Patent Description:
In surgical operations performed on internal organs using the laparoscopic method, various types of surgical instruments are used to hold, deflect and incise the tissue of the operated organs or organs connected to the operated organs with the possibility of simultaneous coagulation. Changing the position of the actuators, for example, the pliers, is realized by changing the position of the lever relative to the handgrip. Commonly used are laparoscopic instruments in which the lever can occupy any position relative to the handgrip to grasp or release the tissue. Similarly, in a scissor-type instrument, the lever can occupy any position relative to the handgrip. Very often, a laparoscopic instrument is equipped with a knob for changing the angular position of the actuators, which makes it easier to operate with difficult access to tissues. There is a demand that the knob allows any angular positioning of the working plane of the actuators.

Equally common are instruments equipped with pliers for holding tissue coupled to a mechanism for holding the jaws of the pliers in a fixed reciprocal operative position providing a specific compression of the tissue, which must remain temporarily maintained due to the course of the operation. The operative position is also understood as holding the tissue to allow temporary deflection or clamping of the tissue. Activities such as grasping, tissue incision can be performed repeatedly during the operation according to the course of the operation, so the design of the laparoscopic instrument should be ergonomic. There is an expectation, that the handling of the laparoscopic instrument should be as simple as possible, and the movement resistance of the mechanisms during the handling of the instrument should be as low as possible.

From the state of the art laparoscopic instruments are known, which are equipped with a handgrip, wherein the handgrip can be two-part such as in scissors, as for which the tightening of the parts of the handgrip against each other results in the handling of the instrument's actuators. Instruments having a handgrip on which a lever is attached for handling the actuators are known. The handgrips of the instruments are often equipped with mechanisms for maintaining a temporarily unchanging position of the lever.

Document <CIT> discloses a laparoscopic instrument comprising a shank with attached actuators, a handgrip and a lever drawn against the handle. The instrument can be used in various positions by the person performing the laparoscopic procedure. The instrument is equipped with a knob for rotating the shank together with the actuators, but the knob is not equipped with a mechanism for locking the shank in the desired angular position.

Document <CIT> discloses a laparoscopic instrument having a handgrip to which a handle is tightened for manipulating the pliers. The instrument has a knob for rotating the shank and actuators. The instrument is equipped with a latching mechanism including an arched toothed bar integrated in the handle and a latch located on the handgrip, wherein the latch encompasses a tooth on the longitudinal support. A deflection lever is installed on the handgrip, which is adapted to occupy two positions, wherein the lever maintains continuous contact with the longitudinal support. In one position of the deflecting lever, the toothed bar remains interlocked with the tooth, and in the other position it deforms the longitudinal support so that the tooth is moved away and out of the interlock so that the latching mechanism does not operate. The disclosed latching mechanism is constructed of multiple components, and furthermore, the performance of the latching mechanism may be impaired with the loss of elastic properties of the components from which the mechanism is constructed.

Document <CIT> discloses a laparoscopic instrument that is equipped with a latching mechanism having two ball-shaped latching elements that alternate the angular position of the shank and the actuators, wherein the recesses for the latching elements are made at the proximal end of the shank. The latching mechanisms operate transverse to the axis of the shank. In addition, the laparoscopic instrument is equipped with a latching mechanism comprising a tooth mounted on a prone component and a tooth bar that engages with this tooth.

The European application <CIT> discloses a laparoscopic instrument comprising a handgrip and an articulated lever, a shank attached to the handgrip, tissue acting actuators installed at the further end of the shank, a string to move the actuators connected to the actuators and to the lever. The instrument is equipped with an integrated latching mechanism, comprising a toothed bar and a latch, designed to hold the actuators in the operating position by holding the lever position in relation to the handgrip. Moreover the instrument is provided with a locking and releasing mechanism equipped with a switching lever to hold the latching mechanism to engage and to disengage the latching mechanism, the switching lever being rotatably mounted on the handgrip.

Document <CIT> discloses an ultrasonic surgical clamp coagulator apparatus configured to effect cutting, coagulation, and clamping of tissue by cooperation of a clamping mechanism of the apparatus with an associated ultrasonic end-effector. In the housing there is provided a clutch mechanism for rotational positioning of an elongated portion and end-effector. The arrangement permits the elongated portion to be rotatably positioned with respect to the apparatus housing and permits rotation of the end-effector relative to the elongated portion.

