fig1 and 2 illustrate one embodiment of a brake according to the invention , in which the rotary member which is to be braked comprises two coaxial discs 10 , 10 &# 39 ; arranged parallel to , and separated from , one another . the brake also has a control member comprising at least one control block 11 arranged axially between the discs 10 , 10 &# 39 ; for application of a brake shoe 12 to disc 10 . in the embodiment shown , two control blocks 11 are provided b tween the discs 10 , 10 &# 39 ;, these control blocks being spaced circumferentially . one of the control blocks 11 is operable to apply a brake shoe 12 against the disc 10 , whilst the other is operable to apply a brake shoe 12 against the disc 10 &# 39 ;. of course , the two control blocks 11 can be separate or , as shown , can form part of one and the same mechanical assembly . moreover , in the embodiment shown , there is , associated with each control block 11 , a further control block 11 &# 39 ;, which is arranged on the other side of the respective disc 10 , 10 &# 39 ; and is operable to apply a brake shoe 12 &# 39 ; to the corresponding face of the latter . the control blocks 11 , 11 &# 39 ; are joined to one another by screws 13 which extend beyond the periphery of the disc 10 &# 39 ;, and the blocks 11 , 11 &# 39 ; together thus form a control member which , in practice , is fixed . for acting on a brake shoe 12 , 12 &# 39 ;, each respective control block 11 , 11 &# 39 ; is provided , in the embodiment shown , with two pistons 14 which are disposed parallel to one another and are each respectively mounted to slide in cylinders 15 , the pistons 14 defining , with these cylinders 15 , hydraulic chambers 16 which can be connected to a pressurised fluid supply ( not shown ). these arrangements are in themselves well known and , since they do not form part of the present invention , they will not be described in greater detail in this text . as will be noted , for the control blocks 11 located between the discs 10 , 10 &# 39 ;, the hydraulic control chambers 16 are disposed relatively closely to that disc which is not acted on by the respective control block 11 , and this is because there is only a small space available between the discs 10 , 10 &# 39 ; in which to locate the control blocks 11 . a heat shield 17 is associated with each control block 11 and is provided so as to minimise propagation to that control block 11 of heat originating from the opposite disc 10 or 10 &# 39 ;, that is to say from the disc 10 or 10 &# 39 ; which is acted on by the control block 11 . according to the invention , the heat shield 17 is carried by the control block 11 with which it is associated , and , being interposed between the latter and the opposite disc 10 or 10 &# 39 ;, forms a reflector . in practice , the heat shield 17 according to the invention is joined by fixing means , such as screws 19 , to that face 20 of the respective control block 11 , which is opposite the disc 10 or 10 &# 39 ;, i . e . the shield is secured to that face of the control block 11 which forms the bottom wall of the hydraulic control chambers 16 belonging to the control block 11 . preferably , and as shown , the heat shield 17 is held away from the control block 11 by means of spacers 22 , which comprise , for example , sleeves engaged on the corresponding screws 19 . thus , air can circulate between this protective screen 17 and the control block 11 with which it is associated . preferably , each heat shield 17 possesses a flange on at least one of its sides . in the embodiment shown , each heat shield 17 used has the general shape of a trough and , by means of flanges 24 , encloses the respective control block 11 on at least two opposite sides of the latter and , in practice , in the embodiment shown , on three sides of this control block 11 , the flanges 24 being directed substantially towards the disc 10 or 10 &# 39 ; to which this control block 11 is adapted to apply a brake shoe 12 . according to a second embodiment illustrated schematically in fig3 there is provided , facing the opposite disc 10a , a heat sheild 10a at least part of which is perforated like a shutter and comprises slats 25 , extending approximately radially relative to this disc , whilst being obliquely inclined to the latter , and openings 26 between the slats 25 . in practice , and as shown , the inclination of the slats 25 of this heat shield 17a , relative to the respective disc 10a , is in the same direction as the direction of rotation of the disc , marked by an arrow f in fig3 so that , during the rotation of the disc 10a , the air surrounding the control block 11 between the latter and the heat shield 17a is drawn through the openings 26 in the heat shield 17a by the air surrounding the disc 10a between the latter and the heat shield 11a , this air itself being entrained