Patent Description:
Past few decades have seen vast development as to surgical procedures - minimally invasive surgery being one of the prime advances of this era. Minimally invasive surgeries, such as arthroscopic surgery and laparoscopic surgery, recently have become widely practiced surgical procedures. Such procedures have gained rapid popularity and generally are preferable over the traditional open surgery which requires cutting large incisions through the skin, muscles and membranes to open and expose the body cavity, thereby necessitating longer hospitalization stays and prolonged recovery periods. In minimally invasive surgery, small incisions are made into which tubular conduits, such as cannulae and trocars, are inserted and directed to the site of the operable internal organ or tissue. One or more surgical instruments are introduced, each through individual tubular conduits in order to perform the surgical procedure. It would be obvious to the reader that said minimally invasive surgical procedures including arthroscopy, endoscopy and laproscopy owe their realization to special tools capable of access to intended site of surgery via small incision made to body of patient and operation of which allows precise performance of intended site-specific surgical manipulations.

Cutting, grasping, suturing, cauterization, distension, stapling form commonality of operations in surgery. Minimally invasive surgery tools of art do provide individually for such functions. However, due to the singularity of function accorded by such tools available, the interchange of tools amidst operations and efforts, time required for such becomes unavoidable, besides causing opportunity for complications during repeated insertion and removal of different tools.

In laparoscopic surgery, specialized long thin tools are inserted via air-tight ports fixed on the CO<NUM> inflated abdomen of the patient. The operation area as seen by the endoscope is displayed on an external display where the surgeon views it. Since only a few thin holes are created for inserting tools, this type of surgery results in fewer injuries to the patient, faster healing periods and less cosmetic damage. This type of surgery requires specialized tools that are characterized by their long shafts (usually around <NUM>) and thin cross sections (usually <NUM>-<NUM> dia). These tools come in various end-tips, such as scissors, blades, graspers, etc. Procurement/ maintenance costs, sterilization requirements of additional equipment are other problems faced by the medical fraternity. Thus, development of minimum invasive surgical tools capable of plural functionality, yet maintaining accuracy, precision and ease of use, are pressing needs of art.

There have been some attempts for resolving said needs of art. Various forms of laparoscopy tools, housings for positioning instruments, extendible blades, multifunctional scissor jaw designs and the like find mention in the art. Many devices which are used commonly for grasping or cutting objects have two elements which can be moved towards one another and away from one another. The elements have surfaces which may be blunt or sharp so that an object positioned between them may be either grasped or cut when the elements are moved towards one another. Examples of such devices include tongs, tweezers, forceps, scissors, guillotines, and wire cutters. Such devices can also be adapted to dissect tissue, for example, by placing the elements of the device into or next to an object and then causing the elements to splay apart thereby dissecting the object. However, these designs have been found to suffer from drawbacks critically affecting their intended function.

<CIT> discloses a combined bipolar scissor and grasper. The instrument disclosed in this patent is a combined bipolar electrosurgical cutting and grasping instrument where the grasping surfaces are contained within the shape of a standard surgical scissor. Accuracy of operation is defined by precise positioning of these portions at site of manipulation. However, being contained within same arm, the cutting and grasping portions are invariably in same angle of motion, thus present risk of accidental cuts or clamps. Also, pivoting of the tool while being inserted is not without risk due to exposed cutting edges.

<CIT> discloses a surgical suturing device which has a tubular elongated shaft terminating into a jaw assembly at the distal end and a handle assembly at the proximal end thereof. The jaw assembly includes a first jaw member pivotally connected to a second jaw member. An actuator rod extending longitudinally within the length of said shaft is connected at its proximal end to said handle assembly and is pivotally connected at its distal end to said jaw assembly. The underside of said first jaw member is provided with a cupped recess having a wheel assembly disposed therein. The wheel assembly includes a needle mount for securely retaining a needle and is configured such that the needle lies within the cupped recess when the jaw members are closed and can be deployed in a protracted position away from the first jaw member when the jaw members are in an open position. In operation, the suturing device offers superior control over both the needle and the tissue to be sutured.

The above mentioned invention suffers from drawback of limited degree of operation due to configuration wherein only one jaw is movable and the other fixed. The said single shaft device presented finds utility for function of suturing having adequate needle control, however, does not offer means to grasp and stabilize the tissue, which is slippery by nature thus mandating that the tissue tending to evade needle carrier manipulation must be grasped by a second instrument. As a result, the surgeon encounters difficulty in controlling and positioning both the needle and the tissue simultaneously, and the patient can suffer complications such as frayed tissue, errant punctures, inadequate stitches, extended surgical duration, hemorrhaging, and the like.

