Forceps- or tweezers-shaped surgical instrument

Forceps have two branches movable opposite one another against a spring force and with a lock that fixes the distance between the branches. The lock engages as the two branches approach one another and is released by closing the branches further. This locking mechanism includes a locking arm mounted between the branches with a free end that rides between a sliding surface located on the inside wall of one of the branches and a guide member. The free end carries a locking element that engages a locking step formed on the sliding surface. The guide urges the locking element against the locking step and then, with a further closing movement of the branches, directs the locking arm free end to its initial, fully opened position. The guide has an enlarged opening that allows the free end to fall back onto the sliding surface.

This invention concerns a forceps- or tweezers-shaped surgical instrument 
as described in the specification of claim 1. 
Such instruments are used in the surgical field in many ways, for example 
as pincers for applying clips, needle holders, and vascular clamps or with 
forceps of the most diverse designs. In all of these instruments, two 
branches can move elastically against one another, for example the two 
arms of a forceps or the branches of a tweezers-shaped instrument 
connected to one another at the ends by a pivot. 
It is already known how to design such instruments so that they can be 
locked in a specific intermediate or closed condition. 
For example, forceps for applying microclips to clamp off blood vessels are 
known in which a locking projection fastened to the inside wall of one 
branch passes through an opening in the other branch when the forceps are 
closed and locks behind it so that the forceps are locked in the closed 
position (AESCULAP brochure 195-C "Micro-, Neuro-, and Blood Vessel 
Surgery", 13th edition, April 1979). When the forceps are to be opened, 
the locking projection must be pushed back through the opening in the 
branch by finger pressure. In the case of tweezers, a so-called sliding 
ring lock is also known for fixing the separation of the two branches. For 
this purpose, one branch has a hook-shaped locking element extending away 
essentially perpendicular to the other, which locks behind the head of a 
pin fastened to the other branch. To release it, the tweezers are 
completely closed. The locking projections then slide on a ring mounted 
movably on the pin and carry this with them during the opening against the 
head of the pin in such a way that the hook-shaped locking elements can 
slide directly over the head of the pin when the ring is pulled back. Such 
systems are relatively complicated in structure and subject to problems 
when dirty, since it cannot then be guaranteed that the ring resting 
loosely on the pin can be pushed up to the head. However, this is a 
prerequisite for reliable operation. 
In tweezers for applying clips, two spring locks have been attached to the 
insides of the branches for setting the mutual separation, one spring lock 
with a knife-shaped end and one spring lock with a V-shaped end whose 
vertex faces the other branch. Upon closing, the knife-shaped end of the 
one element slides past on one side of the V-shaped end of the other 
element and ultimately springs from the rear into the V-shaped end, so 
that the branches are secured against opening. When the tweezers are fully 
closed, the knife-shaped end again comes out of the V-shaped end and 
slides past the V-shaped end along the other side when the tweezers are 
then opened. With such a device, it is intrinsically possible to lock the 
instrument in a specific closed position when closing it, and to release 
the locking again only by further closing (cf. AESCULAP Company brochure 
195-C "Micro-, Neuro-, and Blood Vessel Surgery", 13th edition). However, 
it is a drawback in this locking system that the two parts must be aligned 
very precisely to one another and reliable operation is no longer 
guaranteed even with a slight play when closing the instrument or with 
slight lateral bending of the branches. In the known locking systems, it 
is not possible to vary the particular fixed opening position, i.e., to 
lock the instrument in a smaller or a wider closed position if desired. 
The purpose of this invention is to perfect a generic instrument in a 
structurally simple manner in such a way that a reliable locking of the 
separation of the two branches and a release of this locking by simply 
releasing the branches together is possible under all circumstances. 
This problem is solved in an instrument of the type described initially 
pursuant to the invention by the features specified in the characterizing 
section of claim 1. 
The design pursuant to the invention leads to the fact that upon closing, 
the locking element held on the elastic locking arm slides along between 
the guide on the one hand and the sliding surface of the other, with the 
locking element being pressed elastically against the sliding surface by 
the guide. As soon as the locking element jumps over the locking step, it 
locks on the shoulder formed by the locking step under the action of the 
elastic guide, and prevents the opening of the two branches. Upon further 
closing, the locking element is pushed further forward until it is 
released by the elastic guide. In the subsequent opening of the branches, 
the locking element slides on the guide and slides along the guide, on the 
side of the guide facing away from the sliding surface. The guide then 
constitutes a bridge which permits the locking element to slide over the 
locking step. Upon further opening, the locking element then springs down 
from the guide and again rests elastically on the sliding surface. 
If the two branches are then closed again, the locking element enters the 
gap between the sliding surface and the guide so that the guide again 
pushes the locking element elastically against the sliding surface when it 
is pushed further forward. 
