APPARATUS FOR KNOTTING DRAWSTRINGS OF MEDICAL DEVICES OR MEDICAL DEVICES CONTAINING DRUGS

Abstract

The present invention provides an apparatus for making knots in a flexible element attached to a medical device and methods using said apparatus.

Claims

1. An apparatus that receives a medical device which apparatus makes a knot in a flexible element attached to the medical device, the apparatus comprising: (i) a guiding element (ABC) that guides the flexible element, wherein the guiding element (ABC) forms a geometrical volume that is dimensioned to contain the medical device; (ii) a first fixating element that fixes the medical device at a first position outside the geometrical volume formed by the guiding element (ABC); (iii) a second fixating element that fixes the medical device (1) at a second position entirely within the geometrical volume formed by the guiding element (ABC); and (iv) a tensioning element located outside the guiding element (ABC), wherein the tensioning element is configured to apply tension to the flexible element; wherein the guiding element (ABC), first fixating element and second fixating element are disposed in a mutually fixed positional relation, and are configured to spin as a group constrained around a single axis of rotation positioned within the guiding element (ABC), relative to the tensioning element, and the tensioning element is disposed in fixed positional relation to the single axis of rotation.

2. The apparatus according to claim 1, wherein the guiding element (ABC) comprises guiding element parts a, b and c.

3. The apparatus according to claim 1, wherein the guiding element (ABC) comprises guiding element parts a and bc.

4. The apparatus according to claim 1, wherein the guiding element (ABC) comprises guiding element part abc.

5. The apparatus according to claim 1, wherein the medical device is a contraceptive intrauterine device (IUD), an intrauterine system, a tampon or a hearing aid.

6. The apparatus according to claim 1, wherein the medical device is disposed in a flat horizontal orientation or is cylindrical in shape or comprises a T-shape or comprises a bullet shape.

7. The apparatus according to claim 1, wherein the guiding element comprises at least 2 separate guiding element parts (a+be or a+b+c) and at least one of the guiding element parts (a) is located closest to the second position corresponding to an end of the medical device onto which the flexible element is fixed.

8. The apparatus according to claim 7, wherein a diameter or a location of at least guiding element part (a) with respect to the second position defines the length of the flexible element between the knot and the medical device.

9. The apparatus according to claim 1, further comprising a translational displacer that translates the medical device from the first position to the second position by lifting the medical device over or under and inside one or more closed loops formed in the flexible element by the apparatus.

10. The apparatus according to claim 9, wherein the translational displacer is a robotic arm.

11. The apparatus according to claim 1, wherein the guiding element (ABC) is configured for retraction into or lifting away from the apparatus in order to release the flexible element.

12. The apparatus according to claim 1, wherein the flexible element comprises strands, the strands being directed towards or away from the guiding element (ABC) by the tensioning element.

13. The apparatus according to claim 1, wherein the flexible element is a spindle or bobbin.

14. The apparatus according to claim 1, wherein at least some movement or rotation of the apparatus is automated.

15. The apparatus according to claim 1, wherein the flexible element is capable of maintaining tension.

16. The apparatus according to claim 1, wherein the tensioning element comprises one or more of a coil, spring, weight, suction device, or tensioning reel.

17. A combination comprising the apparatus of claim 1 and a medical device, wherein the apparatus receives the medical device and makes a knot in the flexible element attached to the medical device.

18. The combination according to claim 17, wherein the medical device is insertable into an external body orifice.

19. The combination according to claim 17, wherein the medical device contains a drug.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] FIG. 1A: Schematic representation of the knot making apparatus and the method performed thereby.

[0045] FIG. 1B. Alternative configuration of guiding means of FIG. 1A, comprising one separate guiding means part (a).

[0046] FIG. 1C. Alternative configuration of guiding means of FIG. 1A, comprising two separate guiding means parts (a) and (bc).

[0047] FIG. 2. Block diagram representation of the knot making apparatus (20), an optional robotic arm (12) for automation and for translation of the device (1), and an optional tensioning means (40).

DETAILED DESCRIPTION OF THE INVENTION

[0048] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as is commonly understood by one of skill in the art. All publications referenced herein are incorporated by reference thereto.

[0049] The articles a and an are used herein to refer to one or to more than one, i.e. to at least one of the grammatical object of the article.

