Patent Publication Number: US-2022234724-A1

Title: Linear drive device for an aircraft, a drive arrangement and an aircraft having such a linear drive device

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application claims the benefit of the German patent application No. 102021101487.5 filed on Jan. 25, 2021, the entire disclosures of which are incorporated herein by way of reference. 
     FIELD OF THE INVENTION 
     The invention relates to a linear drive device for driving a movable component of an aircraft, such as a high-lift device. The invention further relates to a drive arrangement, a wing and an aircraft. 
     BACKGROUND OF THE INVENTION 
     In aviation, numerous different linear geared drives are used to actuate or drive external and internal components of an aircraft. Those components include high-lift devices, intake ducts and their covers, control surfaces, loading ramps, cargo transporters, cargo locks and door latches as well as passenger seats. 
     Desirable properties for these drives include zero backlash, large gear reduction from the input to the output, ability to self-lock, better load transfer and reduced wear. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide an improved linear drive device exhibiting at least one of these desired properties. 
     The invention provides a linear drive device for a movable component of an aircraft, comprising a first member, the first member extending in a longitudinal direction and having a plurality of engaging teeth, and a second member configured to be movable relative to the first member in the longitudinal direction, the second member including:
         a plurality of engaging members being supported so as to be movable between a fully extended position, in which the respective engaging member fully engages a pair of engaging teeth, and a fully retracted position, in which the respective engaging member is disengaged from the first member such that the engaging member is movable along the longitudinal direction without encountering an engaging tooth;   a rotatable cam shaft having a control cam portion, the cam portion being configured so as to, upon rotation of the cam shaft, sequentially shift the engaging members thereby causing a linear motion of the movable member relative to the first member along the longitudinal direction.       

     Preferably, the engaging members are configured in a linear arrangement that is aligned parallel to the longitudinal direction. Preferably, the engaging members are configured in a circular arrangement around the first member. 
     Preferably, at least one engaging member is integrally formed with a membrane member, the membrane member being deformable by the control cam portion so that the engaging members are shiftable between the fully retracted and fully engaged positions. 
     Preferably, at least one engaging member has an engaging portion that is arranged to contact the first member, and the engaging portion engages the first member in a planar manner. 
     Preferably, the engaging portion, when viewed in a cross-section, is shaped as a triangle or an ogive. 
     Preferably, at least one engaging member has a cam contact portion that is arranged opposite of the engaging portion and arranged to contact the cam portion. 
     Preferably, at least one engaging member is formed as a rectangular solid member or as a pin-like member; or wherein at least one engaging member is formed as a circular arc shaped solid member. 
     Preferably, the second member supports the cam shaft and/or the engaging members. 
     Preferably, the second member comprises a support member having a plurality of openings, and the engaging members are arranged in the openings so as to be slidable between the fully extended and fully retracted positions. 
     Preferably, the cam shaft is configured as a massive shaft and the cam portion is disposed on the outer circumferential surface of the cam shaft. Preferably, the cam shaft is configured as a hollow shaft and the cam portion is disposed on the inner circumferential surface of the cam shaft. 
     Preferably, the cam shaft comprises a plurality of cam segments and each cam segment includes a different section of the cam portion. 
     Preferably, the cam segments are rotationally offset in a progressive manner along the axial direction of the cam shaft, so as to generate a wave-like motion of the engaging members along the longitudinal direction. 
     Preferably, the cam shaft is configured as an articulated shaft and each cam segment forms an articulated portion of the articulated shaft. 
     Preferably, the first member is configured in a circular arc shape. 
     The invention provides a drive arrangement for a wing of an aircraft comprising a high-lift device and/or a control surface, and a linear drive device according to any the preceding claims, wherein the linear drive is configured for driving the high-lift device and/or the control surface between a fully retracted and a fully extended position, wherein the first member is attached to the high-lift device and/or control surface and the second member is attachable to the wing. 
     The invention provides a wing for an aircraft comprising such a drive arrangement. 
     The invention provides an aircraft comprising a linear drive device, a drive arrangement or a wing as described herein, respectively. 
     The proposed linear drive has a cam shaft on the input/drive side, which is driven by some kind of power unit, e.g., an electric or hydraulic motor. The cam shaft is preferably seated in a housing and supported by bearing assemblies. The cam on the shaft is continuously located along the whole shaft in a spherical arrangement. Between the cam shaft and the rack multiple teeth are located in openings inside the housing. The teeth are movable relative to the housing. 