<CIT> describes a device for dissecting, grasping and/or cutting an object has at least two elongate elements at least a portion of at least one of the elements is formed from a pseudoelastic material, preferably a pseudoelastic shape memory alloy. End portions of the elements can be moved away from one another and then toward one another to dissect, grasp and/or cut an object with the elements. In certain embodiments, the device further comprises an actuating means and at least a portion of the elements and/or the actuating means is formed from a pseudoelastic material. The device is intended for applications including dissecting, grasping and/or cutting objects located in difficult to reach areas, within the body during surgery. However, the cutting / grasping members of this tool are pseudoelastic and thus, allow limited degree of choice while deciding on the angle of cut and portion of tissue being grasped. Unintentional nicks and pinches cannot be ruled out are limitations in rotational ability of the tool proposed.

Laparoscopic Scissor Grasper, a product by Interventional and Surgical Innovations LLC is a minimally invasive surgery tool that can both cut and grasp with aid of two jaws having mated via serrations along their inner surfaces. The jaws separate along two axes apart and sideways to provide grasping and cutting functions respectively. However, this design is subject to certain shortcomings as the grasping serrations are invariably exposed while shearing. Also, pivoting of the jaws about their longitudinal axis is not possible. Also, for cutting edge to work, the chamfered edges necessarily need to press against each other. This pressure is enabled by forging a slight curvature in cutting arms being pressed at pivot by means of rivet or other tightening means. Over period of use, this arrangement looses its original construction leading to either loss of pressure of cutting arms or distancing of said cutting arms which ultimately leads to firstly loss of cutting functionality and secondly, presence of two sharpened (chamfered) edges which act as knives and can cut whether intended or not. Such occurrence, is thus compromise to application intended.

<CIT> discloses radial jaw biopsy forceps which feature a multi element head having a fixed blade juxtaposed between two grasper jaws having mated serrations along their internal edges for grip. However, this design too has shortcomings of limited scope for movement and accidental cuts to material in space between the grasping arms while performing delicate functions.

By and large, innovations cited have not been able to overcome the problems of the art. Design of a pluri-functional device for achievement of surgical operations is a pressing need of the art. The present inventor has undertaken specific research and has arrived at novel construction and operability of a device for addressing said problems of art. The following brief description presents one non-limiting embodiment of constructing and performing the present invention.

<CIT> discloses a bipolar electrosurgical instrument including four shearing members. The shearing members are movable to an open position for grasping tissue, a closed position for desiccating tissue by application of electrical current and a cutting position for shearing tissue. The electrical current may be applied in an X-shaped pattern to thereby localize desiccation to the maximum extent possible. A method of using the bipolar electrosurgical instrument is also disclosed.

The invention provides a surgical apparatus according to claim <NUM> and a method of configuring a surgical apparatus according to claim <NUM>. Further embodiments of the invention are provided in the dependent claims.

The invention may be more fully understood by reference to the cited figures and details of exemplary embodiments. Alternative embodiments of the invention as claimed, and providing the benefits of the novel concepts of the invention, are contemplated and will be obvious from the explanations hereinafter.

The laparoscopic procedure generally involves creating small incisions through the navel and through the abdominal wall for viewing and operating on internal areas of the body, such as the uterus, ovaries, gall bladder and appendix. Typically, a trocar tube is introduced through the navel incision for receiving a camera, magnifying lens or other fiber optic device for viewing the surgery. One or more additional trocar tubes are introduced through incisions in the abdominal wall such that laparoscopic surgical tools can be inserted through the tube(s) for manipulating, cutting and/or suturing an internal organ or tissue. In this manner, while viewing a video monitor via the fiber optic device positioned in the navel trocar, the surgeon can grasp an organ or tissue with one surgical tool and simultaneously cut or suture with another surgical device.

