The invention relates to a steerable instrument for endoscopic and/or invasive type of applications, such as in surgery, the instrument comprising an elongated tubular body having a cylindrical diameter adaptation section. The steerable instrument according to the invention can be used in both medical and non-medical applications. Examples of the latter include inspection and/or repair of mechanical and/or electronic hardware at locations that are difficult to reach. Hence, terms used in the following description such as endoscopic application or invasive instrument, must be interpreted in a broad manner.

Transformation of surgical interventions that require large incisions for exposing a target area into minimal invasive surgical interventions, i.e. requiring only natural orifices or small incisions for establishing access to the target area, is a well-known and ongoing process. In performing minimal invasive surgical interventions, an operator such as a physician, requires an access device that is arranged for introducing and guiding invasive instruments into the human or animal body via an access port of that body. In order to reduce scar tissue formation and pain to a human or animal patient, the access port is preferably provided by a single small incision in the skin and underlying tissue. In that respect the possibility to use a natural orifice of the body would even be better.

Furthermore, the access device preferably enables the operator to control one or more degrees of freedom that the invasive instruments offer. In this way, the operator can perform required actions at the target area in the human or animal body in an ergonomic and accurate manner with a reduced risk of clashing of the instruments used.

Surgical invasive instruments and endoscopes through which these instruments are guided towards the target area are well-known in the art. Both the invasive instruments and endoscopes can comprise a steerable tube that enhances its navigation and steering capabilities. Such a steerable tube preferably comprises a proximal end part including at least one flexible zone, a distal end part including at least one flexible zone, and a rigid intermediate part, wherein the steerable tube further comprises a steering arrangement that is adapted for translating a deflection of at least a part of the proximal end part relative to the rigid intermediate part into a related deflection of at least a part of the distal end part.

Furthermore, the steerable tube preferably comprises a number of co-axially arranged cylindrical elements including an outer element, an inner element and one or more intermediate elements depending on the number of flexible zones in the proximal and distal end parts of the tube and the desired implementation of the steering members of the steering arrangement, i.e. all steering members can be arranged in a single intermediate element or the steering members are divided in different sets and each set of steering members is arranged in a different

intermediate member. The steering arrangement may comprise conventional steering cables with sub 1 mm diameters as steering members, wherein the steering cables are arranged between related flexible zones at the proximal and distal end parts of the tube. However, as steering cables have many well-known

disadvantages, it is preferred to avoid them and to implement the steering members by one or more sets of longitudinal elements that form integral parts of the one or more intermediate elements. Each of the intermediate elements can be fabricated either by using a suitable material addition technique, such as injection moulding or plating, or by a suitable material removal technique, such as laser cutting, photochemical etching, deep pressing, conventional chipping techniques such as drilling or milling or high-pressure water jet cutting systems. Of the

aforementioned material removal techniques, laser cutting is very advantageous as it allows a very accurate and clean removal of material under reasonable economic conditions. Further details regarding the design and fabrication of the

abovementioned steerable tube and the steering arrangement thereof have been described for example in WO 2009/1 12060 Al, WO 2009/127236 Al, US

13/160,949, and US 13/548,935 of the applicant, all of which are hereby

incorporated by reference in their entirety.

Steerable invasive instruments typically comprise a handle that is arranged at the proximal end part of the steerable tube for steering the tube and/or for manipulating a tool that is arranged at the distal end part of the steerable tube. Such a tool can for example be a camera, a manual manipulator, e.g. a pair of scissors, forceps, or manipulators using an energy source, e.g. an electrical, ultrasonic or optical energy source.

In this application, the terms "proximal" and "distal" are defined with respect to an operator, e.g. a physician that operates the instrument or endoscope. For example, a proximal end part is to be construed as a part that is located near the physician and a distal end part as a part located at a distance from the physician.

It is known from the prior art that amplification of a flexion of a distal flexible zone of a distal end part of an elongated tubular body of a steerable instrument, i.e. a bending angle of a flexible zone in the distal end part is at least the same and preferably larger than a bending angle of a corresponding flexible zone in the proximal end part of the elongated tubular body, can be achieved by using a proximal end part having a larger diameter than the distal end part. In the event that the proximal end part has a smaller diameter than the distal end part, a flexion in the proximal end part leads to a corresponding attenuated flexion of the distal end part.

The requirement for an amplified or attenuated flexion of the distal end part in response to a flexion of the proximal end part depends on the specific intervention for which the steerable instrument is used. Amplified flexion of the distal end part may be required in order to be able to exert a larger force at the operating site and/or to compensate for the loss in response due to stretch of the longitudinal steering elements. Attenuated flexion of the distal end part may be required to improve the maneuverability accuracy of the distal end part. It is known that in order to connect the proximal end part and the distal end part having different diameters a diameter adaptation arrangement is required.

A disadvantage of steerable instruments comprising diameter adaptation arrangements known from the prior art is that the construction of these instruments is quite cumbersome and therefore costly at least in part of the diameter adaptation arrangement. Another disadvantage of steerable instruments comprising known diameter adaptation arrangements is that such arrangements have a reduced reliability as they are more susceptible to failure due to damage. A further disadvantage of steerable instruments comprising known diameter adaptation arrangements is that such arrangements add to the diameter of the elongated tubular bodies of the steerable instruments. In the event that multiple steerable instruments are being used during an intervention, an increased diameter of the elongated tubular bodies of the steerable instruments may compromise their maneuverability which of course is highly undesirable. It is an object of the invention to provide a steerable instrument for endoscopic and/or invasive type of applications comprising a cylindrical diameter adaptation section, which instrument preempts or at least reduces the disadvantages of steerable instruments comprising known diameter adaptation arrangements mentioned above.

This is achieved by a steerable instrument comprising an elongated tubular body having a cylindrical diameter adaptation section comprising a first side and a second side, the elongated tubular body at a location of said cylindrical diameter adaptation section comprising:

• an inner cylindrical element arranged at a first diameter from a longitudinal center axis of the elongated tubular body;

• a set of longitudinal elements arranged at a second diameter from the

longitudinal center axis at said first side of said cylindrical diameter adaptation section and arranged at a third diameter from the longitudinal center axis in the direction of said second side of said cylindrical diameter adaptation section, said second diameter being larger than said first diameter, and said third diameter being larger than said second diameter, said set of longitudinal elements being movably arranged in a longitudinal direction of said elongated tubular body;

• a first rigid ring arranged at said first side of said cylindrical diameter

adaptation section and arranged at a fourth diameter from the longitudinal center axis of the elongated tubular body, which fourth diameter is larger than said second diameter;

• a second rigid ring arranged at said second side of said cylindrical diameter adaptation section and a first set of pins arranged at a location between said first and second sides of said cylindrical diameter adaptation section, both said second rigid ring and said first set of pins being arranged at said second diameter from said longitudinal center axis of the elongated tubular body, such that

at said first side of said cylindrical diameter adaptation section, a first portion of said set of longitudinal elements being movably arranged in a longitudinal direction of said elongated tubular body between said inner cylindrical element and said first rigid ring and being confined in a radial direction of the elongated tubular body; at said second side of said cylindrical diameter adaptation section, a second portion of said set of longitudinal elements is supported by said second rigid ring; and at said location between said first and second sides of said cylindrical diameter adaptation section, an intermediate portion of said set of longitudinal elements is located between said first and second portions of said set of longitudinal elements, longitudinal elements of said intermediate portion being circumferentially arranged between pins of said first set of pins at a diameter changing from said second diameter at said first side of said cylindrical diameter adaptation section towards said third diameter at said second side of said cylindrical diameter adaptation section such as to be confined in a circumferential direction of the elongated tubular body.

The steerable instrument according to the invention comprises an internally arranged cylindrical diameter adaptation section that adds significantly less to the diameter of the elongated tubular body of the steerable instrument than diameter adaptation arrangements known from the prior art. In this way the maneuverability of a steerable instrument according to the invention is improved. In addition, as the cylindrical diameter adaptation section is arranged inside the elongated tubular body of the steerable instrument, the reliability of the steerable instrument according to the invention is improved as it is less vulnerable to damage.

