GB2287760A

GB2287760A - Gas-tight seal

Info

Publication number: GB2287760A
Application number: GB9420633A
Authority: GB
Inventors: William John Hoskin; Nicholas Richard Kemp
Original assignee: Microsurgical Equipment Ltd
Current assignee: Microsurgical Equipment Ltd
Priority date: 1994-03-26
Filing date: 1994-10-13
Publication date: 1995-09-27
Anticipated expiration: 2014-10-13
Also published as: GB9420633D0; GB2287760B; GB9406038D0

Abstract

A gas-tight seal module 6 is incorporated in a trocar system to form a gas-tight seal about an instrument 12 inserted into the cannula of the trocar system. The module 6 incorporates an apertured disc 30. The aperture in the disc can be stretched to accommodate a seal about an instrument 12 inserted into the cannula. The disc is carried by a flaccid membrane 20 which extends across the module 6. A pair of rigid washers 32 and 34 clamped on opposite sides of the disc 6 are constrained for movement between two parallel spaced surfaces. The disc is thus freely moveable in its own plane to accommodate off-axis movement of the instrument so avoiding the breakage of the seal with the instrument which would otherwise occur if the disc did not have the same freedom of movement. The disc 30 also acts to clean the surface of the instrument when withdrawn so as to avoid contamination of a flap valve 10 upstream of the disc 30. <IMAGE>

Description

GAS-TIGHT SEALS The present invention relates to gas-tight seals and to trocar systems incorporating such seals.

Trocar systems are used during abdominal operations for maintaining a passage through the abdominal wall of a patient. Trocar systems generally comprise a cannula in the form of an elongate tube terminating in an enlarged upper body and an obdurator or cutting tool which is fed through the enlarged upper body and down the elongate tube to pierce the abdominal wall so that the elongate tube can follow the tool through the wall. The cutting tool is then removed leaving the way clear for elongate surgical instruments or equipment, such as endoscopes, to be fed into the abdomen through the tube.

To provide space within the abdomen, the abdomen is inflated with a gas and this allows easy access to the various organs located within the abdomen. To maintain gas pressure the trocar system is provided with a flap valve which is urged by the pressure of gas into a closed state. The flap valve has, however, to be opened to allow the passage of surgical tools therepast. Accordingly a sealing system is provided in the enlarged upper body to provide a seal around the surgical instrument once it has been inserted into the enlarged upper body. This now creates a gas lock between the flap valve and the seal and so the flap valve can now be opened (either by pushing the instrument against it or by other means) substantially without loss of pressure in the abdomen. The instrument can now be fed into the abdomen and manipulated as required. Usually more than one trocar is used so as to provide multiple entry points into the abdomen.

The diameter of the instruments used is usually much smaller than the diameter of the tube or the enlarged body and so a considerable amount of lateral off-axis movement of the instruments can and does take place in order to effect the desired manipulation of the instrument. Because the seals used are static any movement of the instrument other than axial is liable to strain the seal often to the extent of temporarily breaking the seal and so allowing gas to escape. Also most seals are designed with a specific diameter of instrument in mind and so different seals or adaptors are required when changing instruments.

It is an object of the invention to provide an improved seal.

According to the present invention there is provided a seal comprising a gas impermeable membrane extending across a chamber and secured to make a substantially gas-tight seal with the internal wall of the chamber, said membrane having a central elastic disc shaped portion with an opening which can be stretched to accommodate the passage of elongate instruments of different cross-section to form a substantially gas-tight seal with such instruments, means for constraining said disc shaped portion for displacement in a predetermined plane, the outer annular portion of the membrane being flaccid and sufficiently loose to allow the displacement of said disc shaped portion substantially without impediment.

A gas-tight seal embodying the present invention will now be described, by way of example with reference to the accompanying diagrammatic drawings in which: Figure 1 is a section through a trocar system down which a surgical instrument has been passed; Figure 2 is a fragmentary exploded view of the gas-tight seal module of the trocar system; Figure 3 is a section through the gas-tight seal module accommodating a surgical instrument; Figure 4 is the same section as in Figure 3 but with the surgical instrument laterally displaced; and Figure 5 is a plan view of a valve seal used in the module of Figure 2.

