GB2304799A

GB2304799A - Pressure vessel latch with pressure activated interlock

Info

Publication number: GB2304799A
Application number: GB9617270A
Authority: GB
Inventors: Keith Hannant
Original assignee: Smiths Group PLC
Current assignee: Smiths Group PLC
Priority date: 1995-08-30
Filing date: 1996-08-16
Publication date: 1997-03-26
Anticipated expiration: 2016-08-16
Also published as: GB2304799B; GB9617270D0; GB9517656D0

Abstract

An autoclave has a door lock mechanism 20 comprising a plunger 21 urged by a spring 25 to a locked position in engagement with a rotatable locking plate 7 on the door 5. An electrical solenoid 26 displaces the plunger 21 to an unlocked position against the action of the spring 25, when energized. A pressure actuator 30 has a piston 31 driven by pressure within the autoclave. When internal pressure is above atmosphere, the piston 31 is driven against the rear end of the plunger 21 to displace it forwardly into a locked position. The force of the pressure actuator 30 is such that the solenoid 26 cannot unlock the plunger when it is locked by pressure.

Description

PRESSURE VESSELS This invention relates to pressure vessels.

The invention is more particularly concerned with pressure vessels, such as autoclaves, having a lockable door.

Most autoclaves, or similar pressure vessels, are fitted with a safety mechanism to prevent the user opening its door when the vessel is at elevated pressure. In one form, the safety mechanism is a pressure-operated lock, which mechanically locks the door when the pressure in the vessel rises above atmospheric pressure. An example of such a mechanism is described in GB 917008. One problem with pressure-operated door locks is that, if the autoclave has a vacuum phase, the door lock will be released when pressure in the vessel falls through atmospheric pressure. Some autoclaves also have an electrical door lock that operates at the start of a sterilizing cycle, to lock the door, and only releases at the end of the cycle. Such electrical locks are usually arranged to remain closed if power should fail.An example of an autoclave sterilizer having both a pressure lock and an electrical lock is the "SES Little Sister" sterilizer sold by Eschmann Bros. & Walsh Limited of Lancing, West Sussex, England.

Although such sterilizers can operate safely and reliably, the use of two separate locks complicates manufacture and servicing.

It is an object of the present invention to provide an improved pressure vessel.

According to one aspect of the present invention, there is provided a pressure vessel having a door that can be opened to allow access to the inside of the vessel, a door lock mechanism including a lock member, an electrical actuator, and a pressure actuator responsive to pressure in the vessel, the electrical actuator being operable to cause displacement of the lock member both from an unlocked position to a locked position and from a locked position to an unlocked position, and the pressure actuator being operable to prevent displacement of the lock member from a locked to an unlocked position even when the electrical actuator is operated to cause unlocking.

The lock mechanism preferably includes a spring that urges the lock member into a locked position, the electrical actuator including a solenoid, the solenoid urging the lock member into an unlocked position against the action of the spring when energized and, when unenergized, allowing the spring to urge the lock member to a locked position. The lock member may be a plunger that is displaceable along its length. The pressure actuator preferably includes a piston arranged to contact a rearwardly-facing surface of the plunger and displace it forwardly into a locked position when pressure in the vessel is above atmospheric pressure. The door may include a rotatable locking plate, the lock member being arranged, when locked, to engage the rotatable locking plate and prevent rotation of the locking plate.

According to another aspect of the present invention there is provided an autoclave sterilizer having a door that can be opened to allow access to the inside of the sterilizer, the sterilizer having a door lock mechanism including a lock member, an electrical actuator, and a pressure actuator responsive to pressure in the sterilizer, the electrical actuator being operable to cause displacement of the lock member both from an unlocked position to a locked position and from a locked position to an unlocked position, the pressure actuator being operable only to cause displacement of the lock member from an unlocked to a locked position, and the electrical actuator being unable to unlock the lock member when the pressure actuator holds the lock member in a locked position.

An autoclave sterilizer in accordance with the present invention, will now be described, by way of example, with reference to the accompanying drawing, in which: Figure 1 is a front elevation view of the sterilizer and; Figure 2 is a sectional side elevation of a part of the sterilizer.

The autoclave sterilizer has an outer housing 1 containing a conventional metal pressure chamber or vessel 2 of cylindrical shape, which is closed at its right-hand end by an end wall 3. The left-hand end 4 of the vessel 2 is open and can be closed by a door 5. The door 5 is mounted by a vertical hinge 6 at its left-hand edge so that the door can be swung open or closed. The rear of the door, facing the chamber 2, carries a circular locking plate 7, which can be rotated about a horizontal axis, through a limited angle, by means of a rotatable locking handle 8 on the front of the door. Several lugs 9 project around the outer edge of the locking plate 7 and engage behind brackets 10 on the housing 1 when the plate is rotated to a locked position. An O-ring seal 11 seals the locking plate 7 with an annular flange 12 around the left-hand end 4 of the pressure vessel 2.

A safety lock 20 is mounted in the housing 1 behind the door 5, above the pressure vessel 2. The safety lock 20 has a lock member in the form of a cylindrical plunger 21 with an enlarged head 22, which is shaped to extend within a locking aperture 23 in the locking plate 7. The plunger 21 is mounted in a support 24 for slidable horizontal movement along its length and is urged forwardly, to the left, into locking engagement with the aperture 23, by a helical spring 25 located between the support 24 and the enlarged head 22.

