Liquid dosing device with digital display

Claim 1

Liquid dispensing device comprising: a cylinder; a piston movable within the cylinder in either an intake stroke for drawing liquid into the cylinder from a reservoir of liquid, or a delivery stroke for dispensing such liquid from the cylinder; pulse generating means linked to said piston and cylinder for producing pulses representative of the relative movement of the piston in the cylinder; counting and readout means linked to the pulse generating means and operative to count the pulses and indicate the volume of liquid dispensed from the cylinder during a delivery stroke; a drive system connected to said piston and said pulse generating means, and actuating means which is manually operable to operate the drive system to cause sliding movement of the piston within the cylinder, the manually operable actuating means being connected to the pulse generating means through the said drive system, whereby the number of pulses registered in the counting and readout means being representative of the amplitude of piston movement in a dispensing sense and therefore volume of liquid dispensed, said drive system including ratchet means which ensures that the pulse generating means is driven whenever the piston is moved in a direction corresponding to a delivery stroke, but which prevents the pulse generating means from being driven when the piston is moved in a direction corresponding to an intake stroke, said pulse generating means comprising an actuating member, rotation of which causes pulse to be generated, and in which the ratchet means comprises two ratchet wheels which operate in opposite rotational directions and which have the said actuating member mounted between them whereby, any relative movement of the piston in the cylinder in a direction corresponding to a delivery stroke causes the counting and readout means to indicate a corresponding volume of liquid dispensed and that during an intake stroke any inadvertent relative movement of the piston in the cylinder in a direction corresponding to a delivery stroke causes the counting and readout means to register a volume of liquid dispensed corresponding to the magnitude of the inadvertent movement.