SEPARABLE ECONOMICALLY PARTIALLY DISPOSABLE
FLEXIBLE BIOPSY FORCEPS
Field of the Invention
Biopsy forceps with a flexible support cable, a jaw mount on the support cable with jaws, and a control wire to operate the jaws. The expensive jaw mount and jaws, and the control wire
are readily removable from the support cable so the cable can be discarded, and the more expensive mount, jaws and control wire, may be cleaned and reused. Only the less expensive
support cable need be replaced. Background of the Invention
Biopsy forceps for endoscopic usage characteristically include a pair of pivotally mounted jaws mounted at the distal end of a tubular support member. Rigid instrument constructions
utilize a rigid tube for supporting the jaws. Flexible constructions utilize a flexible tubular cable for supporting the jaws.
Rigid instruments of this type tend to be more expensive, and are intended to be re-used
They are designed for this, and are rather easily cleaned and sterilized for their next use
However, flexible instruments involve a different set of problems, one of which is the near
impossibility of cleaning such instruments, especially when the jaw mount is permanently attached to the support cable. The internal dimensions and clearances are very small, and because the
cables are tightly wound helical springs, it is impractical to reach the inside of the support cable
to clean it. As a consequence, flexible biopsy forceps are usually discarded after a single use. The
mount, the jaws, and the control wire are the greatest part of the cost of the instrument. The
support cable is not very expensive, but the jaws are quite expensive because they are small, held
to close tolerances, and have sharpened cutting edges.
Accordingly, if an arrangement can be made such that the jaw mount can readily be removed and replaced, then it along with the jaws and control wire which are attached to it can
easily be cleaned. Then the inexpensive support cable can be discarded and replaced with a new clean one. The expensive parts of the instrument are thereby saved and re-used. The only cost
for re-use is the small expense of a new support cable.
As simple as this objective sounds, it has not heretofore been attained because of the
difficulty of removably attaching the mount to the resilient spring-wound support cable The spring cannot be threaded, and it is impractical to form internal threads in the small jaw mount
Accordingly, the jaw mounts have been permanently affixed, such as by crimping, which prevents the mount from being removed and re-used. Such an instrument is not re-usable because it cannot
be cleaned.
It is an object of this invention to take advantage of an inherent property of the support cable to enable a jaw mount to be removably mounted to a helically-formed support cable, and then be applied readily to another one.
Brief Description of the Invention
A biopsy forceps according to this invention includes a flexible tubular support cable with
an internal passage. The support cable has a proximal end and a distal end
A jaw mount is mounted to the support cable at its distal end. It supports a pair of pivoted jaws having sharp cutting edges that are moved toward and away from one another by a control
wire. The control wire passes through the passage in the support cable It connects to the jaws
at the distal end
The support cable and control wire are attached to actuation means such as a scissor type
grip, or a thumb loop and handle. Both are well-known means for moving a control wire in a
support cable
According to this invention, the support cable is a tightly wound helical spring. It is made of a suitable metal, and of such dimensions that it can readily bend to conform to bends in a cavity into which it is inserted, such as the colon. Inherently, its outer surface has a helically shaped
groove and crest, much like a helical thread. Because the support cable is inherently springy in
the sense of deflectibility, it can be compressed radially (lengthening slightly to enable this), and will exert a spring-back force against a body tending to compress it.
It follows that if the mount has a tubular socket whose internal diameter is suitably smaller than the outermost diametrical dimension of the support cable's convolutions, and can be placed over them, then the jaw mount will be reliably retained. The nearest known approach to this arrangement is to place the end of the support cable
in a socket in the jaw mount with a net fit or an over-size fit, and crimp it in place. This destroys
the jaw mount for re-use.
According to this invention, the socket makes an interference fit with the convolutions,
and is placed over them by means of rotating it around the cable's axis so that the convolutions tend to "thread" their way into the socket even though the socket has no threads. In fact, it is
cylindrical. Removal is the reverse - the mount is simply turned in the opposite direction.
Accordingly the jaws, jaw mount, and control wire, which are readily cleaned, can be re¬
used indefinitely, requiring only a new support cable each time. The instrument is taken apart to
be cleaned and the jaw mount can readily be applied to a new support cable. The above and other features of this invention will be fully understood from the following
detailed description and the accompanying drawings, in which:
Brief Description of the Drawings
Fig. 1 is a side view of presently-preferred embodiment of the invention;
Fig. 2 is an axial cross-section of the portion marked "2" in Fig. 1; and
Fig. 3 is a fragmentary view showing the embodiment of Fig. 1 disassembled.
Detailed Description of the Invention
A biopsy forceps 10 according to this invention includes a support cable 11. The support cable has a distal end 12 and a proximal end 13. The support cable is a flexible metal helically wound wire structure having coil convolutions 15 with a groove 16 between adjacent
convolutions, and a curved crest 17 at the maximum diameter of the convolutions. The convolutions abut each other closely, but they are not attached to one another. The support cable
can lengthen, and its diameter can be reduced. In this invention, the diameter is reduced, and the support cable lengthens locally and slightly to enable it. A jaw mount 20 has a socket with an internal wall 21. Wall 21 is cylindrical, although it may also have a short bell-mouth section 22 or internal bevel to provide a lead-in for the cable. The diameter 23 of the cylindrical portion is smaller than the maximum diameter 24 of the convolutions of the support cable.
Jaws 30, 31 are hingedly mounted to the jaw mount. They have respective sharp cutting edges 32, 33, which when brought against or past each other will cut the specimen loose. For this
purpose each has a respective lever arm 34, 35 connected to a control wire 40. The control wire
extends through the passage in the support cable.
The instrument is assembled by inserting the control wire into the passage. Then, when
the socket of the jaw mount reaches the distal end of the support cable, it is rotated while being
axially pressed over the distal end. This will slightly compress the coiled structure, and the cable passes along the support cable very much like a threaded movement, except that there is no
thread.
Retention of the jaw mount is quite reliable, because of the substantial spring-back force
exerted radially by the convolutions against the inside wall of the jaw mount. The amount of
compression varies with the dimensions and characteristics of the support cable. A cable having an external diameter of about 2 mm, will generally be compressed diametrically by about 5%, the support cable being a wound stainless steel wire. The dimensions of the mount will be selected so its outer diameter will be about equal to that of the support cable. Often the support cable will have a coating 41 (Fig. 3) of Teflon or some other plastic. It will be stripped from the cable over the inserted length. The outer diameter of the mount and of the layer will be approximately equal.
Accordingly, a flexible biopsy forceps can be provided whose most expensive parts can be cleaned, and which requires the replacement only of a relatively inexpensive length of cable when it is to be cleaned and reused. This invention is not to be limited by the embodiment shown in the drawings and described in the description, which is given by way of example and not of limitation, but only in accordance with the scope of the appended claims.
What is claimed: