21 in rotation at an exactly predetermined angular speed in the direction indicated by arrow s in the figure we consider now the machine 21 which placed at the loading station of the trousers 26 an operator acting at said loading station loads a trouser 26 on to the machine 22 during the rotation movement of frame 21 about axis 0 following the same modalities as described with reference to fig1 once the loading has been carried out the steam and or hot air is immediately injected into the inner part of trouser 26 and trouser 26 is subjected thereto for a predetermined period of time for example 24 seconds until it reaches the unloading position as indicated in fig2 by the position of the machine 25 at this point the steam and or hot air is shut off and the trouser 26 is removed from the machine by a second operator or advantageously by means of an automatic device 30 which will be described in more detail hereinbelow the above described process is continuously repeated for each machine on the frame 21 in this context it is worthwhile noting that fig2 represents a plant equipped with four machines 22 23 24 25 however the number of machines does not constitute a limitation of the present invention which is applicable to any number of machines also noteworthy is the fact that the invention is not limited to a plant assembled on a circular frame preferred embodiments include those having single machines mounted on movable supports moving along tracks following a predetermined route not necessarily circular according to the invention the plant 20 is provided with an automatic unloading device 30.