Fastening assembly

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.

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.

DETAILED DESCRIPTION OF THE INVENTION

Number1inFIGS. 1 to 5indicates as a whole a seal unit, for a shaft2of axis A, featuring a fastening assembly3, also of axis A, in accordance with the teachings of the present invention.

Fastening assembly3serves to lock an annular seal4in a predetermined axial position on shaft2.

More specifically, fastening assembly3substantially comprises a tubular first coupling member5of axis A; a tubular second coupling member6, also of axis A, insertable coaxially inside coupling member5in an insertion direction B coincident with axis A; and releasable fastening means7for locking coupling members5and6to each other in a predetermined angular and axial lock position.

More specifically, coupling member5defines a seat for shaft2, seal4, and coupling member6; and coupling member6defines a seat9for loosely housing shaft2, is interposed radially, in use, between shaft2and coupling member5, and is fitted internally with seal4, which projects to cooperate with an outer lateral surface10of shaft2.

Coupling member5has a cylindrical lateral wall11, of axis A, which at opposite ends has respective raised edges12,13projecting radially inwards. More specifically, edge12is the one first encountered by coupling member6as it is inserted inside coupling member5in direction B.

Coupling member6also has a substantially cylindrical lateral wall14, of axis A, which, close to its axial end15inserted first inside coupling member5in direction B, has an inner annular groove16engaged by seal4, and an outer annular groove20engaged by an O-ring21.

At its axial end22opposite axial end15, lateral wall14of coupling member6has two keys23projecting outwards on diametrically opposite sides of axis A.

Each key23extends from an outer lateral surface24of lateral wall14, and comprises a first portion25in the form of a curved plate; and a second portion26, also in the form of a plate, which lies radially and angularly within the contour of portion25, and is located upstream from portion25in direction B. More specifically, and as shown clearly inFIGS. 1 and 5, portion26of each key23projects in a direction parallel to axis A from the face of relative portion25opposite that facing axial end15.

In the example shown, each portion25extends roughly 60° about axis A, and is roughly 6 times the angular extension of relative portion26. The angular extensions shown of both portions25and26, however, are obviously not binding.

Edge12of coupling member5has two contoured recesses27located on diametrically opposite sides of axis A and complementary in shape to portions25of respective keys23.

Edge12of coupling member5also has a further two contoured recesses28located on diametrically opposite sides of axis A, complementary in shape to portions26of respective keys23, and spaced angularly apart from respective recesses27.

In the example shown, recesses28are aligned along a diameter of edge12of coupling member5perpendicular to the diameter along which recesses27are aligned.

In actual use, portions25of respective keys23engage recesses27to define a foolproof angular position in which to insert coupling member6inside coupling member5, or to release coupling members5and6. Recesses27and portions25of respective keys23are releasable by moving coupling member6into a predetermined axial position inside coupling member5. In the example shown, the predetermined axial position, hereinafter referred to as the limit axial position, is defined by insertion of keys23past edge12of coupling member5when inserting coupling member6inside coupling member5. In other words, in the limit axial position, keys23of coupling member6are positioned beyond edge12of coupling member5and towards edge13.

Portions26of respective keys23engage recesses in a further angular position, different from the angular insertion/release position, of coupling member6, by moving coupling member6axially, from the limit axial position, in a locking direction C opposite direction B, so as to define the lock position of coupling members5and6.

Fastening assembly3also comprises elastic means30interposed between edge13of coupling member5and axial end15of coupling member6, and which exert thrust on coupling member6in direction C. When coupling member6is in the angular position in which portions26of keys23engage respective recesses28of coupling member5, edge12defines an axial stop for portions25of keys23of coupling member6pushed in direction C by elastic means30.

In the example shown, elastic means30comprise a non-flat, undulated annular elastic member31.

With particular reference toFIGS. 4 and 5, seal4comprises an annular body32which partly engages inner groove16in lateral wall14of coupling member6with the interposition of an O-ring33; and two annular sealing lips34projecting from an inner circumferential edge of annular body32, and which cooperate with outer lateral surface10of shaft2.

