Abstract:
A fastening assembly having a tubular first coupling member; a second coupling member insertable coaxially inside the first coupling member in a first direction; and releasable fastening means for locking the first and second coupling member to each other in a predetermined axial lock position. The fastening means include: first and second engaging means formed on the first and second coupling member, connectable to each other to define a foolproof angular insertion/release position, and releasable by positioning the second coupling member in a predetermined axial position inside the first coupling member; and third and fourth engaging means formed on the first and second coupling member and connectable to each other in a further angular position of the second coupling member, different from the angular insertion/release position, by moving the second coupling member axially, from the predetermined axial position, in a second direction opposite the first direction.

Description:
The present invention relates to a fastening assembly, in particular for aircraft applications. 
     BACKGROUND OF THE INVENTION 
     As is known, bolts, screws and retaining rings are normally used for locking and securing two or more coupling members. 
     Fastening systems of this sort invariably require special tools for installation and removal. 
     In aircraft applications, in which weight reduction is an important issue, they also have the drawback of requiring parts in addition to the coupling members. And, in some cases, as when screwing or bolting together cylindrical coupling members, these must be provided with annular flanges with holes for the screws and bolts. 
     Lastly, when using steel retaining rings cooperating with aluminium or magnesium coupling members, galvanically-induced corrosion phenomena may arise. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a fastening assembly which is reliable, easy to install and remove, and designed to provide a simple, low-cost solution to the drawbacks typically associated with known fastening systems of the type described above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Two preferred, non-limiting embodiments of the present invention will be described by way of example with reference to the accompanying drawings, in which: 
         FIG. 1  shows an exploded view in perspective of a rotary shaft seal unit featuring a fastening assembly in accordance with the teachings of the present invention and comprising a first and second coupling member; 
         FIG. 2  shows a larger-scale front view of the  FIG. 1  unit, with the first and second coupling member in a final angular and axial lock position; 
         FIG. 3  shows a section along line III-III in  FIG. 2 ; 
         FIG. 4  shows a larger-scale sectioned view in perspective of the  FIGS. 2 and 3  unit; 
         FIG. 5  shows an exploded sectioned view in perspective of the  FIG. 1  unit; 
         FIG. 6  shows a view in perspective of an aircraft oil filler cap unit featuring a fastening assembly in accordance with the teachings of the present invention; 
         FIG. 7  shows a view in perspective of the  FIG. 6  unit when open; 
         FIG. 8  shows a partly sectioned side view of the  FIG. 6  unit; 
         FIG. 9  shows a smaller-scale exploded view in perspective of the  FIG. 6  unit; 
         FIG. 10  shows a front view of a coupling member of the  FIG. 6  unit; 
         FIG. 11  shows a section along line XI-XI in  FIG. 10 ; 
         FIG. 12  shows a larger-scale front view of another coupling member of the  FIG. 6  unit. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Number  1  in  FIGS. 1 to 5  indicates as a whole a seal unit, for a shaft  2  of axis A, featuring a fastening assembly  3 , also of axis A, in accordance with the teachings of the present invention. 
     Fastening assembly  3  serves to lock an annular seal  4  in a predetermined axial position on shaft  2 . 
     More specifically, fastening assembly  3  substantially comprises a tubular first coupling member  5  of axis A; a tubular second coupling member  6 , also of axis A, insertable coaxially inside coupling member  5  in an insertion direction B coincident with axis A; and releasable fastening means  7  for locking coupling members  5  and  6  to each other in a predetermined angular and axial lock position. 
     More specifically, coupling member  5  defines a seat for shaft  2 , seal  4 , and coupling member  6 ; and coupling member  6  defines a seat  9  for loosely housing shaft  2 , is interposed radially, in use, between shaft  2  and coupling member  5 , and is fitted internally with seal  4 , which projects to cooperate with an outer lateral surface  10  of shaft  2 . 
     Coupling member  5  has a cylindrical lateral wall  11 , of axis A, which at opposite ends has respective raised edges  12 ,  13  projecting radially inwards. More specifically, edge  12  is the one first encountered by coupling member  6  as it is inserted inside coupling member  5  in direction B. 
     Coupling member  6  also has a substantially cylindrical lateral wall  14 , of axis A, which, close to its axial end  15  inserted first inside coupling member  5  in direction B, has an inner annular groove  16  engaged by seal  4 , and an outer annular groove  20  engaged by an O-ring  21 . 
