Abstract:
Disclosed is a cone brake no-back for use with an actuation system. The actuation system may be an aircraft actuation system, for example. The no-back may include cone brakes capable of preventing undesired displacement of an aircraft surface (such as a flap, a leading edge, or a trailing edge of a wing) in the event that an actuator input becomes disconnected or is otherwise insufficient to oppose the load created by the aircraft surface.

Description:
BACKGROUND 
     This disclosure relates to a no-back for use with an actuation system. 
     No-backs are typically used with aircraft actuators, which may be used to displace an aircraft surface, such as a flap, a leading edge, or a trailing edge of a wing. Multiple actuators may be positioned on opposing sides of an aircraft, and are typically driven by an input, which may be a drive line torque shaft. In the event of failure or disconnect of the drive line torque shaft, for example, a no-back will prevent an associated aircraft surface from being displaced from a desired position. 
     SUMMARY 
     Disclosed is a no-back assembly including first and second discs coupled to respective first and second shafts. The first and second discs are arranged radially outward of respective first and second shafts. The no-back assembly also includes first and second brakes arranged radially outward of respective first and second discs. The first and second brakes are configured to prevent the first and second discs from rotating when in a no-back condition. 
     Also disclosed is a system including an actuator with a shaft receiving an input and being coupled to a load. The system further includes a disc in communication with the shaft. When in a no-back condition, the disc is brought into contact with a brake disposed about the outer periphery of the disc such that the shaft is substantially prevented from rotating. 
     Further disclosed is a method wherein a disc is rotated in a first rotational direction when in a first operational state. The disc is then moved in a first axial direction when in a second operational state. A brake is urged in a second axial direction, opposite the first axial direction, in the second operational state such that the brake is wedged into the disc and thus prevents the disc from rotating. 
     These and other features can be best understood from the following specification and drawings, the following of which is a brief description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic representative of an aircraft&#39;s actuation system; 
         FIG. 2  is a typical rotary actuator including a cone brake no-back; 
         FIG. 3   a  is a view of area A from  FIG. 2  depicting the cone brake no-back in a no-load, or opposing load, condition; 
         FIG. 3   b  is a section taken along line A 1 -A 1  from  FIG. 3   a;    
         FIG. 3   c  is a section taken along line B-B from  FIG. 3   b;    
         FIG. 3   d  is a view of area A from  FIG. 2  depicting the cone brake no-back in a no-back condition; 
         FIG. 3   e  is a section taken along line A 2 -A 2  from  FIG. 3   a;    
         FIG. 3   f  is a section taken along line C-C from  FIG. 3   d;    
         FIG. 4  is a schematic representative of the no-back in a no-load condition; 
         FIG. 5  is a schematic representative of the no-back in an opposing load condition; 
         FIG. 6  is a schematic representative of the no-back in a no-back condition; and 
         FIG. 7  is a schematic representative of the no-back in an aiding load condition. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , a schematic representative of an aircraft&#39;s actuation system is shown. Multiple actuators  11  may be arranged about a centerline  10  of the aircraft. Each of the actuators  11  are driven by an input (shown generically as actuator input  20  in  FIG. 2 ) from the drive line torque shaft  12 , and may be coupled to a load  17  by way of a linkage mechanism  15 . The drive line torque shaft  12  is driven by a PDU, or power drive unit,  14 . The load  17  may be a movable aircraft surface, such as a flap, leading edge, or trailing edge of a wing. The load  17  generally imparts a torque, or load, on respective actuators  11 . This load imparted onto the actuators  11  generally opposes the torque generated by the input from the drive line torque shaft  12 . In a system without no-backs  16 , an input insufficient to oppose the load  17  (e.g., if the drive line torque shaft or the PDU were to fail) may cause the actuator  11  to back-drive, thus causing the load  17  to displace from a desired position. Thus, each of the actuators  11  include no-backs  16  to prevent back-drive of the actuators  11  and to prevent unwanted displacement of the load  17 . In this regard, the no-backs  16  help maintain overall aircraft control. The system may further include position sensors  18  at either end of the drive line torque shaft  12  to monitor system position. 