[0050] Throughout this application, the term about is used to indicate that a value includes the standard deviation of error for the device or method being employed to determine the value.

[0051] The recitation of numerical ranges by endpoints includes all integer numbers and, where appropriate, fractions subsumed within that range (e.g. 1 to 5 can include 1, 2, 3, 4 when referring to, for example, a number of elements). The recitation of end points also includes the end point values themselves (e.g. from 1.0 to 5.0 includes both 1.0 and 5.0)

[0052] Throughout this application, the terms device or devices are used to denote any object that is inserted into an external body orifice. The term may be proceeded by medical. Among these devices we consider, but do not limit ourselves to: intra-uterine devices (IUD) or intra-uterine systems (IUS), tampons, hearing aids. As far as IUD and IUS are concerned, the practical use (e.g. contraceptive, medicinal), optional additional components (e.g. antibiotics, antiseptics, hormones) and material (e.g. copper, silver, polyethylene) are not deemed critical for this invention. The medical device has a defined three-dimensional shape. The shape may be constant in a non-deployed (non-inserted) state. The medical device may have a flat shape. The medical device may have a bullet shape. The medical device may be cylindrical in shape. The medical device may comprise a T-shape. The medical device having the defined three-dimensional shape may be contained, preferably entirely, by the geometric shape or volume of the guiding means.

[0053] Throughout this application, the terms flexible element or flexible elements are used to denote any flexible object that can be knotted. Among these elements we consider, but do not limit ourselves to: wires, cables, strings, ribbons, hairs, cords, chains, bands. Furthermore, the type of material in which these elements are fabricated is not deemed critical for this invention. This element can consist of one or multiple strands. The flexible element may be present on e.g. a spindle or bobbin or be already cut beforehand. Said spindle or bobbin should be capable of retaining a certain amount of tension on the element.

[0054] Throughout this application, the term translating means is used to denote any part of the apparatus that can be displaced in a translational fashion. The term translating means may be used interchangeably with translating mechanism. Among these types of movement we consider, but do not limit ourselves to: sliding, rolling, dropping. Furthermore, the type of material in which these translating means are fabricated is not deemed critical for this invention. The translational movement is considered a relative movement between different parts of the apparatus, and not referred to a fixed point of reference.

[0055] Throughout this application, the term rotation is used to denote any relative rotational movement between different parts of the apparatus, and not referred to a fixed attachment. Rotation may be around a (single) point of rotation. Rotation may be around an (single) axis of rotation. Rotation may be around a (single) revolute joint. Rotation may be only one degree of freedom rotation. Among these types of movement we consider, but do not limit ourselves to: turning, twisting, spinning. The guiding means (ABC), first fixating means and second fixating means may be disposed in a mutually fixed positional relation, and may be configured to rotate as a group constrained around the single axis of rotation positioned within the guiding means (ABC).

[0056] Throughout this application, the term guiding means is used to denote any part of the apparatus that guides the flexible element along a certain path. The term guiding means may be used interchangeably with guiding element. The guiding means can form one separate guiding means part that is a geometric shape or volume allowing the making of a loop, or can comprise several individual guiding means parts that together form a geometric shape or volume allowing the making of a loop. The geometric shape or volume is dimensioned to contain the medical device (1). The geometric shape or volume is dimensioned to contain entirely the medical device (1). The medical device may be disposed disposed in any orientation. The medical device that is an IUD may be disposed in a flat horizontal orientation. Among these types of individual guiding means parts we consider, but do not limit ourselves to: bolts, hooks, clamps, arches, staples, holes, trenches, clasps and elements built therefrom. Furthermore, the type of material in which these individual guiding means parts are fabricated is not deemed critical for this invention. The term individual guiding means part may be used interchangeably with individual guiding element part.

[0057] Throughout this application, the term tensioning means is used to denote any part of the apparatus that keeps the flexible element under tension, for instance, constant tension. The term tensioning means may be used interchangeably with tensioning element. Among these types of tensioning means we consider, but do not limit ourselves to include: one or more coils, springs, weights, suction devices, tensioning reel. Furthermore, the type of material in which these tensioning means are fabricated is not deemed critical for this invention.

