GB2315021A - Valved, instrument-receiving cannula - Google Patents

Abstract

The cannula has a bore for the passage of an instrument or trocar therethrough, a gas-sealable port 1 for insertion of the instrument into the bore and a valve in the bore which is arranged to open when the instrument is inserted in the cannula and to seal the bore when the instrument is removed. The valve may comprise a spring-biased ball 6 which bears against an O-ring 5, the ball moving on a track disposed at 15-45{ to the bore. The valve may alternatively be closed by gas pressure within the bore.

Description

Cannula Valve This invention relates to the field of Minimally Invasive Surgery and specifically to the cannula systems used to permit gas insuflation and the passage of instruments into body cavities.

In this field it is already known that there are many designs of cannula valve which employ one of four methods to create a gas tight seal and allow the passage of instruments. These are: side action trumpet valve; spring loaded flap valve; cross cut seal and duckbill valve However these designs have the disadvantage that in their reusable format the valves are prone to damage and are often difficult to clean and reprocess; whilst in their single use/disposable format the devices are expensive having multiple components.

According to the present invention there is provided a cannula having a bore for passage of an instrument therethrough, a gas-sealable port for insertion of the instrument into the bore, and a valve in the bore, the valve being arranged to open when an instrument is inserted into the cannula, and to seal the bore when the instrument is removed.

The valve preferably seals the bore (optionally at an internal location) when the gas-sealable port is opened. Preferably, the act of removing the instrument closes the valve before the seal at the gas-sealable port is disturbed. Similarly the valve is preferably arranged not to open until the seal at the gas-sealable port is engaged, thereby minimizing passage of gas through the bore.

The valve may comprise a ball which bears against an Oring to seal the valve, and can be pushed away from the O-ring by an instrument to open the valve when the instrument is located in the bore and the gas-sealable port is sealed. The ball preferably moves on a track which is disposed at an angle to the bore, and preferably at an angle which is generally between 15 and 45" to the bore, and towards the distal end away from the port. The valve may be closed by a spring acting on the ball, or by gas pressure within the bore.

The ball is preferably spherical, although other shapes with elliptical or other cross sections can be used.

Similarly, the O-ring is preferably circular although other shapes (ie elliptical) can be used. In most preferred embodiments the ball can roll against the track walls with minimal friction.

The invention also provides a valve adapted to be fitted to a cannula and arranged to open when an instrument is inserted into the cannula, and to seal the bore of said cannula when the instrument is removed therefrom.

The utilisation of spring loaded ball with seal seating arrangement acting across the cannula port moves easily out of the way when an instrument is inserted and provides low friction on the instrument whilst it is in use. In this active state a secondary seal at the top of the unit maintains the gas seal. When the instrument is withdrawn, the ball springs across and provides the gas seal before the instrument is removed from the top seal.

While further modifications and improvements may be made without departing from the scope of this invention, the following is a description of one or more examples of the invention, with reference to the accompanying drawings.

In providing a static seal which prevents the lost of gas pressure around an instrument while in use with the cannula, but which also ensures the same effective seal if the shaft itself is at any time immobile within the cannula, a moulded ring 1 forms a flexible annular lip profile which when in compression seals against any circumference of the correct diameter, this ring is positioned at the tope entry point of the cannula, held in a recessed section of spacer 2. The assembly of parts 1 and 2 is then compressed and held together as the top cap 3 is placed on the outer profile of space 2 and fixed in place. This sub-assembly is then located and bonded into the top recess of the main body 4, providing an open easy access which will seal against designated diameters of a particular size.

Spacer 2 along with cap 3 also provide the support required by an instrument or trocar during insertion to ensure that it is vertical and that no side edges cause damage or unseat the primary side seal "0" ring 5.

While in use these components also prevent lateral movement or any instrument away from the sealing profile to the top lip ring and excessive pressure against the side of the inner seal.

