Forceps having adjustable gripping force

Forceps suitable for gripping body tissue or organs including a pair of jaws the gripping force of which can be adjusted. The forceps include an operating rod providing with axially spaced angularly offset cams which are selectively engagable by rotating the control rod with longitudinally slidable link assemblies separated by compression springs of differing stiffnesses. Rotation of the control rod to a particular angular position determines whether no spring or one or more springs are connected in series to determine the gripping force exerted by the forceps when the control rod is axially displaced. A control rod actuating lever is locked in position by means of a locking device.

TECHNICAL FIELD 
The invention relates to forceps with gripping jaws for gripping body 
tissue, body organs or the like, in which at least one jaw is pivotable 
relative to the other by adjustment of an operating rod actuated by a 
lever, and more particularly to forceps in which the jaws and the lever 
can be fixed by a locking device in a closed position. 
BACKGROUND ART 
Forceps of this type must be designed in such a way that they can hold 
tissue absolutely reliably. Patent DE3931577A discloses forceps for 
binding tissue sections together. The forceps guarantee a reliable fixing 
of the gripped tissue by means of a specially developed stop mechanism 
which clicks securely into position after pressure on a first pressure 
point overcomes a threshold to hold the forceps securely closed. The 
release of the forceps is effected by applying pressure to a further 
pressure point. 
It is undesirable if such forceps traumatise the gripped tissue, 
particularly if the gripped tissue becomes detached from the body. When 
organs or tissue parts which need to fulfil their task in the body have to 
be fixed or gripped for manipulation, traumatisation is particularly 
undesirable. In such a situation a soft and non-traumatic grip of the 
tissue or organ must be effected. 
In the prior art forceps it is possible to provide a gentle gripping force 
by means of the force applied to a gripping actuation mechanism. The 
disadvantage of such an arrangement is that a fixing of the clamped jaw 
position with a stop mechanism is not possible and thus not reliable and 
secure holding of the tissue can be guaranteed. 
OBJECTS OF THE INVENTION 
Accordingly, an object of the invention is to provide forceps in which the 
closing force acting on the tissue or the like present between the jaws of 
the forceps can be altered and set in order to prevent traumatisation of 
the tissue . A further object of the invention is to provide forceps which 
meet all the aforementioned requirements, in particular with regard to 
absolutely reliable operation. 
SUMMARY OF THE INVENTION 
Thus, according to the invention there is provided a pair of forceps of the 
type discussed above, in which the gripping force of the jaws is 
adjustable to different values. The forceps can be fixed in a closed 
position by a locking device, and in addition, different closing forces 
can be set, so that tissue gripped by the forceps is not traumatised. 
Preferably the forceps are so designed that the force exerted via the lever 
and the operating rods is transferred directly to the jaws by setting the 
maximum closing power,and is transferred indirectly via at least one 
spring by setting a different lower closing power. With such an 
arrangement, the forceps can be set to maximum gripping force for gripping 
tissue when it is unimportant whether the tissue is traumatised and be set 
to a lower gripping force when used for gripping tissue which should in no 
way be traumatised. 
The operating rod of the forceps consists of a distal first rod part 
connected to the movable jaws and a second rod part extending proximally 
from the distal rod part. For the purpose of setting the different 
gripping forces, the second rod part can be turned about its axis in 
relation to the first and is provided with axially spaced angularly offset 
cams. These cams co-operate with link assemblies so that for a given 
angular orientation of the second rod part only the cams required for a 
desired gripping force are engaged. The gripping force can be transferred 
from the second to the first rod parts either directly, or indirectly via 
springs depending on which of the cams is engaged with associated link 
assemblies. It is understood that the number of components such as cams, 
link assemblies and springs connected in series depends on the number of 
closing force settings required. 
Apertures are provided in the link assemblies which ensure free axial 
passage of the cams in certain angular orientations of the second rod 
part. In addition, the compression springs located between adjacent link 
assemblies urge the link assemblies against stops or ring shoulders. Such 
stops secure the link assemblies in the rest position against movement in 
the proximal direction. 
Furthermore, the operating rod has a switching ring on its proximal end. 
This ring is fitted with a spring possessing an inwardly directed lug and 
can be turned in relation to a stationary part of the forceps. The lug is 
selectively engagable with one of several orifices on the aforementioned 
stationary part and thus permits selective fixing of the angular position 
of the second rod part so as to regulate the jaw gripping force provided. 
