| 摘要 |
A lifting mechanism of the kind which includes two scissor arms (4, 6) hingedly connected to each other and in which the lifting movement takes place in two steps, i.e. a first step where the lifting is accomplished in that rollers (21a, 21b) rotatably connected to a transverse shaft (19) are rolling up along oblique surfaces (23) of one of the scissor arms (4) whereas the lifting movement in a second step is accomplished in that said shaft (19) directly transmits power to one of the scissor arms (6) and where the shaft extends through an oblong hole (20) in said scissor arm (6). According to the invention one of the scissor arms consists of a U-shaped beam (6) having the web portion thereof directed upwardly and said oblong holes (20) being provided in the downwardly directed flanges of the U-shaped beam. The shaft (19) extends through a sliding block (18) displaceable in the U-shaped beam said sliding block at the end of the first lifting movement coming into contact with a stop (22) provided in the U-shaped beam and owing to the fact that the diameter of the shaft (19) is somewhat inferior to the width of the oblong hole contact between the shaft and the wall portions surrounding the hole (20) in the U-shaped beam is prevented. |
