Repeating pipetting device

A repeating pipetting device comprising a syringe including a syringe body having a forward end and a rearward end, a mounting flange located at the rearward end of said syringe body and a plunger, said plunger has a portion that protrudes rearwardly from said mounting flange, said flange being formed with a rearwardly facing, shaped portion having angularly spaced parts differing in axial depth, and

• a device for actuating said syringe, which actuating device comprises
• an elongated housing having at one end a flange holder, in which said mounting flange is removably held,
• a sliding block mounted in said housing and slidable in the elongated direction thereof and coupled to said rearwardly protruding portion,
• a rack located in said housing and extending in the elongated direction thereof, said rack is secured to said sliding block and is formed with a series of teeth along one surface thereof extending in the long direction of said housing,
• an operating lever is pivoted to said housing about an axis extending transversely of the elongated direction of said housing, said operating lever extending partly inside and partly outside said housing, said lever being pivotally displaceable between a starting position and an ending position for a constant step length,
• a pawl pivoted to said operating lever inside said housing and arranged to engage said teeth and being operable by said operating lever to advance said rack toward said flange holder, said pawl is pivotally engageable and disengageble from said teeth,
• a tongue-like slide cover mounted in said housing and slidable in the elongated direction thereof, said cover is positioned between said pawl and said rack and overlies said rack along a part of its length and has one end portion nearer to said flange holder and engagement of said pawl with said rack occurs when said pawl passes said one end portion, and
• adjusting means for adjusting the slidable position of said cover in the elongated direction of said housing, said adjusting means comprising a slider connected to said cover and extending therefrom into connection with said flange holder, and a spring mounted in said housing and urging said slider toward said flange holder and into engagement with one of said angularly spaced parts of said flange of said syringe whereby the position of said cover along said housing is controlled by the axial depth of said part engaged by said slider.