Length measuring instrument

In a length measuring instrument including a flexible measuring scale, a scanning unit, and means for guiding the scanning unit along the scale, the improvement comprising:

• the guiding means being independent of the scale;
• means for defining a spacing member extending parallel to at least a portion of the scale, said spacing member positioned at a predetermined separation from the scanning unit;
• and
• means, included in the scanning unit, for magnetically biasing that portion of the scale adjacent the scanning unit into contact with the spacing member such that the separation between the scale and the scanning unit adjacent the biasing means is maintained substantially constant.

In a longitudinal measuring instrument including a flexible scale having first and second end sections;

• means for mounting the first and second end sections to a first object;
• a housing extending around the scale, said housing defining a groove for receiving the scale and first and second flanges extending along the length of the groove to narrow the groove, thereby capturing the scale in the groove;
• a scanning unit;
• and means for guiding the scanning unit on the housing along the scale within the housing;
• the improvement comprising:
• at least one magnet secured to the scanning unit;
• said scale including a magnetically responsive component such that the magnet operates to bias the scale toward the scanning unit against the first and second flanges, thereby providing a substantially constant separation between the scale and a portion of the scanning unit.

In an encapsulated longitudinal measuring device including a flexible measuring scale extending along a longitudinal direction, a tubular member surrounding at least a portion of the measuring scale and secured to a first object, and a scanning unit guided along the scale by the tubular member and coupled to a second object relatively movable with respect to the first object, the improvement comprising:

• means, included in the tubular member, for embracing the measuring scale inside the tubular member in a longitudinally and laterally displaceable manner, substantially without applying distorting or clamping forces thereto;
• a magnetically responsive component included in the scale;
• and
• means, included in the scanning unit, for magnetically biasing the scale against the embracing means without contacting the scale, the embracing means and the biasing means configured to provide a substantially constant separation between the scanning unit and an adjacent portion of the scale.

An encapsulated longitudinal measuring device comprising:

• a tubular member;
• a groove defined in the tubular member;
• a flange of a substantially constant thickness formed in the tubular member adjacent the groove, said flange operating to narrow the groove to a predetermined width;
• a flexible measuring scale defining first and second end sections, the scale being disposed in the groove so as to be displaceable along the length and depth of the groove and having a width greater than the predetermined width, the scale including a magnetically responsive component;
• means for mounting the tubular element to a first object;
• means for securing the first and second end sections of the scale to the first object;
• a scanning unit connected to a second object, relatively movable with respect to the first object, said scanning unit guided along the scale by the tubular member, the scanning unit including at least one magnet oriented to bias without contacting the flexible scale toward the scanning unit against the flange to provide a substantially constant separation between the scanning unit and the portion of the scale lying adjacent the at least one magnet.