The essence of the invention is a laparoscopic instrument comprising a handgrip; a lever pivotally attached to the handgrip; a shank embedded in a sleeve pivotally attached to the handgrip, wherein the proximal end of the shank is embedded in the sleeve, and wherein the distal end of the shank has attached actuators for acting on the tissue; a knob mounted on the sleeve for rotating the sleeve along with the shank; a latching mechanism for determining the angular position of the sleeve and shank relative to the handgrip; a string for moving the actuators, with the distal end of the string being connected to said actuators and the proximal end of the string being connected to a lever, wherein the string is located inside the shank and the movement of the lever is coupled to the movement of the actuators. The laparoscopic instrument is characterized in that the latching mechanism is located at the tip of the handgrip opposite the lever, wherein the tip is equipped with latching slots and the inner part of the knob adjacent to the sleeve is equipped with a latching element and a spring.

The instrument is characterized in that the sleeve has a flange and a groove, and the cylindrically shaped inner part of the knob has slits separating the inner part into segments, wherein at least one segment has an abutment facing the axis of the shank, wherein at least one abutment is inserted into the groove for determining the position of the knob with respect to the sleeve, while the flange is brought to a retaining surface in the handgrip.

The instrument is characterized in that the latch sockets are made on the front surface of the handgrip tip, and the latching element carries out a movement parallel to the axis of the shank during the movement of the knob.

The instrument is characterized in that the shank is equipped with a recess in the proximal part of the shank, while the sleeve is equipped with an internal projection that is inserted into the recess of the shank for determining the position of the sleeve relative to the shank.

Advantageously, the sleeve has a slit separating the part of the sleeve opposite the flange into two parts.

The instrument is characterized in that the proximal end of the string has a narrowing and is connected to the lever by means of a joint comprising a cylindrical element having a slotted hole, in which an insert having a notch against which the narrowing of the string is located, in addition, the cylindrical element has a transverse hole in which the proximal end of the string is located.

Advantageously, the laparoscopic instrument is equipped with a latching mechanism comprising an arched toothed bar connected to a lever and a latching tooth connected to a handgrip, adapted to hold the position of the actuators in an operative position by holding the position of the lever relative to the handgrip, and a locking and releasing mechanism equipped with a switch lever for holding the latching mechanism in gear and for releasing the latching mechanism, wherein the arched toothed bar is pivotable, and the latching tooth is located stationary on the handgrip, wherein the switching lever, fixed pivotally on the handgrip, is equipped with a pushback element for deflecting the arched toothed bar, which pushback element in the release position of the switching lever triggers the latching mechanism in such a way, that the arched toothed bar is offset from the latching tooth, wherein the pushback element rests against the arched toothed bar of the latching mechanism, while in the locking position the pushback element is offset from the arched toothed bar of the latching mechanism.

Advantageously, the switching lever is fastened with pivots to snap into the first opening in the handgrip.

Advantageously, the lever is equipped with pivots that are adapted for mounting in the second opening in the handgrip.

Advantageously, the lever is equipped with a third opening, which is adapted for mounting a pivot element for the string.

Advantageously, a fourth opening is located next to the third opening for mounting the cap of the third opening.

Advantageously, the pushback element is made as a pin.

The actuators can be selected from a group comprising clamp jaws, window jaws, serrated jaws, hook jaws, scissors.

The handgrip can be equipped with an electrical connector.

The latching mechanism located at the tip of the handgrip allows high resolution angular positioning of the clamping jaws, scissors or other actuators. In addition, the design of the instrument according to the invention comprising a minimum number of parts, the design and assembly are simpler, and the cost of manufacturing the instrument is reduced. Determining the angular position with the latching mechanism is performed on the maximum possible diameter available on the handgrip, so that less force is needed to maintain the fixed position, the resistance to movement of the knob resulting from the latching mechanism is reduced.

The use of a cylindrical joint with a transversely placed insert reduces the resistance to movement during rotation of the string to a very great extent compared to known instruments, the resistance to movement has been reduced to a very small value because the contact area of the insert with the constriction is only a small part of the circular cross-section of the string.