Furthermore, the steerable instrument according to the invention can be

manufactured in a less cumbersome and therefore less costly way.

In an embodiment of the steerable instrument according to the invention, said second rigid ring and said first set of pins are configured and arranged as a first single integral cylindrical element.

In an embodiment of the steerable instrument according to the invention, the steerable instrument further comprises

• a third rigid ring arranged at said second side of said cylindrical diameter adaptation section and a second set of pins arranged at a location between said first and second sides of said cylindrical diameter adaptation section, both said first rigid ring and said second set of pins being arranged at said fourth diameter from said longitudinal center axis of the elongated tubular body, said second rigid ring being arranged to support said third rigid ring and a first portion of said second set of pins at said second side of said cylindrical diameter adaptation section,

such that

at said second side of said cylindrical diameter adaptation section, said second portion of said set of longitudinal elements is supported by said third rigid ring; and at said location between said first and second sides of said cylindrical diameter adaptation section, longitudinal elements of said intermediate portion of said set of longitudinal elements being circumferentially arranged between pins of said second set of pins at a diameter changing from said second diameter at said first side of said cylindrical diameter adaptation section towards a fifth diameter at said second side of said cylindrical diameter adaptation section such as to be confined in a circumferential direction of the elongated tubular body, said fifth diameter being larger than said fourth diameter.

In an embodiment of the steerable instrument according to the invention, said first rigid ring and said second set of pins are configured and arranged as a second single integral cylindrical element.

In an embodiment of the steerable instrument according to the invention, the steerable instrument further comprises a fourth rigid ring arranged at said first side of said cylindrical diameter adaptation section and arranged at a sixth diameter from the longitudinal center axis of the elongated tubular body, which sixth diameter is larger than said fourth diameter, said fourth rigid ring being arranged to confine longitudinal elements of said intermediate portion of said set of

longitudinal elements in a radial direction of the elongated tubular body.

In an embodiment of the steerable instrument according to the invention, the steerable instrument further comprises a third set of pins being arranged at a location between said first and second sides of said cylindrical diameter adaptation section, both said third rigid ring and said third set of pins being arranged at said third diameter from said longitudinal center axis of the elongated tubular body, said third set of pins further being arranged to support said second portion of said set of longitudinal elements at said fifth diameter from said longitudinal center axis.

In an embodiment of the steerable instrument according to the invention, pins of said third set of pins are arranged to be in an interlocking arrangement with pins of said second set of pins.

In an embodiment of the steerable instrument according to the invention, the pins of said second set of pins are attached to at least one of said third rigid ring and the pins of said third set of pins.

In an embodiment of the steerable instrument according to the invention, the steerable instrument further comprises a fourth set of pins being arranged at a location between said first and second sides of said cylindrical diameter adaptation section, both said fourth rigid ring and said fourth set of pins being arranged at said sixth diameter from said longitudinal center axis of the elongated tubular body, at said location between said first and second sides of said cylindrical diameter adaptation section, longitudinal elements of said intermediate portion of said set of longitudinal elements being circumferentially arranged between pins of said fourth set of pins at a diameter changing from said third diameter towards said fifth diameter at said second side of said cylindrical diameter adaptation section such as to be confined in a circumferential direction of the elongated tubular body.

In an embodiment of the steerable instrument according to the invention, the steerable instrument further comprises an outer cylindrical element that is arranged at a seventh diameter from the longitudinal center axis of the elongated tubular body, said seventh diameter being larger than said third diameter, at said second side of said cylindrical diameter adaptation section, said second portion of said set of longitudinal elements being movably arranged in a longitudinal direction of said elongated tubular body between said outer cylindrical element and said second rigid ring and being confined in a radial direction of the elongated tubular body.

In an embodiment of the steerable instrument according to the invention, the steerable instrument further comprises an outer cylindrical element that is arranged at a seventh diameter from the longitudinal center axis of the elongated tubular body, said seventh diameter being larger than said fifth diameter, at said second side of said cylindrical diameter adaptation section, said second portion of said set of longitudinal elements being movably arranged in a longitudinal direction of said elongated tubular body between said outer cylindrical element and said third rigid ring and being confined in a radial direction of the elongated tubular body.

In an embodiment of the steerable instrument according to the invention, said outer cylindrical element is arranged at said second side of said cylindrical diameter adaptation section to be in contact with said second portion of said set of longitudinal elements. In an embodiment of the steerable instrument according to the invention, the elongated tubular body further comprises at least a first distal flexible zone that is attached to said set of longitudinal elements and arranged at one of said first side and said second side of said cylindrical diameter adaptation section such that a displacement of longitudinal elements of said set of longitudinal elements in a longitudinal direction of the elongated tubular body is transferable into a flexion of said at least first distal flexible zone in a radial direction relative to the longitudinal center axis of the elongated tubular body.

In an embodiment of the steerable instrument according to the invention, the elongated tubular body further comprises at least a first actuation flexible zone at a proximal side opposing said side of said at least first distal flexible zone, said at least first actuation flexible zone also being attached to said set of longitudinal elements and arranged such that a flexion of said at least first actuation flexible zone in a radial direction relative to the longitudinal center axis of the elongated tubular body is transferable into a flexion of said at least first distal flexible zone in a radial direction relative to the longitudinal center axis of the elongated tubular body via a displacement of longitudinal elements of said set of longitudinal elements in a longitudinal direction of the elongated tubular body.

Further features and advantages of the invention will become apparent from the description of the invention by way of non-limiting and non-exclusive embodiments. These embodiments are not to be construed as limiting the scope of protection. The person skilled in the art will realize that other alternatives and equivalent embodiments of the invention can be conceived and reduced to practice without departing from the scope of the present invention. Embodiments of the invention will be described with reference to the figures of the accompanying drawings, in which like or same reference symbols denote like, same or

corresponding parts, and in which:

Figure 1 shows a schematic perspective view of a non-limiting embodiment of a invasive instrument assembly having two steerable instruments.

Figure 2a shows a side view of a non-limiting embodiment of a rigid invasive instrument.

Figure 2b shows a side view of a non-limiting embodiment of a steerable invasive instrument. Figure 2c provides a detailed perspective view of a non-limiting embodiment of the elongated tubular body of the steerable instrument.

Figure 2d provides a more detailed view of the distal end part of the elongated tubular body as shown in figure 2c.

Figure 2e shows a longitudinal cross-sectional view of the elongated tubular body of the steerable instrument as shown in figure 2c.

Figure 2f shows a longitudinal cross-sectional view of the elongated tubular body of the steerable instrument as shown in figure 2c, wherein the first proximal and first distal flexible zones are bent, thereby illustrating the operation of the steering arrangement.

Figure 2g shows a longitudinal cross-sectional view of the elongated tubular body of the steerable instrument as shown in figure 2f, wherein additionally the second proximal and second distal flexible zones are bent, thereby further illustrating the operation of the steering arrangement.

Figure 2h shows a perspective view of a part of the elongated tubular body as shown in figure 2c, wherein the outer cylindrical element partially has been removed to show an exemplary embodiment of the longitudinal steering elements that have been obtained after providing longitudinal slits to the wall of an intermediate cylindrical element that interconnects the first proximal flexible zone and the first distal flexible zone of the elongated tubular body.

Figure 2i shows a longitudinal cross-sectional view of an exemplary embodiment of a steerable instrument having one proximal and one distal flexible zone.

Figure 2j shows a perspective exploded view of the three cylindrical elements of the steerable instrument shown in figure 2i.

Figure 2k shows a top view of an unrolled version of an exemplary embodiment of the intermediate cylindrical element of the steerable instrument shown in figure 2j . The intermediate cylindrical element can be formed by rolling the unrolled version into a cylindrical configuration and attaching adjacent sides of the rolled-up configuration by any known attaching means such as by a welding technique.

Figures 3a, 3b and 3c show schematic representation of unrolled views of embodiments of flexible proximal and distal parts of inner, outer and intermediate cylindrical elements.

Figure 4 shows a perspective exploded view of three cylindrical elements of a steerable tube analogous to the exploded view of figure 2j, but with a varying diameter of the cylindrical elements.