The turnable spring can be fitted in such a way that it is engaged by a 
peg and is fixed into the switching ring. This arrangement prevents 
jamming and/or turning of the spring which is located within a circular 
notch in the switching ring. By this arrangement the proximal rod part can 
be fixed in three discrete angular positions. 
The transfer of the turning movement of the switching ring to the proximal 
rod part is achieved by means of a cylindrical casing. The first distal 
and second rod parts are preferably axially displaceable with respect to 
each other, being connected by means of a pin which secures these rod 
parts against radial movement relative to each other.

DETAILED DESCRIPTION 
The forceps shown in the Figures have a pair of jaws 1 and 2 for gripping 
and holding tissue at their distal end. An operating rod 3 comprising 
first second and third parts 8, 9 and 10 extends from the distal end of 
the forceps to a handle 4 with an integrated stop mechanism or locking 
device 5 at the proximal end. The mechanism 5 is used to determine the 
closing position of the jaws 1 and 2. One jaw 1 is pivotable in relation 
to the other 2 by axially displacing the operating rod 3 by means of the 
handle 4. 
The gripping force transferable to the jaw 1 by means of the operating rod 
3 can be adjusted for example to three defined levels. FIG. 3 shows the 
internal components for changing the gripping force. 
Two compression springs 6 and 7 and are provided which transfer the force 
exerted by the handle 4 to the first part 8 of the operating rod 3, and 
thus to the movable jaw 1. The springs 6 and 7 are employed selectively 
for the two lower gripping force settings. Should the maximum closing 
force be required the force exerted by the handle 4 is transmitted 
directly to the first part 8 of the operating rod 3 i.e. without any 
intermediary springs. 
The operating rod 3 consists of a first rod part 8 a second central rod 
part 9 extending proximally from the first part 8 and a third rod part 10 
at a proximal end of the forceps. The first rod part 8 is connected 
directly to the pivotable jaw 1, for example by a linkage. The second rod 
part 9 is turnable about its axis in relation to the first rod part 8. 
Furthermore, the second rod part 9 is fitted with cams 11, 12 and 13 
arranged axially spaced from one another, and angularly displaced with 
respect to one another. These cams co-operate with axially movable link 
assemblies 14, 15, 16, 17, 18, 19 and 20. Distal cam 11 is co-operable 
with distal link assembly 14, 15, 16, middle cam 12 is co-operable with 
middle link assembly 17, 18, and proximal cam 13 is co-operable with 
proximal link assembly 19, 20. Each link assembly includes a sleeve 14, 
17, 19 and one or more apertured plate 15, 16, 18 and 20. These plates and 
inwardly projecting flanges 21 of the sleeves 17 and 19 each include a 
pair of opposed arcuate apertures 22 as shown in FIG. 4. The apertures of 
each link assembly are configured so as to restrain the associated cam 
against longitudinal movement relative thereto in either direction as 
shown in solid lines in FIG. 4, or allow longitudinal movement relative 
thereto as shown in dotted lines in FIG. 4 (by the passage of cams through 
their associated apertures). The cams 11, 12, 13 and apertures 22 in the 
link assemblies are angularly positioned so that in each of three discrete 
angular positions of the operating rod 3, only one of the cams is 
restrained by its associated link assembly as described above. 
Should the maximum closing force be required, the second rod part 9 is 
swivelled to the position shown in FIG. 4. Only the distal cam 11 is 
engaged with the distal link assembly 14, 15 and 16. The force exerted on 
the proximally extending second and third rod parts 9 and 10 is 
transferred via the distal link assembly 14, 15 and 16 to the first rod 
part 8. The middle cam 12 and proximal cam 13 can freely traverse the 
associated middle link assembly 17, 18 and proximal link assembly 19, 20 
respectively, unimpeded. 
The compression springs 6 and 7 urge the link assemblies against circular 
shoulders 24 and 25 such that the circular shoulders 24 and 25 secure the 
link assemblies in the rest position against proximal movement. The 
circular shoulders 24, 25 are arranged in the device in such a way that 
they are fixed immovably in a cylindrical casing 27 fitted coaxially in an 
outer handle 26. Outer handle 26 fits inside a housing part 28, which is 
connected to the proximal housing part 29 by a screw connection. Two 
levers 30 constituting the handle 4 are pivotably fixed to the proximal 
end of the housing part 29. 
