Longitudinal measuring device

In a longitudinal measuring device including a measuring scale, a scanning unit movable along the scale, a driving unit adapted for connection with an object whose position is to be measured, and first and second mutually perpendicular guide surfaces for guiding the scanning unit along the scale, the improvement comprising:

• a housing substantially surrounding the scale;
• a flexible coupling rod extending substantially parallel to the scale, connected at a first point to the driving unit and at a second point to the scanning unit, said rod acting to maintain a substantially constant spacing therebetween;
• a first spring mounted to exert a spring force between the scanning unit and a first opposing surface formed by the housing, to bias the scanning unit towards the first guide surface formed by the scale and exerting substantially no force in any other direction;
• and
• a second spring mounted substantially transversely to the first spring to exert a spring force between the scanning unit and a second opposing surface formed by the housing, to bias the scanning unit towards the second guide surface formed by the housing and exerting substantially no force in any other direction, said two springs operating independently of each other.

In a longitudinal measuring device including a measuring scale, a scanning unit movable along the scale, a driving unit adapted for connection with an object whose position is to be measured, and first and second mutually perpendicular guide surfaces parallel to the measuring scale for guiding the scanning unit along the scale, the improvement comprising:

• a housing substantially surrounding the scale and lying parallel thereto having surfaces parallel to the guide surfaces;
• coupling means flexibly connecting the driving unit to the scanning unit such that the driving unit through the coupling means exerts force on the scanning unit in the direction parallel to the measuring scale to separate the function of the coupling of the scanning unit from the function of biasing of the scanning unit against the guide surfaces;
• a first leaf spring having a roller mounted to one end thereof, the leaf spring extending between the scanning unit and the housing with the roller contacting a surface of the housing parallel to the first guide surface, the leaf spring oriented such that a line lying in the plane of the spring and transverse to the axis of symmetry of the spring is parallel to the first guide surface and perpendicular to the second guide surface, for biasing the scanning unit against the first guide surface formed by the scale and substantially in no other direction;
• and
• a second leaf spring having a roller mounted to one end thereof, the leaf spring extending between the scanning unit and the housing with the roller contacting a surface of the housing parallel to the second guide surface, the leaf spring oriented such that a line lying in the plane of the spring and transverse to the axis of symmetry of the spring is parallel to the second guide surface and perpendicular to the first guide surface, for biasing the scanning unit against the second guide surface formed by the housing and substantially in no other direction, with points at which the first spring is attached to the scanning unit and points at which the second spring is attached to the scanning unit all lying in a plane perpendicular to both guide surfaces, the two springs operating substantially independently of each other.