Figure 5a shows a schematic cross-section of a first exemplary embodiment of a steerable instrument with cylindrical elements comparable as shown in figures 3a, 3b and 3c. The proximal actuating portion of the cylindrical elements has a larger diameter compared to the distal handling end portion. A frusto-conical part schematically representing a cylindrical diameter adaptation section according to the invention has been incorporated in the intermediate rigid part that is arranged between the proximal end part and the distal end part to connect the parts of the elongated tubular body having different diameters.

Figure 5b shows a schematic cross-section of a second exemplary

embodiment of a steerable instrument in which a proximal actuation flexible zone of the actuating portion of the cylindrical elements as well as an intermediate rigid part that is arranged between said proximal actuation flexible zone and a distal actuation flexible zone have a larger diameter than the other parts of the elongated tubular body. A frusto-conical part is shown that schematically represents a diameter adaptation section according to the invention.

Figure 6 shows a schematic perspective view of an exemplary embodiment of a proximal end part of a steerable instrument according to the invention

comprising a frusto-conical part that schematically represents a diameter adaptation section.

Figure 7a shows a schematic perspective view of the exemplary embodiment of the steerable instrument shown in figure 6, but without the meandering spacers between the longitudinal elements in the actuation flexible zone.

Figure 7b shows a schematic perspective view of the exemplary embodiment of the steerable instrument shown in figure 7a, but without one of the longitudinal elements.

Figure 7c shows a schematic perspective view of the exemplary embodiment of the steerable instrument shown in figure 7b, but without a fourth rigid ring and a fourth set of pins.

Figure 7d shows a schematic perspective view of the exemplary embodiment of the steerable instrument shown in figure 7c, but without the pins of a second set of pins.

Figure 8a shows a schematic perspective cross-section of a part of the elongated tubular body comprising the cylindrical diameter adaptation section according to the exemplary embodiment of the steerable instrument shown in figure 6.

Figure 8b shows a schematic cross-section of the part of the elongated tubular body comprising the cylindrical diameter adaptation section according to the exemplary embodiment of the steerable instrument shown in figure 6.

Figure 2a shows a side view of a non-limiting embodiment of a rigid invasive instrument 240 and figure 2b shows a non-limiting embodiment of a steerable invasive instrument 10. Figure 1 shows a non-limiting embodiment of an invasive instrument assembly 1 having an introducer with two such steerable invasive instruments 10. Details of the non-limiting embodiment of the steerable invasive instruments 10 are explained in relation to figures 2c to 2k.

The rigid invasive instrument 240 as shown in figure 2a comprises an elongated shaft 242 having a proximal end part 241 and a distal end part 243. At the distal end part 243 a tool 2, for example a forceps, is arranged. At the proximal end part 241 a handle 3 is arranged that is adapted for manipulating the tool 2, i.e. opening and closing the jaw of the forceps. To that effect, a control rod (not shown) is present within the elongated shaft 242, which rod connects the handle 3 with the tool 2. The rod can be moved by the handle 3 and the movement of the rod is translated into a predetermined movement of the tool 2, as is known to persons skilled in the art and need no further explanation here. Also, the shaft 242 may comprise conducting wires to allow a current to flow to a tool, e.g. to heat said tool in order to perform a heat treatment within a human or animal body.

Figure 2b shows a side view of a steerable invasive instrument 10. The steerable instrument 10 comprises an elongated tubular body 18 having a proximal end part 1 1 including two actuation flexible zones 14, 15, a distal end part 13 including two distal flexible zones 16, 17, and a rigid intermediate part 12. The actuation flexible zones 14, 15 in the present embodiment are configured as flexible proximal zones, and will further be referred to as flexible proximal zones. At the distal end part 13 a tool, like a forceps 2 is arranged. At the proximal end part 1 1 a handle 3 is arranged that is adapted for opening and closing the jaw of the forceps 2.

Figure 2c provides a detailed perspective view of the distal portion of the elongated tubular body 18 of the steerable instrument 10 and shows that the elongated tubular body 18 comprises of a number of co-axially arranged layers or cylindrical elements including an outer cylindrical element 104 that ends after the first distal flexible zone 16 at the distal end portion 13. The distal end portion 13 of the outer cylindrical element 104 is fixedly attached to the cylindrical element 103 located within and adjacent to the outer cylindrical element 104, e.g. by means of spot welding at welding spots 100. However, any other suitable attachment method can be used, including gluing by a suitable glue.

Figure 2d provides a more detailed view of the distal end part 13 and shows that it includes three co-axially arranged layers or cylindrical elements being an inner cylindrical element 101 , a first intermediate cylindrical element 102 and a second intermediate cylindrical element 103. The distal ends of inner cylindrical element 101 , first intermediate cylindrical element 102 and second intermediate cylindrical element 103 are all three fixedly attached to one another. This may be done by means of spot welding at welding spots 100. However, any other suitable attachment method can be used, including gluing by a suitable glue. The points of attachment may be at the end edges of inner cylindrical element 101 , first intermediate cylindrical element 102 and second intermediate cylindrical element 103, as shown in the figures. However, these points of attachment may also be located some distance away from these edges, be it, preferably, between the end edges and the locations of the flexible zone 17.

It will be clear to the skilled person that the elongated tubular body 18 as shown in figure 2c comprises four cylindrical elements in total. The elongated tubular body 18 according to the embodiment shown in figure 2c comprises two intermediate cylindrical elements 102 and 103 in which the steering members of the steering arrangement are arranged. The steering arrangement in the exemplary embodiment of the elongated tubular body 18 as shown in figure 2c comprises the two flexible zones 14, 15 at the proximal end part 1 1 of the elongated tubular body 18, the two flexible zones 16, 17 at the distal end part 13 of the elongated tubular body 18 and the steering members that are arranged between related flexible zones at the proximal 1 1 and distal 13 end parts. An exemplary actual arrangement of the steering members is shown in figure 2e, which provides a schematic longitudinal cross-sectional view of the exemplary embodiment of the elongated tubular body 18 as shown in figure 2c.

Figure 2e shows the four layers or cylindrical elements mentioned above, i.e. the inner cylindrical element 101 , the first intermediate cylindrical element 102, the second intermediate cylindrical element 103, and the outer cylindrical element 104.

The inner cylindrical element 101 , as seen along its length from the distal end to the proximal end of the instrument, comprises a rigid ring 1 1 1 , which is arranged at the distal end part 13 of the steerable instrument 10, a first flexible portion 1 12, a first intermediate rigid portion 1 13, a second flexible portion 1 14, a second intermediate rigid portion 1 15, a third flexible portion 1 16, a third intermediate rigid portion 1 17, a fourth flexible portion 1 18, and a rigid end portion 1 19, which is arranged at the proximal end portion 1 1 of the steerable instrument 10.

The first intermediate cylindrical element 102, as seen along its length from the distal end to the proximal end of the instrument, comprises a rigid ring 121 , a first flexible portion 122, a first intermediate rigid portion 123, a second flexible portion 124, a second intermediate rigid portion 125, a third flexible portion 126, a third intermediate rigid portion 127, a fourth flexible portion 128, and a rigid end portion 129. The longitudinal dimensions of the rigid ring 121 , the first flexible portion 122, the first intermediate rigid portion 123, the second flexible portion 124, the second intermediate rigid portion 125, the third flexible portion 126, the third intermediate rigid portion 127, the fourth flexible portion 128, and the rigid end portion 129 of the first intermediate element 102, respectively, are aligned with, and preferably approximately equal to the longitudinal dimensions of the rigid ring 1 1 1 , the first flexible portion 1 12, the first intermediate rigid portion 1 13, the second flexible portion 1 14, the second intermediate rigid portion 1 15, the third flexible portion 1 16, the third intermediate rigid portion 1 17, the fourth flexible portion 1 18, and the rigid end portion 1 19 of the inner cylindrical element 101 , respectively, and are coinciding with these portions as well. In this

description "approximately equal" means that respective same dimensions are equal within a margin of less than 10%, preferably less than 5%.

The second intermediate cylindrical element 103, as seen along its length from the distal end to the proximal end of the instrument, comprises a first rigid ring 131 , a first flexible portion 132, a second rigid ring 133, a second flexible portion 134, a first intermediate rigid portion 135, a first intermediate flexible portion 136, a second intermediate rigid portion 137, a second intermediate flexible portion 138, and a rigid end portion 139. The longitudinal dimensions of the first rigid ring 131 , the first flexible portion 132 together with the second rigid ring 133 and the second flexible portion 134, the first intermediate rigid portion 135, the first intermediate flexible portion 136, the second intermediate rigid portion 137, the second intermediate flexible portion 138, and the rigid end portion 139 of the second intermediate cylinder 103, respectively, are aligned with, and preferably approximately equal to the longitudinal dimensions of the rigid ring 1 1 1 , the first flexible portion 1 12, the first intermediate rigid portion 1 13, the second flexible portion 1 14, the second intermediate rigid portion 1 15, the third flexible portion 1 16, the third intermediate rigid portion 1 17, the fourth flexible portion 1 18, and the rigid end portion 1 19 of the first intermediate element 102, respectively, and are coinciding with these portions as well.

The outer cylindrical element 104, as seen along its length from the distal end to the proximal end of the instrument, comprises a first rigid ring 141 , a first flexible portion 142, a first intermediate rigid portion 143, a second flexible portion 144, and a second rigid ring 145. The longitudinal dimensions of the first flexible portion 142, the first intermediate rigid portion 143 and the second flexible portion 144 of the outer cylindrical element 104, respectively, are aligned with, and preferably approximately equal to the longitudinal dimension of the second flexible portion 134, the first intermediate rigid portion 135 and the first intermediate flexible portion 136 of the second intermediate element 103, respectively, and are coinciding with these portions as well. The rigid ring 141 has approximately the same length as the rigid ring 133 and is fixedly attached thereto, e.g. by spot welding or gluing. Preferably, the rigid ring 145 overlaps with the second intermediate rigid portion 137 only over a length that is required to make an adequate fixed attachment between the rigid ring 145 and the second intermediate rigid portion 137, respectively, e.g. by spot welding or gluing. The rigid rings 1 1 1 , 121 and 13 1 are attached to each other, e.g., by spot welding or gluing. This may be done at the end edges thereof but also at a distance of these end edges. In an embodiment, the same may apply to the rigid end portions 1 19, 129 and 139, which can be attached together as well in a comparable manner. However, as will be explained hereinafter, the construction may be such that the diameter of the cylindrical elements at the proximal portion is larger, or smaller, with respect to the diameter at the distal portion. In such embodiment the construction at the proximal portion differs from the one shown in figure 2e. As a result of the increase in diameter an amplification is achieved, i.e., the bending angle of a flexible zone at the distal portion will be larger than the bending angle of a corresponding flexible portion at the proximal portion. This will be further described below with reference to figure 4.

The inner and outer diameters of the cylindrical elements 101, 102, 103, and 104 are chosen in such a way at a same location along the elongated tubular body 18 that the outer diameter of inner cylindrical element 101 is slightly less than the inner diameter of the first intermediate cylindrical element 102, the outer diameter of the first intermediate cylindrical element 102 is slightly less than the inner diameter of the second intermediate cylindrical element 103 and the outer diameter of the second intermediate cylindrical element 103 is slightly less than the inner diameter of the outer cylindrical element 104, in such a way that a sliding movement of the adjacent cylindrical elements with respect to each other is possible. The dimensioning should be such that a sliding fit is provided between adjacent elements. A clearance between adjacent elements may generally be in the order of 0.02 to 0.1 mm, but depends on the specific application and material used. The clearance preferably is smaller than a wall thickness of the longitudinal elements to prevent an overlapping configuration thereof. Restricting the clearance to about 30% to 40% of the wall thickness of the longitudinal elements is generally sufficient.

As can be seen in figure 2e, flexible zone 14 of the proximal end part 1 1 is connected to the flexible zone 16 of the distal end part 13 by portions 134, 135 and 136, of the second intermediate cylindrical element 103, which form a first set of longitudinal steering members of the steering arrangement of the steerable instrument 10. Furthermore, flexible zone 15 of the proximal end part 1 1 is connected to the flexible zone 17 of the distal end part 13 by portions 122, 123, 124, 125, 126, 127, and 128 of the first intermediate cylindrical element 102, which form a second set of longitudinal steering members of the steering arrangement. The use of the construction as described above allows the steerable instrument 10 to be used for double bending. The working principle of this construction will be explained with respect to the examples shown in figures 2f and 2g.

For the sake of convenience, as shown in figures 2e, 2f and 2g,the different portions of the cylindrical elements 101 , 102, 103, and 104 have been grouped into zones 151 - 160 that are defined as follows. Zone 151 comprises the rigid rings 1 1 1 , 121 , and 131. Zone 152 comprises the portions 1 12, 122, and 132. Zone 153 comprises the rigid rings 133 and 141 and the portions 1 13 and 123. Zone 154 comprises the portions 1 14, 124, 134 and 142. Zone 155 comprises the portions 1 15, 125, 135 and 143. Zone 156 comprises the portions 1 16, 126, 136 and 144. Zone 157 comprises the rigid ring 145 and the parts of the portions 1 17, 127, and 137 coinciding therewith. Zone 158 comprises the parts of the portions 1 17, 127, and 137 outside zone 157. Zone 159 comprises the portions 1 18, 128 and 138. Finally, zone 160 comprises the rigid end portions 1 19, 129 and 139.

In order to deflect at least a part of the distal end part 13 of the steerable instrument 10, it is possible to apply a bending force, in any radial direction, to zone 158. According to the examples shown in figures 2f and 2g, zone 158 is bent downwards with respect to zone 155. Consequently, zone 156 is bent downwards. Because of the first set of steering members comprising portions 134, 135, and 136 of the second intermediate cylindrical element 103 that are arranged between the second intermediate rigid portion 137 and the second rigid ring 133, the downward bending of zone 156 is transferred by a longitudinal displacement of the first set of steering members into an upward bending of zone 154 with respect to zone 155. This is shown in both figures 2f and 2g.

It is to be noted that the exemplary downward bending of zone 156, only results in the upward bending of zone 154 at the distal end of the instrument as shown in figure 2f. Bending of zone 152 as a result of the bending of zone 156 is prevented by zone 153 that is arranged between zones 152 and 154. When subsequently a bending force, in any radial direction, is applied to the zone 160, zone 159 is also bent. As shown in figure 2g, zone 160 is bent in an upward direction with respect to its position shown in figure 2f. Consequently, zone 159 is bent in an upward direction. Because of the second set of steering members comprising portions 122, 123, 124, 125, 126, 127 and 128 of the first intermediate cylindrical element 102 that are arranged between the rigid ring 121 and the rigid end portion 129, the upward bending of zone 159 is transferred by a longitudinal displacement of the second set of steering members into a downward bending of zone 152 with respect to its position shown in figure 2f.

Figure 2g further shows that the initial bending of the instrument in zone 154 as shown in figure 2f will be maintained because this bending is only governed by the bending of zone 156, whereas the bending of zone 152 is only governed by the bending of zone 159 as described above. Due to the fact that zones 152 and 154 are bendable independently with respect to each other, it is possible to give the distal end part 13 of the steerable instrument 10 a position and longitudinal axis direction that are independent from each other. In particular the distal end part 13 can assume an advantageous S-like shape. In known instruments such as described in EP 1 708 609 A, the position and the direction of the longitudinal axis are always coupled and cannot be individually controlled. The skilled person will appreciate that the capability to independently bend zones 152 and 154 with respect to each other, significantly enhances the maneuverability of the distal end part 13 and therefore of the steerable instrument 10 as a whole.

Obviously, it is possible to vary the lengths of the flexible portions shown in figures 2e to 2g as to accommodate specific requirements with regard to bending radii and total lengths of the distal end part 13 and the proximal end part 1 1 of the steerable instrument 10 or to accommodate amplification or attenuation ratios between bending of at least a part of the proximal end part 1 1 and at least a part of the distal end part 13.

