometer header. One group of wires, as indicated at 61, passes through a passage 62 extending longitudinally of the adapter housing 10, with a second group of wires 63 passing through a similar longitudinallyextending passage. The passage 62 terminates at the mounting face 29 of the adapter housing in an undercut transverse passage 64 whereby the group of wires 61 extending through the passage may extend into the interior of the electrical connector 36. The second longitudinallyextending passage terminates in an undercut passage 65 (Fig. 4) wherein the group of wires 63 can extend into the interior of the electrical connector 36.The aforesaid groups of wires are electrically connected to the inner ends of pins P extending outwardly within the sleeve of electrical connector 36. Additional sets of wires 66 and 67 extend to electronic component boards 68 and 69 which are mounted on the faces 27 and 28 of the adapter housing.

A second set of passages 70 and 71 extends lengthwise throughout the adapter housing 10 and the passages provide mountings for a pair of socket head cap screws 72 and 73 which are retained against removal by a threaded section at one end of the passage, as shown at 74 for the passage 72, and with a lock washer 75 captured under the head of each of the cap screws.

In assembly, the components shown in Fig. 4 are assembled in the manner previously described, with the electrical wiring associated therewith to form the transducer assembly shown in Fig. 2 and without the socket head cap screws 72 and 73. The structure shown in Fig. 2 is then placed in a potting fixture with suitable fixture elements to prevent entry of potting compound into the second pair of passages 70 and 71 in the adapter housing and also to expose the free ends of the safety wire bracket legs 54 and 55. This structure is then encapsulated in an elastomer potting compound, preferably a silicone rubber, such as RTV-60 silicone rubber MFR, of General Electrical Company. This compound has good resistance to hydraulic fluid and jet engine fuel.

The encapsulated transducer assembly is shown in Fig. 1 and in section in Fig. 5 wherein a layer of potting compound surrounds the sides and encloses the ends of the adapter housing and encloses the structure associated therewith including the electrical wiring except for an exposed end of the electrical connector 36, the second pair of passages 70 and 71, parts of the mounting face 29 of the adapter housing surrounding said passages 70 and 71, and the free ends of the safety wire bracket legs 54 and 55. Thereafter, the socket head cap screws can be associated with the adapter housing, as shown in Fig. 5, and the transducer assembly with protective structure is in its final form for use and protected against undesired impacts.More particularly, the layer of elastomer material extends completely around the sides of the adapter housing 10, without interruption, with this section of the layer being indicated at 80. A section 81 of the layer extends beyond the end 30 of the adapter housing and encloses the wiring associated with the accelerometer header 1 5 and is continuous except for openings 82 and 83 for access to the socket head cap screws 72 and 73.

A section 85 of the protective layer encloses the base flange 45 of the electrical connector 36 as well as the connector bracket 37 and spans the entire mounting face 29 of the adapter housing except for parts thereof surrounding the second pair of passages 70 and 71 to provide surfaces to accurately abut a mounting structure and with the safety wire bracket legs exposed for connection of a safety wire to one or both of the brackets. The recessing of the layer section 85 to set back parts of the mounting face 29 protects the mounting surface parts from being damaged.

The transducer assembly T with protective structure must be as small as possible for mounting in a desired location. The size of the transducer assembly T as well as the shape thereof contribute to ease of location and mounting.

The transducer assembly with protective structure has an elongate body with a concaveconvex cross section and which may be defined as a kidney shape. Referring to Figs. 1, 6 and 7, the shaping of the body provides the convex portion 90 and the concave portion 91. This shape facilitates locating and mounting of the structure within a tubular member, such as an axle for an aircraft landing gear. In Fig. 6, the centerline gear axle of an aircraft landing gear is shown in transverse section as a tubular member 92.A pair of the transducer assemblies Tare mounted therein with the convex surfaces 90 thereof lying closely adjacent to the interior surface of the curved wall of the tubular member and with the concave surfaces 91 spaced from the axis of the tubular member and shaped to be closely adjacent to and partially surround structure which may be mounted axially of the tubular member, such as a transducer device used for other purposes.

A nose gear axle is shown in transverse section in Fig. 7 and has a tubular member 95 with a pair of the transducer assemblies T mounted therein and substantially filling the interior space within the tubular member 95. The convex surfaces 90 have a curvature substantially the same as the interior surface of the wall of the tubular member 95 and the concave surfaces 91 of the two transducer assemblies T are in opposed closely spaced relation.

In addition to the protective layer of resilient material to reduce damage against undesired impact and severe usage, the cantilever mounting of the accelerometer within the adapter housing 10 further reduces shock as does the shockmounting of the electrical connector by means of only the two tabs 38 and 39 of the connector bracket 37 and with the base of the electrical connector being entirely embedded within the layer of protective material.

Claims

1. A transducer assembly comprising a housing having a central chamber containing an accelerometer, an electrical connector for the accelerometer extending from an end of the housing, and an elastomeric potting compound encapsulating the housing and part of the connector for protecting the accelerometer against impact.

2. An assembly according to claim 1 in which the potting compound has openings exposing parts of a mounting face of the housing.

3. An assembly according to claim 1 or claim 2 in which the connector is secured to the housing by means of a bracket having tabs fastened to the housing, the bracket being embedded in the compound.

4. An assembly according to any preceding claim in which the compound is a silicone rubber.

5. An assembly according to any preceding claim in which the accelerometer is cantilever mounted in the chamber by means of a glue layer adjacent one end.

6. An assembly according to any preceding claim in which the housing has a pair of longitudinal passages for fastening members.

7. An assembly according to any preceding claim in which the housing has a pair of longitudinal passages for electrical wiring.

8. An assembly according to any preceding claim in which a safety wire bracket for use in mounting the assembly is attached to the housing.

9. An assembly according to claim 8 in which the safety wire bracket is attached by a screw together with a connector bracket tab.

10. An assembly according to any preceding claim which is of kidney-shaped cross-section for mounting lengthwise inside a tube.

11. A transducer assembly as herein described with refrence to the drawings.