In a preferred form of embodiment, it is provided that the locking arm is a 
leaf spring fastened on one end to the inside wall of one branch. It can 
then at the same time assume the task of pressing the two branches 
elastically away from one another so that the spring provided specifically 
for this purpose can be eliminated. 
The locking element is preferably a pin extending laterally away from the 
free end of the locking arm. 
It is also extraordinarily beneficial if the guide is composed of a leaf 
spring. 
In a preferred example of embodiment of the invention, the guide is bent 
away in the closing direction beyond the locking step in the direction 
toward the sliding surface, with the bending of the guide preferably being 
only far enough beyond the locking step that the bent section of the guide 
presses the locking element in the locking position against the locking 
step opposite to the closing direction. 
In a preferred example of embodiment, it is provided that the locking arm 
has a locking element projecting on two sides and a guide is located on 
each side of the locking arm. The two guides are preferably composed of 
two parallel blades which have a separation from one another at the 
section covering the locking step which is at least as large as the width 
of the locking arm but smaller than the width of the locking element, 
while in the section before the locking step in the closing direction it 
is larger than the width of the locking element. This guarantees that the 
locking element is pressed elastically against the sliding surface during 
the motion in the closing direction in the region in front of the locking 
step and in the region of the locking step itself, and that the locking 
element when moving in the direction of opening can again spring onto the 
sliding surface after sliding on the guide in the closing direction in 
front of the locking step. 
It is desirable here if a longitudinal groove is provided in the sliding 
surface into which the free end of the locking arm extends, since the free 
end of the locking arm extending into the longitudinal groove is guided in 
this way against lateral shifting. It is beneficial here if the free end 
of the locking arm extending into the longitudinal groove in the sliding 
surface is bent towards the sliding surface. The locking element is 
preferably held to the end of the locking arm in the region of the bend. 
The guide can be fastened to a step in the sliding surface located in front 
of the locking step in the closing direction whose height is greater than 
the height of the locking element. This ensures that the locking element 
can slide on the sliding guide when moving into the open position by 
spring pressure, and below the guide in the subsequent motion in the 
closing direction. 
In a preferred example of embodiment of the invention, it is provided that 
the upper edge of the locking step projects compared to the rear step 
surface joining the two sliding surface regions. The projecting top edge 
then holds the locking element in its engaged position in direct contact 
with the step and prevents the locking element from springing back 
unintentionally to the upper section of the sliding surface. 
It is particularly beneficial if at least one other locking step is located 
in the sliding surface before the locking step in the closing direction 
and if the guide also presses the locking element elastically against the 
sliding surface in the region of this other locking step. In this way, it 
is possible to lock the two branches at various distances, with each 
locking step corresponding to a specific separation of the branches. 
Basically, the sliding surface can have several such locking steps. The 
guide in such an example of embodiment extends from the last locking step 
in the closing direction across all of the locking steps, so that the 
locking element when moving in the opening direction slides on the guide 
over all of the locking steps and only then springs back to the sliding 
surface. 
Another covered locking step can be located before the beginning of the 
guide in the closing direction, against which the locking element rests 
when the instrument is in the resting position under the action of a 
spring force pushing the branches apart from one another. The locking 
element and the locking arm then have the function of securing the two 
branches at a maximum distance and preventing further separation of the 
branches from one another. 
In a preferred refinement, the locking arm can be lockable in various 
positions in the longitudinal branch direction at its point of fastening 
to the inside of the one branch, preferably by fastening the locking arm 
to the branch with a screw which passes through a longitudinal hole in the 
section of the locking arm resting against the inside wall of the branch. 
In this way, the opening of the two branches which results when the 
locking element engages behind the locking step of the sliding surface can 
be continuously adjusted by varying the fastening of the locking arm in 
the longitudinal direction of the branch. 
To prevent a pivoting of the locking arm with respect to the inside of the 
branch, it can be provided that a longitudinal groove is located in the 
inside wall of the branch on which the locking arm is held, into which a 
projection of the locking arm projects. This projection constitutes 
protection against rotation. 
As mentioned previously, the securing system pursuant to the invention can 
be used for all forceps- or tweezers-shaped surgical instruments whose 
branches are pushed apart from one another by spring force. For example, 
with tweezers for applying clips which have such a mechanism, it is 
possible to hold the clips in the tweezers for applying clips in an only 
slightly opened position, with the latter assuming a fixed open position 
because of the locking system. The clip held becomes completely open only 
when the operating site is reached, by pressure on the forceps. At the 
same time, the locking mechanism of the two branches is thereby unlocked, 
so that in the subsequent opening of the branches, the clip is released 
and the clip tongs can open completely. 
The opening of the clip tongs in the locked position can be selected so 
that the clips are not completely opened, contrary to previously known 
tongs, so that the clips are treated gently and in particular, the clips 
are prevented from losing their stretching force.