The trocar system shown in Figure 1 comprises an elongate tube 2 terminating in an enlarged upper body portion 4-. The enlarged upper body portion 4 accommodates a removable seal module 6. The seal module 6 may be sealingly locked into the body portion 4 by a screw threaded cap 8. An elongate medical instrument 12 (for example the optical probe of an endoscope) passes through the seal module 6 and the tube 2.

The seal module 6 is shown in more detail in Figure 3. The module 6 comprises a cylindrical body portion 14 which is open at one axial end and closed by an end wall 16 at the opposite axial end. The end wall 16 has a central circular opening 18. A membrane 20 extends across the inner chamber defined by the body portion 14.

The membrane 20 has a flat outer circumferential portion 22 (see Figure 2) having an outer circumference substantially equal to the inner circumference of the body portion 14. A cylindrical clamping ring 24 is located within the chamber to urge the circumferential portion 22 against the inner face of the end wall 16.

The membrane 20 has a central disc shaped portion 28 and an intermediate undulating portion 28 which allows the central disc shaped portion 26 to move freely within predetermined limits with respect to the outer circumferential portion. The membrane is of flaccid material, for example latex. The central disc shaped portion 28 is reinforced with a disc 30 of silicone material. The disc 30 is clamped to the disc shaped portion 28 with the aid of a pair of co-operating rigid washers 32 and 34. Pins 36 in the washer 32 pass through mating holes in the disc 30 and portion 26 to engage in a locking (push-fit) manner with corresponding holes 38 in the washer 34.

The clamping ring 24 has a radially inwardly extending flange 40 which when the ring 24 clamps the portion 22 against the wall 16 forms with the wall 16 a space in which the sub-assembly of washers 32 and 34 has just sufficient clearance tor sliding movement in the plane of the disc 30. The central portion 26 and the disc 30 are thus imprisoned or constrained for movement in two dimensions in their own planes.

A locking member 42 is accommodated in the body portion 14 to urge the clamping ring into clamping engagement with the outer circumferential portion 22. The locking member 42 may be a push fit under a circumferential lip 44 at the open axial end of the body portion to lock the components of the module 6 together.

In a modification other methods of locking the locking member in place may be used for example by using a circlip engaging a groove on the inner face of the body portion 14 or by means of a screw thread on the locking member engaging a corresponding screw thread on the inner face of the body portion 14. The locking member has an annular collar 46. The internal diameter of the locking member 42 and the washers 32 and 34 are substantially equal to the diameter of the opening 18.

The silicone disc 30 and the disc shaped portion 26 each have an aperture therein substantially smaller than the opening 18. For example the aperture may have a diameter, when the disc is unstressed, of less than a quarter of the diameter of the opening 18.

The diameter of the aperture in the disc, when unstressed, should also be smaller than the diameter of the smallest instrument that is intended to be used with the seal.

Because the disc is of silicone rubber the aperture can be stretched significantly beyond its original size by the insertion of larger diameter instruments. For example the diameter of the aperture could be more than doubled so as to accommodate different instruments having a diameter in the range of from 4 to 13mm. The locking member 42 has a circular recess which accommodates an elastic circular disc 10 of silicone rubber. The disc is imprisoned between the locking member 42 and the clamping ring 24 but allowed a very slight amount of play so that it can readily resume its original shape when released from being stressed. The disc 10 has a pair of centrally intersecting slits lOB (see Figure 5) which form four flaps lOA in the disc 10 which can be displaced by the pressure of the instrument 12. Normally the flaps lOA are closed and so they provide a valve which acts to prevent the escape of gas from the module.

