Instrument for Endoscopic Surgery

The invention provides an instrument for endoscopic surgery comprising a shaft tube (10), a pull rod (12) which can move axially inside the shaft tube (10) and jaws (20) located at the distal end which are mounted on a single hinge pin (24) and can be pivoted towards each other. Relative axial motion of the shaft tube (10) and the pull rod (12) is converted into the pivot motion of the jaws (20) via contact eccentric to the hinge pin (24). The hinge pin (24) is mounted on the distal end of the pull rod (12). Each jaw (20) has a nib (34) which protrudes radially eccentric to the hinge pin (24). Each nib (34) engages in a cut-out (32) in a sheath (24, 124). The cut-outs (32) are covered by the shaft tube (10).

TECHNICAL FIELD

The invention concerns an instrument for endoscopic surgery.

BACKGROUND OF THE INVENTION

In endoscopic surgery, instruments are used which are often described as tubular shaft instruments. These instruments feature a shaft tube, inside which a pull rod can be moved in an axial manner. A handle located on the proximal end, e.g. a scissor handle, is used to move the pull rod in an axial manner inside the shaft tube, which opens and closes the jaws located on the distal end. The jaws may be designed differently for different applications, e.g. as forceps, scissors, coagulation instruments or similar.

In conventional instruments, the two jaws are usually pivot-mounted on a single hinge pin located on the distal end of the shaft tube. The jaws are designed as dual arm levers, with the pull rod engaging with the proximal lever arm of the jaws via hinged brackets. An example of this type of design is shown in DE 93 17 535 U1. This manner of manipulating the jaws via dual scissor hinges is cumbersome from a construction point of view. The scissor hinges are difficult to clean and sterilise. Additionally, the dual scissor hinges are freely accessible from the exterior and cannot be insulated for electro surgery applications.

An attempt was made to address these problems through an instrument of the type mentioned above, described in DE 10 2010 033 424 A1. In this instrument, the two jaws are pivot-mounted on a single hinge pin located on the distal end of the shaft tube.

The pull rod, which moves axially inside the shaft tube, engages with each jaw eccentrically to the hinge pin, which causes the axial motion of the pull rod to be converted into a pivot motion in the jaws. For this purpose, a pull bar is connected to the distal end of the pull rod; the angled arms of the pull bar, each in an eccentric recess, engage with the perimeter of the jaws. The multi-angled pull bar makes the device elaborate to manufacture and assemble.

An attempt was also made to address these problems in EP 0513471. The jaws were designed as being pivotable around a single hinge pin, each jaw having a nib protruding eccentrically into an opening. The design however had shortcomings in maintaining the jaws in the centre of the assembly and in allowing contamination through the openings. Some embodiments provided an external shank tube to eliminate openings, but these were of complex design.

GB 2,354,170 incorporated a tube and a two part keeper for an actuating member for its jaws. However, in GB 2,354,170, the jaw mechanism provided was complex, the actuating member having arms and extensions which required mating with a notch and recess. As a result, the precision and complexity required made assembly more costly and difficult.

In US 2006/161190, in attempting to solve the same problems, a tube and sheath were used but the jaw mechanism was once again too elaborate.

The invention is based on the aim of simplifying an endoscopic surgical instrument of the type mentioned above in terms of its manufacture and assembly, and improving it in terms of its applications.

DISCLOSURE OF THE INVENTION

Accordingly, this invention provides an instrument for endoscopic surgery comprising:

a shaft tube,

a pull rod which can be moved in an axial manner inside the shaft tube; and

jaws located at the distal end which are mounted on a single hinge pin mounted on the distal end of the pull rod, the jaws being pivotable towards each other, whereby the relative axial motion of the shaft tube and pull rod is converted into the pivot motion of the jaws via contact eccentric to the hinge pin, each of the jaws having a nib which protrudes radially eccentric to the hinge pin, the nibs of the two jaws being diametrically opposed, each engaging in a cut-out,

characterised in that the cut-outs are made in a sheath which is secured coaxially inside the distal end of the shaft tube, the cut-outs being covered by the shaft tube.

