# US 10,871,214 B2 · Secondary load path detection

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- Number: US 10,871,214 B2
- Document ID: US10871214B2
- Status: Granted
- Kind: B2
- Application number: 15/672,459
- Filed: 2017-08-09
- Published: 2018-02-15
- Granted: 2020-12-22
- Earliest claimed: 2016-08-12
- Assignees: Ratier-Figeac SAS
- Applicants: Ratier-Figeac SAS
- Inventors: Ghislain Teyssier; Frédéric Persouyre
- Web page: https://patentgrep.com/patent/US10871214B2

## CPC

- F16H 57/01: Monitoring wear or stress of gearing elements, e.g. for triggering maintenance
- F16H 57/028: characterised by means for reducing vibration or noise
- B64C 13/28: mechanical
- B64C 13/341: {having duplication or stand-by provisions}
- F16H 25/205: {comprising alternate power paths, e.g. for fail safe back-up}
- F16H 25/2204: {with balls}
- F16H 25/2209: {with arrangements for taking up backlash}
- F16H 25/2472: {Safety nuts}
- F16H: GEARING
- B64C: AEROPLANES; HELICOPTERS

## Abstract

A nut arrangement for a screw actuator is disclosed for allowing detection of wear in a primary nut of the screw actuator. The nut arrangement comprises a primary nut for providing a primary load path and a secondary nut for providing a secondary load path. An interface ring may link the secondary nut to the primary nut. A sensor is provided to detect relative axial movement between the primary and secondary nuts. During normal operation, the interface ring is seated by a flexible coupling that allows relative axial displacement of the secondary nut to the primary nut to accommodate wear in the primary nut. The sensor can be used to monitor backlash between the primary and secondary nuts to determine wear of the primary nut.

## Claims

### Claim 1

A nut arrangement for a screw actuator, comprising:
a primary nut for providing a primary load path;
a secondary nut for providing a secondary load path;
a flexible coupling to link the primary nut to the secondary nut during normal operation when the primary load path is active, wherein the flexible coupling provides a bias that allows relative axial movement between the primary and secondary nuts; and
a sensor to detect relative axial movement between the primary and secondary nuts,
wherein the sensor is used as part of a wear detection arrangement to monitor a change in backlash between the primary and secondary nuts;
wherein an interface ring is provided to link the secondary nut to the primary nut and the interface ring is seated with respect to the primary or secondary nut by the flexible coupling;
wherein the interface ring is coupled to the secondary nut with a mechanism which allows the interface ring and the secondary nut to be displaced with respect to each other to test the flexible coupling; and
wherein the mechanism comprises a mount provided on the interface ring for a bolt, a flange provided on the secondary nut and a bolt, the bolt having a tail end portion which extends through the flange of the secondary nut and into the mount, and wherein a spring is provided towards a head end portion of the bolt to bias the head end portion of the bolt away from the flange.

### Claim 2 (depends on 1)

The nut arrangement according to claim 1, wherein the flexible coupling comprises a sprung detent which engages a recess.

### Claim 3 (depends on 2)

The nut arrangement according to claim 2, wherein the sprung detent is located in the primary nut.

### Claim 4 (depends on 2)

The nut arrangement of claim 2 wherein the sprung detent is a ball-spring detent.

### Claim 5 (depends on 4)

The nut arrangement of claim 4, wherein the recess is configured to deflect a ball of the ball-spring detent against a spring bias when permitting relative axial movement between the primary and secondary nuts.

### Claim 6 (depends on 1)

The nut arrangement according to claim 1, wherein the secondary nut comprises a device configured to absorb vibration or high acceleration transmitted into the secondary nut.

### Claim 7 (depends on 6)

The nut arrangement of claim 6, wherein the device comprises a guide ring.

### Claim 8 (depends on 7)

The nut arrangement of claim 7, wherein the guide ring is comprised of PTFE.

### Claim 9 (depends on 1)

The nut arrangement according to claim 1, wherein a claw coupling is provided between the primary nut and the secondary nut to prevent relative rotation of the primary nut and secondary nut.

### Claim 10 (depends on 1)

The nut arrangement according to claim 1, wherein a failsafe connection comprising a transfer member is provided between the primary and secondary nuts to transfer load to the secondary load path in the event the flexible coupling decouples.

### Claim 11 (depends on 10)

The nut arrangement according to claim 10 wherein the transfer member comprises a hole for endoscopic inspection of the primary and secondary nut.

### Claim 12 (depends on 10)

The nut arrangement according to claim 10, wherein the transfer member comprises a pivot ring adapted to allow a lever to be placed through the transfer member and pivoted to test the flexible coupling for wear or jamming.

### Claim 13 (depends on 10)

The nut arrangement of claim 10, wherein a protrusion extends from the secondary nut and projects into a hole provided in the transfer member connected to or providing part of the primary nut for limiting relative axial movement between the primary nut and secondary nut.

### Claim 14 (depends on 13)

The nut arrangement of claim 13, wherein the transfer member substantially encloses the secondary nut.