Apparatus for securing an electronic unit to an avionics tray

Claim 1

Apparatus for removing and securing a plug-in electronic unit or the like from or to an avionics tray, which apparatus comprises (i) a threaded spindle (1) one end of which includes a transverse pin (2) for pivotally mounting the spindle in a retaining member attached to or forming part of the avionics tray such that the spindle (1) can move about the transverse axis of said pin (2) but cannot rotate about its own axis; (ii) a first sleeve (3) having a first portion (4) relatively remote from the transverse pin (2) and having a second, internally threaded portion (5) which is threaded onto the spindle (1), the internal diameter of the first portion (4) being slightly greater than the external diameter of the spindle (1) ; (iii) a first stop member (6) formed in or attached to the end of the first sleeve (3) nearest to the transverse pin (2); (iv) a second stop member (7) arranged to limit the movement of the first sleeve (3) with respect to the spindle (1) in a direction away from the transverse pin (2); (v) a rotatable grip (8) fitted about that end of the first sleeve (3) remote from the transverse pin (2); (vi) a second sleeve (9) coaxial with, and positioned around the first sleeve (3) and having at its end remote from the transverse pin (2) a radial flange (10) including a shoulder (11) facing towards the transverse pin (2), and an annular recess (12) which cooperates with the rotatable grip (8) and the first sleeve (3) to define an annular cavity around the first sleeve (3); (vii) a torque limiting arrangement (13) positioned in said annular cavity and serving to interconnect the rotating grip (8) and the first sleeve (3) such that rotation of the grip (8) in the direction towards the transverse pin (2) causes the first sleeve (3) to move along the threaded portion of the spindle (1) towards the transverse pin (2) so long as the torque between grip (8) and said first sleeve (3) is less than a predetermined value; (viii) a ring member (14) including (a) a sleeve portion (15) coaxial with and positioned for sliding movement on the outer surface of the second sleeve (9), (b) an internal surface (16) open towards the transverse pin (2), and (c) a shoulder (23) facing inwards, and capable of abutting, the shoulder (11) of the second sleeve (9); (ix) a third sleeve (17) coaxial with and positioned for relative sliding movement over that part of the outer surface of the second sleeve (9) nearest to the transverse pin (2), the third sleeve (17) being retained at its end nearest to the transverse pin by the first stop member (6) and having, at that end, (a) a radially inwardly facing abutment (18) which holds the third sleeve (17) away from the first sleeve (3) and which defines in cooperation with the inner surface of the third sleeve (17) the outer surface of the first sleeve (3) and the end of the second sleeve (9), a sheath like cavity (21) around the first sleeve, and (b) a radially outwardly extending flange (19), the other end of said third sleeve (17) being in contact with the radially inward part of the ring (14); (x) a resilient element (20) located in said sheath-like cavity (21) and arranged so as to tend to urge the second and third sleeves (9; 17) away from one another in the axial direction of the spindle (1); (xi) a generally cylindrical, elastomeric spacer element (22) held between the radial flange (10) of the second sleeve (9) and that end of the ring member (14) remote from the transverse pin (2), the arrangement being such that when the ring member (14) and said radial flange (10) move towards each other, their respective shoulders (11; 23) come into abutment so as to retain the compressed elastomeric spacer element (22) within a cavity defined between the ring member (14) and said radial flange (10); and (xii) means (24; 25) for urging the rotating grip (8) towards the torque limiting arrangement (13).