The inner seal, which prevents the loss of gas pressure when no instrument is present, is created by forcing the sphere 6 against the inside diameter of an "0" ring 5, the sphere being held in place by pad 7 and spring 8. Components 6, 7 and 8 are contained within a tubular sleeve insert 9. This sub-assembly or ring, ball, spring, pad and tube is inserted into the side angular recess of the main body 4 and sealed in place by plug 10, this arrangement also maintains the internal spring pressure against the ball.

The hermetic seal is the result of creating a circular nest between the outer surface of a relatively large diameter sphere as it is pressed against the smaller internal diameter of the "0" ring. By positioning the "0" ring and the ball seal assembly at an angle to the vertical, not greater than 450 not less than 150, an elliptical hole is created by the "0" ring in the path of anything inserted vertically through the top seal 1.

Variations on the size of the balls or "0" rings can be used to modify the assembly to suit different sized cannula (designed for use nominally on instruments of 5mm, lOmm and 12mm diameter).

An additional feature is the reduction or friction against any instruments in use by way of two methods, one is minimal point contact only between the sphere's diameter and the side of the shaft and two pads 7 which pushes the sphere against the "0" ring also allows for the rotation of the sphere if friction increases beyond a calculable amount.

Cannula assembly is completed by fixing tube 11 into the base of the main body 4.

At present the assembly methods of permanently fixing parts is by solvent bonding, but this can be adequately performed or substituted by ultra-sonic welding, taper fit or screw fittings, evolution of the manufacturing process will determine the final method.

In some cases an instrument of a smaller diameter than designated must be used. When this is necessary a reducing cap can be fitted to the top of the cannula by way of two bayonet pegs. This allows a gas seal to be maintained once the inner seal has been opened by that of an instrument where the O/D is significantly smaller than the I/D of the top lip ring.

The advantages of the invention and/or the ways in which the disadvantages of previously known arrangements are overcome include: this design provides exceptional sealing capabilities and free passage of instruments with the minimum of components thus allowing a substantial reduction in its manufactured cost.

This will allow the advantages of a disposable device to be available at a far lower cost than is currently possible.

Claims (15)

Claims

1. A cannula having a bore for passage of an instrument therethrough, a gas-sealable port for insertion of the instrument into the bore, and a valve in the bore, the valve being arranged to open when an instrument is inserted in the cannula, and to seal the bore when the instrument is removed.

2. A cannula as claimed in claim 1 wherein the valve seals the bore when the gas-sealable port is opened.

3. A cannula as claimed in claim 1 or 2 wherein the valve seals the bore at an internal location.

4. A cannula as claimed in any of the preceding claims wherein the act of removing the instrument closes the valve before the seal at the gas-sealable port is disturbed.

5. A cannula as claimed in any of the preceding claims wherein the valve is arranged not to open until the seal at the gas-sealable port is engaged.

6. A cannula as claimed in any of the preceding claims wherein the valve comprises a ball which bear against an O-ring to seal the valve and can be pushed away from the O-ring by an instrument to open the valve when the instrument is located in the bore and the gas-sealable port is sealed.

7. A cannula as claimed in any of the preceding claims wherein the ball moves on a track which is disposed at an angle to the bore.

8. A cannula as claimed in claim 7 wherein the track is disposed at an angle of between 15 to 450 to the bore.

9. A cannula as claimed in claim 7 or 8 wherein the track is disposed toward the distal end away from the port.

10. A cannula as claimed in any of the preceding claims wherein the valve is closed by a spring acting on the ball.

11. A cannula as claimed in any of claims 1 to 9 wherein the valve is closed by gas pressure within the bore.

12. A cannula as claimed in any of the preceding claims wherein the ball is spherical.

13. A cannula as claimed in any of the preceding claims wherein the O-ring is circular.

14. A cannula as claimed in any of the preceding claims wherein the ball can roll against the track walls with minimal friction.

15. A valve for use in a cannula as claimed in any of the preceding claims.