Bendable tube with improved elastic hinge

A tube like member having a first flexible portion comprising a first and a second circumferential slits, the first circumferential slit is arranged opposite to the second circumferential slit and comprises a first end and a second end, the second circumferential slit comprises a third end and a fourth end, wherein the first end and the third end are arranged such that a first bridge is provided between said first and second circumferential slits characterized in that the first flexible portion comprises a first longitudinal slit arranged longitudinally along the tube like member and a second longitudinal slit arranged longitudinally along the tube like member, wherein the first circumferential slit is communicatively connected to the first longitudinal slit, wherein the second circumferential slit is communicatively connected to the second longitudinal slit, the first longitudinal slit and second longitudinal slit being arranged to define longitudinal sides of the first bridge.

FIELD OF THE INVENTION

The invention relates to a bendable tube with an improved elastic hinge. The invention relates as well to a flexible tube with an improved flexible section. The invention also relates to a medical device such as an endoscope comprising a bendable tube with an improved elastic hinge and/or an improved flexible section.

BACKGROUND OF THE INVENTION

Bendable tubes with elastic hinges are well known for applications such as minimal invasive surgery or endoscopic examinations of a patient's internal structure such as the alimentary canals and airways, e.g., the esophagus, stomach, lungs, colon, uterus, urethra, kidney, and other organ systems, but they are also applicable for other purposes such as the inspection or reparation of mechanical or electronic installations at locations which are difficult to reach. In the further description the term endoscopic applications or endoscopic instrument will be used but the term must be interpreted as covering also other applications or instruments as explained above. US 2007/0049800 A1 discloses a method for forming an endoscope articulation joint having a number of hinge elements therein, wherein each hinge comprises a pair of opposing V-shaped slits in the outer wall that are separated by a pair of opposing flex points. The hinges are circumferentially arranged in an alternating 90 degree pattern to achieve articulation in two planes. The bending capacity of the hinges is constraint by the tension that the flex points can support. Also, the flex points will abut outwardly when the joint is bent. In this case, when the joint is introduced inside of another tube, the flex point abutments may touch the other tube thereby limiting and/or preventing the movement and/or the bending of the joint. Furthermore, the bendable tube may comprise a proximal end part, an intermediate part and a distal end part wherein the bendable 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 intermediate part into a related reflection of at least one part of the distal end part. In this way, a physician may control the distal end part by operating the proximal end part. However, the hinges providing the bending capacity may be sensitive to torque deviation and torque lag such that the rotation of the proximal end part may not correspond closely to the rotation of the distal end part. In this way, a reliable transmission of the rotation movement may be difficult. Therefore, there is a need for a bendable tube that allows improved transmission of rotation or torque from the proximal end part to the distal end part.

FIG. 1Ashows an exploded view of the three cylindrical members forming an instrument according to EP 2 273 911 B1. The instrument202is composed of three coaxial cylindrical members: an inner member204, an intermediate member206and an outer member208. The inner cylindrical member204is composed of a first rigid end part210, which is the part normally used at the location which is difficult to reach or inside the human body, a first flexible part212, an intermediate rigid part214, a second flexible part216and a second rigid end part218which 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 member208is in the same way composed of a first rigid part, a flexible part, an intermediate rigid part, a second flexible part and a second rigid part. The flexible parts are also called “hinges” in the art. The length of the different parts of the cylindrical members208and212are substantially the same so that when the cylindrical member204is inserted into the cylindrical member208, the different parts are positioned against each other. The intermediate cylindrical member206also has a first rigid end part240and a second rigid end part242which in the assembled condition are located between the corresponding rigid parts respectively of the two other cylindrical members.

The intermediate part of the intermediate cylindrical member206is formed by three or more separate longitudinal elements which can have different forms and shapes. After assembly of the three cylindrical members whereby the member204is inserted in the member206and the two combined members204,206are inserted into the member208, the end faces of the three members may be attached to each other at both ends so as to have one integral unit.

FIG. 1Bshows an unrolled view of a part of an alternative embodiment of the intermediate cylindrical member of the instrument ofFIG. 1A. The intermediate cylindrical member ofFIG. 1Bis formed by a number of longitudinal elements wherein each longitudinal element220is composed of three portions222,224and226, co-existing with the first flexible portion, the intermediate rigid portion and the second flexible portion respectively. In the portion224coinciding with the intermediate rigid portion, each pair of adjacent longitudinal elements220is touching each other in the tangential direction so that in fact only a narrow gap is present there between just sufficient to allow independent movement of each longitudinal element.

In the other two portions222and226each longitudinal element consists of a relatively small and flexible strip228,230as seen in circumferential direction, so that there is a substantial gap between each pair of adjacent strips, and each strip228,230is provided with a number of cams232, extending in circumferential direction and almost bridging completely the gap to the next strip.

SUMMARY OF THE INVENTION

It is an objective of the invention to provide a bendable tube with several improvements including an improved hinge which is more flexible and still very robust.

This is achieved by tube like members as claimed in the attached independent claims.

The tube like member according to the invention has an improved bendable portion because when the tube like member is bent along a bending axis, one of the circumferential slits will open while the other circumferential slit will close, thereby generating a moment over the intermediate part located between the circumferential slits, i.e., over the first bridge.

Furthermore, the tube like member according to the invention has a further improved bendable portion because when the tube like member is bent along the bending axis and one of the circumferential slits will open while the other circumferential slit will close, each of the inclined U-shaped intermediate sections of each of those circumferential slits will interlock thereby avoiding the creation of moments in other directions than the bending axis. In this way, a rotation when applied to one end of the tube like member will be closely transmitted to the other end of the tube like member.

It is another objective of the invention to provide a cylindrical member with several improvements including an improved flexible section.

The cylindrical member according to the invention has an improved flexible section because it comprises a rope equalizer structure between the thin flexible section and a thicker rigid one that compensates for displacement differences between two parallel sub-strips in the thin flexible section. In this way, the connection between the flexible section and the rigid one is improved.

The cylindrical member according to the invention has an improved flexible section because it comprises spacers made of thin slits cut off from the material. This allows a very efficient manufacturing process.

Advantageous embodiments of the invention are claimed in the rest of the dependent claims.

The invention also relates to an instrument for endoscopic applications comprising such a tube like member and/or cylindrical member.

DETAILED DESCRIPTION OF EMBODIMENTS

It is observed that the tube like member as explained hereinafter can be applied in any desired instrument which needs a bendable tube. However, it can advantageously be applied in medical instruments like the ones disclosed/described in WO2015/084157, WO2015/084174, WO2016/089202, PCT/NL2015/050798, PCT/NL2016/050471, PCT/NL2016/050522, NL2016900.

FIG. 2Ashows a schematic perspective view of a tube like member according to a first embodiment. The tube is made of a rigid material and has a hinge comprising one or more bendable portions.

The tube like member1has a bendable portion2comprising bending means6.

