Static mixing element and method of mixing a drilling liquid

1. A static mixer apparatus for mixing a bentonite-water suspension, comprising:

a top piece and at least two mixer elements arranged in series thereafter,

said top piece having an inlet opening for the bentonite-water suspension;

a first mixer element including a housing having a longitudinal axis and being operably connected to said top piece;

said first mixer element housing having a passage opening for the flow of said bentonite-water suspension;

a mixing chamber in flow communication with said passage opening, said mixing chamber being defined by oblique wall surfaces wherein said oblique wall surfaces taper toward said passage opening;

a first, flat deflection surface positioned downstream of said inlet opening, upstream of said first mixer element mixing chamber and generally disposed at an angle between 70°-110° with respect to said longitudinal axis of said first mixer element housing;

a second mixer element including a housing having a longitudinal axis and being operably connected to said first mixer element;

said second mixer element housing having a passage opening for the flow of said bentonite-water suspension;

a mixing chamber defined by oblique wall surfaces wherein said oblique wall surfaces of said second mixer element mixing chamber taper in the same direction as the taper of the wall surfaces of said first mixer element mixing chamber;

a second, flat deflection surface positioned downstream of said first mixer element passage opening and upstream of said second mixer element mixing chamber and generally disposed at an angle between 70°-110° with respect to said longitudinal axis of said second mixer element housing;

wherein the inside walls of said housing of at least one of said mixer elements has a generally circular cross-section;

said deflection surface of at least one of said mixer elements has a generally circular cross-section; and

wherein at least one of said deflection surfaces has a smaller cross-section than the inside walls of said housing of said mixer element at the location where said deflection surface is positioned thereby defining a radially outer annular passageway for the bentonite-water suspension.

2. The static mixer apparatus as claimed in- claim 1 , further comprising:

a plurality of spaced-apart tongues extending from said deflection surface of at least one of said mixer elements; and

wherein said radially outer annular passageway has a width which is generally defined by the length of said tongues measured from said outside edge to said interior surface of said housing of said one of said mixer elements.

3. The static mixer apparatus according to claim 2 , wherein:

said tongues of said first deflection surface are clamped between said top piece and said first mixer element housing;

said tongues of said second deflection surface are clamped between said first mixer element housing and said second mixer element housing.

4. The static mixer apparatus as claimed in claim 1 , further comprising one or more further mixer elements arranged downstream of said first mixer element and upstream of said second mixer element,

said further mixer element including a housing having a longitudinal axis;

said further mixer element having a passage opening for the flow of bentonite-water suspension and

a mixing chamber in flow communication with said passage opening, said mixing chamber being defined by oblique wall surfaces wherein said oblique wall surfaces taper toward said passage opening; and

a further, flat deflection surface positioned downstream of said first mixer element passage opening and upstream of said further mixer element mixing chamber and generally disposed at an angle between 70°-110° with respect to said longitudinal axis of said further mixer element housing;

wherein:

the inside walls of said housing of at least one of said further mixer elements has a generally circular cross-section;

said deflection surface of at least one of said further mixer elements has a generally circular cross-section; and

wherein said deflection surface of at least one of said further mixer elements has a smaller cross-section than the inside walls of said housing of said mixer element at a location where said deflection surface is positioned thereby providing a radially outer annular passageway.

5. The static mixer apparatus as claimed in claim 1 wherein said second mixer element is operably connected to an end piece, said end piece having an outlet opening for the flow of bentonite-water suspension.

6. The static mixer apparatus as claimed in claim 5 wherein said end piece includes

a housing having a longitudinal axis;

a mixing chamber in flow communication with said outlet opening, said mixing chamber being defined by oblique wall surfaces wherein said oblique wall surfaces taper toward said outlet opening;

a third flat deflection surface downstream of said passage opening of said second mixer element and upstream of said outlet opening and generally disposed at an angle between 70°-110° with respect to said longitudinal axis of said first mixer element housing;

wherein:

said deflection surface of said end piece has a generally circular cross-section; and

said deflection surface of said end piece has a smaller cross-section than said mixing chamber of said end piece where said third deflection surface is positioned thereby providing a radially outer annular passageway for the bentonite-water suspension.

7. The static mixer apparatus as claimed in claim 6 , further comprising:

a plurality of spaced-apart tongues extending from said third deflection surface; and

wherein said radially outer annular passageway has a width which is generally defined by the length of said tongues measured from an outside edge of said deflection surface to said interior surface of said housing of said one of said mixer elements.

8. The static mixer apparatus according to claim 7 , wherein:

said tongues of said third deflection surface are clamped between said end piece and said second mixer element housing.

9. The static mixer apparatus according to claim 1 wherein said top piece has one inlet opening.