Instead of intersecting slits a single profiled cut can be made in the disc to form a displaceable flap for the instrument to displace and pass through. In operation the module 6 is locked into the enlarged upper portion of the body portion 4 of the trocar system using the cap 8. Upon the insertion of the instrument 12 the flaps lOA are displaced to allow the passage of the instrument 12 but will form a partial seal around the instrument 12. The instrument is then passed through the silicone disc 30 which will form a tight seal about the instrument. Upon withdrawal of the instrument 12 any debris drawn by the instrument from the abdominal area will be scraped off the instrument by the silicone disc 30 and so there is little or no danger of such debris being lodged in the slits of the disc 10 to prevent complete closure of the flaps upon withdrawal of the instrument. The complete closure of the flaps thus again prevents the escape of gas from the module.

The instrument 12 can be displaced radially of the module 6 substantially without resistance because of the flaccid undulating portion 28 (see Figure 4). The disc 30 is however constrained against angular displacement out of its plane by the washers 32 and 34.

Instead of washers 32 and 34 being used to constrain the disc 30, axially extending projections on the axial end wall 16 and the flange 40 may be used to constrain the disc 30 for movement in its own plane. In this case the disc 30 may be welded or adhesively secured to the membrane 20. In yet another modification, the disc 30 may form an integral part of a composite membrane 20.

It will be appreciated that the module 6 can be manufactured as a disposable module to be discarded after a single use.

If the module is required to be reusable it can readily be removed from the trocar and autoclaved.

Instead the module can be subject to Gamma or ethyleneoxide treatment.

Claims

1. A seal comprising a gas impermeable membrane extending across a chamber and secured to make a substantially gas-tight seal with the internal wall of the chamber, said membrane having a central elastic disc shaped portion with an opening which can be stretched to accommodate the passage of elongate instruments of different cross-section to form a substantially gas-tight seal with such instruments, means for constraining said disc shaped portion for displacement in a predetermined plane, the outer annular portion of the membrane being flaccid and sufficiently loose to allow the displacement of said disc shaped portion substantially without impediment.

2. A seal according to Claim 1 wherein said constraining means comprises a pair of rigid annular rings matingly clamping said disc shaped portion between them and located between a pair of parallel facing surfaces which constrain said rings for slidable displacement in said predetermined plane.

3. A seal according to Claim 1 wherein said disc shaped portion is semi-rigid and wherein said constraining means comprise guides located on opposite sides of the disc shaped portion in closely spaced proximity to said disc shaped portion.

4. A seal according to any one of Claims 1 to 3 wherein said outer annular portion of said membrane is of latex.

5. A seal according to any preceding claim wherein said disc shaped portion is of silicone rubber.

6. A seal according to Claim 2 wherein said annular rings are of plastics.

7. A seal according to any preceding claim comprising a body defining said chamber, said chamber being generally cylindrical, open at one axial end and closed at the opposite axial end except for a central opening substantially similar in size to said disc shaped portion, an annular clamping ring sized to be accommodated in said chamber and to urge the circumferential portion of said membrane against the closed axial end of the chamber, a radially inwardly directed flange extending from said clamping ring and terminating in a central opening aligned with and having a size comparable with that of the central opening in said one axial end of said chamber and a locking member for locking the clamping ring in the chamber of said body.

8. A seal according to Claim 7 wherein said locking member forms a snap fit with said chamber.

9. A seal according to Claim 7 or to Claim 8 wherein said locking member includes an annular collar for guiding said elongate instruments towards the opening in said membrane.

10. A module for a trocar comprising a body, a seal according to any preceding claim located in a chamber in said body so that said membrane extends across an opening in one end portion of said body and a valve extending across an opening in the opposite end portion of said body, said valve being normally closed to prevent the escape of gas from the opening at said opposite end portion of the body, but being openable to allow the passage of a said instrument therethrough.

11. A module according to Claim 10 wherein said valve comprises a laminar member of resilient material provided with a cut defining at least one flap which can be displaced by the passage of said instrument.

12. A module according to Claim 11 wherein said laminar member is provided with intersecting cuts which define a plurality of flaps.

13. A seal substantially as hereinbefore described with reference to the accompanying drawings.

14. A module for a trocar substantially as hereinbefore described with reference to the accompanying drawings.