| 摘要 |
715,444. Photo-electric ; machine guards. SICK, E. Oct. 14, 1952 [Oct. 19, 1951; Sept. 23, 1952], No. 25764/52. Class 40 (3). [Also in Group XXXVIII] In a device for protecting a space, e.g. the front of a machine against undesired entry of bodies (e.g. an operator's hand) the space to be protected is traversed by a beam of light or of ultra-short radio waves which is finally received by a photo-electric cell or radio receiver the path including a reflector which returns the beam along its path of incidence. As shown (Fig. 1) light from a source 1 is formed by a lens 3 on to an oscillating mirror 24 which traverses the beam of light along a trough shaped mirror 11. The beam is reflected from the trough on to a strip 16 consisting of a number of small reflectors which reflect the beam back along its path of incidence to the strip, on to the trough and again to the oscillating mirror which directs the beam on to an annular mirror surrounding lens 3 and from there to a photo-electric cell 28. Since the beam is interrupted intermittently, e.g. by an operator's arm the control circuit may include a quick-release slow-acting relay which will not close if the beam is anywhere interrupted. In an alternative arrangement (Fig. 3) light from source 54 is focused by a lens 57 through a translucent mirror 58 on to the edge between two faces of a rotating pentagonal mirror prism 60. This edge coincides with the focal line of a parabolic mirror 65 the total light reflected on to this mirror by the drum as it rotates being substantially constant. Light is reflected from the mirror through a cylindrical lens 68 which concentrates the beams on to reflex strips 71. The strips reflect the light back via the mirror and the rotating prism on to the translucent mirror 58 which directs it on to a photo-electric cell 72. In a further embodiment (not shown) light is directed on to the joining edge of a pair of mirrors rotating about an axis perpendicular to this edge so as to direct the light on to concave mirror of the type shown in Fig. 3. |
