System and a method for filling tubes in a tube-filling machine

The invention relates to a system and a method for batching a product (liquid and/or pasty solutions) at a same time as filling tubes in an automatic tube-filling machine.

Tube-filling machines include a conveyor line, activated in alternating motion, which bears equidistanced holders, each holder being destined to receive a head of an empty tube provided with a relative cap, such as to keep the tube vertically-arranged with the posterior part thereof open and facing upwards.

The line comprises various work stations:

a tube-loading station;

a tube-orientating station;

a tube-filling station (batching the product);

various stations for closing the posterior end of the tube, conformed according to the nature of the material (for example, aluminum, plastic, laminates, etc.) that the tube is made of;

a tube-coding station;

a station for closing the posterior edge of the tube;

a reject station for discarding tubes considered to be defective;

a full-tube outlet station.

At least an injecting nozzle (if the tube-filling machine is single-channel) is comprised in the filling station, which nozzle is downwardly-orientated, and which nozzle is centered with respect to the posterior mouth of the tube positioned in the station; in suitable phase relation with the position, the holder-lift, in which the tube is inserted, is raised by suitable first activating means, such as to insert the nozzle in the tube.

At this point the nozzle is supplied with the product, in phase relation with the holder-lift, and therefore the tube, up to completion of the filling thereof; completion of the lowering of the holder leads to exit of the nozzle from the tube.

The nozzle is connected to a volumetric filler, constituted by a cylinder in which a piston sealedly slides, which piston is borne by a stem that projects from a head of the cylinder, and which is movable axially by means of second activating means.

The remaining head of the cylinder affords two through-holes, which with the aid of a switching valve adjacent to the head are alternatively connected one to a product supply tank (liquid and/or paste solution) and the other with the nozzle. The valve is switched by third activating means.

In a first phase the batcher aspirates the product from the tank: the length of the piston travel determines the batched amount of the product; when the valve switches, which is performed in phase relation with the inversion of the piston movement, the product is compressed by the piston and is consequently fed to the nozzle and fills the tube.

The first, second and third activating means are constituted by mechanical cams which are driven by relative actuators, conformed such as to respect the above-described mutual phase relations, obviously over the machine cycle of the filling station.

In particular, the second activating means cause: the piston travel (thus the batched amount of the product); the speed of the piston in the cylinder during the product aspiration phase; and the speed of the piston on compression of the product directed towards the nozzle.

As specified, the holder-lift in the filling station is raised towards the nozzle and thereafter lowered during the filling of the tube borne by the holder.

The length of the holder-lift stroke is a function of the tube size and the batched amount of the product; the law of movement with which the holder-lift is lowered is strictly connected to the speed with which the piston compresses the product.

The product inserted into the tubes can exhibit a viscosity comprised within a broad spectrum. The viscosity might be comparable to water, or it might be high as in very pasty creams.

In the case of low viscosity (compatibly with the inertia of the piston and the cam moving it) the aspiration is fast and the compression slow in order to prevent even partial emptying of the conduit connecting the nozzle with the batcher. If the product is highly viscous, the speed of product aspiration has to be such as to prevent cavitation in the product, while the compression speed is as rapid as possible considering the inertia in the masses involved.