Sonotrode

1. A sonotrode comprising:

a head which defines a sealing surface elongated along a first direction orthogonal to a second direction; and

at least one first slot which extends through said head transversally to said first direction;

wherein said at least one first slot extends parallel to a third direction inclined to both said first direction and second direction;

said first direction defining a first angle with said second direction;

said sonotrode further comprising a pair of second slots which extend along respective fourth directions inclined with respect to both said first direction and said second direction; and

said fourth directions being symmetric with respect to a symmetry plane of said sonotrode parallel to said second direction and defining, each, a second angle with said plane.

2. The sonotrode of claim 1 , comprising a pair of first slots extending along respective third directions;

said third directions being symmetric with respect to said symmetry plane of said sonotrode.

3. The sonotrode of claim 1 , wherein said at least one first slot comprises a pair of first slots converging towards said sealing surface.

4. The sonotrode of claim 1 , wherein said second slots converge towards said sealing surface.

5. The sonotrode of claim 1 , comprising a nodal plane at which the amplitude of the oscillation of said head is substantially equal to zero, and which divides said head in a first portion and in a second portion;

said sealing surface being defined by said first portion of said head;

said at least one first slot extending completely within said first portion;

said second slots extending completely within said second portion.

6. The sonotrode of claim 1 , wherein said first angle and said second angle are acute, and in that said first angle is smaller than said second angle.

7. The sonotrode of claim 1 , comprising a unique drive unit which may be electrically fed by a unique generator so as to cause the oscillation of said head.

8. The sonotrode of claim 7 , comprising connecting means for connecting said drive unit to said head;

said connecting means comprising, in turn:

a nut connected to one of said drive unit and said head; and

a stud connected to the other one of said drive unit and said head.

9. The sonotrode of claim 1 , wherein the height of said head measured along said second direction transversal to said sealing surface is substantially equal to the half of the wavelength of the wave oscillating in the direction of said second direction.

10. The sonotrode of claim 1 , wherein said head comprises:

a seat for said drive unit; and

an end wall opposite to said sealing surface and which defines a pair of relieved areas which surrounds said seat.

11. The sonotrode of claim 5 , comprising a casing which accommodates said head and may be connected to a packaging machine; and in that said head comprises an edge which lies on said nodal plane;

said head being connected to said casing along said edge.

12. The sonotrode of claim 1 , wherein said first angle ranges between 5.4 and 6.6 degrees.

13. The sonotrode of claim 1 , wherein said second angle ranges between 18.9 and 23.1 degrees.

14. A packaging machine for producing sealed packages of a pourable food product from a tube of packaging material fed along a vertical path, filled continuously with said food product, and gripped at equally spaced cross sections, said machine comprising:

sealing means for sealing the packaging material of said tube along said cross sections;

said sealing means comprising an anvil and a sonotrode;

wherein said sonotrode is a sonotrode as claimed in claim 1 .

15. A sonotrode comprising:

a head which defines a sealing surface elongated along a first direction orthogonal to a second direction; and

at least one first slot which extends through said head transversally to said first direction;

wherein said at least one first slot extends parallel to a third direction inclined to both said first direction and second direction;

said first direction defining a first angle with said second direction; and

said at least one first slot comprising a pair of first slots converging towards said sealing surface.

16. A sonotrode comprising:

a head which defines a sealing surface elongated along a first direction orthogonal to a second direction; and

at least one first slot which extends through said head transversally to said first direction;

wherein said at least one first slot extends parallel to a third direction inclined to both said first direction and second direction;

said first direction defining a first angle with said second direction;

said sonotrode further comprising a nodal plane at which the amplitude of the oscillation of said head is substantially equal to zero, and which divides said head in a first portion and in a second portion;

said sealing surface being defined by said first portion of said head;

said at least one first slot extending completely within said first portion.