The evolution of minimally invasive surgery has given rise to the need of single-shaft surgical instruments which can be inserted through a trocar and easily manipulated by a surgeon. These instruments are fashioned such that they can be inserted lengthwise through the trocar and comprise hand-held controls on the proximal end thereof to operate the distal, tissue-manipulating end of said instrument. Single shaft devices must have a sufficiently small diameter so that they can be inserted into a trocar tube and guided to the operative tissue site. Typically, such instruments are designed to perform one function, such as grasping and stabilizing tissue, cutting tissue, holding a suturing needle or pulling a suturing needle through tissue, suctioning and irrigating the fluids, cauterizing the tissue, coagulating blood vessels and so on. A major drawback to minimally invasive surgery is that it requires exceptional motor coordination to grasp and stabilize an organ or tissue with one surgical tool and performing a cutting or suturing procedure on said organ or tissue with a second surgical device, all while viewing a two dimensional video monitor. This disadvantage is particularly acute in performing a laparoscopic suturing procedure.

<FIG> is a schematic side perspective view of the four jawed tip of the laparoscopic instrument proposed by the present invention. Also, <FIG> illustrates elements structurally integral to the jaws of the laparoscopic instrument proposed by the present invention which provide for interlocking action. Explanation as to construction of the laparoscopic tool subject of the present invention is now attempted referring to both these figures. The combinational scissor-grasper tool <NUM> comprises a bullet nosed end comprising four independent jaw elements <NUM>, <NUM>, <NUM> and <NUM>. Said jaw elements are in operational association with a single hinge <NUM> and can lock into one another by positive locking mechanism enabled by mated protrusions and depressions corresponding to protrusion <NUM> and depression <NUM> along respective inner surface of each adjacent arm-in-pair. This mechanism ensures that when motion is delivered at the hinge, at all times, a specific combination of arms moves together.

<FIG> illustrates magnified view of the four-jawed tip of the laparoscopic instrument proposed by the present invention. As illustrated therein, the four jawed tip <NUM> is key feature of the present invention capable of performance between both cutting and grasping functionalities via actuation of controller <NUM>.

<FIG> (a,b,c) and <NUM> (a,b,c) are schematic representation of inter-play between two jaw pairs when in grasping and cutting configurations respectively. When viewed from its tip with the tool being oriented such that its hinge <NUM> hosting the jaw elements <NUM>, <NUM>, <NUM> and <NUM> is parallel to the floor (horizontal), locking of jaw <NUM> with <NUM> and jaw <NUM> with <NUM> respectively to each other results in grasper configuration of the tool. In same orientation, locking of the left side jaws <NUM> and <NUM> and right side jaws <NUM> and <NUM> respectively to each other results in the scissor configuration of the tool <NUM>.

<FIG> (a,b,c) are front, perspective and back views of jaw element <NUM>/<NUM> of the laparoscopic instrument <NUM>. It may be seen that <NUM> is a depression into which the extension <NUM> illustrated later in <FIG> enters while the instrument is in the scissor configuration. Generally referring to <FIG>, it may be seen that the shape associated with the depression <NUM> is intended to mate with shape associated with extension <NUM> so that the two elements can snugly slide into one another. <NUM> is an arc section having its geometric centre at point <NUM> which is geometrically mimicked on the inner arc of extension <NUM> thus allowing the extension <NUM> to slide over arc section <NUM> smoothly. This motion is later described in <FIG>. Points <NUM> and <NUM> determine the end-points of slot <NUM>. The hinge <NUM> fits into the slot <NUM>. Along the slot <NUM> jaws <NUM> and <NUM> can slide backward and forward such that either points <NUM> or <NUM> align with central axis of hinge <NUM>, to enable the instrument to function as a grasper or as a scissor, respectively. Jaws <NUM> or <NUM> can rotate about hinge <NUM> either about point <NUM> or point <NUM>. Arcs <NUM> and <NUM> define a slot <NUM>. The arc <NUM> has its geometric centre at point <NUM>, while the arc <NUM> has its geometric center at point <NUM>. Protrusion <NUM> is positioned within the slot <NUM>. Arcs <NUM> and <NUM> define the handle <NUM>. The arc <NUM> has its geometric centre at point <NUM>. This handle gets positioned into the depression <NUM>. When the instrument shifts from grasper to scissor position, the shifter shaft <NUM> moves forward, towards the distal direction. During this forward motion, the proximal vertical surface <NUM> of the depression <NUM> pushes against the surface <NUM>. At the same time, the distal surface <NUM> pushes against surface <NUM>. This pushes the jaws <NUM> and <NUM> forward, towards the distal direction such that they slide on hinge <NUM> along their respective slots <NUM> taking them from being hinged about point <NUM> to being hinged about point <NUM>. As a result of this motion, the protrusion <NUM> in jaws <NUM> and <NUM> gets inserted into depression <NUM> in jaws <NUM> and <NUM> respectively, thus locking jaw <NUM> to <NUM> and jaw <NUM> to <NUM>. During the same motion, the protrusion <NUM> in jaws <NUM> and <NUM> slides out of the depression <NUM> in jaws <NUM> and <NUM> respectively, thus removing the lock between jaws <NUM> and <NUM> and between jaws <NUM> and <NUM>. This is the scissor configuration. When the instrument shifts back from scissor to the grasper configuration, the shifter shaft <NUM> moves backwards, towards the proximal end. During this motion, the distal vertical surface <NUM> of depression <NUM> engages with the surface <NUM>. This pulls the jaws <NUM> and <NUM> backwards, towards the proximal direction such that they slide on hinge <NUM> along their respective slots <NUM> taking them from being hinged about point <NUM> to being hinged about point <NUM>. As a result of this motion, the protrusion <NUM> in jaws <NUM> and <NUM> gets removed from depression <NUM> in jaws <NUM> and <NUM> respectively, thus unlocking jaw <NUM> from <NUM> and jaw <NUM> from <NUM>. During the same motion, the protrusion <NUM> in jaws <NUM> and <NUM> slides into the depression <NUM> in jaws <NUM> and <NUM> respectively, thus engaging the lock between jaws <NUM> and <NUM> and between jaws <NUM> and <NUM>. This is the grasper configuration. Thus, the protrusion <NUM> and depression <NUM> form a male-female pair to lock the device in the scissor configuration. The protrusion <NUM> and depression <NUM> form another male-female pair to lock the device in the grasper configuration. This switching mechanism between grasper and scissor configurations is shown between <FIG> as a side view and also between <FIG> as a close-up perspective view.