The bendable portion2of the tube like member1has a circumferential slit3and a circumferential slit5. The circumferential slit3has an end7and an end9. The circumferential slit3extends from the end7to the end9partly surrounding the tube like member1in a circumferential direction A. The circumferential slit5has an end11and an end13. The circumferential slit5extends from the end11to the end13partly surrounding the tube like member1in a circumferential direction B. The circumferential direction A and the circumferential direction B are opposite circumferential directions. The tube like member1has a central axis29which is an axis of symmetry. The end7and the end11are located on a circumference having a central point located on the central axis29and being located in a surface perpendicular to the central axis29. In the embodiment ofFIG. 2A, the circumferential slits3and5are also located on that circumference. The end7and the end11are arranged facing each other. Preferably, the end7and the end13are connected by a line which intersects central axis29. Moreover, preferably, the end11and the end9are connected by a line which intersects central axis29.

The tube like member1has a bridge15extending longitudinally between the end7and the end11. The bridge15connects a first portion8of tube like member1to a second portion10of tube like member1, which are located on opposite sides of the circumferential slit3and circumferential slit5.

The tube like member1has a longitudinal slit17which is oriented longitudinally along the tube like member1. The tube like member1also has a longitudinal slit19which is also oriented longitudinally along the tube like member1. The longitudinal slit17comprises a longitudinal edge21and a longitudinal edge23. The circumferential slit3is communicatively connected to the longitudinal slit17at the end7and at the longitudinal edge21. The longitudinal slit19comprises a longitudinal edge25and a longitudinal edge27. The circumferential slit5is communicatively connected to the longitudinal slit19at the longitudinal edge27and at the end11. The longitudinal edge23and the longitudinal edge25are facing each other in a longitudinal direction of the tube like member1such that they define longitudinal sides of the bridge15.

As will become more clear with reference toFIG. 6, the tube like member1can be bent by using the bridge15as a point of rotation and opening one of the slits3,5and closing the other one of the slits3,5. The bridge15is stress loaded and is designed such that the exerted stress on the bridge15when one of the slits3,5just closes remains within its stress tolerance above which the bridge15will be overstretched and deformed permanently. E.g., if a bendable portion2is designed to bend at a maximum angle of, for instance, 6° the bridge15may not rupture. Other maximum angles may be applied as well.

The embodiment ofFIG. 2Acan be extended by two further slits (not shown) identical to slits3,5but located at another portion of the tube like member1and shifted longitudinally relative to the slits3,5. Preferably, they are circumferentially rotated 90° about the axis29relative to the slits3,5such that all slits together form a hinge that provide the tube like member with the capacity to be easily bent in all directions. Moreover, more identical pairs of such slits can be provided in the tube like member1, each pair being longitudinally shifted and rotated about a predetermined angle, e.g. 90°, relative to an adjacent pair, thus providing the tube like member1with a section that can be bent about a desired angle.

FIG. 2Bshows a schematic perspective view of another tube like member embodiment31.

InFIG. 2B, same reference numbers as inFIG. 2Ahave been used to refer to common elements.

The circumferential slit3of tube like member31ofFIG. 2Bhas end7and an end39. The circumferential slit3extends from the end7to the end39partly surrounding the tube like member in a circumferential direction C. The circumferential slit5has end11and an end313. The circumferential slit5extends from the end11to the end313partly surrounding the tube like member31in a circumferential direction D. The circumferential direction C and the circumferential direction D are opposite circumferential directions. The tube like member31has a central axis29. The end7, the end39, the end11and the end313are located on a circumference having a center point350located on the central axis. The circumferential slits3,5are located on that circumference. The end39and the end313are arranged facing each other.

Apart from bridge15, the tube like member31has a bridge315extending longitudinally between the end39and the end313.

The tube like member31has a longitudinal slit317which is extending longitudinally along the tube like member31. The longitudinal slit317is located in the tube like member31opposite to the longitudinal slit21. The tube like member31also has a longitudinal slit319which is also extending longitudinally along the tube like member31. The longitudinal slit319is located opposite to the longitudinal slit19. The longitudinal slit317comprises a longitudinal edge321and a longitudinal edge323. The circumferential slit3is communicatively connected to the longitudinal slit317at the end39and at the longitudinal edge321. The longitudinal slit319comprises a longitudinal edge325and a longitudinal edge327. The circumferential slit5is communicatively connected to the longitudinal slit319at the end313and at the longitudinal edge327. The longitudinal edge323and the longitudinal edge325are facing each other in a longitudinal direction of the tube like member such that they define longitudinal sides of the bridge315.

As will become more clear with reference toFIG. 6, the tube like member31can be bent by using the bridge15and bridge315as points of rotation and opening one of the circumferential slits3,5and closing the other one of the circumferential slits3,5. The bridge15and bridge315are stress loaded and are designed such that the exerted stress on the bridge15and the bride315when one of the slits3,5just closes remains within their stress tolerance above which the bridge15and bridge315will be overstretched and deformed permanently. E.g., if a bendable portion2is designed to bend at a maximum angle of, for instance, 6° (or other value) the bridges15,315may not rupture.

The embodiment ofFIG. 2Bcan be extended by two further circumferential slits (not shown) identical to the pair of circumferential slits3,5with longitudinal slits identical to the longitudinal slits17,19,317,319and located at another portion of the tube like member31, shifted longitudinally relative to the circumferential slits3,5. Preferably, they are circumferentially rotated 90° about the axis29relative to the circumferential slits3,5such that all circumferential slits together form a hinge that provide the tube like member31with the capacity to be easily bent in all directions. Moreover, more pairs of such circumferential slits with longitudinal slits at their ends can be provided in the tube like member31, each pair being longitudinally shifted and rotated about a predetermined angle relative to an adjacent pair, thus providing the tube like member31with a section that can be bent about a desired angle in any desired direction.

FIG. 3shows a schematic perspective view of another tube like member embodiment41.

InFIG. 3, same reference numbers as inFIGS. 1A and 2Ahave been used to refer to common elements.

The tube like member41has a circumferential slit43and a circumferential slit45. The circumferential slit43has end7and an end49. The circumferential slit43extends from the end7to the end49partly surrounding the tube like member in a circumferential direction E. The slit45has end11and an end413. The circumferential slit45extends from the end11to the end413partly surrounding the tube like member in a circumferential direction F. The circumferential direction E and the circumferential direction F are opposite directions. The tube like member has a central axis29. The end7and the end11are located on a circumference400having a central point402on the central axis29and as its radius404a line extending from the end7to the central axis29and perpendicular to the central axis29. The end7and the end11are arranged facing each other. The bridge15extends longitudinally between the end7and the end11.

The tube like member41has the same longitudinal slit17and the same longitudinal slit19as the tube like member1. The longitudinal slit17and the longitudinal slit19are also located longitudinally along the tube like member41such that they define the sides of the bridge15.

The circumferential direction E forms an angle406with the circumference400. The circumferential direction F forms an angle408with the circumference400. The angles406and408are preferably between −10° and +10° degrees, more preferably between −8° and +8° degrees. Preferably, angles406and408have the same value.