In the instrument according to the invention, the two jaws are pivot-mounted on a single hinge pin which is mounted on the distal end of the pull rod. Preferably, the relative axial motion between the pull rod and the shaft tube is converted into the pivot motion by which the jaws open and close through a nib which protrudes radially from the perimeter of each jaw, eccentric to the pivot axis of the hinge pin, and which engages in a cut-out in the shaft tube. Each nib is held axially in its cut-out so that the axial motion of the hinge pin is converted through the pull rod into a rotary or pivot motion in the respective jaw.

The instrument is simple in terms of its manufacture and assembly. The jaws simply need to be mounted on the distal end of the pull rod by means of the hinge pin, without any need for additional components for the distal working end of the instrument. The pull rod with the jaws is inserted in the shaft tube so that the nibs on the jaws engage with their respective cut-outs. Only the working ends of the jaws protrude from the distal end of the shaft tube, while the actuating and pivot mechanism is located inside the distal end of the shaft tube. This allows the jaws to be easily cleaned and sterilised. The distal end of the shaft tube encompasses the swivel joint of the jaws and their actuation, making it possible to fit electrical insulation along the outer circumference of the shaft tube, up to the exposed working ends of the jaws at the distal end. If the instrument is designed for electro surgery purposes, e.g. as a coagulation instrument, the exposed electrode surface of the jaws is advantageously small so as to allow a defined and targeted application of high-frequency electric current to the tissue.

The cut-outs in which the nibs of the jaws engage in the sheath may take the form of apertures made in the wall of the sheath which is inserted coaxially and anchored inside the distal end of the shaft tube. The cut-outs formed as apertures in the wall of the sheath are thus covered and sealed at the outer circumference by the shaft tube. The shaft tube being completely closed along its outer circumference up to the distal end greatly reduces or prevents the penetration by contaminants into the pivot mechanism.

Furthermore, it enables the outer circumference of the shaft tube to be fully fitted with electrical insulation without interruption, up to the distal end of the shaft tube.

In a further preferred embodiment, either one end or both ends of the hinge pin on which the jaws are pivot-mounted may protrude beyond the outer circumference of the pull rod. This protruding end of the hinge pin engages in an axial slit made in the shaft tube, or preferably in the sheath. The hinge pin engaging in the axial slit prevents the pull rod, and therefore also the jaws mounted on the pull rod, from twisting in relation to the shaft tube. The positioning of the pivot plane of the jaws in relation to the instrument's proximal handle is thus clearly determined, which is of crucial importance for using the instrument.

It is preferred that a shaft retainer is fitted to the pull rod to serve as a limit stop to limit distal movement of the pull rod when it is pushed in a distal direction inside the sheath. The shaft retainer may take the form of a circlip.

In an alternate embodiment, the shaft retainer may be a limit pin through the pull rod, the limit pin cooperating with the sheath. In this embodiment, the limit pin may have one or each end protruding and accommodated in an aperture in the sheath to limit distal movement of the pull rod.

DETAILED DESCRIPTION OF THE DRAWINGS

The first embodiment of the instrument for endoscopic surgery according to the invention is shown inFIGS. 1 to 7. It features a rigid shaft tube10in which a pull rod12can be moved in an axial manner. There is a handle located on the proximal end of the instrument; this is a known feature and is not included in the drawing. The handle, which may for example be designed as a scissor handle, features a fixed handle part, as well as a movable handle part which actuates the instrument. The proximal end of the shaft tube10is connected to the fixed part of the handle via a stop bush14and union nut16. The proximal end of the pull rod12features a spherical head18which is seated in the moving part of the handle, so that manipulating the movable part of the handle causes the pull rod12to be move axially inside the shaft tube10.