     Referring to  FIG. 2 , an actuator  11  including a no-back  16  is shown. As explained, the no-back  16  may be driven by an actuator input  20 , which may be the drive line torque shaft  12 . The drive line torque shaft  12  may rotate in forward and reverse directions. The drive line torque shaft  12  drives the no-back input shaft  30  which, in turn, drives the no-back output shaft  36 . The no-back output shaft  36  is operatively coupled to the actuator output  22 . The actuator output  22  may include input and output planetary gears  26  and  28 , respectively, in communication with the no-back output shaft  36 . The actuator output  22  is coupled to the load  17  by way of a linkage mechanism  15  (represented in  FIG. 1 ). The elements included within the no-back  16  are generally within area A. Area A is shown in detail in  FIG. 3   a.    
       FIG. 3   a , is representative of the arrangement of the no-back  16  in a no-load condition, and in an opposing-load condition (schematically represented in  FIGS. 4 and 5 , respectively). In the opposing load condition, for example, the no-back  16  is positioned such that it allows the no-back input shaft  30  to transfer rotation to the no-back output shaft  36 . The no-back input shaft  30 , which may be supported by bearing  52 , is coupled to the no-back output shaft  36  by way of input and output discs  32 ,  38  arranged about the outer periphery of input and output shafts  30 ,  36 . The input and output discs  32 ,  38  may be made of a hardened steel or bronze and may be coated with Teflon®, for example. Notably, as shown, the no-back output shaft  36  is only coupled to the output disc  38 , whereas the no-back input shaft  30  is operatively coupled to both of the input and output discs  32 ,  38 . 
     The input and output discs  32 ,  38  are rotatably coupled to the no-back input shaft  30  by way of pins  42  arranged about the outer diameter of the no-back input shaft  30 , for example. The no-back input shaft  30  may include recesses  51  about its outer diameter, each of which may receive a portion of a pin  42 . The input and output discs  32 ,  38  may also include recesses  41  and  39 , respectively. Each of the recesses  39 ,  41  are aligned with the recesses  51  to receive a portion of the pins  42 . Further, the output disc  38  may be coupled to the no-back output shaft  36  by way of a geared, or splined, connection  33 . 
     Cone brakes  34 ,  40  are arranged about the outer periphery of (or, radially outward of) the input and output discs  32 ,  38 , respectively. The cone brakes  34 ,  40  may be made of a known steel, for example. In the example shown, the cone brakes  34 ,  40  are coupled to a housing  50  by way of pins  48 . The cone brakes  34 ,  40  may be coupled to the housing  50  such that they are rotatably fixed with respect to the input and output discs  32 ,  38 , but can axially slide in the direction of the pins  48 . The pins  48  may extend generally parallel to the axis  31 , and thus the cone brakes  34 ,  40  may axially slide in the direction of the axis  31 . A spring  46  may be disposed on one axial side of the cone brake  40  (in  FIG. 3   a , the spring  46  is disposed to the left of the cone brake  40 ) and may bias (or preload, or urge) the cone brake  40  to the other axial side (in  FIG. 3   a , the spring  46  biases the cone brake  40  to the right). Alternatively, the spring  46  may be disposed on the right side of the input disc  32  and may bias the cone brake  34  to the left (again, with reference to  FIG. 3   a ). The spring  46  may be a single compression spring, or a set of compression springs, and may be selected of an appropriate material, which may be a hardened steel, for example. 
     In the no-load and opposing load conditions, the spring  46  may contact the cone brake  40 , which in turn contacts output disc  38 , but it does not do so with sufficient force to prevent the input and output discs  32 ,  38  from rotating relative to respective cone brakes  34 ,  40 . The spring  46  is utilized to urge (or, preload) the cone brake  40  and the output disc  38  into alignment with input disc  32  and cone brake  34 , such that the balls  44  are positioned in the deep center portions  62  of the ballramps  35  and  37  (explained in detail below). The inner periphery of the cone brakes  34 ,  40  may include sloped, or angled, surfaces (generally represented at  70 ,  72 ). The outer periphery of the input and output discs  32 ,  38  also include sloped, or angled, surfaces (generally represented at  70 ,  72 ) such that the sloped surfaces of the cone brakes  34 ,  40  correspond with the sloped surfaces of a respective input disc  32 ,  38 . Respective sloped surfaces of output disc  38  and cone brake  40  are generally represented by reference numeral  70 . The sloped surfaces of input disc  32  and cone brake  34  are generally represented by reference numeral  72 . As seen in  FIG. 3   a , respective sloped surfaces  70 ,  72  of the input and output discs  32 ,  38  and the cone brakes  34 ,  40  are sloped such that they extend generally parallel to one another. One will further appreciate that the sloped surfaces  70 ,  72  are sloped, or angled, relative to the axis  31 . 
