The present invention relates to a device for the dosage of volume dosable products, for instance cream type products as tooth paste, construction paste, chewing gum, creams etc.

The problem behind the invention is to optimize the num¬ ber of active elements and thereby reduce the number of sealings in volume dosing devices of the reciprocating plunge type.

Dosing devices of this general type have a plunge arranged for reciprocating movement in a dosage chamber and said plunge is provided with, in a conventional manner, for instance sealing rings and/or elastic sealing elements of the 0-ring type in order to provide a desired dosing pressure in a dosing chamber.

Prior art dosing devices have an additional movable ele¬ ment in excess to the plunge and said element is to be re¬ garded as an active element for realizing the intended func¬ tion. This further element (valve) normally is arranged as a ringshaped, cylindrical sleeve body having an opening in the sleeve. The sleeve is rotatable around the longitudinal axis of the dosing chamber, such that the opening in the sleeve may be brought in communication with either the inlet or the outlet.

This sleeve body (valve) requires sealing against the cylinder and, in practice, it means a need for at least one sealing location merely for this element, i.e. sealings around moving elements for rotating the valve.

The device according to the present invention reduces the number of active elements in a dosing device of the re¬ ciprocating plunge type and implies a more reliable and cheaper structure than the known dosing devices.

The present invention provides a dosing device for vo¬ lume dosable products, for instance paste type products, comprising a dosing chamber and an inlet and an outlet for

the product connectable to the dosing chamber, and a plunge arranged for reciprocating movement in the chamber. The do¬ sing device is characterized in that the plunge comprises means forming an axial plunge extension, and that the plunge has members for rotating the plunge around the longitudinal axis thereof, that the outlet and the inlet are arranged such that the inlet is open and the outlet covered by the plunge extension when the plunge is drawn into the dosing chamber and the plunge located in a first rotational posi¬ tion, and that the outlet is open and the inlet covered by the plunge extension when the plunge is moved in a direc¬ tion out from the dosing chamber and the plunge is in a se¬ cond rotational position.

In one embodiment the plunge extension is arranged as a direct extension of the cylindrical envelope surface of the plunge around a portion of the circumference thereof.

The axial length of the plunge extension is at least equal to the stroke of the plunge.

In one- embodiment the inlet and the outlet are arranged diametrically opposite each other at one end of the dosing chamber, and the plunge extension is arranged for being accommodated in a ringshaped extension chamber having a depth at least equal to the length of the plunge extension and arranged at said end of the dosing chamber.

In one embodiment the plunge is attached to a rod arranged for reciprocating movement and provided with man¬ oeuvring members for placing the plunge in either of said rotational positions.

One embodiment of the invention is illustrated on the accompanying drawing, where

Fig. 1 in a schematic, partly in section, longitudinal view shows a dosing device according to the in¬ vention, and Fig. 2 is a section along line II-II in Fig. 1.

In a housing 10 supported in a stand (not shown) there is arranged a cylindric dosing chamber 11 and a ringshaped, cylindric extension chamber 12 arranged axially in register with the dosing chamber.

A plunge rod is journalled in the housing 10 for reci¬ procating movement in the direction of the double arrow 15. The plunge is also arranged for rotational movement around the common axial longitudinal axis 16 of the dosing chamber and the plunge rod. The axial movement as well as the rota¬ tional movement is accomplished by conventional means, as schematically shown at 18 in Fig. 1.

The plunge rod is attached to a plunge 19 acting as "pump plunge" in the device. In a conventional manner the plunge is sealed, at 20, against the chamber 11 such that it resists the over pressure, of several bars, obtained in this particular case.

A skirt or screen 21 forms an axial extension of the plunge and is arranged as a direct continuation of the enve¬ lope surface of the plunge. The skirt extends approximately 180° around the circumference of the plunge in the actual embodiment.

The ringshaped extension chamber is dimensioned such that it fully accommodates the skirt when the plunge is in the position according to Fig. 1. The width of the ring¬ shaped gap of the chamber is such that the plunge 19 with the skirt integral therewith is allowed to reciprocate and rotate when members 18 for such operation are activated.

In the groove 12 there will be filling goods. This does not affect the function as the plunge 19 accomplishes the sealing against the critical side, i.e. to the right in Fig. 1. The dosing volume will neither be affected as it is possible to compensate for the volume of the fillings goods in the extension chamber by giving the dosing chamber 11 a nominal size taking in account the "rest volume" in the ex¬ tension chamber 12.

An inlet 22 is arranged at one end of the dosing chamber 11. An outlet 23 is located diametrically opposite to the inlet.

In Fig. 1 the plunge 19 has just fulfilled the stroke thereof for discharging the product through the outlet 23.

The next step will be to activate the members 18 for rotation approximately 180° of the plunge rod 14, the

plunge 19 and the skirt 21. Thereafter the members 18 are activated for an axial withdrawal of the plunge and the skirt member integral therewith. This skirt member will cover the outlet 23 progressively such that the outlet is fully covered when the inlet 22 is fully open.

The filling goods is brought to flow into the dosing chamber until the intended volume has been reached by pla¬ cing the plunge in the right hand end position thereof.

Hereby the members 18 again are activated for with¬ drawing the plunge and the skirt integral therewith to a position where the skirt covers the inlet 22 and the out¬ let is open.

During the following forward movement of the plunge (to the left in Fig. 1 ^" ) the product/filling goods is pumped out through the outlet 23 till the end position according to Fig. 1 is reached.

Although a specific embodiment of the invention has been described with reference to the drawing it is realized that modifications and alternative embodiments are possible with¬ in the scope of the accompanying claims.