When the instrument is in the scissor configuration, the jaws <NUM> and <NUM> rotate about the point <NUM> on hinge <NUM>. In this configuration, the shifter shaft <NUM> has kept the jaws <NUM> and <NUM> pushed in this position. Hence, the surfaces <NUM> and <NUM> slide over surfaces <NUM> and <NUM> respectively. As the jaws <NUM> and <NUM> rotate about point <NUM>, it is essential that the arcs <NUM> and <NUM> have their geometric centers at point <NUM>. When the instrument is in the grasper configuration, the jaws <NUM> and <NUM> rotate about the point <NUM> on hinge <NUM>. In this configuration, the shifter shaft <NUM> has kept the jaws <NUM> and <NUM> pulled in this position. Hence, the surface <NUM> slides over surface <NUM>. As jaws <NUM> and <NUM> rotate about point <NUM>, it is essential that the arc <NUM> has its geometric centre at point <NUM>.

While shifting between scissor and grasper configurations, a single stroke motion engages one lock and disengages the other. The serrated surfaces <NUM> of jaws <NUM> or <NUM> and serrated surfaces <NUM> of jaws <NUM> and <NUM> are used for the grasping action. The distance between each tooth of the serrated surfaces <NUM> and <NUM> is greater than or equal to the distance between points <NUM> and <NUM>. While the tool jaws are in the closed position and the tool needs to be shifted between scissor and grasper configurations in either direction, this particular distance between the teeth on serrated surfaces <NUM> and <NUM> ensures that jaw <NUM> can slide over jaw <NUM> and jaw <NUM> can slide over jaw <NUM>, without letting the teeth physically interfere with each other.

According to another aspect of the present invention, edge <NUM> of jaws <NUM> or <NUM> is hardened and angled to create a sharp shearing edge. As shown in <FIG> and <FIG>, the edge <NUM> in jaw <NUM> moves against the edge <NUM> of jaw <NUM> to create the necessary shearing action required for the instrument to function as a scissor.

The serrated surfaces <NUM> and <NUM> are physically distinct and independent of the shearing edge <NUM>. This makes it possible to pick a great variety of grasping serration independently of a variety of scissor edge. Thus, a large number of combinations of different scissor and grasper types are possible to be incorporated in the instrument.

According to another aspect of the present invention, the handle <NUM> is created with a step <NUM> such that the depression <NUM> can be accommodated with the protrusion <NUM> positioned in the slot <NUM>.