[0058] Throughout this application, the term restraining means is used to denote any part of the apparatus that keeps the translating means restrained to a certain position on the apparatus. The term restraining means may be used interchangeably with restraining element. Among these types of restraining means we consider, but do not limit ourselves to: studs, pins, hooks, bolts, clamps, clasps. Furthermore, the type of material in which these restraining means are fabricated is not deemed critical for this invention.

[0059] Throughout this application, the term releasing action is used to denote any action that releases the flexible element from the guiding means. Among these types of releasing steps we consider, but do not limit ourselves to: lifting, retracting, sliding off.

[0060] Throughout this application, the term fixating means is used to denote any part of the apparatus that keeps the device fixed to a certain position. The term fixating means may be used interchangeably with fixating element. Among these types of fixating means we consider, but do not limit ourselves to: studs, pins, hooks, bolts, clamps, clasps, adhesive tape, magnets. Furthermore, the type of material in which these fixating means are fabricated is not deemed critical for this invention.

[0061] In the following detailed description of the invention, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration only of specific embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present invention. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims.

[0062] In one embodiment, the apparatus (20) comprises two settings defined by a fixating means (10 and 10), to which a device (1) is secured, while part of the apparatus (20) provides a rotational movement. The device is connected to a flexible element (2), which is to be knotted. The end of the flexible element (2) (all ends in case of multiple strands) is attached to a tensioning means (40), which maintains tension on the string. The apparatus (20) contains a guiding means (ABC) surrounding the fixating means (10). Said guiding means (ABC) is placed in such a way that the surface area defined by the guiding means (ABC) is large enough to allow mechanical threading of the device (1) through said guiding means (ABC).

[0063] In one embodiment of the invention, guiding means (ABC) comprises at least 1 individual guiding means parts (e.g. (abc) in FIG. 1B or (a), (bc) in FIG. 1C; or (a), (b), (c) in FIG. 1A).

[0064] In one embodiment of the invention, guiding means (ABC) comprises at least 2 individual guiding means parts (e.g. (a), (bc) in FIG. 1C; or (a), (b), (c) in FIG. 1A).

[0065] In one embodiment of the invention, guiding means (ABC) comprises at least 3 individual guiding means parts (e.g. (a), (b) and (c) in FIG. 1A).

[0066] In a preferred embodiment of the invention, guiding means (ABC) comprises 3 individual guiding means parts (a), (b) and (c).

[0067] In an alternative embodiment, guiding means (ABC) forms one continuous guiding means, which can be any geometrical shape allowing for the making of a loose loop around device (1). In other words, the guiding means (ABC) comprises 1 individual guiding means part (abc) which can be any geometrical shape allowing for the making of a loose loop around device (1).

[0068] In an alternative embodiment, guiding means (ABC) comprises 2 individual guiding means parts (a) and (bc), which together can form any geometrical shape allowing for the making of a loose loop around device (1).

[0069] In an alternative embodiment, guiding means (ABC) comprises 3 individual guiding means parts (a), (b) and (c), which together can form any geometrical shape allowing for the making of a loose loop around device (1).

[0070] If applicable, the diameter of individual guiding means part (a) and its position with respect to device (1) can define the position of the knot vis vis the device (1) and can hence be optimized according to the preferred position of said knot for a certain application (i.e. will be dependent on the type of device).

[0071] The fixating means (10) ensure optimal placement of the device (1) and can serve to fine-tune the position of the knot vis vis the device. Again, said position can help in optimizing said position of the knot for a certain application (i.e. will be dependent on the type of device).

[0072] During the first step (labeled as step 1 in FIG. 1A), the device (1), to which the element is attached (2), is mounted on a first fixating means (10). The first fixating means fixes the device (1) at a first position (10) outside the geometrical volume formed by the guiding means (ABC). The starting position of the device (1) is outside the area defined by the guiding means (ABC), and restrained as such by the first fixating means (10). Indicated is a point of rotation (5)

[0073] In a second step (labeled as step 2 in FIG. 1A), the apparatus (20) effectuates one or more rotations, creating one or more loops of the flexible element (2). The constant tension of the flexible element (2) provided by the tensioning means (40) ensures that the loops remain tightened around the guiding means (ABC).

[0074] In a third step (labeled as step 3 in FIG. 1A), the device (1) is released from the first fixating means (10). The device (1) is subsequently attached to the second fixating means (10) from above the loops. The second fixating means that fixes the device (1) at a second position (10) entirely within the geometrical volume formed by the guiding means (ABC). This threading action effectively creates the knot (3).