     At its axial end  22  opposite axial end  15 , lateral wall  14  of coupling member  6  has two keys  23  projecting outwards on diametrically opposite sides of axis A. 
     Each key  23  extends from an outer lateral surface  24  of lateral wall  14 , and comprises a first portion  25  in the form of a curved plate; and a second portion  26 , also in the form of a plate, which lies radially and angularly within the contour of portion  25 , and is located upstream from portion  25  in direction B. More specifically, and as shown clearly in  FIGS. 1 and 5 , portion  26  of each key  23  projects in a direction parallel to axis A from the face of relative portion  25  opposite that facing axial end  15 . 
     In the example shown, each portion  25  extends roughly 60° about axis A, and is roughly 6 times the angular extension of relative portion  26 . The angular extensions shown of both portions  25  and  26 , however, are obviously not binding. 
     Edge  12  of coupling member  5  has two contoured recesses  27  located on diametrically opposite sides of axis A and complementary in shape to portions  25  of respective keys  23 . 
     Edge  12  of coupling member  5  also has a further two contoured recesses  28  located on diametrically opposite sides of axis A, complementary in shape to portions  26  of respective keys  23 , and spaced angularly apart from respective recesses  27 . 
     In the example shown, recesses  28  are aligned along a diameter of edge  12  of coupling member  5  perpendicular to the diameter along which recesses  27  are aligned. 
     In actual use, portions  25  of respective keys  23  engage recesses  27  to define a foolproof angular position in which to insert coupling member  6  inside coupling member  5 , or to release coupling members  5  and  6 . Recesses  27  and portions  25  of respective keys  23  are releasable by moving coupling member  6  into a predetermined axial position inside coupling member  5 . In the example shown, the predetermined axial position, hereinafter referred to as the limit axial position, is defined by insertion of keys  23  past edge  12  of coupling member  5  when inserting coupling member  6  inside coupling member  5 . In other words, in the limit axial position, keys  23  of coupling member  6  are positioned beyond edge  12  of coupling member  5  and towards edge  13 . 
     Portions  26  of respective keys  23  engage recesses in a further angular position, different from the angular insertion/release position, of coupling member  6 , by moving coupling member  6  axially, from the limit axial position, in a locking direction C opposite direction B, so as to define the lock position of coupling members  5  and  6 . 
     Fastening assembly  3  also comprises elastic means  30  interposed between edge  13  of coupling member  5  and axial end  15  of coupling member  6 , and which exert thrust on coupling member  6  in direction C. When coupling member  6  is in the angular position in which portions  26  of keys  23  engage respective recesses  28  of coupling member  5 , edge  12  defines an axial stop for portions  25  of keys  23  of coupling member  6  pushed in direction C by elastic means  30 . 
     In the example shown, elastic means  30  comprise a non-flat, undulated annular elastic member  31 . 
     With particular reference to  FIGS. 4 and 5 , seal  4  comprises an annular body  32  which partly engages inner groove  16  in lateral wall  14  of coupling member  6  with the interposition of an O-ring  33 ; and two annular sealing lips  34  projecting from an inner circumferential edge of annular body  32 , and which cooperate with outer lateral surface  10  of shaft  2 . 
     Unit  1  is assembled as described below, from an initial configuration in which shaft  2  loosely engages seat  8  of coupling member  5 ; coupling member  6  is outside coupling member  5 ; seal  4  is fitted inside inner annular groove  16  of coupling member  6 ; and elastic member  31  is fitted inside coupling member  5 , resting against edge  13 . 
     At this point, coupling member  6  is moved in direction B into the angular insertion/release position, in which keys  23  are aligned axially with respective recesses  27 ; and coupling member  6  is inserted inside coupling member  5 , until the outer edges of portions  25  slide along the edges of respective recesses  27 , and elastic member  31  is compressed. 
     Insertion is terminated when keys  23  are inserted completely past edge  12  of coupling member  5 , i.e. when coupling member  6  reaches the limit axial position inside coupling member  5 . 
     At this point, coupling member  6  is rotated about axis A into the angular position in which portions  26  of keys  23  are aligned axially with respective recesses  28 . When released by the fitter, coupling member  6  is pushed axially in direction C by elastic member  31 , so that portions  26  of keys  23  engage respective recesses  28 , and portions  25  are pushed against the portions of edge  12  adjacent to recesses  28 . 
     Unit  1  can be disassembled easily, with no tools required, by simply pressing coupling member  6  axially in direction B in opposition to elastic member  31 , to restore keys  23  to the limit axial position beneath edge  12  of coupling member  5 . 
