base 6 i e the position shown in fig1 and 11 the scm 4 is simply raised by pulling on the lifting cable s not shown which in turn causes the plunger 13 to be lifted upwardly as illustrated in fig6 and 10 this upward movement in relation to the situation illustrated in fig1 will cause the annular abutment 13b of the plunger 13 to progressively compress the coil springs 14 15 and 16 and also allow the three latch cams 25 26 and 27 to rotate in a counterclockwise direction about their respective pivots 28 as the tapered portion 13c moves past the first latch portions of the latch cams 25 26 and 27 it should be noted that there is no requirement to have these cams spring loaded so that they will rotate in a counterclockwise direction because as the latching arrangement reaches the position shown in fig8 and then in fig6 the annular groove 29 and in particular an end button 13d will by virtue of engagement with the first latched portions cause the respective cams 25 26 and 27 to rotate in a counterclockwise direction about their respective pivots 28 in order to bring the latch cams 25 26 and 27 into the radially withdrawn position shown in fig6 and 7 thus the essence of the present invention lies in providing the latching mechanism with means for storing energy within the mechanism itself such energy being derived from the weight of the scm although the preferred embodiment of the invention employs coil springs as described above and shown in the drawings other means for storing such energy could also be employed while still giving the advantage of the present invention which is to eliminate the necessity for having separate.