Abstract: A portable power supply assembly (24) capable of providing electrical power to an electric motor of a flexible shutter assembly (13) and a torsion spring assembly (21) capable of reducing load on the electric motor of a shutter assembly. The portable power supply assembly includes a portable supply of power (26), a detachable body (24) capable of electrically connecting the portable supply of power (26) to the receiving port(25) and a means of controlling the portable supply of power (29). The torsion spring assembly (21) includes a housing (57, 58) able to be mounted at or towards one end of the shaft; a torsion spring (56) mounted within the housing, one end (63) of the torsion spring being held with respect to the housing (57, 58) and a shaft adapter (64) rotatably mounted with respect to the housing, the other end (67) of the torsion spring being held with respect to the shaft adapter.