| 摘要 |
A linear actuator has a screw threaded shaft (11) mounted so that it is restrained from rotational movement, a cage (13) is mounted in sliding relationship on the shaft (11) and an internally threaded member (20) is mounted at one end of the cage (13) in a spherical bearing (21). The threadform of the internally threaded member (20) is similar to that of the shaft (11) but of larger diameter. The internally threaded member (20) has a skirt formation (23) which extends towards the other end of the cage (13), a circumferential portion of the skirt formation (23) being made of ferromagnetic material. A series of angularly spaced coils (25) are provided around the cage (13) adjacent the ferromagnetic portion of the skirt formation (23), the coils (25) being adapted to be energised sequentially so that they will attract the ferromagnetic portion of the skirt formation (23) and cause the internally threaded member (20) to skew so that the threads thereof engage the threads of the shaft (11), sequential energisation of the coils (25) causing the point of contact of the thread of the internally threaded member (20) and shaft (11) to move round thus causing relative rotation and axial movement therebetween. |