by the disc a . the protection of the control block 11 from heat is therby improved . fig4 and 5 illustrate the application of the invention to a brake in which the rotary member comprises a single rotary disc 10b with which two control blocks 11b , 11 &# 39 ; b are associated , which are operable to apply brake shoes 12b , 12 &# 39 ; b to the single disc , on the two opposite faces of the latter . according to arrangements analogous to those briefly described above , each control block 11b , 11 &# 39 ; b possesses a piston 14b , 14 &# 39 ; b for this purpose . in practice , in the embodiment shown in fig4 and 5 , the control blocks 11b , 11 &# 39 ; b together form a fixed control member , the said control blocks 11b , 11 &# 39 ; b being joined to one another , into a unitary element , by means of spacers 27 which extend parallel to the axis of the disc 10b , beyond the periphery of the latter , on either side of the brake shoes 12b , 12 &# 39 ; b . a heat shield 28 , 28 &# 39 ; is associated with each control block 11b , 11 &# 39 ; b respectively and is carried by the respective control block 11b , 11 &# 39 ; b . each shield 28 is interposed between the control block 11b , 11 &# 39 ; b and the disc 10b and thus forms a reflector . each heat shield extends substantially transversely , parallel to the disc 10b , passing round the corresponding brake shoe 12b , 12 &# 39 ; b by means of an aperture 29 , 29 &# 39 ;. in the embodiment shown , laterally , each heat shield 28 , 28 &# 39 ; extends a very considerable distance beyond the corresponding control block 11b , 11 &# 39 ; b by means of flanges 30 , 30 &# 39 ; which progressively diverge from the corresponding face of the disc 10b . each heat shield 28 , 28 &# 39 ; is joined to the corresponding control block 11b , 11 &# 39 ; b with the aid of any suitable fixing means , for example screws 32 , whilst being kept separated from the latter by means of spacers 33 which consist , in the embodiment shown , of washers engaged on the fixing means . fig6 also illustrates the application of the invention to a brake in which the rotary member to be braked consists of a single disc , but , in fig6 neither the disc nor the brake shoes are shown in order to improve the clarity of the fig . in the embodiment illustrated in fig6 the control member of the brake comprises , on the one hand , a control block 11c for application of a first brake shoe to a first face of the disc in question , and , on the other hand , a transfer part 35 for application , by reaction , of a second brake shoe to the opposite face of the disc . the control block 11c can be fixed ; it can also be carried by the transfer part 35 . in the embodiment shown , the transfer part has the general shape of a ring which extends substantially along a chord of the disc in question , passing round the latter . brakes of this kind are well known and , since they do not form part of the scope of the present invention , they will not be described in greater detail in this text . according to the embodiment shown in fig 6 , a heat shield 37 is associated with the control block 11c and is joined thereto by means of screws 38 , according to methods similar to those described above , and is formed with an aperture 39 for passing round the corresponding brake shoe . moreover , on that side of the disc which is opposite to that on which the control block 11c is located , the transfer piece 35 also carries , again in a similar manner to those arrangements described above , a heat shield 40 disposed parallel to the disc . in the embodiment shown , this heat shield 40 is joined by a lug 41 to the transfer piece 35 , with the aid of a screw 42 , and , laterally , it is provided with extensions 43 which , passing round the disc , approximately rejoin the heat shield 37 associated with the control block 11c . in all cases , the heat shield according to the invention can be made , for example , of sheet metal ; it can also be made of a material chosen for possessing good heat - insulation properties , such as , for example , the material marketed under the name &# 34 ; ferobestos &# 34 ;. in the case where it is made of sheet metal , the heat shield according to the invention can also be provided on one surface with a coating which is a poor heat conductor , for example paint or an oxide layer . the present invention is not limited to the embodiments which have been described and shown , but includes any modified construction and / or modified combination of the various elements within the scope of the appended claims . moreover , the field of application of the invention is not limited only to that of brakes in which the rotary member comprises one or two discs , but equally well extends to that of brakes in which the rotary member to be braked has a different form such as for example , a ring or drum .