The laparoscopic instrument according to the invention enables aural control of the change in the angular position of the actuators, both intentional caused by the operator and unintentional caused by accident, which is appreciated as the specificity of endoscopic procedures limits the surgeon to observe the movement of the hands and instruments. In the instrument according to the invention, the execution of the function of rotation through the shank of the instrument is clearly perceptible and/or heard by means of a series of clicks, which allows auditory control of the rotation of the actuators. The device according to the invention is equipped with a latching mechanism that provides high angular resolution, i.e. it allows the shank to be retained together with the jaws after rotation by a very small angle.

The object of the invention is described below in relation to the illustrated embodiments shown in the drawing, in which:.

In the following description, the terms "proximal" and "distal" are used to refer to the elongated or curved support or string elements of the instrument, wherein the term "proximal" refers to the end of the elongated element on the side opposite the handgrip, while the term "distal" refers to the end of such element on the side opposite the handgrip.

The laparoscopic instrument <NUM> shown in <FIG> in the embodiment has a handgrip <NUM> and a lever <NUM> adapted to be operated with the hand, wherein the handgrip <NUM> and the lever <NUM> are in the form of handles as for scissors, with finger openings. The lever <NUM> is operated with the thumb, and the handgrip <NUM> is gripped with the other fingers, wherein the handgrip <NUM> is pointed essentially downward when using the laparoscopic instrument <NUM>. In the laparoscopic instrument shown in <FIG>, the position of the lever <NUM> relative to the handgrip <NUM> can be varied as desired, the actuators <NUM> for this instrument are scissors. The laparoscopic instrument <NUM>' shown in <FIG> is constructed similarly, wherein the lever <NUM> is provided with a latching mechanism <NUM> which allows the lever <NUM> to be locked relative to the handgrip <NUM>, in the example of manufacture shown, the laparoscopic instrument <NUM>' is provided with clamping jaws <NUM>. In both embodiments, the lever <NUM> and the handgrip <NUM> are connected to each other with their upper parts 3A and 2A by means of a joint <NUM>. In the upper part 2A of the handgrip <NUM> there is a cylindrical longitudinal opening <NUM> (<FIG> and <FIG>), in which an m-axis shank <NUM> is fixed by means of a sleeve <NUM>, wherein the shank <NUM> in the form of a tubular support passes centrally through the sleeve <NUM>. The sleeve <NUM> is fixed pivotally in the handgrip <NUM>. A knob <NUM> is mounted on the sleeve <NUM>, which is equipped with an outer part 9A for gripping the knob <NUM> and a cylindrically shaped inner part 9B, which is adjacent to the sleeve <NUM>. The knob <NUM> will be discussed later in the description. The knob <NUM> is used for determining the angular position of the shank <NUM> and thus the actuators <NUM>, <NUM> of the laparoscopic instrument <NUM>, <NUM>' at the same time. The cylindrically shaped inner portion 9B comprising four segments 14A, 14B, 14C and 14D separated by slits <NUM>. The slits <NUM> may extend parallel to the m-axis of the shank <NUM> and along the cylindrically shaped inner portion 9B, the slits <NUM> may be of any shape. The sleeve <NUM> has a flange 5A and a groove 5B, which serve to fix the position of the sleeve <NUM> in the handgrip <NUM> in the direction of the m-axis of the shank <NUM>. The flange 5A is brought against the retaining surface <NUM>, i.e., it rests against the retaining surface <NUM> in the handgrip <NUM>, and the abutment 14E on the segment 14A, 14C is inserted into the groove 5B, wherein the segment 14A rests against the front surface <NUM> of the tip 2F of the handgrip <NUM>. Opposite segment 14A, segment 14C (<FIG> and <FIG>), i.e. the segment resting on the other side of the m-axis, is also equipped with an abutment 14E inserted into groove 5B. Segment 14C also rests against the front surface <NUM> of the handgrip <NUM> tip 2F.

The sleeve <NUM> has a longitudinal slit 5C separating parts 5D and 5E (<FIG> and <FIG>), wherein the plane of the slit 5C rests on the axis m. Parts 5D and 5E can be symmetrical with respect to the plane passing through the axis of the sleeve <NUM> and can be tilted. On the wall of the opening 5F of the sleeve <NUM> an inner protrusion <NUM> is located, which is inserted into the recess 6C of the shank <NUM>. When the inner protrusion <NUM> is inserted into the recess 6C, the position of the sleeve <NUM> with respect to the shank <NUM> is fixed. The recess 6C can take the form of an opening with an axis perpendicular to the m-axis.

