FI86811B - Liquid-metering process and device - Google Patents

Description

1 86811

The present invention relates to a method for dispensing a liquid, and in particular to a viscous liquid, and to a dispensing device specially developed for this purpose. Förfarande och anordning för dosering av vätska 5

Various methods and apparatus are known for dispensing liquid-10, as well as highly viscous liquid, in several successive doses from one and the same container with a dispensing opening, by reducing its volume periodically. Prior art dispensing devices have generally been pneumatically operated, and the disadvantage of such devices is that there is always a slight pressure in the dispensing device after each dispensing cycle, whereby the flow of liquid, especially high-viscosity, from the container dispensing opening may continue for some time. In particular, the dosing of the highly viscous liquid 20 is cumbersome because such a substance forms a strand which does not easily break after each dosing cycle, which contributes to the difficulty of accurate dosing. The main disadvantage of these known devices is the dose size dependence on the viscosity of the substance, which can vary during dose-25 administration.

It is therefore an object of the present invention to obviate the drawbacks of the above-mentioned methods and devices and to provide a method for dispensing a liquid, and in particular a viscous liquid, in several successive doses from a single container with a dispensing opening by periodically reducing its volume by one dose. from one dose to another. To achieve accurate dosing, each dosing cycle in the method of the invention is terminated by slightly increasing the volume of the fine container to provide a suction effect to the dispensing opening and then reducing the volume of the container by an amount corresponding to the previous increase of 2,86811 immediately before the next period. In this way, no overpressure remains in the tank and the dosing ends at exactly the desired time.

In a preferred embodiment of the invention, the volume of the container is increased by a steeper change in volume / time gradient than in the dosing to break the liquid fiber flowing out of the dosing opening before the next dosing cycle.

The invention also relates to an apparatus for carrying out the above-mentioned method, wherein the container is a cylinder provided with a piston and a metering opening, the piston rod of which is connected to an actuator for moving the piston in the cylinder. In the device according to the invention, the actuator is a stepper motor to which an ball screw is axially connected and the piston rod is pushed out to the ball screw to convert the rotational movement of the stepper motor into a linear movement of the piston.

The stepper motor is preferably provided with a programmed control unit for controlling the speed, direction, and length of movement of the piston, which control unit is programmed to return the piston slightly backward at the end of each dosing cycle and advance accordingly before the next dosing cycle. In addition, the control unit is preferably programmable to move the piston backwards at a higher speed than during the dosing cycle.

The invention will be described in more detail below with reference to the accompanying drawing, in which Fig. 1 shows a cross-sectional vertical view of a dispensing device according to the invention and Fig. 2 shows a diagram of the piston dispensing movement as a function of time.

In Fig. 1, a disposable, easily replaceable container, i.e. a cylinder, is generally indicated by reference numeral 1 and a dispensing opening at its other end by reference numeral 2. A reciprocating piston 3 inside the cylinder 1 is connected to a stepper motor 7 ball screw 6 by a piston 3 the operation is controlled by the programmed control unit 8.

The function of the dispensing device is to dispense a liquid and preferably a highly viscous liquid in portions from a cylinder 1 provided with a piston 3 through a dispensing opening 2 to a dispensing object. The dosing is controlled by a pusher 5 driven by a stepper motor 7, to which the piston 3 of the cylinder 1 is attached. This achieves good dosing accuracy. When the piston 3 has completed the dosing movement programmed for it, it quickly returns to the programmable distance, whereby the flow of the substance from the cylinder 1 ceases. Before the next dosing cycle, the piston 3 first moves quickly back to the same programmable distance and only then the dosing distance, then returns quickly. The dosing equipment can be connected to a so-called X-Y table, whereby the liquid can be dispensed exactly on the desired track in exactly the desired amount. The amount of liquid to be dispensed by the dispensing device 20 according to the invention does not depend on its viscosity, but the amount to be dispensed remains constant regardless of the viscosity. The rotational movement of the stepper motor 7 is made linear by means of a ball screw and a nut 6.

The speed, direction and length of the stepper motor are controlled by a programmed control unit 8 connected to the stepper motor 7 according to the diagram shown in Fig. 2.

Thus, if n-volume doses of volume V are desired, the control unit is programmed so that the piston 3 first moves down a distance corresponding to volume V and then up a distance corresponding to the suction volume. When the next dose is desired, the plunger 3 moves down the same distance and only then down the distance corresponding to the dose volume in the same direction 35 and then again up the distance corresponding to the suction volume. This is repeated n times. The suction movement effectively prevents the flow of liquid from the cylinder 1 and the accuracy of the dosing 4 86811 is thus not dependent on the viscosity of the liquid.

The dispensing device according to the invention is particularly suitable for dispensing 5 protective epoxies on the surface of the body as a uniform layer in the desired area, but it is also suitable for dispensing other various liquids.

Claims (6)

5,86811 A method for dispensing a liquid, and in particular a viscous liquid, in several successive doses from one and the same container (1) 5 with a dispensing opening (2) by periodically reducing its volume by one dose, characterized in that each dispensing period is terminated by adding a small amount (1) ) to provide a suction effect to the dispensing opening (2) and then reducing the volume of the container 10 by an amount corresponding to the previous addition before the next dispensing cycle. Method according to Claim 1, characterized in that the volume of the container (1) is increased by a steeper volume change / time gradient than in the dosing in order to break the liquid thread flowing from the dosing opening (2). 3. Apparatus for dispensing a liquid, in particular a viscous liquid, in several successive doses from one and the same cylinder (1) with a dispensing opening (2) and a piston (3), the piston rod (4) of which is connected to an actuator (7) for moving the piston (3) in the cylinder (1), characterized in that the actuator is a stepper motor (7) to which a ball screw (6) is axially connected and that the stem (4) of the piston 25 (3) is connected to the ball screw (6) by a pusher (6) 7) to convert the rotational movement into a linear movement of the piston (3). Device according to claim 3, characterized by a programmed control unit (8) of the stepper motor (7) for controlling the speed, direction and length of movement of the piston (3), programmed so that the piston returns slightly backwards at the end of each dosing cycle and moves forward accordingly before the next dosing cycle. 35 Device according to Claim 4, characterized in that the control unit (8) is programmed to move the piston (3) backwards at a higher speed than during the dosing cycle. 6 86811