FIG. 4shows a schematic perspective view of another embodiment of a tube like member51according to this invention.

InFIG. 4, the same reference numbers as inFIGS. 1 and 3have been used to refer to the same elements.

The tube like member51comprises circumferential slit43and circumferential slit45. The circumferential slit43has end7and end49. The circumferential slit43extends from the end7to the end49partly surrounding the tube like member in circumferential direction E. The slit45has end11and end413. The circumferential slit45extends from the end11to the end413partly surrounding the tube like member in circumferential direction F. The circumferential direction E and the circumferential direction F are opposite directions. The tube like member51has a central axis29. The end7and the end11are located on circumference400. The end7and the end11are arranged facing each other. The bridge15extends longitudinally between the end7and the end11.

Like tube like members1and41ofFIGS. 2A and 4, the tube like member51has longitudinal slit17and longitudinal slit19which are located longitudinally along the tube like member51such that they define the longitudinal sides of the bridge15.

The circumferential direction E forms angle406with the circumference400. The circumferential direction F forms angle408with the circumference400. The angles406and408are preferably between −10° and +10° degrees, more preferably between −8° and +8° degrees. They may have the same value.

The tube like member51has a circumferential slit543and a circumferential slit545. The circumferential slit543has an end57and an end549(not shown inFIG. 4). The circumferential slit543extends from the end57to the end549partly surrounding the tube like member in a circumferential direction. The circumferential slit545has an end511and an end513. The circumferential slit545extends from the end511to the end513partly surrounding the tube like member in a circumferential direction G. The circumferential direction F and the circumferential direction G are opposite directions. The end57and the end511are located at the circumference400. The end57and the end511are arranged facing each other. The tube like member51has a bridge515extending longitudinally between the end57and the end511.

The tube like member51has a longitudinal slit517and a longitudinal slit519which are extending longitudinally along the tube like member51such that they define longitudinal sides of the bridge515.

The circumferential direction H forms an angle506with the circumference400. The circumferential direction G forms an angle508with the circumference400. The angles506and508are preferably between −10° and +10° degrees, more preferably between −8° and +8° degrees. Preferably, angles506and508have the same value.

The longitudinal slit517comprises a longitudinal edge521and a longitudinal edge523. The longitudinal slit517is communicatively connected to the circumferential slit543at the end57and at the longitudinal edge521. The longitudinal slit519comprises a longitudinal edge525and a longitudinal edge527. The longitudinal slit519is communicatively connected to the circumferential slit545at the end511and at the longitudinal edge527. The longitudinal edge523and the longitudinal edge525are facing each other in a longitudinal direction of the tube like member51such that they define longitudinal sides of the bridge515.

Bridges15and515are, preferably, located on locations on tube like member51rotated 180° away from each other on the circumference400.

As shown inFIG. 4, circumferential slit43and circumferential slit545overlap circumferentially, i.e. a part of circumferential slit43is located adjacent to a part of circumferential slit545as seen in a longitudinal direction, however, without these parts engaging one another. A circumferential strip12is present between these parts of circumferential slit43and circumferential slit545.

As is also shown inFIG. 4, circumferential slit45and circumferential slit543overlap circumferentially, i.e. a part of circumferential slit45is located adjacent to a part of circumferential slit543as seen in a longitudinal direction, however, without these parts engaging one another. A circumferential strip14is present between these parts of circumferential slit45and circumferential slit543.

The way the hinge ofFIG. 4operates will become apparent fromFIG. 6and the associated description.

InFIG. 5, the same reference numbers as inFIGS. 2A, 2B, 3 and 4have been used to refer to the same elements. Basically,FIG. 5shows a tube like member61comprising the bendable portion2ofFIG. 4and an additional bendable portion2′. The description of the flexible portion2ofFIG. 4will not be repeated here. Only the additional flexible portion2′ will be described in detail here. The additional flexible portion2′ has a circumferential slit643and a circumferential slit645. The circumferential slit643has an end67and an end649. The circumferential slit643extends from the end67to the end649partly surrounding the tube like member in a circumferential direction I. The circumferential slit645has an end611and a end6413. The circumferential slit645extends from the end611to the end6413partly surrounding the tube like member in a circumferential direction J. The circumferential direction I and the circumferential direction J are opposite directions. The end67and the end611are located in a circumference600having a central point a point602located in the central axis29. The end67and the end611are arranged facing each other. The tube like member61has a bridge615extending longitudinally between the end67and the end611.

The tube like member61has a longitudinal slit617which is extending longitudinally along the tube like member61. The tube like member61also has a longitudinal slit619which is also extending longitudinally along the tube like member61. The longitudinal slit617comprises a longitudinal edge621and a longitudinal edge623. The circumferential slit643is communicatively connected to the longitudinal slit617at the end67and at the longitudinal edge621. The longitudinal slit619comprises a longitudinal edge625and a longitudinal edge627. The circumferential slit645is communicatively connected to the longitudinal slit619at the end611and at the longitudinal edge627. The longitudinal edge623and the longitudinal edge625are facing each other in a longitudinal direction of the tube like member such that they define longitudinal sides of the bridge615.

The circumferential direction I forms an angle606with the circumference600. The circumferential direction J forms an angle608with the circumference600. The angles606and608are preferably between −10° and +10° degrees, more preferably between −8° and +8° degrees. Preferably, angles606and608have the same value.

The tube like member61has a circumferential slit6543and a circumferential slit6545. The circumferential slit6543has an end657and an end6549. The circumferential slit6543extends from the end657to the end6549partly surrounding the tube like member in a circumferential direction K. In the same way, the circumferential slit6545has an end6511and another end which is not shown inFIG. 5. The circumferential slit6545extends from the end6511to its other end partly surrounding the tube like member61in a circumferential direction L. The circumferential direction K and the circumferential direction L are opposite directions. The end657, the end611, the end6511and the end67are located on the circumference600. The end657and the end6511are arranged facing each other. The tube like member61has a bridge6515extending longitudinally between the end657and the end6511.

The tube like member61has a longitudinal slit6517and a longitudinal slit6519which are located longitudinally along the tube like member61such that they define sides of the bridge6515.

The circumferential direction K forms an angle614with the circumference600. The circumferential direction L forms an angle612with the circumference600. The angles612and614are preferably between −10° and +10° degrees, more preferably between −8° and +8° degrees. Preferably, angles612and614have the same value.

The longitudinal slit6517comprises a longitudinal edge6521and a longitudinal edge6523. The circumferential slit6543is communicatively connected to longitudinal slit6517at the end657and at the longitudinal edge6521. The longitudinal slit6519comprises a longitudinal edge6525and a longitudinal edge6527. The circumferential slit6545is communicatively connected to the longitudinal slit6519at the end6511and at the longitudinal edge6527. The longitudinal edge6523and the longitudinal edge6525are facing each other in a longitudinal direction of the tube like member61such that they define longitudinal sides of the bridge6515.