The laparoscopic instrument is equipped with a latching mechanism <NUM> for determining the angular position of the shank <NUM> relative to the handgrip <NUM> (<FIG>). The latching mechanism <NUM> comprises latching sockets <NUM> formed on the front surface <NUM> of the tip 2F of the handgrip <NUM>, as well as a latching element <NUM> and a spring <NUM>. The tip 2F of the handgrip <NUM> is located opposite to the lever <NUM>. The latching seat <NUM> may be in the form of a spherical or spherical-roller recess, while the latching element <NUM> may be in the form of a ball or a ball-ended roller. The latching element <NUM> is embedded in the segment 14D of the inner portion 9B of the knob <NUM>. The knob <NUM> may be provided with two latching elements <NUM>, the second latching element <NUM> in an invisible segment 14B. The latching element <NUM> is provided with the ability to perform movement in the direction parallel to the m-axis of the handgrip <NUM> while rotating the knob <NUM> and jumping between the latching seats <NUM>. When setting the position of the actuators <NUM>, <NUM> required during the operation by rotating the knob <NUM>, the operating personnel can hear a series of clicks of the latching mechanism <NUM>. Regardless of the aural evaluation of the change in the position of the actuators, the operating personnel can feel the successive latches of the latching mechanism <NUM> with their hand. The operating personnel obtains information about the intended or accidental rotation of the shank and at the same time the actuators, which are located inside the patient during the surgery, without having to look at the handgrip of the laparoscopic instrument.

In the upper part 2A of the handgrip <NUM> an opening <NUM> is located, in which the electrical connector HF <NUM> is fixed over the spring latch <NUM>. The electrical connector HF <NUM> presses against the spring latch <NUM> so that, by tensioning the spring, the latch <NUM> holds a frictionally conductive connection to the shank <NUM>, while in the section from the knob <NUM> to the actuators of the laparoscopic instrument <NUM>, <NUM>', the shank <NUM> is enclosed by an insulating film 6A, for example, of heat-shrinkable material. The laparoscopic <NUM>, <NUM>' instrument equipped with an electrical connector can be used in laparoscopic surgery as a monopolar instrument. The banana-type electrical connector <NUM> is a standard connector used in electrosurgery for supplying current to the actuators. The connector <NUM> is located at a <NUM>-degree angle to the axis of the shank <NUM>, so that the power cord is arranged in a way that does not interfere with the movements and precision of the surgeon. The laparoscopic instrument <NUM>, <NUM>' is equipped with a seal <NUM> embedded in the groove 23B of the string <NUM>, which is adjacent to the inner surface of the stem <NUM>.

The lever <NUM> is attached to the handgrip <NUM> in an articulated manner on an axis k. The lever <NUM> is equipped in its upper part 3A with two coaxial pivots <NUM> located on two opposite sides of the shaded part 3B. The pivots <NUM> and the openings <NUM> form a joint <NUM>. The shaded part 3B is located in the recess 2B of the handgrip <NUM>, wherein the pivots <NUM> are placed in the second openings <NUM>, the k-axis of which passes through the walls of the recess 2B, wherein the k-axis is below the m-axis of the shank <NUM> when the instrument is in use. Due to this arrangement of the m and k axes, the joint <NUM> of the lever <NUM> is below the string <NUM>, and the lever <NUM> does not enter the area of the string <NUM>.