The distal end of the instrument features two jaws,20.1and20.2, which can be moved towards each other in a closing movement or apart from each other in an opening movement by the axial displacement of the pull rod12. The closing movement results from active actuation of the instrument, and requires a greater force to act on the jaws20. For this reason, it is preferable to actuate the closing movement through pulling force applied to the pull rod12in a proximal direction, which is why this component is called a “pull rod”.

Pushing the pull rod12in a distal direction generates a distal thrust which causes the jaws20to move apart. The jaws20may be designed in a known manner, depending on the intended use of the instrument. In the illustrated example embodiment, the jaws20are designed as grasping forceps. The jaws20may equally be designed as scissors, as a clamp or as a coagulation clamp.

As shown inFIG. 4, the distal end of the pull rod12is designed as a bracket22which opens in the distal direction. The bracket22has a bore, running perpendicular to the axis of the pull rod12, into which a hinge pin24is inserted. Only the proximal parts of jaws20.1and20.2are shown. The proximal ends of the jaws20.1and20.2are designed as flat discs26.1and26.2. The discs26.1and26.2are inserted into the bracket22side by side with the flat sides contiguous. The hinge pin24passes through the centre of the discs26.1and26.2, so that the jaws20.1and20.2are pivot-mounted on the hinge pin24on the same plane as the discs26.

On the distal end of the pull rod12, there is a sheath28, which can slide freely in an axial manner; the sheath28for this embodiment is illustrated in detail inFIG. 7. The sheath28is inserted coaxially into the distal end of the shaft tube10, and is secured axially and against rotation inside the shaft tube10. For this purpose, the proximal end portion30of the sheath28is provided with an external thread31which screws into a corresponding internal thread (not labelled) in the shaft tube10. Other alternatives for securing the sheath28inside the shaft tube10are also possible. For example, the end portion30(FIG. 7) of the sheath28can be secured inside the shaft tube10by means of a bayonet joint, glue, pressing or by other means.

The distal end portion of the sheath28has two cut-outs,32.1and32.2, which are designed as diametrically opposing apertures in the wall of the sheath28. Each of the discs,26.1and26.2, on the jaws,20.1and20.2, features a moulded nib,34.1and34.2. Each nib,34.1and34.2, is moulded on the outer circumference of the discs,26.1and26.2, eccentric to the hinge pin24, and protrudes from the circumference of the discs26.1and26.2in an essentially radial manner. The nibs,34.1and34.2, are located on the circumference of the discs,26.1and26.2, such that that they are diametrically opposed to each other and protrude outwards from the hinge pin24. The nibs34.1and34.2on each jaw20.1and20.2engage in the cut-outs32.1and32.2in the sheath28; this is most clearly illustrated inFIG. 4.

If, while the instrument is in use, the pull rod12is pushed forward axially in the shaft tube in the distal direction by means of the handle which is not illustrated, this moves the hinge pin24on which the jaws20.1and20.2are mounted in a distal direction in relation to the shaft tube10and to the sheath28which is fitted securely inside the shaft tube10. At the same time, the nibs34.1and34.2on the jaws20.1and20.2are secured axially in the corresponding cut-outs32.1and32.2in the sheath28. Because of the eccentric position of the nibs34.1and34.2, this causes the jaws20.1and20.2to pivot around the hinge pin24. As illustrated inFIG. 4, the jaw20.1is pivoted anticlockwise, owing to nib34.1engaging in cut-out32.1, while jaw20.2is pivoted clockwise, owing to nib34.2engaging in cut-out32.2. Pushing the pull rod12forwards in the distal direction thus causes the jaws20.1and20.2to open.

Conversely, if the pull rod12is pulled in the proximal direction inside the shaft tube10by means of the handle, which is not illustrated, this moves the hinge pin24with the jaws20.1and20.2into the sheath28. The nibs34.1and34.2engaging in the axially fixed cut-outs32.1and32.2are pivoted in opposing directions around the hinge pin24, so that jaw20.1illustrated inFIG. 4is pivoted clockwise and jaw20.2is pivoted anticlockwise; this causes the mouth formed by these jaws to close.