Bridges615and6515are, preferably, located on locations on tube like member61rotated 180° away from each other on the circumference600. Moreover, the pair of bridges615,6515is rotated, preferably, about 90° circumferentially relative to the pair of bridges15,515.

As shown inFIG. 5, circumferential slit6543and circumferential slit645overlap circumferentially, i.e. a part of circumferential slit6543is located adjacent to a part of circumferential slit645as seen in a longitudinal direction, however, without these parts engaging one another. A circumferential strip18is present between these parts of circumferential slit6543and circumferential slit645.

As is also shown inFIG. 5, circumferential slit6545and circumferential slit643overlap circumferentially, i.e. a part of circumferential slit6545is located adjacent to a part of circumferential slit643as seen in a longitudinal direction, however, without these parts engaging one another. A circumferential strip20is present between these parts of circumferential slit6545and circumferential slit643.

FIG. 6shows a schematic perspective view of the tube like member ofFIG. 5in a bent position.

InFIG. 6, the same reference numbers as inFIGS. 2A-5have been used to refer to the same elements.

As can be seen inFIG. 6, when the tube like member61is bent along a bending axis (which will normally be the central axis29), for instance circumferential slits43,513may open while circumferential slits45,549may close. I.e., parts8and10may rotate about bridges15and515. The side of the bridge15defined by the longitudinal edge23, i.e., the side of the bridge15that is nearest to the circumferential slit43, will experience two opposite longitudinal forces away from each other, i.e. one directed towards part8and one directed towards part10, as indicated by arrows M and N, respectively. Under the effect of these opposite forces M and N, due to the elasticity of the bridge15, the bridge15at its longitudinal edge23will longitudinally expand in size. On the other hand, the side of the bridge15defined by the longitudinal edge25, i.e., the side of the bridge15that is nearest to the circumferential slit45, will experience two opposite longitudinal forces towards each other, i.e. one directed from part8towards the centre of bridge15and one directed from part10towards the centre of bridge15, as indicated with arrows O and P, respectively. Under the effect of these opposite forces O and P, due to the elasticity of the bridge15, the bridge15at its longitudinal edge25will shrink longitudinally. A similar effect occurs in bridge515.

Again, the bridges15,515should be designed such that when circumferential slits45and549are just closing during a bending action, the stress in bridge15remains within its stress tolerances such that no overstretching in bridges15,515is caused and the material is damaged irreversibly. E.g., if a bendable portion2is designed to bend at a maximum angle of, for instance, 6° (or other value) the bridge15may not rupture.

The bending portions formed by the rest of the circumferential slits and longitudinal slits ofFIG. 2A-2Bwork in a similar manner.

By providing the respective tube like members1,31,41,51,61with respective circumferential slits3,5,43,45,543,545,643,645,6543,6545and at least one respective longitudinal slit17,19,517,519,617,619,6517,6519which is communicatively connected to the respective circumferential slit3,5,43,45,543,545,643,645,6543,6545at one end, bending of the tube like member1,31,41,51,61by opening/closing of respective circumferential slits3,5,43,45,543,545,643,645,6543,6545is greatly facilitated and material stress at the ends of circumferential slits3,5,43,45,543,545,643,645,6543,6545where they touch respective bridges15,515,615,6515is reduced.

Moreover, torsional stiffness of the tube like members51,61is improved because of the circumferential strips12,14,18,20. I.e., as seen in a circumferential direction, two partially overlapping circumferential slits provide the tube like member51,61with the capacity to open along almost 180° when the tube like member is bent, without the tube like member51,61being provided with a circumferential slit extending along almost 180° which would weaken the construction and reduce the torsion stiffness. The width and length of the circumferential strips12,14,18,20are selected such that the tube like members51,61have a desired torsional stiffness, which also depends on the used material. Moreover, the width and thickness of the circumferential strips12,14,18,20is selected such that they have a certain flexibility but remain within their stress tolerance during maximal bending of the bendable portion2. E.g., if a bendable portion2is designed to bend at a maximum angle of, for instance, 6° (or other value) the circumferential strips12,14,18,20may not rupture.

FIGS. 7A-7Dshow another embodiment of a tube like member71. The tube like member71comprises several features indicated with references signs already used in above figures and which refer to the same features. Their explanation will not be repeated here.

Here, bendable portion2comprises the circumferential slit3which is communicatively connected to longitudinal slit17via a curved intermediate slit22. I.e. curved intermediate slit22has one end connected to end7of circumferential slit3and another end connected to an end of longitudinal slit17.

Similarly, the circumferential slit5is communicatively connected to longitudinal slit19via a curved intermediate slit24. I.e. curved intermediate slit24has one end connected to end11of circumferential slit5and another end connected to an end of longitudinal slit19. Longitudinal slits17and19define the bridge15.

As can best be seen inFIG. 7B, which shows a 3D view of the tube like member71, circumferential slit5, at its end313, is connected to a curved intermediate slit28which connects the circumferential slit5to an end of longitudinal slit319.FIG. 7Balso shows that circumferential slit3, at its end39, is connected to a curved intermediate slit26which connects circumferential slit3to an end of longitudinal slit317.

Longitudinal slits48and52define bridge315. Bridges15and315are, preferably, located in locations on the tube like member71which are circumferentially rotated about 180°.

Adjacent to circumferential slits3,5and shifted in the longitudinal direction is another pair of circumferential slits44,30of second bendable portion2′.

The circumferential slit44is communicatively connected to a longitudinal slit38via a curved intermediate slit42. I.e. curved intermediate slit42has one end connected to one end of circumferential slit44and another end connected to another end of longitudinal slit38.

Similarly, the circumferential slit30is communicatively connected to a longitudinal slit34via a curved intermediate slit32. I.e. curved intermediate slit34has one end connected to one end of circumferential slit30and another end connected to another end of longitudinal slit34. Longitudinal slits38and34define a bridge40. Bridge40is, preferably located on a location on tube like member71rotated about 90° circumferentially relative to bridge15.

As can best be seen inFIG. 7B, circumferential slit44, at its other end, is connected to a curved intermediate slit46which connects the circumferential slit44to an end of longitudinal slit48.FIG. 7Balso shows that circumferential slit30, at its other end, is connected to a curved intermediate slit54which connects circumferential slit30to an end of a longitudinal slit52.

Longitudinal slits317and319define a bridge50. Bridges40and50are, preferably, located in locations on the tube like member71which are circumferentially rotated about 180°.

Preferably, circumferential slits30,44are located on a same circumference.

By suitably selecting the geometry of the slits in tube like member71, the first bendable portion2with slits317,26,3,22,17,19,24,5,28,319can be located quite close to the second bendable portion2′ with slits38,42,44,46,48,52,54,30,32,34. Thus, large bending angles, up to 90°, can be achieved in small tube like members having a diameter of only a few mm, e.g. between 0.5 and 3 mm, and a length between 30 and 50 mm.

FIGS. 7C and 7Dshow different side views of tube like member71.

