Patent Publication Number: US-2023150652-A1

Title: Attachment for rotary actuator

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to European Patent Application No. 21275158.0 filed Nov. 16, 2021, the entire contents of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure is concerned with means for mounting or attaching a rotary actuator to a wing assembly of an aircraft. 
     BACKGROUND 
     Modern aircraft include a number of movable surface or panels such as flight control surface of wing tips that are configured to be movable relative to another part of the aircraft e.g. to another, fixed or stationary part of a wing. The movable parts are typically moved relative to the stationary part by means of an actuator. In applications where it is important to minimise weight and size of parts on an aircraft, rotary actuators are used comprising a fixed stator part and a movable rotor part. Rotary geared actuators (RGAs) have been developed in which the input and the output are linked by a series of gears to step down high speed, low torque rotation to provide slower speed, high torque positioning of a movable part. These actuators are typically positioned along the hinge line between a stationary part of the structure e.g. wing, and a relatively rotatable part. The RGA has so called earth members for fixing the actuator to one of the parts and output members for attachment to the other part. Typically, the earth members are attached to the stationary part of the structure and are mounted via flanges and bolts. The output members are then attached to the movable part also by known attachment means such as bolts or the like. 
     The attachment lugs and mounts required to attach the earth members to the wing structure and to attach the output members to the moveable part (or vice versa) add to the overall size and weight of the actuator assembly and the envelope required to accommodate the assembly. Where space and weight allowance is limited. Such as in aircraft, there is a desire to reduce the size and weight of mounting/attachment components whilst maintaining the required secure attachment. 
     In addition, attaching an RGA to the structure is generally time and labour intensive and as each lug/fixing mechanism needs to be fastened securely by hand, there is a risk of human error each time. 
     Furthermore, each attachment point where a lug or the like is fastened to the structure, is subject to loads that cause local stresses particularly during flight and during operation that can loosen or damage the fastening. 
     There is, therefore, a need for an improved way of securing an RGA to a structure whilst maintaining secure attachment. 
     SUMMARY 
     According to the present disclosure, there is provided a rotary actuator assembly for moving a first relatively movable part relative to a second relatively movable part, the assembly comprising a rotary actuator having a plurality of circumferential earth members for attachment to one of the first and the second relatively movable parts and a plurality of circumferential output members for attachment to the other of the first and second relatively movable parts, and wherein at least the plurality of circumferential earth members or the plurality of circumferential output members is provided with radially outwardly extending locking features e.g. splines around their circumference configured to be received in a mounting sleeve having complementary splines to engage with the radially extending splines. 
     In some examples, both the plurality of circumferential earth members and the plurality of circumferential output members are provided with such radially extending splines. 
     In another aspect, there is provided a mounting assembly comprising a rotary actuator assembly as described above and a mounting sleeve having a plurality of radially inwardly extending circumferential splines positioned along the length of the sleeve so as to engage with the radially outwardly extending splines of the rotary actuator assembly when inserted in the mounting sleeve. 
    
    
     