The steering arrangement of the steerable invasive instrument 10 may comprise conventional steering cables as steering members that are fixedly attached to the respective rigid rings 121 , 133. However due to well-known disadvantages of conventional steering cables, the steering members preferably comprise one or more sets of longitudinal elements that form integral parts of the one or more intermediate cylindrical elements 102, 103. Preferably, the longitudinal elements comprise remaining parts of the wall of an intermediate cylindrical element 102, 103 after the wall of the intermediate cylindrical element 102, 103 has been provided with longitudinal slits that define the remaining longitudinal steering elements.

Further details regarding the fabrication of the latter longitudinal steering elements are provided with reference to figures 2i to 2k regarding an exemplary embodiment of a steerable instrument that comprises only one flexible zone at both its proximal 1 1 and distal end 13 parts.

Figure 2i shows a longitudinal cross-section of a steerable instrument 2201 comprising three co-axially arranged cylindrical elements, i.e. inner cylindrical element 2202, intermediate cylindrical element 2203 and outer cylindrical element 2204. Suitable materials to be used for making the cylindrical elements 2202, 2203, and 2204 include stainless steel, cobalt-chromium, shape memory alloy such as Nitinol®, plastic, polymer, composites or other cuttable material.

The inner cylindrical element 2202 comprises a first rigid end part 2221 , which is located at the distal end part 13 of the instrument 2201 , a first flexible part 2222, an intermediate rigid part 2223, a second flexible part 2224 and a second rigid end part 2225, which is located at the proximal end part 1 1 of the instrument 2201 .

The outer cylindrical element 2204 also comprises a first rigid end part 2241 , a first flexible part 2242, an intermediate rigid part 2243, a second flexible part 2244 and a second rigid end part 2245. The lengths of the different parts of the cylindrical elements 2202 and 2204 are substantially the same so that when the inner cylindrical element 2202 is inserted into the outer cylindrical element 2204, the different parts are positioned against each other.

The intermediate cylindrical element 2203 also has a first rigid end part 233 1 and a second rigid end part 2335 which in the assembled condition are located between the corresponding rigid parts 2221 , 2241 and 2225, 2245 respectively of the two other cylindrical elements 2202, 2204. The intermediate part 2333 of the intermediate cylindrical element 2203 comprises three or more separate

longitudinal elements which can have different forms and shapes as will be explained below. After assembly of the three cylindrical elements 2202, 2203 and 2204 whereby the element 2202 is inserted in the element 2203 and the two combined elements 2202, 2203 are inserted into the element 2204, at least the first rigid end part 2221 of the inner cylindrical element 2202, the first rigid end part 233 1 of the intermediate cylindrical element 2203 and the first rigid end part 2241 of the outer cylindrical element 2204 at the distal end of the instrument are attached to each other. In the embodiment shown in figures 2i and 2j, also the second rigid end part 2225 of the inner cylindrical element 2202, the second rigid end part 2335 of the intermediate cylindrical element 2203 and the second rigid end part 2245 of the outer cylindrical element 2204 at the proximal end of the instrument are attached to each other such that the three cylindrical elements 2202, 2203, 2204 form one integral unit.

In the embodiment shown in figure 2j the intermediate part 2333 of

intermediate cylindrical element 2203 comprises a number of longitudinal elements 2338 with a uniform cross-section so that the intermediate part 2333 has the general shape and form as shown in the unrolled condition of the intermediate cylindrical element 2203 in figure 2k. From figure 2k it also becomes clear that the intermediate part 2333 is formed by a number of over the circumference of the intermediate cylindrical part 2203 equally spaced parallel longitudinal elements 2338. Advantageously, the number of longitudinal elements 2338 is at least three, so that the instrument 2201 becomes fully controllable in any direction, but any higher number is possible as well. Preferably, the number of longitudinal elements 2338 is 6 or 8.

The production of such an intermediate part is most conveniently done by injection moulding or plating techniques or starting from a cylindrical tube with the desired inner and outer diameters and removing parts of the wall of the cylindrical tube required to end up with the desired shape of the intermediate cylindrical element 2203. However, alternatively, any 3D printing method can be used.

The removal of material can be done by means of different techniques such as laser cutting, photochemical etching, deep pressing, conventional chipping techniques such as drilling or milling, high pressure water jet cutting systems or any suitable material removing process available. Preferably, laser cutting is used as this allows for a very accurate and clean removal of material under reasonable economic conditions. The above mentioned processes are convenient ways as the member 2203 can be made so to say in one process, without requiring additional steps for connecting the different parts of the intermediate cylindrical member as required in the conventional instruments, where conventional steering cables must be connected in some way to the end parts. The same type of technology can be used for producing the inner and outer cylindrical elements 2202 and 2204 with their respective flexible parts 2222, 2224, 2242 and 2244.

Figure 2h shows an exemplary embodiment of longitudinal (steering) elements 4 that have been obtained after providing longitudinal slits 5 to the wall of the second intermediate cylindrical element 103 that interconnects proximal flexible zone 14 and distal flexible zone 16 as described above. I.e., longitudinal steering elements 4 are, at least in part, spiraling about a longitudinal axis of the instrument such that an end portion of a respective steering element 4 at the proximal portion of the instrument is arranged at another angular orientation about the longitudinal axis than an end portion of the same longitudinal steering element 4 at the distal portion of the instrument. Were the longitudinal steering elements 4 arranged in a linear orientation, than a bending of the instrument at the proximal portion in a certain plane would result in a bending of the instrument at the distal portion in the same plane but in a 180 degrees opposite direction. This spiral construction of the longitudinal steering elements 4 allows for the effect that bending of the instrument at the proximal portion in a certain plane may result in a bending of the instrument at the distal portion in another plane, or in the same plane in the same direction. A preferred spiral construction is such that the end portion of a respective steering element 4 at the proximal portion of the instrument is arranged at an angularly shifted orientation of 180 degrees about the longitudinal axis relative to the end portion of the same longitudinal steering element 4 at the distal portion of the instrument. However, e.g. any other angularly shifted orientation, e.g. 90 degrees, is within the scope of this document. The slits are dimensioned such that movement of a longitudinal element is guided by adjacent longitudinal elements when provided in place in a steerable instrument.

The flexible portions 1 12, 132, 1 14, 142, 1 16, 144, 1 18, and 138 as shown in figure 2e, as well as the flexible parts 2222, 2224, 2242, and 2244 shown in figures 2i and 2j can be obtained by the methods described in the European patent application 08 004 373.0 filed on 10.03.2008, page 5, lines 15-26, but any other suitable process can be used to make flexible portions.

Such flexible parts may have a structure as shown in figures 2c and 2d. I.e., the flexibility may be obtained by a plurality of slits 14a, 15a, 16a, 17a. E.g., two circumferential slits may be provided in a cylindrical element along a same circumferential line where both slits are located at a certain distance from one another. A plurality of identical sets of circumferential slits 14a, 15a, 16a, 17a is provided at a plurality of distances in the longitudinal direction of the instrument , where consecutive sets are arranged at an angularly rotated position, e.g. each time 90 degrees rotated. In such an arrangement, all parts of the cylindrical element are still connected to each other.

Figures 3a, 3b and 3c show alternative manners of how such flexibility in part can be obtained. Figure 3a shows a schematic representation of a flat rolled-out flexible proximal or distal cylindrical zone. The intermediate cylindrical elements are then made by rolling-up the flat element and attaching the side edges together in any suitable fashion that is known as such, such as by a welding technique. In the embodiment shown in figure 3 a, the part of the cylindrical tube to become flexible has been provided with slits 14a, 15a, 16a, 17a extending in a helical manner over the length of the flexible zone. The flexibility can be controlled by the number of slits and/or the angle of the slits with respect to the axial direction of the cylindrical member. In the embodiment of figure 3b the part of the cylindrical tube to become flexible has been provided with a number of short slits 14a, 15a, 16a, 17a. The slits can be divided into groups, the slits in each group being located in the same line extending perpendicular to the axis of the cylindrical member. The slits of two neighboring groups are offset. In the embodiment of figure 3c the part of the cylindrical tube to become flexible has been provided by making slits 14a, 15a, 16a, 17a producing a number of swallow's tails between the slits, which fit into each other as shown. It will be obvious that other systems of providing a flexible zone in a cylindrical tube wall may be used as well. More specifically it is possible to use combinations of the systems shown above. However, any other suitable flexible construction may be used instead. For instance, any of the flexible constructions shown and described in EP 0 764 423 A and EP 0 782 836 A may be used as well.

