FI67434C - FOER REFRIGERATION DOSERING AV SMAO VAETSKEMAENGDER - Google Patents

Abstract

1. Process for metering small quantities of liquid without leaving a residue by means of a micro-piston pump having a capillary cylinder in which a piston, which fits in gastight manner therein, is mounted so as to be movable between a top dead centre and a bottom dead centre, the cylinder at its end located opposite the base of the piston opening into a twoway valve which connects the space in the cylinder alternately to an inlet and to an outlet (which connects the cylinder to the atmosphere during the first stage of the intake operation), characterised in that the piston and the valve are moved in such a way that, during the intake operation, first a defined quantity of air and then a defined quantity of liquid is transported into the cylinder, the quantity of air being such that, as the piston moves downwards to bottom dead centre, all the liquid is expelled through the outlet line.

Description

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Patent and registration authorities AmMun utiagd och utijkrtfun publicarad 30.11.84 (32) (33) (31) Pyy · »· **)>« uoikuu. -B * g «r4 pnoritut 20.08.79

Federal Republic of Germany-Förbundsrepubliken Tyskland (DE) P 2933617.2 (71) C.H. Boehringer Sohn, D-6507 Ingelheim am Rhein, Federal Republic of Germany - Förbundsrepubl i ken Tyskland (DE) (72) Bernd Zierenberg, Ingelheim, Federal Republic of Germany-Förbundsrepubliken Tyskland (DE) (74) Leitzinger Oy (54) The present invention relates to a method for repeatedly dispensing small amounts of liquid by means of a microbial piston pump having a capillary cylinder in which the piston is gas-tightly adapted to move between the upper and lower dead centers, the cylinder terminating in and an outlet pipe.

Micropumps, which take small amounts of liquid from the tank and continue to dispense, have the disadvantage that the amount of liquid delivered by each piston stroke varies greatly. This is because liquid residues adhere to the cylinder walls of the pump that do not follow with the movement of the piston.

This error is substantially affected by the ratio of the volume of fluid delivered by each piston stroke to the fluid-wetted inner walls of the pump. In the case of small volumes, the liquid-volume ratio to the inner walls of the pump is particularly unfavorable 2 67434, in which case the amount of liquid delivered by each piston stroke is no longer accurately reproducible.

When dispensing drug solutions, the liquid residue in the pump is particularly disadvantageous because it provides a good growth base for bacteria and other infectious embryos, especially when the outlet is in direct contact with the non-sterilized environment.

It is therefore an object of the invention to provide a method by which small amounts of liquid can be repeatedly dispensed by means of a micro-piston pump, by which the entire amount of liquid dispensed with each stroke of the piston can be removed from the pump without leaving any liquid residue.

This object is achieved by a method, the features of which are set out in the claim.

The method can advantageously be used, for example, by dispensing a certain amount of drug onto a spray plate of a piezoelectric sprayer (e.g. according to DE-A-2537795).

U.S. Pat. No. 3,299,827 discloses a micropump for dispensing various liquids. However, this known pump does not use the capillary structure of the pump cylinder and does not control the operation of the pump so that a certain amount of air is sucked into the cylinder before the liquid is drawn into the pump.

The capillary structure of the pump cylinder has also not been utilized in a pump according to DE-C-254111, in which no air is also used as an auxiliary to completely empty the pump.

The miniature pump used in the invention consists essentially of a capillary-shaped cylinder with a gas-tight piston, a two-way valve inlet and outlet pipe at the opposite end of the cylinder piston, and a control device which coordinates piston movement and valve setting.

3,674,334

The miniature pump used in the invention is preferably intended for dosing liquid volumes from 10 to 50, however, by changing the dimensions, larger or smaller volumes can also be obtained. In this case, by using a sufficiently narrow cylinder, care is taken to ensure that the air column between the piston and the liquid is maintained even with changes in the position of the filled mini-piston pump due to the capillary action.

This ensures that there is always an air column above the amount of liquid sucked, and when the piston moves in the discharge direction, the liquid is first removed and then the amount of air above it through the exhaust pipe. The air column following the amount of liquid removes all liquid from the cylinder and valve ducts. Thus, no liquid or only very small amounts remain in the inner wall of the pump. In this way, a precisely defined amount of fluid can be dispensed repeatedly with a single stroke of the piston.

In the first stage, the amount of air sucked is so dimensioned that it at least corresponds to the dead volume of the cylinder, valve and exhaust pipe. With this air sucked into the pump in advance, a jet of liquid can be removed from the pump which flows out of the cylinder, valve and outlet pipe without residue.

A typical micropiston pump used in the invention is shown in the accompanying drawing, in which:

Figure 1 shows the miniature piston pump in the initial state, Figure 2 shows the miniature piston pump in the filled state, and Figure 3 shows a vertical section from the center of the lower part of the miniature piston pump, perpendicular to the section shown in Figure 1.

Preferably, the stainless steel piston 1 moves in a very low cylinder 2, which may be made of glass or metal. The cylinder 2 terminates, for example, in a piece 4 of a valve, such as "Teflon", in which a gas-tight valve pusher 5 of suitable stainless steel can in each case be moved to the stop 6, 7, by the position of the neck 6 of the valve pusher 5 in the inlet pipe 9. relative to the outlet pipe 10, there is a connection between the inlet pipe vast, the outlet pipe and the cylinder cavity 11. Piston 1 is at its lower dead center when the piston knob or gripper 12 contacts the cylinder. The product in the cylinder and the blow between marks a and c determine the dosage. The movement of the piston 1 and the valve pusher 5 is controlled so as to provide operation: a) With the outlet open (the stop 7 is against the valve body) the piston 1 moves from the position shown in Fig. 1 in direction A until a certain amount of air is sucked into the cylinder under). The amount of air is dimensioned so that it safely forces all the liquid out of the valve and outlet pipe when emptying the miniature piston pump.

b) In the second stage, moving the valve pusher in the direction D to the stop releases the connection between the inlet pipe 9 (and thus the storage tank) and the cylinder.

c) The piston 1 continues to move in the direction A until the stroke and the volume of liquid determined by the cross-section of the cylinder have been sucked in (end position according to Fig. 2, where the end face of the piston is at mark C).

d) The valve pusher 5 is returned in the direction C to the stop, whereby the connection between the cylinder 2 and the outlet pipe 10 is opened.

e) The piston 1 moves to its lower dead center (position according to Figure 1). In this case, first the liquid and then the air penetrates out of the cylinder 2 and is forced out through the outlet pipe. Air is used to blow the valve and exhaust pipe empty. After this emptying step, the initial state is reached again.

The operation described above can be controlled in the simplest case: · ίί, 'ι't' * 67434 in the case of mass. However, mechanical or electrical means known per se are also useful. A simple device for this purpose is a combination of gears, racks and levers, which device is constructed as follows:

The four gears are arranged in parallel and rigidly connected to each other. The circumference of the gears is only partially provided with teeth and specifically in such a way that at a given time essentially only one gear becomes effective. Thus, while, for example, the first gear via the rack and lever provides the function a), the other three gears rotate freely until the desired amount of air has entered the cylinder. The second gear then takes care of setting the valve pusher, while the first gear moves the piston to its upper dead center. The first gear then rotates freely, and the third gear brings the valve pusher to its initial position. The fourth gear then takes the transfer members with it, to move the piston to a lower dead center. The steering mechanics are made so that after 360 ° rotation of the gears, all parts are in their initial position.

In another embodiment of the control device, the rotational movement is replaced by a reciprocating movement.

For this purpose, the cylinder and the valve can advantageously be arranged so that the directions of movement of the piston and the valve pusher are parallel.

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