The invention will be explained below with the use of tweezers for applying 
clips, which are used to bring clips into position for clamping off blood 
vessels. It is understood that the invention can also be used for other 
forceps- and tweezer-shaped surgical instruments. 
The tweezers for applying clips illustrated in FIG. 1 have two arms or 
branches 1 and 2 which can pivot with respect to one another by means of a 
connection 3. At the forward ends, the two branches are formed as tweezers 
to hold a clip not shown in the drawings, and the ends of the two branches 
are designed as spring arms 4 and 5 which interpenetrate at the end and 
are bent overall in such a way that they press the two branches away from 
one another. Because of the force of these spring arms, the tweezers are 
in the open position at rest. 
To lock the two branches in a partially closed position, a locking 
mechanism is provided which comprises an elongated thin leaf spring 6 
attached to the inside of one branch and a sliding surface 7 fastened to 
the inside wall of the opposite branch. The construction of these parts 
will be described below in detail with the use of the illustration of 
FIGS. 2 through 6. 
The sliding surface 7 is divided into an upper surface 8 and a lower surfce 
9, both of which run essentially parallel to the inside wall 10 of the 
branch holding the sliding surface. The upper surface 8 has a greater 
distance from the inside wall 10 then the lower surface 9, and in the 
transition region of the two partial surfaces they form a locking step 11 
which has an essentially circular arc-shaped cross section in its vertical 
region, so that the upper edge 12 of the locking step projects in a 
horizontal direction beyond the rear wall 13 of the step (FIG. 6). Another 
step 14 is located at the end of the upper surface 8, which has a similar 
form in cross section to that of the locking step 11. 
The described sliding surface is defined by a sliding body 15, which is 
fastened to the branch by screws 16, for example (FIG. 6). This sliding 
body 15 has a central longitudinal groove 17 which divides the entire 
sliding surface 7 into two halves (FIG. 5). The purpose of this 
longitudinal groove 17 will be described below in detail. 
The vertically bent end 18 of a leaf spring 19 is fastened to the rear of 
the sliding body 15, and the spring extends essentially parallel to the 
upper surface 8. Its free end 20 bent in the direction of the sliding 
surface terminates just beyond the locking step 11. In the area of the 
step 14, the distance of the leaf spring 19 from the upper partial surface 
8 is determined by the height of the step 14, while the leaf spring in the 
resting state rests against the upper edge 12 of the locking step 11, as 
can be seen from the illustration of FIG. 6. 
The leaf spring 19 is divided into two blades 22 and 23 by a gap 21 
essentially covering the longitudinal groove 17, with the gap running from 
the free end 20 of the leaf spring 19 to a broadened, elongated opening 
24. The opening 24 is located above the upper surface 8 in the region 
before the step 14 and is arranged so that its edge 25 facing the step 14 
slightly overlaps the step 14 (cf. FIG. 6). 
The opening 24 is wider than the gap 21, so that the two blades 22 and 23 
are connected to the end of the leaf spring 19 held on the sliding body by 
narrow bridges 26 and 27. 
The leaf spring 6 held on the other branc constitutes a locking arm, to 
whose free end 28 is fastened a locking pin 29 projecting out on both 
sides. The leaf spring is bent around this locking pin 29 in the direction 
of the other branch and forms a tab 30 projecting approximately 
perpendicular to the leaf spring. 
The locking arm formed by the leaf spring is fastened to the one branch by 
means of a screw 31 which passes through a longitudinal hole 32 arranged 
in the longitudinal direction at the fixed end of the leaf spring 6. To 
prevent rotation of the leaf spring on the branch, the branch has a 
longitudinal groove 33 into which extends the end of the leaf spring 6 
bent towards the branch. The width of the longitudinal groove 33 
corresponds to the width of the end 34 projecting into it. 
The leaf springs are arranged on the two branches in such a way that the 
locking pin carried by the free end of the leaf spring slides on the two 
halves of the sliding surface 7 with its two laterally projecting sections 
when the tweezers are closed, i.e., when the branches are approaching one 
another (cf. FIG. 2). The width of the longitudinal groove 17 of the 
sliding body 15 corresponds essentially to the width of the tab 30 on the 
free end of the leaf spring 6 which extends into the longitudinal groove 
17 when the locking pin moves along the sliding surface, and thus guides 
the free end of the leaf spring relative to the sliding body. The width of 
the gap between the two blades 22 and 23 is at least as great as the width 
of the leaf spring 6 in this region, so that the leaf spring can be pushed 
between the two blades without hindrance. However, the gap is less wide 
than the locking pin 29 at the free end of the leaf spring 6. On the other 
hand, the opening 24 is wider than this locking pin 29. 
The method of operation of the lock pursuant to the invention will be 
described below with the use of FIGS. 2 through 4. 