Furthermore, if the portions 122, 123, 124, 125, 126, 127, and 128 of the first intermediate cylindrical element 102 and the portions 134, 135, and 136 of the second intermediate cylindrical element 103 that respectively form the first and second set of longitudinal steering members, as shown in figure 2e, are

implemented as longitudinal steering elements 4 as shown in figure 2h, the fabrication methods described above can be used. The same applies to the longitudinal elements 2338 of figures 2j and 2k. Moreover, any embodiment described in EP 2 762 058 A can be used according to the invention.

Otherwise, the longitudinal elements 4, 2338 can also be obtained by any other technique known in the art such as for example described in EP 1 708 609 A. The only restriction with respect to the construction of the longitudinal elements used in these portions is that the total flexibility of the instrument in these locations where the flexible portions coincide must be maintained.

The different co-axially arranged layers or cylindrical elements 101 , 102, 103, 104, 2202, 2203 and 2204 as described above in relation to the exemplary embodiments of the steerable instruments shown in figures 2e and 2i, respectively, may be produced by any of the known methods, provided that they are suitable to make a multilayer system. A multilayer system is to be understood as being a steerable instrument that comprises at least two separate sets of longitudinal elements 4, 2338 for transferring the movement of the proximal end part to the distal end part. The assembly of the different cylindrical elements can be realized in the same way as well. Preferred methods of producing the different cylindrical elements have been described in the above mentioned EP 2 762 058 A which is hereby incorporated by reference in its entirety.

In the above embodiments, the proximal portions and distal portions are constructed in a similar way. However, that need not be the case always as will be explained now.

E.g., the proximal portion may have a wider diameter as shown in figure 4, which shows a special embodiment of an instrument according to the invention. The inner cylindrical element 2202 is composed of a first rigid end part 2225, a first flexible part 2224, an intermediate rigid part 2223, a second flexible part 2222 and a second rigid end part 2221 which is normally used as the operating part of the instrument in that it serves to steer the other end of the unit. The outer cylindrical element 2204 is in the same way composed of a first rigid part 2245 , a first flexible part 2244, an intermediate rigid part 2243, a second flexible part 2242 and a second rigid part 2241. The intermediate cylindrical element 2203 also has a first rigid end part 2335 and a second rigid end part 2331 which in the assembled condition are located between the corresponding rigid parts 2225 , 2245 and 2221 , 2241 , respectively, of the two other cylindrical elements 2202, 2204. In the embodiment shown the longitudinal elements 2338 are of the type shown in figure 2j, but it will be obvious that any other type described above may be used as well. So far the construction is comparable to the instruments described above. The main difference with respect to the above embodiments is the use of a different set of diameters for some parts of the instrument. In the embodiment shown in figure 4 the parts 2222, 2221 , 2331 , 2242 and 2241 have a larger diameter than the other parts. In the parts 2223, 2333 and 2243 frusto-conical portions 2212, 2213, 2214 have been made in order to connect the small diameter parts with the large diameter parts. As shown in figure 4 the different parts can easily be assembled by inserting one into the other. The main reason, however, to have such an instrument with different diameters is that by using an operating part with a larger diameter, the movement of the other end is amplified, whereas if a smaller diameter is used the movement of the other end is attenuated. Dependent of the application and its requirements larger diameters can be used to have the amplified movement or smaller diameters can be used to attenuate the movement and increase

maneuverability accuracy of the handling head.

Such widening of the instrument with increasing diameter towards the proximal portions can also be applied in an instrument with more than two bendable portions, as shown in figures 5a and 5b.

In figure 5a there is shown a first exemplary embodiment of a steerable instrument according to the invention having four layers and as such the instrument is comparable to the instrument of figure 2e but the distal actuation flexible zone 156 and the proximal actuation flexible zone 159 of the proximal end part of the instrument have a larger diameter compared to the respective corresponding distal flexible zones 154 and 152 of the distal end part of the instrument. In the zone 155 a frusto-conical part has been incorporated that schematically represents a cylindrical diameter adaptation section 162 of a steerable instrument according to the invention. The cylindrical diameter adaptation section 162 in the context of this invention comprises at least a distance in an axial or longitudinal direction of the elongated tubular body over which the longitudinal elements change from a second diameter at a first side of the cylindrical diameter adaptation section to a third diameter at a second side of the cylindrical diameter adaptation section. As a result of the larger diameter of the proximal actuation flexible zone 156 and the proximal actuation flexible zone 159 of the proximal end part, the flexion of the respective corresponding distal flexible zones 154 and 152 will be amplified upon bending, thereby amplifying the flexion of the handling head. It is also possible to work in the opposite direction with distal flexible zones 154 and 152 having a larger diameter than the proximal actuation flexible zones 156 and 159, whereby the degree of flexion is attenuated, thereby improving accuracy of movement of the handling head.

Figure 5b shows a schematic cross-section of a second exemplary

embodiment of a steerable instrument according to the invention in which a proximal actuation flexible zone 159 of the actuating portion of the cylindrical elements as well as an intermediate rigid zone 158, that is arranged between said proximal actuation flexible zone 159 and a proximal actuation flexible zone 156, have a larger diameter than the other parts of the elongated tubular body. A firusto- conical part schematically representing a cylindrical diameter adaptation section 164 of a steerable instrument according to the invention has been incorporated in zone 158. The cylindrical diameter adaptation section 164 in the context of this invention comprises at least a distance in an axial or longitudinal direction of the elongated tubular body over which the longitudinal elements change from a second diameter at a first side of the cylindrical diameter adaptation section to a third diameter at a second side of the cylindrical diameter adaptation section. It will be clear to the skilled person that only the flexion of the corresponding distal flexible zone 152 will be amplified upon bending of the corresponding proximal actuation flexible zone 159 of the proximal end part. The degree of flexion of the distal flexible zone 154 will in principle be the same as the degree of flexion of the corresponding proximal actuation flexible zone 156, because of the fact that the intermediate cylindrical element, which comprises the longitudinal elements that are configured and arranged to transfer the flexion of the proximal actuation flexible zone 156 to the corresponding distal flexible zone 154, has the same diameter in these zones. In practice there may be slight differences between these degrees of flexion due to stretching of the longitudinal elements.

Figure 6 shows a schematic perspective view of an exemplary embodiment of a proximal end part of a steerable instrument according to the invention

comprising a cylindrical diameter adaptation section 164. The proximal end part comprises one actuation flexible zone 15 that is arranged at a distal side of the proximal rigid end portion 129. Rigid end portion 129 is attached to longitudinal elements 128, e.g., by laser welding, but other attaching techniques may be used as well. Figure 6 shows that meandering spacers 500 have been arranged between the longitudinal elements 128 of the intermediate cylindrical element in order to preserve the geometrical integrity of the longitudinal elements in the actuation flexible zone 15 during operation, i.e. bending thereof to operate a corresponding distal flexible zone of the steerable instrument (not shown). In the shown exemplary embodiment, the longitudinal elements 128 of the intermediate cylindrical element in the actuation flexible zone 15 are arranged at a larger diameter than the longitudinal elements 127 of the intermediate cylindrical element that is arranged at a distal side of the cylindrical diameter adaptation section 164. A detailed explanation of the construction of the cylindrical diameter adaptation section will be given with reference to figures 8a and 8b. Due to the larger diameter of the intermediate cylindrical element in the actuation flexible zone 15 of the proximal end part, the flexion of a corresponding distal flexible zone (not shown) will be amplified upon bending of the actuation flexible zone 15.

Figure 6 furthermore shows a fourth rigid ring 426 and a fourth set of pins 428. It can be observed that respective longitudinal elements 128 are arranged between respective pins of the fourth set of pins 428. In addition, a first rigid ring 400 is shown. The specific function of the first rigid ring 400, the fourth rigid ring 426 and the fourth set of pins 428 will be explained in greater detail with reference to figures 8a and 8b.