     A certain number of these teeth are pressed towards the rack by the cam. Based on the rotational position of the cam shaft, different teeth are pressed down and the downwards movement of the tooth can be described by a wave. In that way the down pressed teeth drive the rack along its longitudinal axis. The minimum transmission speed from drive side to linear drive is at least one tooth of the rack per cam shaft rotation. Different transmission ratios are possible when multiple cam segments with offset phases are used. To drive the rack, the drive side (preferably including the housing) and the cam shaft are preferably rigidly mounted in relation to the rack in its drive direction. 
     It is also possible that the proposed device has an inverted cam shaft build as a hollow shaft with an internal cam that is used to press down multiple teeth. The teeth are mounted in a housing surrounding the piston. The piston is built like a rack with gear teeth. These teeth are continuously formed around the piston main axis. The internal cam geometry in the cam hollow shaft is preferably designed in a spiral form. The movement of the teeth towards the piston build a wave. In that way, always a certain number of teeth are engaged and the piston is transported by the teeth in its drive direction. The cam shaft is, in its main axis direction, rigidly connected to the housing and driven by some kind of external powered device. 
     The piston may also be a curved piston. The cam shaft in this case must consist of many segments correlating to the tooth positions. The segments must be coupled rotational to rotate synchronously. 
     While the linear drive device is subsequently described with reference to high-lift devices for the sake of brevity, it should be noted that the linear drive device may also be configured to drive other external movable components or internal movable components of an aircraft. External movable components include high-lift devices, intake ducts and their covers and control surfaces, whereas internal movable components include loading ramps, cargo transporters, cargo locks and door latches, as well as passenger seats. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Examples of the invention are subsequently described in more detail with reference to the accompanying drawings. Therein: 
         FIG. 1  depicts an embodiment of an aircraft; 
         FIG. 2  depicts a first embodiment of a linear drive device; 
         FIG. 3  depicts a variant of the linear drive device of  FIG. 2 ; 
         FIG. 4  depicts an isometric view of a cam shaft in more detail; 
         FIG. 5  depicts a side view of the cam shaft of  FIG. 4 ; 
         FIG. 6 a    depicts a front view (top),  FIG. 6 b    depicts a cross-section through A-A (middle) and  FIG. 6 c    depicts a cross-section through B-B (bottom) of the cam shaft of  FIG. 4 ; 
         FIG. 7  depicts a sequence of cam shaft positions; 
         FIG. 8  depicts a stroke-timing diagram for the cam shaft of  FIG. 4 ; 
         FIG. 9  depicts a second embodiment of the linear drive device; 
         FIG. 10  depicts a front view of the linear drive device of  FIG. 9 ; and 
         FIG. 11  depicts a variant of the linear drive device of  FIG. 9 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIG. 1 , an exemplary embodiment of an aircraft  10  comprises a fuselage  12  to which a pair of wings  14  is attached. Further attached to the wings  14  is a pair of turbine engines  16 . It should be noted that the number and type of engines may vary. At the rear of the fuselage  12  a horizontal tail plane (HTP)  18  and a vertical tail plane (VTP)  20  are arranged. 
     The wings  14 , the HTP  18  and the VTP  20  have a plurality of control surfaces  22  for steering the aircraft  10 . In addition, the wings  14  also contain a plurality of high-lift devices  24 , such as slats and flaps. 
     Referring to  FIG. 2 , the high-lift device  24  is driven between a retracted and an extended position by a linear drive device  26 . 
     The linear drive device  26  comprises a first member  28  that extends in a longitudinal direction. The first member  28  has a plurality of engaging teeth  30 . The first member  28  can be a toothed rack  32 . The first member  28  is coupled to the high-lift device  24 . 
     The linear drive device  26  comprises a second member  34 . The second member  34  can be moved relative to the first member  28  along the longitudinal direction. The second member  34  is coupled to the wing  14 . 
     The second member  34  has a plurality of engaging members  36 . The engaging members  36  can be shifted between a fully extended position and a fully retracted position. In the fully extended position, the engaging members  36  mesh with the engaging teeth  30 , whereas in the fully retracted position the engaging members  36  are able to pass the engaging teeth  30  along the longitudinal direction. 
     The second member  34  includes a support member  38 . The support member  38  is configured to individually support the engaging members  36 . In the present example, the support member  38  is formed by a housing  40 . 
     The second member  34  comprises a cam shaft  42 . The cam shaft  42  is supported in a rotating manner, preferably by the housing  40 . The second member  34  may include one or more bearings  43  for supporting the cam shaft  42 . 