Unit1is assembled as described below, from an initial configuration in which shaft2loosely engages seat8of coupling member5; coupling member6is outside coupling member5; seal4is fitted inside inner annular groove16of coupling member6; and elastic member31is fitted inside coupling member5, resting against edge13.

At this point, coupling member6is moved in direction B into the angular insertion/release position, in which keys23are aligned axially with respective recesses27; and coupling member6is inserted inside coupling member5, until the outer edges of portions25slide along the edges of respective recesses27, and elastic member31is compressed.

Insertion is terminated when keys23are inserted completely past edge12of coupling member5, i.e. when coupling member6reaches the limit axial position inside coupling member5.

At this point, coupling member6is rotated about axis A into the angular position in which portions26of keys23are aligned axially with respective recesses28. When released by the fitter, coupling member6is pushed axially in direction C by elastic member31, so that portions26of keys23engage respective recesses28, and portions25are pushed against the portions of edge12adjacent to recesses28.

Unit1can be disassembled easily, with no tools required, by simply pressing coupling member6axially in direction B in opposition to elastic member31, to restore keys23to the limit axial position beneath edge12of coupling member5.

At this point, coupling member6is rotated about axis A into the angular insertion/release position, in which portions25of keys23are aligned axially with respective recesses27.

In this case, too, when released by the fitter, coupling member6is pushed partly outwards by elastic member31, so that portions25of respective keys23engage recesses27.

Number1′ inFIGS. 6 to 9indicate as a whole a cap unit, for a known aircraft oil filler (not shown), featuring a fastening assembly3′ in accordance with a different embodiment of the present invention.

Unit1′ substantially comprises a receiving member40defining a through oilflow seat41; and a cap42which fits releasably to receiving member40to seal seat41.

In this case, fastening assembly3′ serves to lock cap42in a position sealing seat41.

As described with reference to unit1, fastening assembly3′ substantially comprises a tubular first coupling member5′ of axis A; a tubular second coupling member6′, also of axis A, insertable coaxially inside coupling member5′ in an insertion direction B coincident with axis A; and releasable fastening means7′ for locking coupling members5′ and6′ to each other in a predetermined angular and axial lock position.

In the example shown, coupling member5′ is defined by receiving member40, and coupling member6′ by a stem of cap42. As shown inFIGS. 7 to 9, cap42also comprises a head portion43fixed releasably to and projecting radially from the stem or coupling member6′.

Coupling member5′ (FIGS. 6,7,8,9,12) comprises a lateral wall44, of axis A, defined by a cylindrical first portion45with a threaded portion46for connection to another component part (not shown) of the filler; and by a roughly cylindrical second portion47, which has an undulated outer edge, is larger in diameter than portion45, and is connected to portion45by an annular shoulder48.

At opposite ends, lateral wall44has respective raised edges49,50projecting radially inwards. More specifically, edge49is the one first encountered by coupling member6′ as it is inserted inside coupling member5′ in direction B.

Between shoulder48and threaded portion46, the outer surface of portion45of lateral wall44has an annular groove51engaged by an O-ring52.

Coupling member6′ has a substantially cylindrical lateral wall53, of axis A, which, close to its axial end54opposite head portion43, has two outer annular grooves55spaced axially apart and engaged by respective O-rings56.

Where it attaches to head portion43, lateral wall of coupling member6′ has two keys60projecting outwards on diametrically opposite sides of axis A.

More specifically, each key60projects from an outer lateral surface61of lateral wall53, and comprises a first portion62in the form of a curved plate; and a second portion63, also in the form of a plate, which lies radially and angularly within the contour of portion62, and is located upstream from portion62in direction B. More specifically, and as shown clearly inFIGS. 9 and 10, portion63of each key60projects in a direction parallel to axis A from the face of relative portion62opposite that facing axial end54.

In the example shown, each portion62extends roughly 60° about axis A, and is roughly 6 times the angular extension of relative portion63. The angular extensions shown of both portions62and63, however, are obviously not binding.

Edge49of coupling member5′ has two contoured recesses65located on diametrically opposite sides of axis A and complementary in shape to portions62of respective keys60.