Figure 7a shows a schematic perspective view of the exemplary embodiment of the steerable instrument shown in figure 6, but without the meandering spacers 500 between the longitudinal elements 128 in the actuation flexible zone 15. In this view the connection between a third rigid ring 404 and a flexible portion 408 that is located in the actuation flexible zone 15 can be seen.

Figure 7b shows a schematic perspective view of the exemplary embodiment of the steerable instrument shown in figure 7a, but without one of the longitudinal elements 128. This allows for a pin of a third set of pins 406 to be seen. In addition a connection between the third rigid ring 404 and the pin of the third set of pins 406 can be observed. Furthermore, a part of a second rigid ring 422 can be seen. In the cylindrical diameter adaptation section 164, the second rigid ring 422 is partially positioned below the pins of the third set of pins 406 as can more clearly be seen from figures 8a and 8b. Finally, figure 7b provides a view on a part of the proximal inner cylinder 424 of the elongated tubular body.

Figure 7c shows a schematic perspective view of the exemplary embodiment of the steerable instrument shown in figure 7b, but without the fourth rigid ring 426 and the fourth set of pins 428. This allows for a pin of a second set of pins 402 to be seen. A comparison between figures 7b and 7c learns that in this exemplary embodiment, the pins of the fourth set of pins 428 and the pins of the second set of pins 402 are arranged on top of each other in a radial direction of the elongated body of the steerable instrument. Furthermore, it can be seen that the pins of the second set of pins 402 and the pins of the third set of pins 406 are arranged in an interlocking engagement. It is noted that the pins of the second set of pins 402 are attached to at least one of the pins of the third set of pins 406 and the third rigid ring 404, e.g. by laser welding. Furthermore, it can be seen that the longitudinal elements 128 are supported by the pins of the third set of pins 406, the third rigid ring 404 and the flexible portion 408. Finally, it is noted that the pins of the second set of pins 402 preferably are made as a single part with the first rigid ring 400 from one cylinder. In this way the manufacturability of the steerable instrument according to the invention can be improved.

Figure 7d shows a schematic perspective view of the exemplary embodiment of the steerable instrument shown in figure 7c, but without the pins of the second set of pins 402. This allows for a first set of pins 420 to be seen. Furthermore, it can clearly be seen that the pins of the third set of pins 406, the third rigid ring 404 and the flexible portion 408 of the third guiding mechanism are connected to each other. Preferably, the aforementioned parts 406, 404 and 408 are made together with a fifth rigid ring 418 as a single integral part from one cylinder. It is noted that a so-called bending or flexion limiter, which is a device that is configured and arranged to limit the degree of bending or flexion of a flexible zone of the elongated tubular body, can be arranged around the actuation flexible zone 15.

Figure 8a shows a schematic perspective cross-section of a part of the elongated tubular body comprising the cylindrical diameter adaptation section according to the exemplary embodiment of the steerable instrument shown in figure 6.

Figure 8b shows a schematic cross-section of the part of the elongated tubular body comprising the cylindrical diameter adaptation section according to the exemplary embodiment of the steerable instrument shown in figure 6.

It is noted that the construction of the cylindrical diameter adapter section will be described using seven different diameters from an elongated center axis of the elongated tubular body of the steerable instrument. This will become clear from the following description.

Figures 8a and 8b show that an inner cylindrical element 424 is arranged at a first diameter from a longitudinal center axis of the elongated tubular body . A set of longitudinal elements 127, 128 is arranged at a second diameter from the longitudinal center axis at a first side of the cylindrical diameter adaptation section 164 and arranged at a third diameter from the longitudinal center axis in the direction of a second side of the cylindrical diameter adaptation section 164. The second diameter is larger than the first diameter, and the third diameter is larger than the second diameter. The set of longitudinal elements 127, 128 is movably arranged in a longitudinal direction of the elongated tubular body of the steerable instrument. Furthermore, a first rigid ring 400 is arranged at said first side of the cylindrical diameter adaptation section 164 and arranged at a fourth diameter from the longitudinal center axis of the elongated tubular body. The fourth diameter is larger than the second diameter. A second rigid ring 422 is arranged at said second side of the cylindrical diameter adaptation section 164 and a first set of pins 420 is arranged at a location between said first and second sides of the cylindrical diameter adaptation section 164. Both the second rigid ring 422 and the first set of pins 420 are arranged at the second diameter from said longitudinal center axis of the elongated tubular body. It is noted that at said first side of the cylindrical diameter adaptation section 164, a first portion of the set of longitudinal elements 127, 128 is movably arranged in a longitudinal direction of the elongated tubular body between the inner cylindrical element 424 and the first rigid ring 400. In addition, in this way the first portion of the set of elongated elements is confined in a radial direction of the elongated tubular body.

It is also noted that at said second side of the cylindrical diameter adaptation section 164, a second portion of the set of longitudinal elements 127, 128 is supported by the second rigid ring 422. In addition, at said location between said first and second sides of the cylindrical diameter adaptation section 164, an intermediate portion of said set of longitudinal elements 127, 128 is located between said first and second portions of the set of longitudinal elements.

Longitudinal elements of said intermediate portion are circumferentially arranged between pins of the first set of pins 420 at a diameter changing from said second diameter at said first side of the cylindrical diameter adaptation section 164 towards said third diameter at said second side of the cylindrical diameter adaptation section 164. In this way, the longitudinal elements of the intermediate portion of the set of longitudinal elements are confined in a circumferential direction of the elongated tubular body.

From figures 8a and 8b it will be clear that the second rigid ring 422 is arranged to guide the longitudinal elements of the set of longitudinal elements 127, 128 from the second diameter at the first side of the diameter adaptation section 164 to the larger third diameter at the second side of the diameter adaptation section 164. From the above, it will be clear that the second rigid ring 422 does not confine the movement of the longitudinal elements 128 in an axial or longitudinal direction of the elongated tubular body. As a result, the longitudinal elements of the set of longitudinal elements 127, 128 are freely movable in a longitudinal direction of the elongated tubular body.

In figures 8a and 8b it can also be seen that the pins of the first set of pins 420 extend from the second rigid ring 422 in an axial direction of the elongated tubular body towards the first side of the diameter adaptation section 164. In figure 7d it can be seen that the pins of the first set of pins 420 are spaced at equal distances in a circumferential direction of the elongated tubular body. In this way, the pins of the first set of pins 420 guide parts of the longitudinal elements that are located in said intermediate portion of the set of longitudinal elements such that they are freely movable in an axial direction of the elongated tubular body and are confined in a circumferential direction of the elongated tubular body between adjacent pins of the first set of pins 420.

It is noted that in the case of an exemplary embodiment of the steerable instrument according to the invention (not shown) in which the longitudinal elements of the set of longitudinal elements 127, 128 are brought from said second diameter to said third diameter by using the first rigid ring 400, the second rigid ring 422 and the first set of pins 420, confinement in a circumferential direction of the elongated tubular body of said second portion of said set of longitudinal elements 128 at said third diameter at said second side of the cylindrical diameter adaptation section 164 can be achieved for example by local widening of the longitudinal elements 128 in a circumferential direction of the elongated tubular body, or by using spacers that are arranged between the longitudinal elements 128. It is also possible to establish confinement in a circumferential direction of the elongated tubular body of said second portion of said set of longitudinal elements 128 at said third diameter at said second side of the cylindrical diameter adaptation section 164 by applying a second set of pins 402 as will be described in more detail below.

Furthermore, confinement in a radial direction of the elongated tubular body of said second portion of said set of longitudinal elements 128 at said third diameter at said second side of the cylindrical diameter adaptation section 164 can be achieved for example by arranging an outer cylindrical element 430 at a seventh diameter from the longitudinal center axis of the elongated tubular body. The seventh diameter is larger than the third diameter at which said second portion of said set of longitudinal elements 128 is arranged at said second side of the cylindrical diameter adaptation section 164. By arranging said second portion of said set of longitudinal elements 128 between the outer cylindrical element 430 and the second rigid ring 422 confinement in a radial direction of the elongated tubular body at said second side of said cylindrical diameter adaptation section can be established while said second portion of said set of longitudinal elements 128 remains movably arranged in a longitudinal direction of the elongated tubular body.