Between the levers 30 a return spring 31 is provided. Compressing the 
levers 30 transfers power from the levers 30 to the proximal rod part 10, 
so as to move the rod parts 8, 9 and 10 distally. Moreover, the return 
spring 31 automatically returns the levers 30 and the operating rod 3 to 
the starting position after releasing the locking device 5. 
FIG. 5 shows a cross section on the line V--V through a switching ring 32 
formed by a hollow cylinder which is rotatable by hand and provided on the 
proximal rod part 10 in order to set the different gripping forces, by 
defining three discrete rotational positions for the rod part 9. The 
switching ring 32 has a circular spring 34 received in a circumferentially 
extending notch 33 thereof and secured therein against circumferential 
movement relative to the ring 32 by a peg 40. The ring 32 and the spring 
33 are jointly turnable in relation to a fixed part 39. An inwardly 
directed cam 35 on the spring 34 engages in one of the orifices 36, 37 or 
38 provided on the fixed part 39 according to the gripping force to be 
set. By means of this design, different settings can be achieved and more 
securely effected, since the actual position of the rod part 9 is felt by 
clicking of the cam 35 into position in one of the orifices 36, 37, 38. 
If the second rod part 9 is turned by means of the connecting ring 32 via 
the cylindrical casing 41 so that the circular spring 34 with its cam 35 
is retracted from the orifice 36 and by further turning engages the 
orifice 37, the middle cam 12 engages with the corresponding link assembly 
17 and 18. Both the distal cam 11 and the proximal cam 13 become 
disengaged from the corresponding link assemblies 14, 15, 16 and 19, 20. 
In this position the reduced gripping force is determined by the stiffness 
of the compression spring 6. By further turning the connecting ring 32, by 
the same angle, the third position is reached, wherein the cam 35 engages 
the orifice 38 and the proximal cam 13 engages the proximal link assembly 
19, 20. Distal cam 11 and middle cam 12 will become disengaged from their 
respective link assemblies. In this configuration force is applied to the 
jaws 1, 2 via spring 6 and 7 acting in series. As the stiffness of spring 
7 is less than that of spring 6, the resulting gripping force will be 
correspondingly reduced. 
The transfer of the turning movement of the switching ring 32 to the 
turnable rod part 9, 10 is effected via the cylinder casing 41, which is 
permanently connected at its ends to the second rod part 9 and connecting 
ring 32 as well as to the cylindrical casing 42. In order to be able to 
retract the rod 3 proximally, the cylindrical casing 45 is connected to 
the rod part 10 adjacent to the distal end of the cylindrical casing 42. 
At the distal end of the second rod part 9, there is a central axial hole 
44 which accommodates a pin 43 secured centrally in the rod part 8. The 
rod parts 8 and 9 are secured against relative radial movement by the 
centring action of the pin 43. 
In order to prevent the gripping force from being released and in order to 
avoid resultant possible operational disturbances, the operating rod 3 
shifted distally from the rest position is secured against turning. Thus 
it is not possible to turn the operating rod 3 during operation of the 
forceps by turning the connecting ring 32. This is effected by keys 11a, 
12a and 13a provided on the operating rod 3. Proximal displacement on the 
rod 3 will cause any key 11a, 12a, 13a adjacent a cam 11, 12, 13 not 
engaged by a link assembly to engage an aperture 22 in an adjacent link 
assembly plate 16, 18, 20. The rods is thereby secured against turning. 
In order to guarantee the reliability and functional efficiency of the 
forceps designed according to the invention, the sleeves 14, 17 and 19 
should advantageously be secured against turning, for example, by means of 
a peg engaging an axially extending groove at all times. Furthermore the 
three link assemblies should be permanently fixed to one another, in order 
to guarantee that the complementarily designed apertures 22 always take up 
the same position in relation to one another. This is to ensure that the 
relative twisting of the link assemblies during use is precluded. Such 
twisting would prevent the forceps operating in the same manner described 
above. 
Having described the invention in detail with reference to the preferred 
embodiment, it will be apparent that modifications and variations are 
possible without departing from the scope of the invention defined in the 
appended claims.