[0075] In a fourth step (labeled as step 4 in FIG. 1A), the flexible element (2) is released from the individual guiding means parts (b) and (c) (or (bc) when combined in one individual guiding means parts (a)) by a releasing action. This action effectively tightens the knot (3) around individual guiding means parts (a) by the tension provided by the tensioning means (40). The position of the device (1) vis--vis the individual guiding means parts (a) will define the length of string between the device and the knot.

[0076] In a fifth step (labeled as step 5 in FIG. 1A), the flexible element (2) is released from individual guiding means parts (a) by a releasing action, tightening the final knot (3). The device is subsequently released from fixating means (10). After these steps, the flexible element (2) may be cut to desired length.

[0077] In an alternative embodiment of the invention, the individual guiding means parts (b) and (c) of FIG. 1A form one combined individual guiding means parts (bc) (see FIG. 1C) which undergoes a releasing action in the fourth step.

[0078] In an alternative embodiment of the invention, the individual guiding means parts (a), (b) and (c) of FIG. 1A form one combined individual guiding means parts (abc) (see FIG. 1B), which undergoes a releasing action in the fourth step and does not require the fifth step.

[0079] The type and thickness of the knot (3) can be varied by the number of rotations effectuated by the apparatus (20).

[0080] The length of the string between the device and the knot can be accurately defined by the final position of the fixating means (10) with respect to individual guiding means parts (a). This can be achieved by either modifying the position of the fixating means (10), or by modifying the position of individual guiding means parts (a).

[0081] The number and positioning of the guiding means can be varied to better emulate the shape of the device (1) and ease the threading action. The order during which the guiding means undergo a releasing action with respect to the flexible element (2) is not deemed critical for the invention. Nevertheless, a final releasing step from individual guiding means parts (a) is the preferred embodiment of the invention.

[0082] In one embodiment, the apparatus (20) consists of a translating means (10), which can provide a translational movement. This translating means (10) contains a setting (11) to which the device (1) can be secured. The device is connected to a flexible element (2), which is to be knotted. The end of the flexible element (2) (all ends in case of multiple strands) is attached to a tensioning means (40), which maintains tension on the string. The apparatus (20) contains a guiding means (ABC) adjacent to the translating means (10). Said guiding means (ABC) is placed in such a way that the surface area defined by the guiding means is large enough to allow mechanical threading of the device (1) through said guiding means (ABC).

[0083] The diameter and position of individual guiding means parts (a) will define the position of the knot vis vis the device and can hence be optimized according to the preferred position of said knot for a certain application (i.e. will be dependent on the type of device).

[0084] Additional restraining means (50) ensure optimal placement of the translating means (10) on the apparatus (20) and can help in fine-tuning the position of the knot vis vis the device. Again, said position can help in optimizing said position of the knot for a certain application (i.e. will be dependent on the type of device).

[0085] Below, a preferred embodiment of the method according to the invention is described:

[0086] During the first step, the device (1), to which the element is attached (2), is mounted on the setting (11) in the translating means (10). The starting position of the translating means (10) holding the device (1) is outside the area defined by the guiding means (ABC), labeled as position 1 in FIG. 1A, and restrained as such by the restraining means (50).

[0087] In a second step, the apparatus (20) effectuates one or more rotations, creating one or more loops of the flexible element (2). The constant tension of the flexible element (2) provided by the tensioning means (40) ensures that the loops remain tightened around the guiding means (ABC).

[0088] In a third step, the device (1) is released from the translating means (10).

[0089] In a fourth step, the translating means (10), without the device, is moved under the loops, so that it is located in the area defined by the guiding means (ABC), and restrained as such by the restraining means (50).

[0090] In a fifth step, the device (1) is re-attached to the translating means (10) from above the loops. This threading action effectively creates the knot (3).

[0091] In an optional sixth step, the translating means (10), holding the device (1), is moved with respect to individual guiding means part (a) to define the final length of the element between the knot (3) and the device (1), and restrained as such by the restraining means.

[0092] In a seventh step, the flexible element (2) is released from the individual guiding means parts (b) and (c) by a releasing action. This action effectively tightens the knot (3) around individual guiding means part (a) by the tension provided by the tensioning means (40).

