Apparatus for positioning objects

An apparatus ( 1 ) for positioning objects ( 2 ) relative to a substantially horizontal working surface ( 5 ) having a longitudinal extension ( 3 ) in the X-direction and a transversal extension ( 4 ) in the Y-direction; with the apparatus ( 1 ) for moving objects ( 2 ) being arranged at least in a Z-direction standing substantially perpendicular to the working surface ( 5 ) and comprising at least two toothed racks ( 8,8 ′) which extend at an axial direction adjacent to each other in the Z-direction at an axial distance ( 6 ) and are provided for receiving an object ( 2 ) to be moved each; with said toothed racks ( 8,8 ′) being provided with a movable arrangement over a Z-displacement path ( 9 ), such that they are in engagement with a pinion ( 10,10 ′) of a Z-drive ( 11 ) which is each motively driven in an individual fashion and exerts a pressing force on the respective toothed rack ( 8,8 ′), with the toothed racks ( 8,8 ′) comprising two Z-rails ( 15,15 ′) which project laterally in the Y-direction and extend in the Z-direction and which are slidingly held in Z-guide means ( 16,16 ′) of an associated cage ( 17,17 ′) carrying the individual pinion ( 10,10 ′), with the toothed racks ( 8,8 ′) being arranged together with the respectively associated cage ( 17,17 ′) alternating adjacent to each other along an axis ( 7 ) extending in the Y-direction in such a way that the cages ( 17,17 ′) are alternatingly situated in front of and behind the axis ( 7 ), and with the Z-rails ( 15,15 ′) of the similarly oriented toothed racks ( 8,8 ′) being each arranged on a line ( 18,18 ′) which extends parallel to the axis ( 7 ) and between the same and the teeth ( 19,19 ′) of the toothed racks ( 8,8 ′); with the axial distance ( 6 ) of the toothed racks ( 8,8 ′) being variable in the Y-direction by means of Y-drives ( 20 ) and the toothed rack packet ( 23 ) being movable to a compact position with a minimal axial distance ( 6 ) which substantially corresponds to the grating distance ( 12 ) of wells ( 13 ) of a microplate ( 14 ). The apparatus in accordance with the invention is characterized in that at least every other toothed rack ( 8,8 ′) comprises spacers ( 21,21′,31,31′,31 ″) fastened to or arranged on the same, which spacers-for defining the minimum axial distance in the compact position of the toothed rack packet ( 23 )-are abutted by a rail ( 15′,15, 30,30 ′) extending in the Z-direction of each of the adjacent racks.