     The cam shaft  42  has a control cam portion  44 . The control cam portion  44  sequentially engages with the engaging members  36  upon rotation of the cam shaft  42 . As indicated in  FIG. 2 , upon rotation of the cam shaft  42  in a clockwise direction, the control cam portion  44  engages with the engaging members  36  in sequence from right to left, thereby pushing the engaging members  36  into the fully extended position. 
     The engaging members  36  extend and retract in a wave-like pattern and as a result force the first member  28  along its longitudinal direction, for example to the left. 
     Referring to  FIG. 3 , a variant of the linear drive device  26  is described only insofar as it differs from the embodiment of  FIG. 2 . In this variant, the engaging members  36  are formed on a flexible sheet member  39 . The flexible sheet member  39  can be a metal sheet, for example. The flexible sheet member  39  is flexible in the sense that the flexible sheet member  39  is reversibly deformed upon rotation of the cam shaft  42  by the control cam portion  44 , so that as a result the engaging members  36  are moved between the fully extended and fully retracted position. The flexible sheet member  39  can perform the function of a leaf spring such that the pushing of the engaging members  36  is caused by the control cam portion  44 , whereas the retraction is caused by the elastic tension of the flexible sheet member  39 . 
     Referring to  FIG. 4  to  FIG. 8 , the configuration and function of the cam shaft  42  are described in more detail. 
     The control cam portion  44  comprises a plurality of cam segments  46 . Each cam segment  46  has a circular portion  48 . The circular portion  48  makes up the majority of the respective cam segment&#39;s  46  circumference. The circular portion  48  has a radius that allows the corresponding engaging member  36  to be moved into its fully retracted position. 
     Each cam segment  46  includes a control cam  50 . The control cam  50  makes up the remainder of the cam segment&#39;s  46  circumference. The control cam  50  is configured such that, upon rotation of the cam segment  46 , the control cam  50  pushes the respective engaging member  36  from the fully retracted position into the fully extended position. 
     As depicted, in particular in  FIG. 4  to  FIGS. 6 a   - 6   c,  the cam segments  46  are arranged on the cam shaft  42  such that neighboring cam segments  46  are offset by a certain offset angle θ. The offset angle θ is preferably measured between the lines through the largest radial extent of the cam segment  46  that cross in the center of the cam shaft  42 , as illustrated in  FIGS. 6 a   - 6   c.    
       FIG. 7  and  FIG. 8  illustrate more closely the action of a single cam segment  46 . 
     Each control cam  50  includes three functional sections. A first functional section  52  is the section that upon rotation of the cam shaft  42  makes initial contact with the engaging member  36  and pushes it. A second functional section  54  is the section which supports the engaging member  36  in the fully extended position for a small part of the rotation of the cam shaft  42 . A third functional section  56  is the section that recedes back upon rotation of the cam shaft  42  so that the engaging member  36  may disengage from the engaging teeth  30 . Disengaging may be caused by the engaging teeth  30  pushing the engaging member  36  due to the longitudinal movement of the first member  28  or an elastic spring force generated by the flexible sheet member  39 . 
     As shown in  FIG. 7 , the cam shaft  42  turns clockwise. The first member  28  may move into the drawing layer. If the cam shaft  42  turns counter-clockwise, the motion of the first member  28  is also reversed. 
     Initially in step I, the cam segment  46  makes contact with the engaging member  36  by means of the first functional section  52 . As a result, the engaging member  36  is pushed out of the fully retracted position towards the first member  28  and the driving force is transmitted from the cam shaft  42  to the first member  28 . 
     In step II, the cam segment  46  has moved on so that the second functional section  54  keeps the engaging ember in the fully extended position, in which the engaging member  36  and the engaging teeth  30  are meshing. 
     In steps III and IV, the cam segment  46  has rotated further and the third functional section  56  is contacting the engaging member  36 . Thus, the engaging member  36  is prevented from being fully pushed into the fully retracted position by forces acting on the first member  28 . Albeit the third functional section  56  allows the engaging member  36  to recede from full engagement with the engaging teeth  30 . As a result, a force acting on the first member  28  may be transmitted via the engaging member  36  to the cam shaft. 
     In steps V to VIII, the cam segment  46  may contact the engaging member  36  with its circular portion  48 . In this configuration, no force is transmitted from the cam shaft  42  to the first member  28 . 
     Taking into account that the steps I to VIII are performed by each individual cam segment  46 , the entire linear drive device  26  has no backlash and is self-locking. Furthermore, the offset angle θ influences the reduction ratio. The smaller θ is, the larger is the reduction ratio. 