     The input and output discs  32 ,  38  are spaced apart by a distance X 1  when in the no-load, or opposing load, condition shown in  FIG. 3   a . The spacing of the input and output discs  32 ,  38  with respect to one another is regulated, in part, by the position of the balls  44  between the input and output discs  32 ,  38 . Each of the input and output discs  32 ,  38  includes a ballramp  37 ,  35 , respectively. The ballramps  35 ,  37  may extend into the input and output discs  32 ,  38  at a varying depth. The relationship of the position of the balls  44  within the ballramps  35 ,  37  to the spacing of the input and output discs  32 ,  38  is explained in detail below. 
     Referring to  FIG. 3   b , a view taken along line A 1 -A 1 , from  FIG. 3   a , is shown. As explained, the recesses  39  formed in the output disc  38  may be arranged to correspond with the recesses  51  formed in the no-back input shaft  30 . As shown, each of the recesses  39  and  51  receives a portion of a pin  42 . In this manner, the no-back input shaft  30  is rotatably (or, operatively) coupled to the output disc  38  such that rotation of the no-back input shaft  30  is transferred to the output disc  38 . Pins  48  may be arranged about the outer periphery of the cone brake  40 . The pins  48  may be grounded to the housing  50 , thereby preventing the cone brake  40  from rotating, but allowing it to slide axially. Kidney-shaped ballramps  35  are formed within the output disc  38 , and are sized to receive at least a portion of a ball  44  therein. The ballramps  35  are explained in detail below. 
       FIG. 3   c  is a view taken along line B-B, from  FIG. 3   b , and is representative of the varying depth of the ballramps  35 ,  37  as they extend into the input and output discs  32 ,  38 . As shown, the ballramp  35  may include a deep center portion  62 , which is the deepest portion of the ballramp  35 . Shallow ends  60 ,  64  of the ballramp  35  may be sloped, or may taper, downwardly from an outer surface  61  of the output disc  38  toward the deep center portion  62 . When the no-back  16  is in the no-load and opposing-load conditions (as shown in  FIG. 3   a  and as schematically represented in  FIGS. 4 and 5 ), the balls  44  may generally be positioned in the deep center portion  62  of respective ballramps  35 ,  37 . This position may be referred to as a neutral position, shown in  FIG. 3   e . In this way, the balls  44  are positioned such that they extend into the input and output discs  32 ,  38  relatively deeply, and thus the distance X 1  between the input and output discs  32 ,  38  is relatively small. That is, the input and output discs  32 ,  38  may be positioned such that the deep center portions  62  of the ballramps  35 ,  37  are in alignment, and such that the balls  44  are positioned between respective deep center portions  62  of the ballramps  35 ,  37 . In the no-load and opposing-load conditions, the spring  46  generally urges the brake  40  such that the input and output discs  32 ,  38  are aligned, thus causing the balls  44  to settle in the deep center portions  62 . 
     Referring to  FIG. 3   d , the no-back  16  is shown in a no-back (or, holding-load) condition (schematically represented in  FIG. 6 ). Such a no-back condition may be created when the actuator input  20  is insufficient to oppose the load  17 , or when the actuator input  20  fails (due to a failure of the PDU  14  or the drive line torque shaft  12 , for example). In absence of actuator input  20 , or when the actuator input  20  is insufficient to oppose the load  17 , the load  17  may cause reverse rotation of the no-back output shaft  36 , which in turn may cause output disc  38  to rotate relative to input disc  32  (because the no-back output shaft  36  is only coupled to the output disc  38 , and not both of the input and output discs  32 ,  38 ). In this regard, the deep center portions  62  of the ballramps  35 ,  37  will also rotate out of alignment, and the balls  44  will be moved toward the shallow ends  60 ,  64  of the ballramps  35 ,  37 , as shown in  FIG. 3   f . Because the shallow ends  60 ,  64  do not extend as deeply into the respective input and output discs  32 ,  38  as the deep center portion  62 , the positioning of the balls  44  causes the output disc  38  to become axially spaced from input disc  32  by a distance X 2  (this position may be referred to as an extended position, shown in  FIG. 3   f ), which is greater than the distance X 1 . This positioning of the balls  44  generates an axial load on the input and output discs  32 ,  38  greater than the preload (or biasing force) generated by the spring  46 . 