FIG. 8shows an embodiment of a tube like member81having alternative bridges72,74. Like reference numbers refer to the same elements as in other figures.FIG. 8shows a side view of the embodiment ofFIGS. 5 and 6with the alternative bridges. However, such alternative bridges can also be applied in the other embodiments of the invention, as explained with reference toFIG. 2A-7D.

FIG. 8shows how circumferential slit45ends in longitudinal slit19. However, here longitudinal slit19is communicatively connected to a longitudinal slit60via a curved slit62which may have a U-shape. Circumferential slit43ends in longitudinal slit17. However, here longitudinal slit17is communicatively connected to a longitudinal slit56via a curved slit58which may have a U-shape. Thus, a bridge72is present which has a mirrored S-shape. Of course, the shape may alternatively be equal to an S-shape. Alternatively, the shape may be a Z-shape or mirrored Z-shape.

FIG. 8also shows how circumferential slit645ends in longitudinal slit619. However, here longitudinal slit619is communicatively connected to a longitudinal slit68via a curved slit70which may have a U-shape. Circumferential slit643ends in longitudinal slit617. However, here longitudinal slit617is communicatively connected to a longitudinal slit64via a curved slit66which may have a U-shape. Thus, a bridge74is formed. The shape of the bridge74may have any one of the shapes discussed above with reference to bridge72.

It is observed that a tube like member having alternative bridges as shown inFIG. 8have a much larger bending angle than embodiments with single straight longitudinal bridges. A tube like member81with two such alternative bridges, located 180° rotated relative to each other, and having four circumferential slits43,45,643,645may be bent about a bending angle of up to 20°, at least up to 15°. So, the embodiment shown inFIG. 8may be bent about a bending angle of up to 40 This is about 2 to 3 times more than the embodiments ofFIGS. 2A to 7D.

FIG. 9shows an embodiment of a tube like member91wherein circumferential slit43comprises an intermediate section82and circumferential slit45comprises an intermediate section80. The other circumferential slits may comprise also intermediate sections. Like reference numbers refer to the same elements as in other figures.FIG. 9shows a side view of the embodiment ofFIGS. 5 and 6with the intermediate sections. However, such intermediate sections can also be applied in the other embodiments of the invention, as explained with reference toFIG. 2A-8. First, the structure of the intermediates sections will be explained. After that, it will follow an explanation of the function of the intermediates sections.

FIG. 9shows how circumferential slit45ends in longitudinal slit19. However, here circumferential slit45comprises the intermediate section80having a U-shape. The U-shape has two parallel long sides connected to one another by a base side. Both long sides are curved, preferably such that the curve shape of one long side coincides with a portion of a first circle. The second long side has a curve shape preferably coinciding with a portion of a second circle. The first and second circle preferably have a common center point. This is implemented as follows.

The intermediate section80is arranged between the longitudinal slit19and the end513. The intermediate section80is communicatively connected to the circumferential slit45via a first curved slit88. Furthermore, the intermediate section80is communicatively connected to the circumferential slit45via a second curved slit90. The first curved slit88may have the same or a different length than the second curved slit90. The first curved slit88may be shorter than the second curved slit90. The first curved slit88extends between a first end at the circumferential slit45and a second end. The second curved slit90extends between a first end at the circumferential slit45and a second end wherein the second end of the first curved slit88is communicatively connected to the second end of the second curved slit90via an intermediate slit92. The first curved slit88and the second curved slit90are curved towards the bridge15. I.e., the concave sides of the first and second curved slits are facing the longitudinal slit19of the bridge15.

The first curved slit88may extend between its first end and second end following the first circle wherein the first circle has as a center the center point of the bridge15and as a radius the length of a segment extending from the center point of the bridge15to the end of the first curved slit88. The first curved slit88may extend from its first end to its second end following the first circle in a first circular direction.

The second curved slit90may extend between its first end and second end following the second circle wherein the second circle has as a center the center point of the bridge15and as a radius the length of a segment extending from the center point of the bridge15to the end of the second curved slit90. The second curved slit90may extend from its first end to its second end following the second circle in the same first circular direction as the first curved slit88.

As observed, the circumferential slit43may comprise as well intermediate section82. The intermediate section82of the circumferential slit43may have also a U-shape. The U-shape has two parallel long sides connected to one another by a base side. Both long sides are curved, preferably such that the curved shape of one long side coincides with a portion of a third circle. The second long side has a curved shape preferably coinciding with a portion of a fourth circle. The third and fourth circle preferably have a common center point. This is implemented as follows.

The intermediate section82is communicatively connected to the circumferential slit43via the third curved slit98. Furthermore, the intermediate section82is communicatively connected to the circumferential slit43via a fourth curved slit100. The first curved slit extends between a first end at the slit43and a second end. The fourth curved slit100extends between a first end at the slit43and a second end wherein the second end of the third curved slit98is communicatively connected to the second end of the fourth curved slit100via an intermediate slit102. The third curved slit98and the fourth curved slit100are curved towards the bridge15.

The third curved slit98may extend between its first end and second end following the third circle having as a center the center point of the bridge15and as a radius the length of a segment extending from the center point of the bridge15to the first end. The third curved slit98may extend from its first end to its second end following the third circle in a second circular direction.

The fourth curved slit100may extend between its first end and its second end following the fourth circle having as a center the center point of the bridge15and as a radius the length of a segment extending from the center point of the bridge15to the first end of the fourth curved slit100. The fourth curved slit100may extend from its first end to its second end following the fourth circle in the same second circular direction as the third curved slit98.

The first circular direction in which the first and the second curved slits of the first intermediate section80extend and the second circular direction in which the third and the fourth curved slits of the second intermediate section82extend may be opposite circular directions. I.e., the first intermediate section80defines a U-shape enclosing a first lip extending in the first circular direction, and the second intermediate section82defines a U-shape enclosing a second pin extending in the second circular direction.

The first curved slit88of the first intermediate section80and the third curved slit98of the second intermediate section82may extend following the same circle C1but in opposite directions such that the first circle and the third circle are the same circles. I.e., the distance from the center point of the bridge15to the first end of the first curved slit88is equal to the distance from the center point of the bridge15to the first end of the third curved slit98.

The second curved slit90of the first intermediate section80and the fourth curved slit100of the second intermediate section82may extend following the same circle C2but in opposite directions such that the first circle and the third circle are the same circles. I.e., the distance from the center point of the bridge15to the first end of the second curved slit90is equal to the distance from the center point of the bridge15to the first end of the fourth curved slit100.

FIG. 9also shows how circumferential slits645and643, respectively, comprise intermediate sections94and96, respectively, having a U-shape. Each one of the intermediate sections94and96may be designed in accordance with any one of the arrangements discussed above with reference to intermediate sections80and82. Intermediate section94is associated with bridge615shown inFIG. 5, and intermediate section96is associated with bridge6515shown inFIG. 5. It will be evident to persons skilled in the art that, preferably, every bridge15,515,615,6515is associated with two intermediate sections arranged in a circular direction about their respective centers, like the ones shown and explained with reference to intermediate sections80,82.