     It should be noted that while the control cam portion  44  was previously described as being formed from separate discreet cam segments  46 , the size of the cam segments  46  may be chosen so small that for practical purposes the cam segments  46  and the cam portion  44  are continuous or without step-like features between adjacent cam segments  46 . 
       FIG. 8  depicts the stroke of adjacent cam segments  46  over their rotational angle. They are offset by the offset angle θ. The zero stroke or dwell corresponds to the circular portion  48 , the rising portion corresponds to the first functional section  52 , the upper flat portion at maximum stroke corresponds to the second functional portion  54  and the falling portion corresponds to the third functional section  56 . 
     It should be noted that while the curves in  FIG. 8  are depicted having a linear characteristic over the rotational angle, this need not be the case. Depending on various parameters for the drive, other characteristics are possible. 
     Referring to  FIG. 9  and  FIG. 10 , another embodiment of a linear drive device  26  is described insofar as it differs from the previously described embodiment. 
     The linear drive device  26  comprises a first member  28  that extends in a longitudinal direction. The first member  28  has a plurality of engaging teeth  30 . The engaging teeth  30  are configured as circumferential teeth. 
     The linear drive device  26  comprises a second member  34 . The second member  34  can be moved relative to the first member  28  along the longitudinal direction. 
     The second member  34  has a plurality of engaging members  36 . The engaging members  36  are arranged circumferentially and preferably surround the first member  28 , as depicted in particular in  FIG. 10 . 
     The second member  34  includes a support member  38 . The support member  38  is configured to individually support the engaging members  36 . In the present example, the support member  38  takes the form of a bushing. 
     The second member  34  comprises a cam shaft  42 . The cam shaft  42  is supported in a rotating manner, preferably by a housing. The housing is omitted in  FIG. 9  and  FIG. 10  so as to allow view of the mechanism. 
     The cam shaft  42  is configured as a hollow shaft. The cam shaft  42  has a control cam portion  44  arranged on its inner circumferential surface. The control cam portion  44  functions as previously described with reference to  FIG. 4  to  FIG. 8 . 
     As a result, the engaging members  36  extend and retract in a wave-like pattern and force the first member  28  along its longitudinal direction, for example to the left. 
     Referring to  FIG. 11 , a variant of the linear drive device  26  is described only insofar as it differs from the embodiment of  FIG. 9  and  FIG. 10 . 
     In this variant, the first member  28  is configured in a circular arc shape. 
     The engaging teeth  30  are arranged on individual first member segments  58 . Similarly, the second member  34  is configured as a plurality of individual second member segments  60 . 
     Each second member segment  60  includes a cam shaft segment  62  of the cam shaft  42 , a support member segment of the support member  38  (not depicted for sake of a better view), and part of the engaging members  36 . The whole configuration is kept together by means of a housing (again not depicted for better view). 
     In order to improve linear drives on aircraft with regards to backlash, gear reduction, self-lock capability, load transfer and wear, the invention provides a linear drive device ( 26 ) that has a first member ( 28 ) with engaging teeth ( 30 ), such as a toothed rack ( 32 ) and a second member ( 34 ) which functions as a drive unit. The second member ( 34 ) includes a plurality of movable teeth ( 36 ) that are actuated by a cam shaft ( 42 ). The cam shaft ( 42 ) has a control cam portion ( 44 ) that is shaped such that the movable teeth ( 36 ) perform a wave-like motion that forces the first member ( 28 ) along its longitudinal direction relative to the second member ( 34 ). 
     While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms “comprise” or “comprising” do not exclude other elements or steps, the terms “a” or “one” do not exclude a plural number, and the term “or” means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority. 
     LIST OF REFERENCE SIGNS 
       10  aircraft 
       12  fuselage 
       14  wing 
       16  turbine engine 
       18  horizontal tail plane (HTP) 
       20  vertical tail plane (VTP) 
       22  control surface 
       24  high-lift device 
       26  linear drive device 
       28  first member 
       30  engaging teeth 
       32  toothed rack 
       34  second member 
       36  engaging members 
       38  support member 
       39  flexible sheet member 
       40  housing 
       42  cam shaft 
       43  bearing 
       44  control cam portion 
       46  cam segment 
       48  circular portion 
       50  control cam 
       52  first functional section 
       54  second functional section 
       56  third functional section 
       58  first member segment 
       60  second member segment 
       62  cam shaft segment θ offset angle