Arrangement for checking dimensional accuracy

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG.
1 shows a perspective view of an embodiment of the invention arranged to check the dimensions of a car body.
The car is hoisted by means of a lifting device (not shown).
Rulers 2-7 are attached to suitable measuring points beneath the car 1.
These measuring points are placed in different positions for different car models.
Measuring points and dimensions for a standard vehicle of each car model are specified in special measuring records.
A measuring guide bar 8 is located to the side of and obliquely below in relation to the hoisted car and at a suitable working height for the operator who is to perform the measurement check.
A light source 9 is fixedly located at one end of the beam 8.
The important thing about the light source is that it must be able to emit a narrow collimated light beam having sufficient intensity for impingement on one of the rulers to be clearly readable by the operator where he stands at the guide bar.
A laser of He--Ne type satisfies these requirements.
Shown on the guide bar are two deflection units 10 and 11, each of which deflects a beam emanating from the light source in the horizontal plane in mutually different directions so that the ruler 2 is impinged on from two directions.
The position of the point of impingement in a beam-oriented coordinate system is unambiguously determined by the location along the guide bar of the deflection units 10 and 11 and the two angles between the deflected light beam from each deflection unit and the distance.
In the Figure, the deflected light beams are shown to lie in a horizontal plane and to impinge on a point on the ruler in this plane but it is also possible instead of suspending rulers at the measuring points on the vehicle also to deflect the light beams with the deflecting units in the vertical plane so that they impinge directly on the different measuring points.
This is particularly applicable in those cases when the positions and deflections for the two deflection units are fed to a central computer unit, as will be described further on in the description