In the open position, the tweezers are in the position illustrated in FIG. 
2. The two branches are pushed apart from one another by the spring arms 4 
and 5, so tht the locking pin 29 is drawn towards the step 14. In this 
position, the locking pin is fixed by the leaf spring 19 whose edge 25 
extends beyond the step 14 towards the front. Consequently, the leaf 
spring 6 secured at its free end between the leaf spring 19 and the 
sliding surface 7 at the step 14 limits the opening of the tweezers. 
By pressing the two branches together, the free end of the leaf spring 6 
with the locking pin 29 is pushed along the upper surface 8 in the closing 
direction, with the locking pin 29 sliding at the end of the opening 24 
away from the step 14 beneath the two blades 22 and 23 of the leaf spring 
19 and being pressed elastically against the upper surface 8 of the 
sliding surface 7 by these blades which form a guide during the further 
advance. It is essential for this purpose that the distance of the leaf 
spring 19 at the beginning of the blades 22 and 23 from the upper partial 
surface be greater than the height of the locking pin. 
In the further advance of the locking pin in the closing direction, the 
locking pin finally jumps over the locking step 11 to the lower partial 
surface 9 and is pressed against the rear wall of the locking step 11 by 
the bent free end 20 of the leaf spring 19. The locking pin is fixed in 
this position, since it can no longer reach the upper surface because of 
the projecting upper edge 12 of the locking step 11 and because of the 
force of the leaf spring 19. The tweezers are therefore now locked in an 
intermediate position (FIG. 3). 
In pressing the branches further together, the locking pin is shifted on 
the lower partial surface 9 farther into the closed position, while it 
bends the ends of the leaf spring 19 elastically backward and slides 
forward beneath this leaf spring. The tweezers can now be moved into the 
maximum shut position, with the locking pin reaching its forwardmost 
position on the sliding surface 7 (FIG. 4). 
When the distance between the branches is then again increased under the 
influence of the two spring arms 4 and 5, the locking pin finally reaches 
the bent free end 20 of the leaf spring 19 and slides onto the two blades 
22 and 23, since the distance of the front edge of the leaf spring 19 from 
the lower surface 9 is smaller than the height of the locking pin. During 
the further opening, therefore, the locking pin slides over the side of 
the blades 22 and 23 away from the sliding surface, which thus constitute 
a guide for the locking pin, until the locking pin snaps elastically onto 
the upper surface 8 in the region of the opening 24. In the further 
opening, the locking pin 29 again finally reaches the initial position 
illustrated in FIG. 2, described above, in which the tweezers are opened 
to the maximum. 
In this way it is possible to close the tweezers without producing a 
locking in an intermediate position if the tweezers are closed until the 
locking pin comes out of the gap between the leaf spring 19 and the 
sliding surface (FIG. 4). However, if the tweezers are closed only until 
the locking pin engages behind the locking step 11 (FIG. 3), the tweezers 
remain in this open position, which can be selected, for example, so that 
in this position a clip is held but only slightly opened, so that it can 
be introduced into the operating area in this position. To release the 
lock, it suffices to close the tweezers further briefly and then to open 
them again. 
The exact position of the maximum open position and the central locking 
position can be chosen by shifting the fixed end of the leaf spring 6 
along the branch. This is possible continuously because of the 
longitudinal hole 32. 
Various modifications of the preferred example of embodiment decribed with 
the use of FIGS. 1 through 6 are possible. For example, the upper surface 
can be divided into several partial surfaces 36 and 37 subdivided in each 
case by another locking step 35, as illustrated in FIG. 7. In this example 
of embodiment also, the leaf spring 19 covers the entire upper surface up 
to just beyond the lowest locking step. In this way, two fixed 
intermediate positions can be occupied. Of course, it is also possible to 
divide the sliding surface into partial surfaces by a larger number of 
locking steps and thus to provide a number of possible intermediate 
positions. 
In the examples of embodiment illustrated, the leaf spring 6 constituting a 
locking arm is arranged in such a way that the locking pin (locking 
element) is shifted in the direction towards the closing of the branches; 
this is not absolutely necessary. It would also be possible to attach the 
leaf spring 6 to the opposite branch in such a way that the free end is 
shifted in the opposite direction while closing the tweezers. In such a 
design, the entire sliding body would be positioned on the opposite 
branch, rotated by 180.degree.. 
The design of the locking arm as a leaf spring with suitable dimensions 
would also make it possible to dispense with the spring arms 4 and 5 
pushing the two branches apart from one another, since the leaf spring 6 
shows the same action. 
The locking arm does not necessarily have the form of a leaf spring. For 
example, it would also be possible to link the locking arm with the 
ability to pivot on the inside of one branch, and by means of a 
compression spring against the inside wall of the opposite branch, and 
thus to press against the sliding surface located there.