Edge49of coupling member5′ also has a further two contoured recesses66located on diametrically opposite sides of axis A, complementary in shape to portions63of respective keys60, and spaced angularly apart from respective recesses65.

In the example shown, recesses66are aligned along a diameter of edge49of coupling member5′ perpendicular to the diameter along which recesses65are aligned.

In actual use, portions62of respective keys60engage recesses65to define a foolproof angular position in which to insert coupling member6′ inside coupling member5′, or to release coupling members5′ and6′. Recesses65and portions62of respective keys60are releasable by moving coupling member6′ into a predetermined axial position inside coupling member5′. In the example shown, the predetermined axial position, hereinafter referred to as the limit axial position, is defined by insertion of keys60past edge49of coupling member5′ when inserting coupling member6′ inside coupling member5′. In other words, in the limit axial position, keys60of coupling member6′ are positioned beyond edge49of coupling member5′ and towards edge50.

Portions63of respective keys60engage recesses66in a further angular position, different from the angular insertion/release position, of coupling member6′, by moving coupling member6′ axially, from the limit axial position, in a locking direction C opposite direction B, so as to define the lock position of coupling members5′ and6′.

The further angular position of coupling member6′ is defined by portion62of each key60rotating onto a respective stop portion68(FIG. 6) formed inside seat41of coupling member5′ and extending from edge49to portion45of lateral wall44.

A similar stop arrangement is also provided in coupling member5of fastening assembly3, but is not visible inFIGS. 1 to 5.

Fastening assembly3′ also comprises elastic means70, which exert thrust on coupling member6′ in direction C. When coupling member6′ is in the angular position in which portions63of keys60engage respective recesses66of coupling member5′, edge49defines an axial stop for portions62of keys60of coupling member6′ pushed in direction C by elastic means70.

In the example shown, elastic means70comprise a cylindrical coil spring71housed in portion45of lateral wall44of coupling member5′ and interposed between edge50and coupling member6′.

More specifically, portion45of lateral wall44is engaged axially by an axial end portion73of a cylindrical filter74of the oil filler, so spring71is interposed between edge50of lateral wall44and a raised edge72projecting radially outwards from end portion73of filter74. As shown, particularly inFIG. 8, a plate75, with a number of through openings76equally spaced about axis A, is interposed axially between end portion73of filter74and axial end54of coupling member6′.

In actual use, cap42is fitted to receiving member40to seal seat41as described below.

Firstly, cap42and therefore coupling member6′ are moved in direction B into the angular insertion/release position, in which keys60are aligned axially with respective recesses65; and coupling member6′ is inserted inside coupling member5′, until the outer edges of portions62slide along the edges of respective recesses65, and elastic member71is compressed.

Insertion is terminated when keys60are inserted completely past edge49of coupling member5′, i.e. when coupling member6′ reaches the limit axial position inside coupling member5′.

At this point, coupling member6′ is rotated about axis A into the angular position in which portions63of keys60are aligned axially with respective recesses66, and which is defined by portions62of keys60rotating (clockwise inFIG. 6) onto respective stop portions68of coupling member5′. When released by the fitter, coupling member6′ is pushed axially in direction C by elastic member71, so that portions63of keys60engage respective recesses66, and portions62are pushed against the portions of edge49adjacent to recesses66.

Unit1′ can be opened easily by simply pressing coupling member6′ axially in direction B in opposition to elastic member71, to restore keys60to the limit axial position beneath edge49of coupling member5′.

At this point, coupling member6′ is rotated about axis A into the angular insertion/release position, in which portions62of keys60are aligned axially with respective recesses65.

When released by the fitter, coupling member6′ is pushed partly outwards by elastic member71, so that portions62of respective keys60engage recesses65.

The advantages of fastening assemblies3,3′ 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 members5,6and5′,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 assemblies3,3′ is reduced as compared with known solutions of the same size.

Clearly, changes may be made to fastening assemblies3,3′ as described and illustrated herein without, however, departing from the protective scope defined in the accompanying Claims.