The protrusion <NUM> is of a shape comprising an arc with the geometric centre at point <NUM>. This curvature also matches with the curvature of depression <NUM>. The depression <NUM> is of a shape comprising an arc with the geometric centre at point which is offset towards the distal end of the tool from point <NUM> by a distance that is equal to the distance between points <NUM> and <NUM>. This is also the distance by which the shifter shaft <NUM> moves while switching between the scissor and grasper mechanisms. Point <NUM> is the position of a hole in jaws <NUM> or <NUM> in which the hinge <NUM> resides. Jaws <NUM> and <NUM> always rotate about the axis through point <NUM>.

The connecting link <NUM> hinges to the jaws <NUM> and <NUM> at the hole <NUM> using pin <NUM>. Pin <NUM> can be in the form of a rivet that joins holes <NUM> and <NUM>. A step <NUM> accommodates the thickness of the connecting link <NUM>. Inner shaft <NUM> has a means of connecting with link <NUM> by a pin <NUM> at holes <NUM> and <NUM>. The pin <NUM> can be in the form of a rivet.

The entire system of the inner shaft <NUM> connected to jaws <NUM> and <NUM> by means of connecting links <NUM> hinged respectively at <NUM> and <NUM> by pins <NUM> and <NUM>, is shown in <FIG>. The jaws <NUM> and <NUM> are forced to open by a simple parallelogram mechanism when the inner shaft <NUM> is moved forward in the distal direction. The connecting links <NUM> and the distance between points <NUM> to <NUM> on jaws <NUM> and <NUM> form the segments of this parallelogram mechanism. The user's action at element <NUM> creates this required motion in <NUM>. When the proposed surgical tool is in the grasper configuration, the protrusion <NUM> in jaws <NUM> and <NUM> locks in with depression <NUM> in jaws <NUM> and <NUM> respectively, thus locking jaws <NUM> and <NUM> together on one hand, and jaws <NUM> and <NUM> on the other. At this time the protrusion <NUM> in jaws <NUM> and <NUM> and depression <NUM> in jaws <NUM> and <NUM> are no longer engaged. When the jaws <NUM> and <NUM> are forced to open up by the parallelogram mechanism movement initiated by the user acting on inner shaft <NUM>, they also, in turn force jaws <NUM> and <NUM> to move along with them respectively. This creates the grasper configuration as shown in <FIG> and <FIG>.

When the tool is in the scissor configuration, the protrusion <NUM> in jaws <NUM> and <NUM> locks in with depression <NUM> in jaws <NUM> and <NUM> respectively, thus locking jaws <NUM> and <NUM> together on one hand, and jaws <NUM> and <NUM> on the other. At this time the protrusion <NUM> in jaws <NUM> and <NUM> and depression <NUM> in jaws <NUM> and <NUM> respectively are no longer engaged. When the jaws <NUM> and <NUM> are forced to open up by the parallelogram mechanism movement initiated by the user acting on inner shaft <NUM>, they also, in turn force jaws <NUM> and <NUM> to move along with them respectively. This creates the scissor configuration as shown in <FIG> and <FIG>.

Thus, when the instrument is in the grasper configuration, jaw <NUM> locks with jaw <NUM> while jaw <NUM> locks with jaw <NUM>. On the other hand, when the instrument is in the scissor configuration, the jaw <NUM> locks with jaw <NUM> while jaw <NUM> locks with jaw <NUM>.

A step <NUM> is created at the distal tip of inner shaft <NUM> in order to accommodate the thickness of connecting link <NUM>. The combined widths of the section <NUM> and two instances of link <NUM> are accommodated by pin <NUM> within the cut out gap <NUM> of shifter shaft <NUM>. This in turn must fit within the cut out gap <NUM> of outer holder <NUM>. In this outer holder <NUM> the hole <NUM> holds the hinge <NUM>.

A means to provide for the backward and forward movement of the shifter shaft is created. Any standard method to achieve this in a user-friendly manner would work. Other requirements of a surgical instrument, such as the ability rotate and fit within a <NUM> diameter, are also fulfilled.

According to another aspect of the present invention, the surfaces involved in grasping and cutting are independent of each other. Hence they may be sharpened, knurled, and formed independently for optimal performance.

Since both scissor and grasper operate about the same common hinge <NUM>, there is no inherent need for a <NUM>° rotation about the tool's axis for a shift of configuration.