The string <NUM> is connected to the lever <NUM> by means of a joint <NUM> of the string <NUM> located in the shaded portion 3B of the lever <NUM> adjacent to the wider portion 3C of the upper portion 3A of the lever <NUM>. The joint <NUM> of the string <NUM> comprising a cylindrical element <NUM>, an insert <NUM> and a proximal end of the string <NUM> having a narrowing 23A. The cylindrical element <NUM> is pivotally embedded in a cylindrical third opening <NUM> having an n-axis in the shaded portion 3B. The cylindrical element <NUM> has a transverse opening <NUM> made transversely to the n-axis of the cylindrical element <NUM>. The proximal end of the string <NUM> is inserted into the transverse opening <NUM>. The cylindrical element <NUM> is positioned in the third opening <NUM> symmetrically with respect to the upper portion 3A so that the n-axis is located perpendicular to the symmetry plane of the slotted cutout <NUM>. The diameter of the transverse opening <NUM> is adapted to the diameter of the proximal end of the string <NUM>. The cylindrical element <NUM> has a slotted opening <NUM> made in the base of the cylinder parallel to the n-axis of the cylindrical element <NUM>, and an insert <NUM> is placed in the slotted opening <NUM>. The insert <NUM> has a cutout 64A, which is applied to the narrowing 23A of the proximal end of the string <NUM> after the proximal end of the string <NUM> is inserted into the opening <NUM> (<FIG>). The insert <NUM> is provided with latches 64B, which enter the cutouts 61A in the cylindrical element <NUM>. When the insert <NUM> is latched, the cutout 64A comprises the narrowing 23A. The cutout 64A can be V-shaped or U-shaped. The narrowing 23A is in the form of a circumferential groove the width of which is greater than the thickness of the insert <NUM>, and the diameter of the narrowing is less than or equal to the width of the cutout 64A. The string <NUM> can rotate while remaining in contact with the insert <NUM>, wherein only a small portion of the circular section of the string <NUM> remains in contact with the insert <NUM>. The joint <NUM> of the string <NUM> has two degrees of freedom, one degree of freedom being imparted by the cylindrical connection of the cylindrical element <NUM> with the third opening <NUM>, and the other degree of freedom being imparted by the connection of the narrowing 23A of the proximal end of the string <NUM> with the cutout 64A of the insert <NUM>. The resistance to movement in rotating the actuators from friction between the insert <NUM> and the narrowing 23A is negligible.

In the shaded portion 3B of the upper portion 3A, a slotted cutout <NUM> is made, the plane of which is perpendicular to both the k-axis and the n-axis, wherein the k- and n-axes intersect the slotted cutout <NUM>. The third opening <NUM> is closed by a cap 19A snapped into a fourth opening 19B located next to the third opening <NUM>.

The laparoscopic instrument may be equipped with actuators selected from a group comprising: clamp jaws, window jaws, toothed jaws, hooked jaws, scissors, in medical terminology known as graspers, dissectors and scissors of various types. In the second embodiment shown, in the laparoscopic instrument <NUM>', pliers <NUM> are used comprising two toothed clamping jaws <NUM>, <NUM> fixed pivotally on the r-axis (<FIG> and <FIG>) by means of a pin <NUM> embedded in a bracket <NUM> at the distal end of the shank <NUM>. Each clamping jaw <NUM>, <NUM> is made as a double-sided lever, one arm of 26A, 27A respectively has a clamping surface <NUM>, <NUM>, the other arm of 26B, 27B respectively is provided with an opening <NUM>, <NUM> into which a pin <NUM> is inserted and fixed in the distal end of string <NUM>. The pin <NUM> moves in the openings <NUM>, <NUM>, which makes the jaws move.