[0093] In an eighth step, the flexible element (2) is released from individual guiding means part (a) by a releasing action, tightening the final knot (3).

[0094] In a final step, the flexible element (2) is cut to desired length and the device (1) is released from the translating means (10).

[0095] In an alternative embodiment of the invention, the individual guiding means parts (b) and (c) form one guiding means (bc).

[0096] In an alternative embodiment of the invention, the individual guiding means parts (a), (b) and (c) form one guiding means (ABC), which undergoes a single releasing action in the seventh step and does not require the eighth step.

[0097] In essence, the invention provides a method for making a knot in a flexible element connected to a device using the apparatus (20) according to the invention comprising the steps of:

[0098] a) placing the device (1), to which the flexible element (2) is attached, in the first position (10) on the apparatus (20), outside the area defined by guiding means (ABC);

[0099] b) rotating the guiding means (ABC) one or more times with respect to the tensioning means (40), thereby forming one or more closed loops in flexible element (2);

[0100] c) translating the device (1) from its first position (10) to its second position (10) inside the area defined by guiding means (ABC), by lifting it over or under the closed loop(s) formed in step b);

[0101] d) releasing flexible element (2) from guiding means (ABC), under constant tension by the tensioning means (40), thereby forming the final knot (3).

[0102] The type and thickness of the knot (3) can be varied by the number of rotations effectuated by the apparatus (20).

[0103] The type and thickness of the knot (3) can also be varied by the number of translations effectuated by the translating means (10).

[0104] The type and thickness of the knot (3) can furthermore be varied by the number of threading actions effectuated by release and re-attachment of the device (1) to the translating means (10).

[0105] The type and thickness of the knot (3) can be varied by any combination of rotations, translations and/or threading actions mentioned above in any order and/or repetition.

[0106] The length of the string can be accurately defined by the final position of the setting (11) on the translating means (10) with respect to individual guiding means parts A. This can be achieved by either optional step six, or by modifying the position of individual guiding means part (a).

[0107] The number and positioning of the guiding means can be varied to better emulate the shape of the device (1) and ease the threading action. The order during which the guiding means undergo a releasing action with respect to the flexible element (2) is not deemed critical for the invention. Nevertheless, a final releasing step from individual guiding means part (a) is the preferred embodiment of the invention.

[0108] The apparatus (20) of the invention can make knots while one or more ends of the flexible elements are already attached to the device. The apparatus (20) of the invention renders it possible to make knots in flexible elements each of which consists of two or more strands.

[0109] Examples of certain alternative embodiments according to the invention are given below.

[0110] In an embodiment, the invention relates to an apparatus (20) for making a knot in a flexible element (2) attached to a medical device (1), which optionally contains a drug, comprising:

[0111] (i) a guiding means (ABC) for guiding the flexible element (2) fixed to the device (1), wherein guiding means (ABC) forms a geometrical figure which is large enough to contain the device (1);

[0112] (ii) a first position (10) outside the geometrical figure formed by guiding means (ABC), to which the device (1) can be affixed;

[0113] (iii) a second position (10) to which the device (1) can be affixed after being lifted over or under the closed loop(s) to form a relatively loose knot in the flexible element (2), wherein said second position (10) is inside the geometrical figure formed by guiding means (ABC);

[0114] (iv) means for tightening the knot through a tensioning means (40);

[0115] wherein means (i), (ii) and (iii) can be rotated with respect to means (iv).

[0116] In an embodiment, the invention relates to an apparatus (20) as described above, wherein the guiding means (ABC) comprises one or more individual guiding means parts (e.g. (a), (b), (c) in FIG. 1A; or (a), (bc) in FIG. 1C; or (abc) in FIG. 1A). The individual guiding means part(s) form(s) a geometric shape or volume dimensioned to contain the medical device (1). In one embodiment of the invention, guiding means (ABC) comprises at least 1 individual guiding means parts (e.g. (abc) or (a), (bc); or (a), (b), (c)). In one embodiment of the invention, guiding means (ABC) comprises at least 2 individual guiding means parts (e.g. (a), (bc); or (a), (b), (c)). In one embodiment of the invention, guiding means (ABC) comprises at least 3 individual guiding means parts (e.g. (a), (b) and (c)).