An electric solenoid coil 26 embraces the plunger 21 to the right of the support 24.

The coil 26 is connected to the autoclave control unit 27 and, when energized, the coil operates as an electrical actuator to apply a force to the plunger 21, tending to pull it rearwardly, to the right, against the action of the spring 25, to a position where the head 22 is out of the aperture 23 and the lock 20 is unlocked.

The lock 20 also includes a pressure actuator 30 mounted at the rear, right-hand end of the plunger 21. The pressure actuator 30 has a piston 31 aligned axially with the plunger 21 and slidable along a cylinder 32. The rear end of the cylinder 32 is connected via a pipe 33 to the interior of the pressure vessel 2, so that change in pressure in the vessel causes movement of the piston 31.

The sterilizer also includes a heater, water supply, vacuum pump and other conventional features, not shown.

When the autoclave is in its stand-by mode, the control unit 27 energizes the solenoid coil 26 so that the plunger 21 is pulled rearwardly, or inwardly, into an unlocked position.

Articles to be sterilized are placed in the vessel 2, the door 5 is swung closed and the handle 8 is turned so that the lugs 9 on the locking plate 7 engage the brackets 10 on the housing 1; the locking aperture 23 is then in alignment with the head 22 of the plunger 21. As soon as the user starts the sterilization cycle, the control unit 27 de-energizes the solenoid coil 26 so that the spring 25 can displace the plunger 21 outwardly into locking engagement with the aperture 23. This prevents the door 5 being opened, because the locking plate 7 cannot now be rotated to disengage the lugs 9 from the brackets 10. At this stage, the pressure in the vessel 2 is at atmospheric pressure, so the pressure actuator 30 remains disengaged from the plunger 21. As steam is generated in the vessel 2 and pressure rises above atmospheric pressure, the piston 31 of the pressure actuator 30 is displaced to the left, into contact with a rearwardly-facing surface of the plunger 21. This provides force in addition to that of the spring 25 to hold the plunger 21 in the locking position.

When pressure falls within the vessel 2, such as during a vacuum phase of the sterilization cycle, the piston 31 of the actuator 30 is displaced to the right but, because the piston is not attached to the plunger 21, it cannot move the plunger out of its locking position.

At the end of the sterilization cycle, pressure in the vessel 2 again falls to atmospheric pressure, and the control unit 27 supplies power to the solenoid coil 26 to cause the solenoid to displace the plunger 21 against the action of the spring 25 into an unlocked position.

Because both the pressure actuator 30 and the electrical actuator 26 are in an unlocked state, the plunger 21 is moved out of the aperture 23 and the user can tum the handle 8 to rotate the locking plate 7 and disengage the lugs 9 from the brackets 10, thereby enabling the door 5 to be swung open.

If the control unit 27 should develop a fault and apply power to the solenoid coil 26 to open the lock 20 while the vessel 2 contains pressurized steam, the pressure actuator 30 would hold the plunger 21 in the locked position against the action of the solenoid, the power of the solenoid being insufficient to overcome that of the pressure actuator.

The present invention provides a reliable safety lock at a single location, which simplifies manufacture, installation and maintenance.

Claims

1. A pressure vessel having a door that can be opened to allow access to the inside of the vessel, a door lock mechanism including a lock member, an electrical actuator, and a pressure actuator responsive to pressure in the vessel, wherein the electrical actuator is operable to cause displacement of the lock member both from an unlocked position to a locked position and from a locked position to an unlocked position, and wherein the pressure actuator is operable to prevent displacement of the lock member from a locked to an unlocked position even when the electrical actuator is operated to cause unlocking.

2. A pressure vessel according to Claim 1, wherein the lock mechanism includes a spring that urges the lock member into a locked position, wherein the electrical actuator includes a solenoid, and wherein the solenoid urges the lock member into an unlocked position against the action of the spring when energized and, when unenergized, allows the spring to urge the lock member to a locked position.

3. A pressure vessel according to Claim 1 or 2, wherein the lock member is a plunger that is displaceable along its length.

4. A pressure vessel according to Claim 3, wherein the pressure actuator includes a piston arranged to contact a rearwardly-facing surface of the plunger and displace it forwardly into a locked position when pressure in the vessel is above atmospheric pressure.

5. A pressure vessel according to any one of the preceding claims, wherein the door has a rotatable locking plate, and wherein the lock member is arranged, when locked, to engage the rotatable locking plate and prevent rotation of the locking plate.

6. An autoclave sterilizer having a door that can be opened to allow access to the inside of the sterilizer, the sterilizer having a door lock mechanism including a lock member, an electrical actuator, and a pressure actuator responsive to pressure in the sterilizer, wherein the electrical actuator is operable to cause displacement of the lock member both from an unlocked position to a locked position and from a locked position to an unlocked position, wherein the pressure actuator is operable only to cause displacement of the lock member from an unlocked to a locked position, and wherein the electrical actuator is unable to unlock the lock member when the pressure actuator holds the lock member in a locked position.

7. A pressure vessel substantially as hereinbefore described with reference to the accompanying drawing.

8. Any novel feature or combination of features as hereinbefore described.