     As the balls  44  are positioned toward the shallow ends  60 ,  64  of the ballramps  35 ,  37 , the output disc  38  engages the cone brake  40  (by way of their respective sloped surfaces  70 ) and causes the cone brake  40  to axially slide with the output disc  38  (to the left in  FIG. 3   d ). Again, as the load  17  is applied to the no-back output shaft  36 , and then to the output disc  38 , an axial load is generated by the balls  44  that is transferred to both discs  32  and  38 . This axial load generated by the balls  44  passes from the input and output discs  32 ,  38  to the cone brakes  34 ,  40 , thus displacing output disc  38  and cone brake  40  (to the left in  FIG. 3   d ) relative to their position in the no-load and opposing-load conditions shown in  FIG. 3   a . The cone brake  40  thus compresses the spring  46  against the spacer  80  and retaining ring  81 , both of which are fixed to the housing  50 . By way of the compression of the spring  46 , the cone brake  40  is urged toward the output disc  38  against the axial load generated by the positioning of the balls  44 . In this manner, the cone brake  40  is wedged into the output disc  38  by way of the respective sloped surfaces  70 . This wedging action thus creates a frictional force between the cone brake  40  and the output disc  38  and between cone brake  34  and the input disc  32 , respectively, creating a combined resistance torque (T r ) sufficient to overcome the torque created by load  17  on the no-back output shaft  36  (T load ). In this manner, the no-back input and output shafts  30 ,  36  and the input and output discs  32 ,  38  are prevented from rotating. Thus, the load  17  is prevented from being displaced, and the no-back condition is effectively provided. 
     The following relationship may be referred to as gain (G). 
     
       
         
           
             G 
             = 
             
               
                 T 
                 r 
               
               
                 T 
                 load 
               
             
           
         
       
     
     One of ordinary skill will appreciate that several factors may affect gain (G) including: the materials chosen for the input and output discs  32 ,  38  and the cone brakes  34 ,  40 ; the slope of the sloped surfaces  70 ,  72 ; the dimensions of the ballramps  35 ,  37 , etc. In order for the no-back  16  to work properly, the gain (G) must be greater than 1 when in the no-back condition. That is, the above-mentioned factors must be set such that T r &gt;T load  when in the no-back condition. 
       FIG. 3   e  is a view taken along line A 2 -A 2  from  FIG. 3   a  and shows the balls  44  arranged between the ballramps  35 ,  37  of the input and output discs  32 ,  38  such that the discs are spaced apart by a distance X 1 .  FIG. 3   e  is representative of a neutral position. The neutral position may be present during a no-load condition (schematically represented in  FIG. 4 ) and an opposing load condition (schematically represented in  FIG. 5 ). The neutral position exists when the deep center portions  62  of the respective input and output discs  32 ,  38  are in alignment, and the balls  44  are positioned between respective deep center portions  62 . 
       FIG. 3   f  is a view taken along line C-C from  FIG. 3   d  and shows the balls  44  arranged between the ballramps  35 ,  37  of the input and output discs  32 ,  38  such that input and output discs  32 ,  38  are spaced apart by a distance X 2 .  FIG. 3   f  is representative of an extended position. The extended position may be present during the no-back condition or during an aiding-load condition (schematically represented in  FIGS. 6 and 7 , respectively). The extended position exists when the deep center portions  62  of the respective input and output discs  32 ,  38  are out of alignment, and the balls  44  are positioned between respective shallow ends  60 ,  64  of the ballramps  35 ,  37 . This positioning of the balls  44  creates an axial load on the input and output discs  32 ,  38  sufficient to overcome the preload (or biasing force) of the spring  46 . 
     Referring to  FIG. 4 , the no-back  16  is schematically represented in a no-load condition. The no-load condition is also represented in  FIG. 3   a . Notably, in the no-load condition, the load  17  may be present, but may be positioned in a rest position so as to not impart a torque, or load (such as T load ), on the no-back output shaft  36 . Thus, there may be no input (e.g., from actuator input  20 ), as there is no load for the input to oppose. As can be seen in  FIG. 4 , the ball  44  is positioned in the center (shown as the deep center portion  62  in  FIG. 3   c ) of respective ballramps  35 ,  37 . That is, the input and output discs  32 ,  38  are aligned such that the center of the ballramps  35 ,  37  are in alignment. Cone brakes  34 ,  40  are positioned outside of, or about the outer periphery of, the input and output discs  32 ,  38 . As shown, spring  46  is positioned between the cone brake  40  and the housing  50  (the spring  46  may actually be in operative connection with the housing  50  by way of the spacer  80  and retaining ring  81 , as shown in  FIG. 3   a , for example). 