     At this point, coupling member  6  is rotated about axis A into the angular insertion/release position, in which portions  25  of keys  23  are aligned axially with respective recesses  27 . 
     In this case, too, when released by the fitter, coupling member  6  is pushed partly outwards by elastic member  31 , so that portions  25  of respective keys  23  engage recesses  27 . 
     Number  1 ′ in  FIGS. 6 to 9  indicate as a whole a cap unit, for a known aircraft oil filler (not shown), featuring a fastening assembly  3 ′ in accordance with a different embodiment of the present invention. 
     Unit  1 ′ substantially comprises a receiving member  40  defining a through oilflow seat  41 ; and a cap  42  which fits releasably to receiving member  40  to seal seat  41 . 
     In this case, fastening assembly  3 ′ serves to lock cap  42  in a position sealing seat  41 . 
     As described with reference to unit  1 , fastening assembly  3 ′ substantially comprises a tubular first coupling member  5 ′ of axis A; a tubular second coupling member  6 ′, also of axis A, insertable coaxially inside coupling member  5 ′ in an insertion direction B coincident with axis A; and releasable fastening means  7 ′ for locking coupling members  5 ′ and  6 ′ to each other in a predetermined angular and axial lock position. 
     In the example shown, coupling member  5 ′ is defined by receiving member  40 , and coupling member  6 ′ by a stem of cap  42 . As shown in  FIGS. 7 to 9 , cap  42  also comprises a head portion  43  fixed releasably to and projecting radially from the stem or coupling member  6 ′. 
     Coupling member  5 ′ ( FIGS. 6 ,  7 ,  8 ,  9 ,  12 ) comprises a lateral wall  44 , of axis A, defined by a cylindrical first portion  45  with a threaded portion  46  for connection to another component part (not shown) of the filler; and by a roughly cylindrical second portion  47 , which has an undulated outer edge, is larger in diameter than portion  45 , and is connected to portion  45  by an annular shoulder  48 . 
     At opposite ends, lateral wall  44  has respective raised edges  49 ,  50  projecting radially inwards. More specifically, edge  49  is the one first encountered by coupling member  6 ′ as it is inserted inside coupling member  5 ′ in direction B. 
     Between shoulder  48  and threaded portion  46 , the outer surface of portion  45  of lateral wall  44  has an annular groove  51  engaged by an O-ring  52 . 
     Coupling member  6 ′ has a substantially cylindrical lateral wall  53 , of axis A, which, close to its axial end  54  opposite head portion  43 , has two outer annular grooves  55  spaced axially apart and engaged by respective O-rings  56 . 
     Where it attaches to head portion  43 , lateral wall of coupling member  6 ′ has two keys  60  projecting outwards on diametrically opposite sides of axis A. 
     More specifically, each key  60  projects from an outer lateral surface  61  of lateral wall  53 , and comprises a first portion  62  in the form of a curved plate; and a second portion  63 , also in the form of a plate, which lies radially and angularly within the contour of portion  62 , and is located upstream from portion  62  in direction B. More specifically, and as shown clearly in  FIGS. 9 and 10 , portion  63  of each key  60  projects in a direction parallel to axis A from the face of relative portion  62  opposite that facing axial end  54 . 
     In the example shown, each portion  62  extends roughly 60° about axis A, and is roughly 6 times the angular extension of relative portion  63 . The angular extensions shown of both portions  62  and  63 , however, are obviously not binding. 
     Edge  49  of coupling member  5 ′ has two contoured recesses  65  located on diametrically opposite sides of axis A and complementary in shape to portions  62  of respective keys  60 . 
     Edge  49  of coupling member  5 ′ also has a further two contoured recesses  66  located on diametrically opposite sides of axis A, complementary in shape to portions  63  of respective keys  60 , and spaced angularly apart from respective recesses  65 . 
     In the example shown, recesses  66  are aligned along a diameter of edge  49  of coupling member  5 ′ perpendicular to the diameter along which recesses  65  are aligned. 
     In actual use, portions  62  of respective keys  60  engage recesses  65  to define a foolproof angular position in which to insert coupling member  6 ′ inside coupling member  5 ′, or to release coupling members  5 ′ and  6 ′. Recesses  65  and portions  62  of respective keys  60  are releasable by moving coupling member  6 ′ into a predetermined axial position inside coupling member  5 ′. In the example shown, the predetermined axial position, hereinafter referred to as the limit axial position, is defined by insertion of keys  60  past edge  49  of coupling member  5 ′ when inserting coupling member  6 ′ inside coupling member  5 ′. In other words, in the limit axial position, keys  60  of coupling member  6 ′ are positioned beyond edge  49  of coupling member  5 ′ and towards edge  50 . 