As described hereinabove, the mechanism for interlocking of jaw elements comprises male and female locking elements. Said interlocking elements are completely internal to the jaws themselves and thus do not interfere with the surgical environment.

According to another aspect of the present invention, the mechanism to shift between the grasper and scissor configurations is also contained completely internal to arm of the tool. It has so been designed to allow the tool to be manufactured within a <NUM> diameter. It should be appreciated that the instrument can be provided with a different shape of jaws to perform other actions besides straightforward grasping and cutting. Different types of graspers, scissors can be incorporated to this mechanism. The actuation of the instrument may be carried out by either the means of a regular handle operated by hands or it can be motorized to be applied in a robotic setting. In either case the mechanism of the front tip does not change.

If the jaw members and internal mechanism members are coated with appropriate insulation layers, the function of bipolar cauterization may also be added into the tool. The bipolar cauterization will occur between the jaw elements when the instrument is in the grasper configuration.

According to yet another aspect of the present invention, the mechanism to shift between the grasper and scissor configurations operates with a strictly linear motion along the axis of the tool. Inner and outer shafts of the main shaft body <NUM> are separable and thus, allow for rotation along the longitudinal axis. This allows for the tool to be rotated infinitely clockwise or anticlockwise about the axis of its main shaft body <NUM> and thus enable a <NUM>° field of operation.

According to another aspect of the present invention, it is intended by the present inventor to make the device of the present invention amendable to controllers of common art, thus negating design of customized control architecture and / or user interfaces. This also means easy migration between tools for surgeons.

Thus, it would be now evident to the reader that the user interface or controlling means is same for both cutting as well as grasping functions and that the selection of function is enabled via actuation of a switch which controls interlocking of pairs of jaws of the device proposed by the present invention in accordance with functionality required. This switch may be selected among common art easy switching mechanisms such as turning knobs, trigger or toggle levers. Thus, the user has ability to migrate from one mode of operation to other with single stroke of switch and without having to remove / reinsert in body of patient being operated. Further, the scissor grasper combination can be made able to withstand infinite rotation of the tool along its longitudinal axis using a common art thumb-wheel. As common art controllers are utilized, the user maintains same tactile feel and dexterity while adapting to use of the proposed tool.

According to other embodiments of the present invention, the inner shafts of the tool are constructed to allow disassembly and reassembly to the main outer shaft by means chosen among press-fit, threading/screw mechanism or key-slot mechanism. This makes it possible to easily autoclave or sterilize the tip of the proposed instrument. It also allows for just the tip to be replaced without having to replace the handle or outer shaft.

According to another embodiment of the present invention, a cleaning port may be introduced in the shaft of the proposed laparoscopic tool for allowing sterilization and multiple use thereafter.

Claim 1:
A surgical apparatus for cutting and grasping, the apparatus comprising:
first and third jaw elements (<NUM>, <NUM>) each comprising a surface, an extension (<NUM>), and a protrusion (<NUM>);
second and fourth jaw elements (<NUM>, <NUM>) each comprising a surface and first and second depressions (<NUM>, <NUM>);
a hinge (<NUM>) coupling the jaw elements at their respective bases;
a shifter shaft (<NUM>) coupled to the second and fourth jaw elements (<NUM>, <NUM>) at a distal end of the shifter shaft (<NUM>), there being a longitudinal axis defined by opposite ends of the shifter shaft (<NUM>);
the shifter shaft (<NUM>) in a first position along the longitudinal axis causing the first and second jaw elements (<NUM>, <NUM>) to be coupled to each other by the first depression (<NUM>) of the second jaw element (<NUM>) receiving the extension (<NUM>) of the first jaw element (<NUM>), and further causing the third and fourth jaw elements (<NUM>, <NUM>) to be coupled to each other by the first depression (<NUM>) of the fourth jaw element (<NUM>) receiving the extension (<NUM>) of the third jaw element (<NUM>); and
the shifter shaft (<NUM>) in a second position along the longitudinal axis different from the first position causing the first and fourth jaw elements (<NUM>, <NUM>) to be coupled to each other by the second depression (<NUM>) of the fourth jaw element (<NUM>) receiving the protrusion (<NUM>) of the first jaw element (<NUM>), and further causing the second and third jaw elements (<NUM>, <NUM>) to be coupled to each other by the second depression (<NUM>) of the second jaw element (<NUM>) receiving the protrusion (<NUM>) of the third jaw element (<NUM>).