Fastening assembly

1. A fastening assembly having a longitudinal axis, and comprising a tubular first coupling member coaxial with said axis, a second tubular coupling member insertable coaxially and at least partly inside said tubular first coupling member in a first direction, at least one sealing element interposed between an inner surface of said tubular first coupling member and an outer surface of said second coupling member, and fastening means that are releasable for locking said tubular first coupling member and said second coupling member to each other in a predetermined angular and axial lock position;

said fastening means comprising:

a first and a second engaging element, which are carried by said tubular first coupling member and said second coupling member, respectively, that are complementary in shape to engage with each other to define An angular insertion/release position in which to insert/release said second coupling member into/from said tubular first coupling member, and are releasable as a result of the positioning of said second coupling member in a predetermined axial position inside the tubular first coupling member; and

a third and a fourth engaging element, which are carried by said first and second coupling member respectively, are complementary in shape, and are connectable to each other in a further angular position of said second coupling member, different from said angular insertion/release position, by moving said second coupling member axially, from said predetermined axial position, in a second direction opposite said first direction, to define said lock position of said first and second coupling member;

said assembly further comprising:

stop means formed on said tubular first coupling member and defining an axial stop for said second coupling member in said further angular position, in which said third and fourth engaging elements are mutually engaged,

wherein said stop means comprise a raised edge projecting radially inwards from a first axial end of said tubular first coupling member through which the second coupling member is inserted;

said second coupling member comprises at least one key projecting from a lateral surface at a first axial end of the second coupling member extending about said axis, said key comprising a first portion that has a contour defining said second engaging element, and a second portion that has a contour which defines said fourth engaging element lies radially and angularly within the contour of said first portion, and is located upstream from the first portion in said first direction;

said first engaging element comprises at least one first recess that has a contour formed in said raised edge of said tubular first coupling member and complementary to said first portion of said key; and

said third engaging element comprises at least one second recess that has a contour which is formed in said raised edge of said tubular first coupling member, at a predetermined angular distance from said first recess about said axis, and is complementary in shape to said second portion of said key; and

elastic means which are distinct from said sealing element, are interposed between a second axial end of said tubular first coupling member and a second axial end of said second coupling member and exert thrust on said second coupling member in said second direction.

2. An assembly as claimed in claim 1 , wherein, when said second coupling member is in said further angular position and said second recess is engaged by said second portion of said key, said raised edge of said tubular first coupling member defines an axial stop for said first portion of the key.

3. An assembly as claimed in claim 2 , wherein said elastic means are interposed between said second coupling member and a further raised edge projecting radially inwards from a portion of said tubular first coupling member and facing said raised edge.

4. An assembly as claimed in claim 2 , wherein said second coupling member comprises two said keys on diametrically opposite sides of said axis, and wherein said tubular first coupling member comprises two said first recesses on diametrically opposite sides of said axis, and two said second recesses also on diametrically opposite sides of said axis and at predetermined angular distances from said first recesses.

5. A fastening assembly having a longitudinal axis, and comprising a tubular first coupling member coaxial with said axis, a second tubular coupling member insertable coaxially and at least partly inside said tubular first coupling member in a first direction, at least one sealing element interposed between an inner surface of said tubular first coupling member and an outer surface of said second coupling member, and fastening means that are releasable for locking said tubular first coupling member and said second coupling member to each other in a predetermined angular and axial lock position;

said fastening means comprising:

a first and a second engaging element which are carried by said tubular first coupling member and said second coupling member, respectively, that are complementary in shape, engage with each other to define an angular insertion/release position in which to insert/release said second coupling member into/from said tubular first coupling member, and are releasable as a result of the positioning of said second coupling member in a predetermined axial position inside the tubular first coupling member; and

a third and a fourth engaging element, which are carried by said first and second coupling member respectively, are complementary in shape, and are connectable to each other in a further angular position of said second coupling member, different from said angular insertion/release position, by moving said second coupling member axially, from said predetermined axial position, in a second direction opposite said first direction, to define said lock position of said first and second coupling member;

said assembly further comprising:

stop means formed on said tubular first coupling member and defining an axial stop for said second coupling member in said further angular position, in which said third and fourth engaging elements are mutually engaged,

wherein said stop means comprise a raised edge projecting radially inwards from a first axial end of said tubular first coupling member through which the second coupling member is inserted;

said second coupling member comprises at least one key projecting from a lateral surface at a first axial end of the second coupling member extending about said axis, said key comprising a first portion that has a contour defining said second engaging element, and a second portion that has a contour which defines said fourth engaging element lies radially and angularly within the contour of said first portion, and is located upstream from the first portion in said first direction;

said first engaging element comprises at least one first recess that has a contour formed in said raised edge of said tubular first coupling member and complementary in shape to said first portion of said key; and

said third engaging element comprises at least one second recess that has a contour which is formed in said raised edge of said tubular first coupling member, at a predetermined angular distance from said first recess about said axis, and is complementary in shape to said second portion of said key; and

elastic means which are distinct from said sealing element and do not perform sealing action, are interposed between a second axial end of said tubular first coupling member and an second axial end of said second coupling member and exert thrust on said second coupling member in said second direction.