The distal end of the sheath28features one, or, as illustrated in the first embodiment, two diametrically opposed axial slits36which are open at the distal edge of the sheath28. The slits36are each offset from the cut-outs32by 90°. As illustrated most clearly inFIG. 6, one end or preferably both ends of the hinge pin24protrude beyond the outer circumference of the pull rod12. This protruding end of the hinge pin24engages radially in the slit36. The axial length of the slit36enables the pull rod12and hinge pin24to move axially inside the sheath28which is secured inside the shaft tube10. The engaging of the hinge pin24in the slit36prevents the pull rod12from twisting while being moved inside the shaft tube10. As a result, the pivot plane of the jaws20mounted on the pull rod12is set in relation to the shaft tube10and the handle connected to the shaft tube, and cannot be twisted.

The first embodiment of the instrument is assembled as follows:

First, jaws20.1and20.2are inserted into the bracket22of the pull rod12, and mounted on the pull rod by means of the hinge pin24. Then the sheath28is slid onto the pull rod12and pushed forwards in the distal direction towards the jaws20. During this process, the jaws20should be open wide enough that the nibs34.1and34.2are fully inserted into the openings in the inner profile of the sheath28. The sheath28can thus be slid over the inwardly pivoted nibs34. Once the sheath28with the cut-outs32.1and32.2is aligned axially with the nibs34.1and34.2, the jaws20.1and20.2are pivoted into the closed position so that the nibs34.1and34.2engage in the corresponding cut-outs32.1and32.2in the sheath28. Then the pull rod12with the sheath28fitted is inserted into the shaft tube10. The sheath28is secured axially on the pull rod12by the nibs34engaging in the cut-outs32, while the hinge pin24engaging in the slits36prevents the sheath28from twisting on the pull rod12. Using the pull rod12, the threaded31end portion30of the sheath28can thus be screwed into the internal thread of the shaft tube10so as to anchor the sheath28inside the shaft tube10. A recessed part37(FIG. 7) delimits the distal end of the thread on the end portion30.

Once the sheath28is fully inserted into the distal end of the shaft tube10, the shaft tube10overlaps the apertures created by the cut-outs32and the slits36so that they are fully covered and sealed at the outer circumference of the shaft tube10. The shaft tube10is therefore fully closed and without apertures right up to the jaws20at the distal end. Preferentially, the outer lateral surface of the shaft tube10can be fitted with electrical insulation38(FIG. 4), which likewise is uninterrupted right up to the jaws20at the distal end. This makes the instrument particularly suitable for electro surgery applications.

Before the pull rod12with the sheath28fitted is inserted into the shaft tube10, a shaft retainer40is preferentially inserted proximally behind the sheath28into a recess on the pull rod12. The shaft retainer40can move freely in an axial manner inside the shaft tube10; however, inside the sheath28anchored in the shaft tube10it forms a limit stop which limits the movement of the pull rod12when pushed forward in the distal direction. In this way, the shaft retainer40limits the forward movement in the distal direction of the pull rod12. This prevents the pull rod12from being pushed so far forward that the jaws20.1and20.2are opened to the maximum extent, causing the nibs34.1and34.2to pivot inwards and come out of the cut-outs32.1and32.2.

In the first embodiment, the shaft retainer40is in the form of a circlip.

Turning now to the second embodiment of the instrument of the invention, as illustrated inFIGS. 8 to 10, this embodiment works in much the same way as the first embodiment, except for the arrangement concerning the sheath and the shaft retainer. The parts which are the same as those in the first embodiment are referred to using the same labels.