It is observed that the pins80,82,94,96do not introduce any extra friction when the tube like member is bent about a hinge because they are curved and arranged on the circle of rotation as defined by the centers of the respective bridges15,515,615,6515. I.e., the intermediate sections80,82,94and96are shaped to form equally curved channels in which they can freely move.

It is observed that the tube like member having intermediate sections80,82,94, and96as shown inFIG. 9has an improved torque stiffness. The reason is as follows. In the above explained embodiments ofFIGS. 4-8, the tube like member has one or more circumferential strips, like12,18, which cause the tube like member not to have any totally continuous circumferential slit. Such circumferential strips absorb torque forces caused by users trying to rotate the tube like member until they deform permanently or even break. The maximum tension these circumferential strips can support determines the maximum allowable rotation force that can be applied by a user.

However, when a user tries to rotate a tube like member as shown in the embodiment ofFIG. 9, the pins80,82,94,96can move in the circumferential direction at a maximum distance of one curved slit88,90,98,100, and will then be blocked from any further circumferential movement. So, the elastic deformation of and tension in the circumferential strips12,18will never exceed a certain threshold as determined by the design of the intermediate sections80,82,94,96.

FIG. 10shows an embodiment of a tube like member101having alternative bridges. Like reference numbers refer to the same elements as in other figures.FIG. 10shows a side view of the embodiment ofFIG. 8with such alternative bridges. However, such alternative bridges can also be applied in the other embodiments of the invention, as explained with reference toFIGS. 2A-7D and 9A-9B.

FIG. 10shows circumferential slit45. The term inclined will be used here for indicating a direction forming an angle with the longitudinal direction.

Here the circumferential slit45ends in a first inclined slit110wherein first inclined slit110is communicatively connected to a second inclined slit112via a curved slit114. Together, the first inclined slit110, the second inclined slit112and curved slit114, preferably, have an U-shape in which the first and second inclined slits110,112form respective long, parallel sides of the U-shape and curved slit114forms its base side.

Circumferential slit43ends in a third inclined slit116wherein third inclined slit116is communicatively connected to a fourth inclined slit118via a curved slit120. Together, the third inclined slit116, the second inclined slit118and curved slit120, preferably, have a U-shape in which the third and fourth inclined slits116,118form respective long, parallel sides of the U-shape and curved slit120forms its base side.

Preferably, both U-shapes are arranged in a hooked orientation such that all first, second, third and fourth inclined slits are in parallel, and second inclined slit110is located on a center line of the U-shape defined by third inclined slit116, fourth inclined slit118and curved slit120, and fourth inclined slit118is located on a center line of the U-shape defined by first inclined slit110, second inclined slit112and curved slit114. Alternatively, the shape may be an inclined Z-shape or inclined mirrored Z-shape.

It is observed that a tube like member having alternative bridges as shown inFIG. 10may have a much larger bending angle than embodiments with longitudinal bridges. As will be clear, the tube like member101will have two such alternative bridges located 180° rotated relative to each other. Then, the tube like member can be bent about the centers of these two alternative bridges. The center of bridge122is indicated with reference sign124since total length of bridge122can be made much longer, preferably 2-10 times, than the length of bridges15,515,615,6515, tensions caused by bending the tube like member will be distributed over a much greater length of material.

One can conceive the S-shape of the embodiment ofFIG. 10as having three portions extending in, possibly different, directions having a certain inclination relative to both the circumferential direction and the longitudinal direction of the tube like member. When a user wishes to rotate the tube like member this S-shape therefore forms a blockage for further relative rotation of portions of the tube like member at opposite sides of the circumferential slits43,45once the inclined slits110,112,116,118are completely pressed together.

FIG. 11shows a 3D embodiment of a tube like member111having alternative bridges118,170identical to alternative bridge122ofFIG. 10and intermediate sections150,152,154,156identical to intermediate sections80,82ofFIG. 9. Like reference numbers refer to the same elements as in other figures and those elements will not be explained again as their functions are the same as those inFIG. 9. Everything that has been said in reference toFIGS. 9 and 10, can be applied toFIG. 11.

In all tube like members1,31,41,51,61,71,81,91,101,111all longitudinal slits and inclined slits may be straight slits with an equal width along their length. In tube like member71, the longitudinal slits may have the same width as the curved intermediate slits, i.e. may have a width deviation of less than 20% or less than 10%. In all tube like members1,31,41,51,61,71,81,91,101,111the circumferential slits may be wider, e.g. at maximum 2 times wider, in their center than at their ends. By using slits only, the tube like members can be made with a laser beam without leaving any loose material parts as a result of the laser cutting.

The tube like members1,31,41,51,61,71,81,91,101,111may be a cylindrical tube. The tube like member may, however, have another suitable cross section. E.g., the hollow tube may have an oval or elliptical or rectangular cross section. The tube like member is hollow, at least at the location where the hinge is provided. The tube like members1,31,41,51,61,71,81,91,101,111comprise an outer wall. The bendable portion is formed in the outer wall.

The tube like members1,31,41,51,61,71,81,91,101,111may be formed using a suitable biocompatible polymeric material, such as polyurethane, polyethylene, polypropylene or other biocompatible polymers. The tube like member may be made of any other suitable material and/or in any other suitable way. Other suitable materials may be stainless steel, cobalt-chromium, shape memory alloy, such as Nitinol®, plastic, polymer, composites or other curable material.

The circumferential and longitudinal slits may be made by means of any known material removal technique such as photochemical etching, deep pressing, chipping techniques, however, preferably by laser cutting. All slits are open both to the outside and inside of the tube like member.

The circumferential slits may have any suitable length, as required by the envisaged application. The circumferential slits in the same tube like member may have the same length or different lengths. The circumferential slits have a length of less than half of the external circumference of the tube like member. Preferably, their length is between 25 and 50%, more preferably between 30 and 45%, and most preferably between 35 and 40% of the external circumference of the tube like member. The circumferential slits may have any suitable width. The circumferential slits of the same tube like member may have the same width or different widths. The circumferential slits may be narrower next to their ending points and wider in their central part.

The longitudinal slits and the inclined slits may have also any suitable length and width, as required by the envisaged application. The longitudinal slits and the inclined slits of a tube like member may have the same or different lengths and/or widths.

Variations in bending and torsion fidelity along the length of the tube like member can be achieved by varying the durometer rating of materials that are used to mold the different segments. Also, the flexibility of the tube like member may be varied by changing the dimensions and locations of the circumferential slits, longitudinal slits and inclined slits and/or by varying the angles between the circumferential slits and the radial circumference.

