Measuring and/or tracing device

In a measuring and tracing device, of the kind having:

• (i) a vertical column
• (ii) a transverse sliding unit secured to said column and movable in a vertical direction,
• (iii) a cross arm held by said unit and movable horizontally
• (iv) a holder on the end of said cross arm for a measuring and tracing tool
• (v) a counterweight to balance the transverse sliding unit, said counterweight being disposed inside the column so that it can move freely and being attached to the transverse sliding unit by a cable passing over a guide roller at the upper end of the column, the improvement which consists in that:
• (a) a safety braking device is attached to the transverse sliding unit and acts in conjunction with the external surfaces of the column, the cable being secured to the braking device so that, in consequence of the cable tension exerted, the braking device is held in a disengaged position out of contact with the outer surfaces of the column, whereas when the cable tensions falls, the braking device drops automatically into braking position and engages with the outer surfaces of the column, thereby preventing movement,
• (b) the column is of rectangular cross-section and has two outer surfaces opposite and approximately parallel to one another, the braking device having a pivoted frame mounted on the transverse sliding unit so that it can rotate around an axis disposed at a distance from the center of the column, the cable being attached to one side of the frame at a spacing from the pivoting axis, the other side of said frame having fitted thereto at a spacing from the pivoting axis
• at least one vertical brake adjusting spring acting in the same direction as the force of the cable, said pivoted frame when rotating about the pivoting axis into the disengaged position and the braking position striking against braking elements fitted in the area of two opposite outer faces of the column and located, in the disengaged position, substantially out of contact with and at a spacing from the corresponding outer surface and, in the braking position, in contact with the corresponding outer surface in such a way as to prevent movement, said braking elements being cylindrical gripping rollers fitted in the region of both mutually opposite outer surfaces of the column.