     Referring to  FIG. 5 , the no-back  16  is schematically represented in an opposing-load condition (which is also represented in  FIG. 3   a ). In this condition, a forward input, I forward , is sufficient to oppose, or overcome a load, L. That is, the forward input, I forward , drives the no-back output shaft  36  in a forward rotational direction, such that the load L, which generally urges the no-back output shaft  36  in a reverse rotational direction, is opposed. In this manner, the load  17  is generally maintained in a desired position by virtue of the forward input, I forward . Note that the forward input, I forward , is shown as engaging the input and output discs  32 ,  38  by way of a pin  42  (as described above). 
     Referring to  FIG. 6 , the no-back  16  is shown in a no-back condition (also depicted in  FIG. 3   d ). The no-back condition, which is generally described above, may be caused by the failure of the drive line torque shaft  12  or the PDU  14 , for example. In either case, the no-back input shaft  30  would not impart a forward input I forward  sufficient to oppose the load L. In fact, when in the no-back condition there may be no input present at all (as the drive line torque shaft may have completely failed, for example). Regardless, when the forward input I forward  is insufficient to oppose the load L, the no-back output shaft  36  is urged in a reverse rotational direction. Since the no-back output shaft  36  is only coupled to the output disc  38 , rather than both of the input and output discs  32 ,  38 , the input and output discs  32 ,  38  are brought out of alignment. That is, the ballramps  35 ,  37  of the input and output discs  32 ,  38  are brought out of alignment with one another. As explained above, this misalignment causes the balls  44  to be positioned away from the center of the ballramps  35 ,  37  and toward the shallow end portions  60 ,  64 , for example (see  FIG. 3   c ). Because of this positioning of the balls  44  within the ballramps  35 ,  37 , the input and output discs  32 ,  38  are spaced relative to one another (generally indicated as the distance X 2  in  FIGS. 3   d  and  3   f ). In  FIG. 6 , this relative movement of the input and output discs  32 ,  38  is represented by downward movement of the output disc  38 . Movement of the output disc  38  also causes the cone brake  40  to move toward the spring  46  and the housing  50  (the spring  46  may contact the housing  50  by way of the spacer  80  and retaining ring  81 ). The axial load that is generated by the positioning of the balls  44  within the ballramps  35  and  37  is sufficient to generate friction between the cone brake  40  and the output disc  38  and between the cone brake  34  and the input disc  32 . This friction between the input and output discs  32 ,  38  and the cone brakes  34 ,  40  generates a combined resistance torque (T r ) sufficient to overcome the torque imparted onto the no-back output shaft  36  by the load L, defined above as T load . Thereby, no-back  16  prevents the load  17  from being displaced, and the no-back condition is effectively provided. 
     Referring to  FIG. 7 , the no-back  16  is shown in an aiding-load condition, wherein the no-back  16  may be released from the no-back condition. Essentially, the no-back  16  can be released by adjusting the resistance torque (T r ). This may be accomplished by applying, a reverse input, I reverse , to the no-back input shaft  30  of a sufficient magnitude to reduce the gain (G) to less than 1. In this way, the resistance torque (T r ) is reduced and rotation of the input and output discs  32 ,  38  and input and output shafts  30 ,  36  is again possible. 
     A worker of ordinary skill in this art would recognize that certain modifications of the instant disclosure would come within the scope of the claims. For example, although the no-back  16  has been described with reference to cone brakes  34 ,  40 , alternate brake designs are contemplated within the scope of this disclosure. That is, the cone brakes  34 ,  40  may be representative of any brake arranged radially outward of the input and output discs  32 ,  38 . Further, while the no-back  16  has been described with reference to use in aircrafts, one of ordinary skill would recognize that the no-back  16  need not be limited to use in aircrafts, and indeed may be applicable for use in other settings. Accordingly, the following claims should be studied to determine their true scope and content.