[0117] In an embodiment, the invention relates to an apparatus (20) as described above, wherein the guiding means (ABC) comprises at least three individual guiding means parts, (a), (b) and (c), or comprises two individual guiding means parts (a) and (bc), forming a geometrical figure which is large enough to contain the device (1).

[0118] In an embodiment, the invention relates to an apparatus (20) as described above, additionally comprising a translating means, capable of translating the device from position 10 to position 10, by lifting the device over or under and inside the one or more closed loops formed in the flexible element (2) by the apparatus (20).

[0119] In an embodiment, the invention relates to an apparatus (20) as described above, wherein guiding means (ABC) can be retracted into or lifted away from the apparatus (20) in order to release flexible element (2).

[0120] In an embodiment, the invention relates to an apparatus (20) as described above, wherein the diameter and/or location of individual guiding means part (a) of the guiding means with respect to position (10) defines the length of the element between knot and device.

[0121] In an embodiment, the invention relates to an apparatus (20) as described above, wherein one or more strands of the element are directed towards or away from the guiding means (ABC) by tensioning means (40).

[0122] In an embodiment, the invention relates to an apparatus (20) as described above, wherein individual guiding means part (a) is located closest to the end of the device (1) whereon the flexible element (2) is fixed.

[0123] In an embodiment, the invention relates to an apparatus (20) as described above, wherein the flexible element (2) is provided to the apparatus in the form of a spindle or bobbin or already cut, preferably capable of maintaining a certain tension on the element.

[0124] In an embodiment, the invention relates to an apparatus (20) as described above, wherein all movements or rotations of the apparatus are automated.

[0125] In an embodiment, the invention relates to an apparatus (20) as described above, wherein said translation means is a robotic arm.

[0126] In an embodiment, the invention relates to a method for making a knot in a flexible element connected to a device using the apparatus (20) according to any one of claims 1 to 10, comprising the steps of:

[0127] a) placing the device (1), to which the flexible element (2) is attached, in the first position (10) on the apparatus (20), outside the area defined by guiding means (ABC);

[0128] b) rotating the guiding means (ABC) one or more times with respect to the tensioning means (40), thereby forming one or more closed loops in flexible element (2);

[0129] c) translating the device (1) from its first position (10) to its second position (10) inside the area defined by guiding means (ABC), by lifting it over or under the closed loop(s) formed in step b);

[0130] d) releasing flexible element (2) from guiding means (ABC), under constant tension by the tensioning means (40), thereby forming the final knot (3).

[0131] In an embodiment, the invention relates to a method as described above, wherein the number of rotations, translations and threading actions can be adjusted to tailor the thickness of the knot.

[0132] In an embodiment, the invention relates to a method as described above, which is automated.

[0133] In an embodiment, the invention relates to a method as described above, wherein the translation movement of device (1) is performed by a robotic arm.

[0134] In an embodiment, the invention relates to a method as described above, wherein the device is an intra uterine device (IUD), for contraceptive purposes or for intra uterine treatment, a tampon, a hearing aid, or the like.

[0135] In an embodiment, an apparatus (20) is provided that receives a medical device (1) which apparatus (20) makes a knot in a flexible element (2) attached to the medical device (1), the apparatus (20) comprising:

[0136] a guiding element (ABC) that guides the flexible element (2), wherein the guiding element (ABC) forms a geometrical volume that is dimensioned to contain the medical device (1),

[0137] (ii) a first fixating element that fixes the medical device (1) at a first position (10) outside the geometrical volume formed by the guiding element (ABC);

[0138] (iii) a second fixating element that fixes the medical device (1) at a second position (10) entirely within the geometrical volume formed by the guiding element (ABC); and

[0139] (iv) a tensioning element (40) located outside the guiding element (ABC), wherein the tensioning element is configured to apply tension to the flexible element;

[0140] wherein the guiding element (ABC), first fixating element and second fixating element are disposed in a mutually fixed positional relation, and are configured to spin as a group constrained around a single axis of rotation positioned within the guiding element (ABC), relative to the tensioning element (40), and the tensioning element is disposed in fixed positional relation to the single axis of rotation.

[0141] In one embodiment, the guiding element (ABC) comprises guiding element parts a, b and c. In one embodiment, the guiding element (ABC) comprises guiding element parts a and bc. In one embodiment, the guiding element (ABC) comprises guiding element part abc.