FIG. 12shows a schematic view of a rope equalizer structure to explain its principle way of working. The rope equalizer structure500ofFIG. 12comprises an origin of rotation point502, a first rotation point504and a second rotation point506wherein the origin of rotation point502is attached to a first wire508wherein the first wire508extends from the origin of rotation point502in a direction R, the first rotation point504is attached to a second wire510wherein the second wire510extends from the first rotation point504in a direction S, and the second rotation point506is attached to a third wire512wherein the third wire512extends from the second rotation point506in a direction S, wherein the direction R and the direction S are opposite directions. The origin of rotation point502, the first rotation point504and the second rotation point506are connected by a rigid bar514wherein the rigid bar514extends from the first rotation point504to the second rotation point506in a direction T wherein the direction T and the direction R are perpendicular directions and wherein the origin of rotation point502is the middle point of the rigid bar514.

The second wire510and the third wire512can move in the direction R and the direction S, respectively. The rigid bar514can rotate about the origin of rotation point502. In this way, when there is a difference between a displacement movement of the second wire510and a displacement movement of the third wire512, the rigid bar514will rotate about the origin of rotation point502to compensate for the displacement movement difference between the second wire510and the third wire512. Displacement forces as exerted on the second wire510and third wire512are added in first wire508.

InFIG. 12it can be seen that, when the second wire510is displaced in the direction S along a distance l1and the third wire512is displaced in the same direction S along a distance l2wherein l2−l1=Δl, then the rigid bar514rotates about the origin of rotation point502to a new position (shown with discontinuous lines inFIG. 12) in order to compensate for the difference in displacement Δl between the second wire510and the third wire512.

FIG. 13shows an unrolled view of a part of an intermediate cylindrical member of an instrument according to the invention in which the principle of such a rope equalizer is used. This intermediate cylindrical member is part of a larger, tube like instrument, e.g. a surgical instrument as described and disclosed in EP 2 273 911 B1.FIGS. 1A and 1Bsummarize that prior art and have been described above.

In some embodiments of the instrument shown inFIG. 1B, there is a need to make the small and flexible strips228,230even more flexible. One could do so by splitting these small and flexible strips228,230in the longitudinal direction such as to render two (or more) sub-strips.

In another embodiments of the instrument shown inFIG. 1B, there is a need to make the small and flexible strips228,230stronger, such that they don't break easily, but without losing flexibility. One could do so by adding an extra small and flexible strip to each of these small and flexible strips228,230in the longitudinal direction such as to render two (or more) sub-strips.

The two sub-strips have preferably a same width in the tangential direction of the instrument. These two sub-strips are then again attached to the portion224which has a larger width in the tangential direction of the instrument. In the actual instrument, the tangential cross-section of the portion224and the two sub-strips has the shape of a circle portion. As one may understand, during operation of the instrument as described in EP 2 273 911 B1, the instrument is bent about the centre longitudinal axis of the instrument at the location of the two flexible sub-strips. In most cases these two sub-strips will not bend symmetrically causing mutual longitudinal movement of the two sub-strips relative to one another. This causes different displacements of the two sub-strips potentially resulting in a breaking off of one of them from portion224. In view of this, there is a need to further increase the flexibility or further increase the strength of portions228,230while at the same time avoiding this effect.

The intermediate cylindrical member440ofFIG. 13has a first rigid end part260and a second end rigid part262. The intermediate cylindrical member440is formed by a number of longitudinal elements242wherein each longitudinal element242is composed of three portions244,246and248, and two connection sections250,454. The intermediate cylindrical member440preferably comprises three or more longitudinal elements242. First portion244is attached to second portion246through a connection section250. The second portion246is attached to the third portion248through a connection section454. In the second portion246coinciding with an intermediate rigid portion of the instrument (cf.FIG. 1A), each pair of adjacent longitudinal elements242may touch each other in the tangential direction so that in fact only a narrow gap is present there between just sufficient to allow independent longitudinal movement of each longitudinal element242.

In the other two portions244and248each longitudinal element consists of a relatively small and flexible strip254,256as seen in the circumferential direction, so that there is a substantial gap between each pair of adjacent strips. The strip254, has a longitudinal slit258extending from the first rigid part260to the first connection section250. Thus, strip254has two parallel sub-strips266,270. The slit258, which preferably results from laser cutting, is so small that, in use, the sub-strips266,270may often touch one another. Similarly, the strip256has a longitudinal slit264extending from the second rigid part262to the connection section252. Thus, strip256has two parallel sub-strips268,272. The slit264, which preferably results from laser cutting, is so small that, in use, the sub-strips268,272may often touch one another. The width of the sub-strips266,270and sub-strips268,272may be the same.

Each strip254,256may be provided with a number of cams (not shown inFIG. 13), extending in the circumferential direction of the instrument and almost bridging completely the gap to the next, adjacent strip, such that they function as spacers. The cams may have any shape. Further details of such cams, or spacers, may be derived from EP 2 273 911 B1, but also from WO2017082720.

AlthoughFIG. 13shows an embodiment with two symmetric portions244and248connected to portion246through connection sections250,454, respectively, the intermediate cylindrical member440may have only one portion248connected to portion246through second connection section454.

Intermediate cylindrical member440comprises also connection sections452,284wherein the connection section284connects portion246to portion244and the connection section452connects portion246to portion248. Connection section454will be explained in detail.

Intermediate cylindrical member440comprises a bridge414attaching portion246to connection section454. Bridge414is defined by two longitudinal slits410,412which extend longitudinally in at least one of portion246and connection section454.

The connection section454comprises an opening476which has a half moon shape and is surrounded by curved sub-strips490,492. The convex side of the opening476is facing the portion248and the longitudinal slit264is communicatively connected to the opening476at the middle part of its convex side. The opening476is further delimited by a straight side perpendicular to the longitudinal direction and which is facing the concave side of the opening476. The connection section454comprises also slits402and404which extend longitudinally respectively from each end of the straight side of the opening476in the direction of the portion246and are surrounded at one side respectively by curved sub-strips490,492. The connection section454comprises further circumferential slits406and408, which extend in a circumferential direction, and both longitudinal slits410and412, which extend longitudinally. The circumferential slits406,408are respectively communicatively connected at one of their ends to longitudinal slits410,412and at the other one of their ends to the gap that is present between adjacent portions246. When the longitudinal slits410,412extend both in portion246and in connection section454, circumferential slits406,408end, preferably, in a middle part thereof, respectively.

The sides of the slits410and412define the borders of bridge414extending in the longitudinal direction. The distance between slits410and412is smaller than the distance between slits402and404. Furthermore, the slits410,412are partially parallel in a longitudinal direction with the slits402and404such as to define bridges416and418. I.e., slit402and slit410define the sides of bridge416while slit404and slit412define the sides of bridge418.

The arrangement ofFIG. 13also acts as a rope equalizer like the one shown inFIG. 12. By providing the arrangement ofFIG. 13with bridge414, the flexibility of the attachment of portion246to connection section454in the tangential direction of the instrument is improved. The center of the bridge414inFIG. 13acts as the origin of rotation point502ofFIG. 12, wherein the first rotation point504is located in the straight portion that is connected to curved sub-strip490and surrounds the slit402, and wherein the second rotation point506is located in the straight portion that is connected to curved sub-strip492and surrounds the slit402such that when there is a difference in a displacement movement between sub-strip268and sub-strip272, the rope equalizer structure in the connection section454rotates about the center of the bridge414and compensates the difference in displacement between sub-strip268and sub-strip272. Preferably, the first rotation point504and the second rotation point506are located in said straight portions as closed to the center of the bridge414as possible.