As shown inFIG. 8, on the distal end of the pull rod12there is a sheath128mounted on the pull rod12. The sheath128is inserted coaxially into the distal end of the shaft tube10(shown inFIG. 10) and is secured axially and against rotation inside the shaft tube10as explained further below.

The distal end portion of the sheath128has two cut-outs,32.1and32.2(32.2is not visible), which are the same as those in the previous embodiment and which are designed as diametrically opposing apertures in the wall of the sheath128. Cut-outs32.1and32.2accommodate moulded nibs,34.1and34.2as described for the previous embodiment.

Jaws20.1and20.2operate as described for the previous embodiment.

In the second embodiment, the distal end of the sheath128features two diametrically opposed axial apertures136which are not open at the distal edge of the sheath128but are fully within the wall of the sheath128. (Only one aperture136is visible inFIGS. 8 to 10.) The apertures136are each offset from the cut-outs32by 90°.

A fixed limit pin50has each end protruding as shown inFIG. 9. Pin50may be fixed by laser welding or any other suitable method. When sheath128is assembled, the ends of pin50are accommodated in apertures136(seeFIG. 8). The engaging of the pin50in the aperture136prevents the pull rod12from twisting relative to sheath128while being moved inside the shaft tube10. Sheath128is fixed to shaft tube10, such as by screw threads or adhesive or by a bayonet fitting cooperating with apertures in shaft tube10. As a result, the pivot plane of the jaws20mounted on the pull rod12is set in relation to the shaft tube10and the handle connected to the shaft tube10, and cannot be twisted.

Movement of sheath128distally and proximally is limited by the length of apertures136and engagement by the protruding ends of the pin50. At the same time, pin50in apertures136forms a limit stop which limits the movement of the pull rod12when pushed forward in the distal direction. In this way, the pin50limits the forward movement in the distal direction of the pull rod12. This prevents the pull rod12from being pushed so far forward that the jaws20.1and20.2are opened to the maximum extent, causing the nibs34.1and34.2to pivot inwards and come out of the cut-outs32.1and32.2, so that the distal movement of the pull rod12with the jaws20inside the shaft tube10is no longer limited.

Although pin50is shown with both ends protruding (FIG. 9), requiring diametrically opposed apertures136in sheath124(one aperture136being shown inFIG. 8, the other aperture not visible), it is within the scope of the invention that pin50may instead protrude at one end only, in which case a single aperture136would be required to accommodate that end.

The second embodiment of the instrument is assembled as follows:

First, jaws20.1and20.2are inserted into the bracket22of the pull rod12, and mounted on the pull rod by means of the hinge pin24. Then the sheath128is slid onto the pull rod12. During this process, the jaws20should be open wide enough that the nibs34.1and34.2are fully inserted into the openings in the inner profile of the sheath128. The sheath128can thus be slid over the inwardly pivoted nibs34. Once the sheath128with the cut-outs32.1and32.2is aligned axially with the nibs34.1and34.2, the jaws20.1and20.2are pivoted into the closed position so that the nibs34.1and34.2engage in the corresponding cut-outs32.1and32.2in the sheath128.

Limit pin50is fixed to pull rod12, such as by laser welding, with one end protruding into and being received in aperture136of sheath124. Alternately, each end of limit pin50protrudes into and is received by an aperture136.

The limit pin50engaging in the aperture or apertures136prevents the sheath128(and pull rod12) from twisting.

Shaft tube10is then fitted and fixed to sheath128.

Once the sheath128is fully inserted into the distal end of the shaft tube10, the shaft tube10overlaps the apertures created by the cut-outs32and the aperture/s136so that they are fully covered and sealed at the outer circumference of the shaft tube10. The shaft tube10is therefore fully closed and without apertures right up to the jaws20at the distal end. Preferentially, the outer lateral surface of the shaft tube10can be fitted with electrical insulation38(FIG. 10), which likewise is uninterrupted right up to the jaws20at the distal end. This makes the instrument particularly suitable for electro surgery applications.