The exemplary embodiment of the cylindrical diameter adaptation section shown in figures 8a and 8b further comprises a third rigid ring 404 arranged at said second side of said cylindrical diameter adaptation section 164 and a second set of pins 402 arranged at a location between said first and second sides of said cylindrical diameter adaptation section. Both the first rigid ring 400 and the second set of pins 402 are arranged at the fourth diameter from the longitudinal center axis of the elongated tubular body. It can be seen that the second rigid ring 422 is arranged to support the third rigid ring 404 and a first portion of the second set of pins 402 at said second side of the cylindrical diameter adaptation section. At said second side of the cylindrical diameter adaptation section 164, the second portion of said set of longitudinal elements 127, 128 is supported by the third rigid ring 404. At said location between said first and second sides of the cylindrical diameter adaptation section, longitudinal elements of said intermediate portion of the set of longitudinal elements 127, 128 are circumferentially arranged between pins of the second set of pins 402 at a diameter changing from said second diameter at said first side of the cylindrical diameter adaptation section towards a fifth diameter at said second side of the cylindrical diameter adaptation section. In this way, the longitudinal elements of said intermediate portion are confined in a circumferential direction of the elongated tubular body at said location between said first and second sides of the cylindrical diameter adaptation section. It is noted that the fifth diameter is larger than the fourth diameter.

In figures 8a and 8b it can be seen that the pins of the second set of pins 402 extend from the first rigid ring 400 in an axial direction of the elongated tubular body towards the second side of the diameter adaptation section 164. In figure 7c it can be seen that the pins of the second set of pins 402 are spaced at equal distances in a circumferential direction of the elongated tubular body. In this way, the pins of the second set of pins 402 guide parts of the longitudinal elements that are located in said intermediate portion of the set of longitudinal elements such that they are freely movable in an axial direction of the elongated tubular body and are confined in a circumferential direction of the elongated tubular body between adjacent pins of the second set of pins 402.

In figures 8a and 8b it can further be seen that the third rigid ring 404 extends less far in an axial direction of the elongated tubular body towards the first side of the diameter adaptation section 164 than the second rigid ring 422. The third rigid ring 404 is arranged to guide the longitudinal elements of the second portion of the set of longitudinal elements 127, 128 at said fifth diameter at said second side of the cylindrical diameter adaptation section 164 such that they are freely movable in an axial direction of the elongated tubular body and are confined in a radial direction of the elongated tubular body between the third rigid ring 404 and the outer cylindrical member 430. The outer cylindrical member 430 is arranged at said seventh diameter from the longitudinal center axis of the elongated tubular body. The seventh diameter is larger than the fifth diameter.

The exemplary embodiment of the cylindrical diameter adaptation section shown in figures 8a and 8b further comprises a fourth rigid ring 426 that is arranged at said first side of the cylindrical diameter adaptation section 164 and is arranged at a sixth diameter from the longitudinal center axis of the elongated tubular body. The sixth diameter is larger than the fourth diameter. The fourth rigid ring 426 is arranged to confine longitudinal elements of said intermediate portion of said set of longitudinal elements 127, 128 in a radial direction of the elongated tubular body.

Figures 8a and 8b show that the exemplary embodiment of the cylindrical diameter adaptation section further comprises a third set of pins 406 that is arranged at a location between said first and second sides of the cylindrical diameter adaptation section. Both the third rigid ring 404 and the third set of pins 406 are arranged at the third diameter from the longitudinal center axis of the elongated tubular body. The third set of pins 406 is further arranged to support said second portion of the set of longitudinal elements at the fifth diameter from the longitudinal center axis. In figures 8a and 8b it can be seen that the pins of the third set of pins 406 extend from the third rigid ring 404 in an axial direction of the elongated tubular body towards the first side of the diameter adaptation section 164. The pins of the third set of pins 406 are spaced at equal distances in a circumferential direction of the elongated tubular body and are being arranged to interlock with the pins of the second set of pins 402, as was shown in figure 7c. The pins of the third set of pins 406 extend less far in an axial direction of the elongated tubular body towards the distal side of the diameter adaptation section 164 than the first rigid ring 422.

The cylindrical diameter adaptation section 164 shown in figures 8a and 8b further comprises a fourth set of pins 428 that is arranged at a location between said first and second sides of the cylindrical diameter adaptation section 164. Both the fourth rigid ring 426 and the fourth set of pins 428 are arranged at the sixth diameter from the longitudinal center axis of the elongated tubular body. At said location between said first and second sides of said cylindrical diameter adaptation section, longitudinal elements of said intermediate portion of the set of longitudinal elements 127, 128 are circumferentially arranged between pins of the fourth set of pins 428 at a diameter changing from the third diameter towards the fifth diameter at said second side of the cylindrical diameter adaptation section. In this way, the longitudinal elements of said intermediate portion are confined in a circumferential direction of the elongated tubular body at said location between said first and second sides of the cylindrical diameter adaptation section. In figures 8a and 8b it can be seen that the pins of the fourth set of pins 428 extend from the fourth rigid ring 426 in an axial direction of the elongated tubular body towards the second side of the diameter adaptation section 164. In figures 7a and 7b it can be seen that the pins of the fourth set of pins 428 are spaced at equal distances in a circumferential direction of the elongated tubular body. In this way, the pins of the fourth set of pins 428 guide parts of the longitudinal elements that are located in said second portion of the set of longitudinal elements such that they are freely movable in an axial direction of the elongated tubular body and are confined in a circumferential direction of the elongated tubular body between adjacent pins of the fourth set of pins 428.

In figure 8b it can most clearly be observed that the cylindrical diameter adaptation section in fact comprises a first set of passageways and a second set of passageways for allowing the longitudinal elements 128 to be moved freely in an axial direction of the elongated tubular body and to be confined in a circumferential direction of the elongated tubular body when passing from a second diameter at the first side of the diameter adaptation section 164 to a fifth, larger diameter at the second side of the diameter adaptation section 164.

Each passageway of the first set of passageways comprises a first set of boundaries. The second rigid ring 422 and the first rigid ring 400 are arranged relative to each other at respective first and second positions in an axial direction of the elongated tubular body to define respective first and second boundaries of said first set of boundaries. The first set of pins 420 and the second set of pins 402 are arranged relative to each other in a circumferential direction of the elongated tubular body and at least between the first and the second boundaries at coinciding positions in an axial direction of the elongated tubular body, to define respective third and fourth boundaries of the first set of boundaries.

Each passageway of the second set of passageways comprises a second set of boundaries. The third rigid ring 404 and the fourth rigid ring 426 are arranged relative to each other at respective third and fourth positions in an axial direction of the cylindrical diameter adaptation arrangement to define respective first and second boundaries of said second set of boundaries. The third set of pins 406 and the fourth set of pins 428 are arranged relative to each other in a circumferential direction of the cylindrical diameter adaptation arrangement and at least between said third and fourth boundaries at coinciding positions in an axial direction of the cylindrical diameter adaptation arrangement to define respective third and fourth boundaries of said second set of boundaries.

It will be clear to a person skilled in the art that the scope of the invention is not limited to the examples discussed in the foregoing, but that several amendments and modifications thereof are possible without deviating from the scope of the invention as defined in the attached claims. While the invention has been illustrated and described in detail in the figures and the description, such illustration and description are to be considered illustrative or exemplary only, and not restrictive. The present invention is not limited to the disclosed embodiments but comprises any combination of the disclosed embodiments that can come to an advantage.

Variations to the disclosed embodiments can be understood and effected by a person skilled in the art in practicing the claimed invention, from a study of the figures, the description and the attached claims. In the description and claims, the word "comprising" does not exclude other elements, and the indefinite article "a" or "an" does not exclude a plurality. In fact it is to be construed as meaning "at least one". The mere fact that certain features are recited in mutually different dependent claims does not indicate that a combination of these features cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope of the invention.