     Portions  63  of respective keys  60  engage recesses  66  in a further angular position, different from the angular insertion/release position, of coupling member  6 ′, by moving coupling member  6 ′ axially, from the limit axial position, in a locking direction C opposite direction B, so as to define the lock position of coupling members  5 ′ and  6 ′. 
     The further angular position of coupling member  6 ′ is defined by portion  62  of each key  60  rotating onto a respective stop portion  68  ( FIG. 6 ) formed inside seat  41  of coupling member  5 ′ and extending from edge  49  to portion  45  of lateral wall  44 . 
     A similar stop arrangement is also provided in coupling member  5  of fastening assembly  3 , but is not visible in  FIGS. 1 to 5 . 
     Fastening assembly  3 ′ also comprises elastic means  70 , which exert thrust on coupling member  6 ′ in direction C. When coupling member  6 ′ is in the angular position in which portions  63  of keys  60  engage respective recesses  66  of coupling member  5 ′, edge  49  defines an axial stop for portions  62  of keys  60  of coupling member  6 ′ pushed in direction C by elastic means  70 . 
     In the example shown, elastic means  70  comprise a cylindrical coil spring  71  housed in portion  45  of lateral wall  44  of coupling member  5 ′ and interposed between edge  50  and coupling member  6 ′. 
     More specifically, portion  45  of lateral wall  44  is engaged axially by an axial end portion  73  of a cylindrical filter  74  of the oil filler, so spring  71  is interposed between edge  50  of lateral wall  44  and a raised edge  72  projecting radially outwards from end portion  73  of filter  74 . As shown, particularly in  FIG. 8 , a plate  75 , with a number of through openings  76  equally spaced about axis A, is interposed axially between end portion  73  of filter  74  and axial end  54  of coupling member  6 ′. 
     In actual use, cap  42  is fitted to receiving member  40  to seal seat  41  as described below. 
     Firstly, cap  42  and therefore coupling member  6 ′ are moved in direction B into the angular insertion/release position, in which keys  60  are aligned axially with respective recesses  65 ; and coupling member  6 ′ is inserted inside coupling member  5 ′, until the outer edges of portions  62  slide along the edges of respective recesses  65 , and elastic member  71  is compressed. 
     Insertion is terminated when keys  60  are inserted completely past edge  49  of coupling member  5 ′, i.e. when coupling member  6 ′ reaches the limit axial position inside coupling member  5 ′. 
     At this point, coupling member  6 ′ is rotated about axis A into the angular position in which portions  63  of keys  60  are aligned axially with respective recesses  66 , and which is defined by portions  62  of keys  60  rotating (clockwise in  FIG. 6 ) onto respective stop portions  68  of coupling member  5 ′. When released by the fitter, coupling member  6 ′ is pushed axially in direction C by elastic member  71 , so that portions  63  of keys  60  engage respective recesses  66 , and portions  62  are pushed against the portions of edge  49  adjacent to recesses  66 . 
     Unit  1 ′ can be opened easily by simply pressing coupling member  6 ′ axially in direction B in opposition to elastic member  71 , to restore keys  60  to the limit axial position beneath edge  49  of coupling member  5 ′. 
     At this point, coupling member  6 ′ is rotated about axis A into the angular insertion/release position, in which portions  62  of keys  60  are aligned axially with respective recesses  65 . 
     When released by the fitter, coupling member  6 ′ is pushed partly outwards by elastic member  71 , so that portions  62  of respective keys  60  engage recesses  65 . 
     The advantages of fastening assemblies  3 ,  3 ′ according to the present invention will be clear from the above description. 
     In particular, they provide for safely locking in the desired position and releasing coupling members  5 ,  6  and  5 ′,  6 ′ with no need for additional parts or special tools, such as wrenches, screwdrivers, pliers, etc, thus greatly simplifying locking and release, while still maintaining the same degree of safety. 
     Moreover, the overall weight of fastening assemblies  3 ,  3 ′ is reduced as compared with known solutions of the same size. 
     Finally, fastening assemblies  3 ,  3 ′ described provide for eliminating galvanically-induced corrosion phenomena. 
     Clearly, changes may be made to fastening assemblies  3 ,  3 ′ as described and illustrated herein without, however, departing from the protective scope defined in the accompanying Claims.