       BRIEF DESCRIPTION 
         FIG.  1    shows a typical rotary actuator with a conventional attachment mechanism. 
         FIG.  2    shows an example of the rotary actuator assembly according to the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    shows a rotary actuator  10  positioned between and attached to two relatively moveable parts  1 , 2 . Such as, but not limited to, a fixed wing structure  1  and a relatively movable part  2  e.g. a slat or flap or a foldable wing tip. The actuator can be any known type of rotary actuator having a stator part and a rotor part. Input rotation is provided to the actuator by a drive means such as a motor (not shown) that drives an input shaft  3 . This causes rotation of the gears (not shown in detail) of the actuator which result in rotation of the rotor  11 . The rotor  11  is fixed to the second relatively movable part  2 . The actuator operation is known in the art and will not be described in any detail. The drawing is schematic only. Different types of rotary actuator are possible. With a geared actuator, as shown, the gears of the actuator operate such that the output rotor  11  rotates in response to, but at a different speed to the input rotation to cause relative rotation of the other part  2 , to which the output rotor  11  is attached. 
     The rotary actuator extends axially along an axis A defined by the shaft  3  and the gears, earth members  12  and rotor  11  are arranged around the axis such that the rotor rotates about the axis. The earth members  12  are annular or circumferential rings mounted around the shaft  3  and several earth members  12  may be positioned around the actuator spaced apart in the axial direction. The number of earth members can be selected according to the use and design requirements of the actuator. 
     In a conventional arrangement, the actuator is mounted to the first relatively moveable part  1  via earth members  12  on the actuator. The earth members around the body of the actuator are secured to the wing part  1  in any known way by a fixed fastener such as a bolt attached to the earth member by an external housing (not shown). In the example shown, the earth members  12  are formed with radially extending lugs  22  with a hole therethrough. The lugs fit into attachment mounts  23  provided on the relatively movable part  1  which also have holes therethrough. The earth members are secured in positioned by passing a bolt  24  through the holes in the attachment mounts and the lugs. Each earth member may be provided with several lugs (two are shown for each earth member in the example of  FIG.  1   ) and two bolts. A single bolt or rod can be passed through the whole row of earth members and secured by a fastener  124  at each end. It is also feasible that each lug and attachment mount pair could be fastened with a separate fastener. 
     Outlet members  110  are mounted around, and rotate with the rotor  11 . The outlet members  110  may be provided at locations along the length of the actuator between earth members  12  but, again, the number and spacing of the outlet members will depend on specific design requirements. The outlet members  110  are arranged to be attached to the other of the relatively movable parts  2 . As with the earth members  12 , typically, the outlet members are provided with lugs  112  with holes therethrough which fit between mounting attachments  114  affixed to the second relatively movable part and one or more bolts  116  is passed through the matched-up holes to secure the outlet members to the relatively movable part. The bolts  116  can be secured by fasteners  116  either at each lug location or a single bolt passes through all lugs and is secured at its ends. 
     In this way, the earth members, which do not rotate with the actuator rotor, are fixed to one part of, say, the wing, and the relatively rotatable output members, that rotate with the actuator rotor  11 , are attached to move the other part of the wing to rotate it relative to the first part. 
     As mentioned above, and as can be seen from  FIG.  1   , although the earth members, output members, lugs, attachment mounts and bolts do not actually contribute to the actuator function, they add substantially to required space envelope and to the overall weight of the assembly. 
     In the assembly according to this disclosure, an example of which is shown in  FIG.  2   , the mounting of the actuator with respect to the relatively movable parts, is by means of circumferential splines around the actuator instead of radially extending lugs and mounts and bolts therethough. This greatly simplifies assembling the actuator and also takes up less space and has reduced weight compared to the assembly shown in  FIG.  1   . 
     The general structure and function of the rotary actuator according to the disclosure is as described above and will not be described again herein. The difference lies in the way the actuator  100  is attached to the relatively moveable parts e.g. the wing parts. 
     Instead of the earth members having lugs, the earth members  1120  of the disclosure are provided with radially extending locking features e.g. splines  1121  around the circumference of the annular ring forming the earth member, the splines extending radially outwards. The splines  1121  are configured to engage with complementary splines (not shown) extending inwardly from a socket or sleeve (not shown) formed on the first relatively movable part e.g. the fixed wing part. Instead of splines, the locking features may take other forms that engage to provide the desired locking between the earth members and the receiving sleeve. 
     Similarly, the output members  1140  may be provided with similar splines  1141  around their circumference with will engage with complementary splines formed in a sleeve part provided on the other relatively movable part e.g. a movable wing panel. 
     In the example shown, all of the earth members  1120  and the output members  1140  are provided with splines. In other examples, though, it may be that only some of the earth members and/or output members are provided with splines. For example, only the earth members might have a spline fitting with one wing part, while the output members have a conventional lug/mount fitting, or vice versa. 
     A sleeve for receiving the actuator will be defined by sleeve parts formed on or attached to the adjacent edges of the relatively movable parts i.e. the resulting sleeve formed by the sleeve parts will define the hinge between the two parts and will have inwardly extending splines. The actuator can then be pushed into the sleeve for assembly such that the splines on the earth members  1120  will engage with splines of the sleeve part attached to a fixed structure part and the splines on the output members will engage with splines on the other part of the sleeve that is affixed to the other part. 
     Once inserted in the sleeve, the actuator can be locked axially in position by any suitable means e.g. bolts, locking rings, caps etc. 
     Attaching the actuator to the relatively movable parts in this way allows the actuator to be easily mounted but ensures a secure attachment and reliable rotation operation. The fastening components have reduced size and weight compared to known mounting assemblies and spread the stress locations around the rings rather than providing single stress points at the lugs. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, element components, and/or groups thereof. 
     While the present disclosure has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this present disclosure, but that the present disclosure will include all embodiments falling within the scope of the claims.