The connection section452works in a similar manner as has been explained with reference to connection section454. Furthermore, the intermediate cylindrical member440may have similar connection sections250,284between the portion246and the portion242.

FIG. 14shows a 3D view of one embodiment according toFIG. 13. Like reference numbers refer to the same elements as inFIG. 13. Everything that has been explained in relation toFIG. 13applies toFIG. 14. The intermediate cylindrical member440comprises 8 connection sections454as the ones described with relation toFIG. 13.FIG. 14also shows M-shaped spacers as are explained in detail in WO2017/082720.

FIG. 15shows an unfolded view of a part of an intermediate cylindrical member540comprising spacers554,556,574,576according to another embodiment of the invention. The spacers ofFIG. 15have the same function as the spacers ofFIG. 14. However, the spacers ofFIG. 15differ from the spacers ofFIG. 14both in shape and in the way they are cut into the intermediate cylindrical member540. As can be seen inFIG. 15, the spacers554,556,574,576have a U-shape wherein one of the legs of the U is shorter than the other, while the spacers ofFIG. 14have an M-shape. Also, the spacers ofFIG. 15are formed in the intermediate cylindrical member540by cutting thin slits in the material. In this way, the manufacturing process is very efficient as any loose material after cutting the U-shape will disappear by itself.

The intermediate cylindrical element540ofFIG. 16comprises longitudinal elements542,544,678,680. The intermediate cylindrical element540further comprises longitudinal slits546,548,550,552. The longitudinal slit546and the longitudinal slit550define the sides of the longitudinal element542. The longitudinal slit548and the longitudinal slit552define the sides of the longitudinal element544. The longitudinal slit548defines one side of the longitudinal element678.

The longitudinal elements542,678are separated by spacers554,556. The spacer554is defined by a circumferential slit558, a longitudinal slit560and a circumferential slit562wherein the circumferential slit558extends in a circumferential direction X from the longitudinal slit550towards the longitudinal element678and wherein the circumferential slit558is communicatively connected to the longitudinal slit550. The longitudinal slit560is communicatively connected to the circumferential slit558and extends from the circumferential slit558in a longitudinal direction Y. The circumferential slit562is communicatively connected to the longitudinal slit560and extends from the longitudinal slit560towards the second longitudinal slit550in a circumferential direction opposite to the circumferential direction X. The circumferential slit562is not connected to the second longitudinal slit550such that a bridge564is defined between the end of the circumferential slit562and the second longitudinal slit550. The distance between the second longitudinal slit550and the longitudinal slit560of the spacer554is preferably larger than the distance between that longitudinal slit560and the first longitudinal slit548that defines the adjacent longitudinal element544. The distance between the second longitudinal slit550and the longitudinal slit560of the spacer544may be at least 1.5 times the distance between that longitudinal slit560and the first longitudinal slit548that defines the adjacent longitudinal element544.

The circumferential slit558of the spacer may be 1.5 times longer than the circumferential slit562. The longitudinal slit560may be 0.5-10 times larger than the circumferential slit558.

The intermediate cylindrical element540may have any number of spacers.

FIG. 16shows an unrolled view of a part of an intermediate cylindrical member640comprising alternative spacers644,646,674,676according to another embodiment of the invention. Like reference numbers refer to the same elements as inFIG. 15.

The main difference between the spacers of the embodiment ofFIG. 15and the alternative spacers of the embodiment ofFIG. 16is that the alternative spacers of the embodiment ofFIG. 17are further defined by an inverted U-shape slit680wherein the inverted U-shape slit680is communicatively connected to the circumferential slit562at the end of one of the legs of the inverted U-shape slit680. The inverted U-shape slit680is oriented such that the end of the other leg of the inverted U-shape is facing the longitudinal slit560and the convex side of the inverted U-shape is facing the second longitudinal slit550.

FIG. 17shows a 3D view of the embodiment according toFIG. 16. Like reference numbers refer to the same elements as inFIGS. 15-16. Everything that has been explained in relation toFIG. 16applies toFIG. 17. The intermediate cylindrical member640comprises 8 longitudinal elements separated by spacers as the ones described with relation toFIG. 16.

In all intermediate cylindrical members242,440,540,640all longitudinal slits may be straight slits with an equal width along their length. In intermediate cylindrical member640, the longitudinal slits and the circumferential slits may have the same width as the U-shape slits, i.e. may have a width deviation of less than 20% or less than 10%. In intermediate cylindrical members242,440the circumferential slits may be wider, e.g. at maximum 2 times wider, in one of their ends than at their other end. By using slits only, the intermediate cylindrical members242,440,540,640can be made with a laser beam without leaving any loose material parts as a result of the laser cutting.

The intermediate cylindrical members242,440,540,640may be a cylindrical member. The intermediate cylindrical member may, however, have another suitable cross section. E.g., the intermediate cylindrical member may have an oval or elliptical or rectangular cross section. The intermediate cylindrical member may completely or partially hollow. The intermediate cylindrical members242,440,540,640comprise an outer wall.

The intermediate cylindrical members242,440,540,640may be formed using a suitable biocompatible polymeric material, such as polyurethane, polyethylene, polypropylene or other biocompatible polymers. The intermediate cylindrical members242,440,540,640may be made of any other suitable material and/or in any other suitable way. Other suitable materials may be stainless steel, cobalt-chromium, shape memory alloy, such as Nitinol®, plastic, polymer, composites or other curable material.

The circumferential, longitudinal slits and the U-shaped slits may be made by means of any known material removal technique such as photochemical etching, deep pressing, chipping techniques, however, preferably by laser cutting. All slits are open both to the outside and inside of the intermediate cylindrical members.

The longitudinal slits, the circumferential slits and the U-shaped slits may have any suitable length and width, as required by the envisaged application. The longitudinal slits, the circumferential slits and the U-shaped slits of an intermediate cylindrical member may have the same or different lengths and/or widths.

The examples and embodiments described herein serve to illustrate rather than to limit the invention. The person skilled in the art will be able to design alternative embodiments without departing from the scope of the claims. Reference signs placed in parentheses in the claims shall not be interpreted to limit the scope of the claims. Items described as separate entities in the claims or the description may be implemented as a single or multiple hardware items combining the features of the items described.

It is to be understood that the invention is limited by the annexed claims and its technical equivalents only. In this document and in its claims, the verb “to comprise” and its conjugations are used in their non-limiting sense to mean that items following the word are included, without excluding items not specifically mentioned. In addition, reference to an element by the indefinite article “a” or “an” does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements. The indefinite article “a” or “an” thus usually means “at least one”.