Steerable instrument comprising a radial spacers between coaxial cylindrical elements

1. A steerable instrument for endoscopic and/or invasive type of applications, such as in surgery, the instrument comprising an elongated tubular body extending in a longitudinal direction and having at least one actuation means at a proximal side of the steerable instrument and at least one bendable zone at a distal side of the steerable instrument, said at least one actuation means being arranged to control bending of said at least one bendable zone by means of at least one longitudinal element,

the instrument comprising a first cylindrical element, a second cylindrical element and a third cylindrical element, the first cylindrical element surrounding the second cylindrical element and the second cylindrical element surrounding the third cylindrical element,

the second cylindrical element comprising a zone with a longitudinal element portion of said at least one longitudinal element, said longitudinal element portion having a first height in a radial direction of said instrument,

wherein at least one of the first cylindrical element, the second cylindrical element and the third cylindrical element comprises at least two radial spacers at mutual sides of said longitudinal element each one of said radial spacers having, at least locally, a second height in the radial direction larger than the first height.

2. The steerable instrument according to claim 1 , wherein said second height is in a range of 1-40% more than the first height.

3. The steerable instrument according to claim 1 , wherein

said instrument comprises at least two longitudinal element portions in said zone and defining a space between them, one radial spacer being arranged in said space such as to also form a tangential spacer between said adjacent at least two longitudinal element portions.

4. The steerable instrument according to claim 1 , wherein the radial spacers are flexible spacers.

5. The steerable instrument according to claim 4 , wherein the radial spacers comprise a plurality of distinct portions separated by slits.

6. The steerable instrument according to claim 5 , wherein the distinct portions are wire shaped units extending in the longitudinal direction and separated by the slits.

7. The steerable instrument according to claim 5 , wherein the slits comprise at least one of: slit portions extending in the longitudinal direction, the slit portions extending in a tangential direction, and the slit portions having a curved shape.

8. The steerable instrument according to claim 4 , wherein the radial spacers are located in the at least one bendable zone of the steerable instrument.

9. The steerable instrument according to claim 1 , wherein the at least one bendable zone comprises at least a first bendable zone at its distal end and a second bendable zone at its distal end, the first bendable zone being controllable by a first set of one or more longitudinal elements of said at least one longitudinal element, and the second bendable zone being controllable by a second set of one or more longitudinal elements of said at least one longitudinal element, at least one longitudinal element of said first set and at least one longitudinal element of said second set being located in parallel between said at least two radial spacers.

10. The steerable instrument according to claim 1 , wherein the radial spacers include a bent lip shaped portion.

11. The steerable instrument according to claim 10 , wherein the lip shaped portion is part of the first cylindrical element and bent inwardly against a portion of said second cylindrical element adjacent said longitudinal element portion.

12. The steerable instrument according to claim 10 , wherein the lip shaped portion is part of the first cylindrical element and bent inwardly against a portion of said third cylindrical element through a free space 3 in said second cylindrical element adjacent said longitudinal element portion.

13. The steerable instrument according to claim 1 , wherein said second height is in a range of 1-30% more than the first height.

14. The steerable instrument according to claim 1 , wherein said second height is in a range of 1-15% more than the first height.

15. A method of manufacturing a steerable instrument according to claim 1 , wherein the method comprises:

providing said first cylindrical element;

inserting said second cylindrical element into said first cylindrical element and locally welding said at least two radial spacers to said first cylindrical element such as to cause said at least two radial spacers to locally obtain said second height; and

inserting said third cylindrical element into said second cylindrical element;

or:

providing said second cylindrical element;

inserting said third cylindrical element into said second cylindrical element and locally welding said at least two radial spacers to said third cylindrical element such as to cause said at least two radial spacers to locally obtain said second height; and

inserting said second cylindrical element and third cylindrical element together into said first cylindrical element;

or:

providing an assembly of said first, second and third cylindrical elements such that said third cylindrical element is inserted into said second cylindrical element and said second cylindrical element is inserted into said first cylindrical element; and

locally welding said at least two radial spacers to at least one of said first cylindrical element and said third cylindrical element such as to cause said at least two radial spacers to locally obtain said second height.