An adjustable spacer

An adjustable spacer for adjusting a spacing between two bodies comprising:

• i) a first cam member rotatable about a rotational axis, the first cam member having a first mating face;
• ii) a second cam member rotatable about the rotational axis, the second cam member having a second mating face;
• and
• iii) an intermediate cam member interposed between the first cam member and the second cam member, the intermediate cam member being configured to be rotatable about the rotational axis and having an first intermediate mating face configured for engaging with the first mating face to define a first rotatable indexing mechanism, and a second intermediate mating face configured for engaging with the second mating face to define a second rotatable indexing mechanism;
• wherein each mating face of the first intermediate mating face and the first mating face has a profile or contour with a variable thickness in a circumferential direction such that rotation of the first cam member relative to the intermediate cam member in a first rotational direction about the rotational axis by a given angular rotation will cause a length of the adjustable spacer along the rotational axis to change by a first length, and each mating face of the second intermediate mating face and the second mating face having a profile or contour with a variable thickness in the circumferential direction such that rotation of the intermediate cam member relative to the second cam member in a second rotational direction opposite the first rotational direction about the rotational axis by a same given angular rotation will cause the length of the spacer along the rotational axis to change by a second length,
• wherein each of the first intermediate mating face and the first mating face includes a plurality of teeth to provide the first rotatable indexing mechanism, and each of the second intermediate mating face and the second mating face includes a plurality of teeth to provide the second rotatable indexing mechanism, the plurality of teeth of each of the first and second intermediate mating faces being configured and arranged such that the first intermediate mating face will provide a fine level of adjustment of the length of the adjustable spacer and the second intermediate face will provide a coarse level of adjustment of the length of the adjustable spacer so that the first length is less than the second length.

A method of levelling a grid structure of a grid framework structure claim 42, the method comprising:

• i) measuring a first vertical position of a robotic grid levelling device at a first grid cell of the grid structure relative to one or more fixed reference points;
• ii) moving the robotic levelling device on the grid structure to a second grid cell on the grid structure,
• iii) measuring a second vertical position of the robotic levelling device on the grid structure at the second grid cell relative to the one or more fixed reference points;
• iv) calculating a difference between the second vertical position and the first vertical position;
• whereby:
• v) when the calculated difference is greater than a predetermined value, adjusting a length of an adjustable spacer by engaging an adjustment tool with the adjustable spacer so as to rotate a first and/or a second rotatable indexing mechanism in a respective first and/or second rotational direction about a rotational axis until the calculated difference is less than the predetermined value;
• vi) repeating steps (i) to (v) until the grid structure lies in a substantial horizontal plane.