Handgrip <NUM> and lever <NUM> together form a gripping-handling device. Handgrip <NUM> is equipped with a first central element 2D and a first gripping element 2E, while lever <NUM> is equipped with a second central element 3D and a second gripping element 3E (<FIG>). The laparoscopic instrument <NUM>' in the second embodiment is equipped with a latching mechanism <NUM> comprising a toothed bar <NUM> and a cooperating latching tooth <NUM> acting as a latch (<FIG>). The arched toothed bar <NUM> is integrated with the second gripping element 3E, i.e., it can be made in combination with the gripping element 3E, the toothed bar <NUM> is equipped with a plurality of teeth <NUM> adapted to cooperate with the tooth <NUM> located on the first gripping element 2E. The toothed bar <NUM> is positioned so that the teeth <NUM> of the toothed bar <NUM> come into contact with the tooth <NUM>, i.e., they engage the tooth <NUM>. Both the teeth <NUM> and the tooth <NUM> are triangular in shape. Between each of the teeth <NUM> there is a recess matching the tooth <NUM>. During the movement marked as G that tightens the lever <NUM> to the handgrip <NUM>, i.e. the second gripping element 3E to the first gripping element 2E, the teeth <NUM> jump over the tooth <NUM> i.e. successive surfaces 39A of the teeth <NUM> come into contact with the surface 38A of the tooth <NUM> (<FIG> and <FIG>), while the toothed bar <NUM> is flexible and can be deflected to allow the teeth <NUM> to jump over. The movement of lever <NUM> in the direction of G affects the clamping of the pliers, i.e. the pressing of lever <NUM> against handgrip <NUM>, and causes the jaws <NUM>, <NUM> or any other actuators to move closer together. When the operator reaches the required operating position, in this case clamping i.e. the required position of the pliers <NUM>, <NUM> with respect to each other and when the pulling movement of the lever <NUM> to the handgrip <NUM> is stopped, the tooth <NUM> remains in the recess between the teeth <NUM>. Self-withdrawal of the lever <NUM> and thus self-release of the clamp is not possible because the surface 39B of the tooth <NUM> rests against the surface 38B of the tooth <NUM>. The laparoscopic instrument <NUM>' is equipped with a locking and releasing mechanism <NUM>, which is adapted to occupy two positions - a locking position, in which it is possible to clamp the pliers <NUM> to any degree of clamping and retain such clamping, and a release position, in which the operating personnel can freely clamp the pliers <NUM> and release the clamp, but it is not possible to retain the clamping of the pliers. The locking and releasing mechanism <NUM> comprise a switching lever <NUM> articulated on the first gripping element 2E in the first opening <NUM> (<FIG>), wherein the t-axis of the joint <NUM> is located substantially parallel to the k-axis and the n-axis. The switching lever <NUM> is provided with a pushback element <NUM>, which can be positioned depending on the position of the switching lever <NUM> in either the first slot <NUM> for the locking position (<FIG> and <FIG>) or the second slot <NUM> for the releasing position (<FIG> and <FIG>). The pushback element <NUM> provides a movement stop to the switching lever <NUM>, in the embodiment shown, the pushback element <NUM> is in the form of a cylindrical pin. Switching lever <NUM> is adapted to change its position from locking to releasing and vice versa by pressing tip <NUM>. The joint <NUM> of the switching lever <NUM> comprises two pivots 41A located opposite to each other, situated on the arms 41B of the switching lever <NUM>. The arms 41B are flexible, which allows them to be gently tilted during installation on the handgrip <NUM> so that the switching lever <NUM> is attached to the latch by inserting the pivots 41A into the first opening <NUM> in the handgrip <NUM>.

In the locking position of the locking and releasing mechanism <NUM> as shown in <FIG> and <FIG>, the switching lever <NUM> is in the locking position and the latching mechanism <NUM> works as described above, i.e., it is possible to lock the appropriate operating position of the actuators, in the embodiment shown, the clamping of the jaws <NUM>, <NUM> of the pliers <NUM> of the laparoscopic instrument <NUM>' by the operating personnel. In <FIG> and <FIG>, the locking and releasing mechanism <NUM> is in the releasing position, it is possible to withdraw the lever <NUM> in the direction marked as R. Switching lever <NUM> is in the release position, where pushback element <NUM> is resting in the second socket <NUM> of gripping element 2E.

Claim 1:
The laparoscopic instrument (<NUM>, <NUM>') comprising
a handgrip (<NUM>);
a lever (<NUM>) pivotally attached to the handgrip (<NUM>);
a shank (<NUM>) embedded in a sleeve (<NUM>) pivotally attached to the handgrip (<NUM>), wherein the proximal end of the shank (<NUM>) is embedded in the sleeve (<NUM>), however, on the distal end of the shank (<NUM>) actuators (<NUM>, <NUM>) are attached to interact with the tissue;
a knob (<NUM>) mounted on the sleeve (<NUM>) for rotating the sleeve (<NUM>) along with the shank (<NUM>); a latching mechanism (<NUM>) for determining the angular position of the sleeve (<NUM>) and shank (<NUM>) relative to the handgrip (<NUM>);
a string (<NUM>) for moving actuators (<NUM>, <NUM>), wherein the distal end of the string (<NUM>) is connected to said actuators (<NUM>, <NUM>), and the proximal end of the string (<NUM>) is connected to the lever (<NUM>), wherein the string (<NUM>) is located inside the shank (<NUM>), and the movement of the lever (<NUM>) is coupled to the movement of the actuators (<NUM>, <NUM>), characterized in that the latching mechanism (<NUM>) is located at the tip (2F) of the handgrip (<NUM>) opposite the lever (<NUM>), wherein the tip (2F) is provided with latching seats (<NUM>), and the inner part (9B) of the knob (<NUM>) adjacent to the sleeve (<NUM>) is provided with a latching element (<NUM>) and a spring (<NUM>).