WO2004105932A2

WO2004105932A2 - An autoclave

Info

Publication number: WO2004105932A2
Application number: PCT/GB2004/002246
Authority: WO
Inventors: Christoper Storey
Original assignee: Rodwell Engineering Group Limited
Priority date: 2003-05-28
Filing date: 2004-05-27
Publication date: 2004-12-09
Also published as: WO2004105932A3; GB0312198D0; GB2403906A

Abstract

An autoclave (1) comprises a chamber (3) with a vertically oriented opening (5), closed by a door (7). The door (7) is raised from below the opening (5) to opposite the opening (5). A plurality of cams (91) are movable to a closing position in which the cams (91) bear on the door (7) to hold it against a seal (33) to form an airtight seal between the door (7) and the chamber (3) when the door (7) is locked. Control means are provided to electrically control the movement of the door (7) and the cams (91).

Description

An Autoclave

The present invention relates to an autoclave, and particularly to an autoclave which is used for sterilisation of materials and equipment using high pressure steam.

In autoclaves which are fed with pressurised steam, the closed vessel is required to withstand a high internal pressure and temperature, typically a test pressure of 60 p.s.i. and a working pressure of 38 p.s. . To meet the pressure requirements, an autoclave door is typically locked shut against the autoclave chamber at a plurality of points.

Prior art devices include the use of a plurality of bolts which are mounted to turn freely in the door and which engage in threaded holes provided adjacent the chamber opening. Typically four such bolts are provided, each being turned manually. Another arrangement uses a central wheel which is spun to drive home or release a plurality of locking members.

When the door is closed, the door presses on a seal which is mounted continuously around the outer face of the opening of the chamber, which provides an airtight seal for the chamber. These prior art devices suffer the drawback of requiring a considerable length of time to lock the door, which may lead to misuse of the apparatus when the operative is in a hurry. Different operatives may tighten the lock mechanism on the door to a differing degree, which may lead to excessive tightening of the lock mechanism which will put undue pressure on the rubber seal leading to excessive wear in that part and/or damage to the thread, where a threaded bolt is used. Due to the wear on the seal of such devices, it is often necessary to replace these seals, which is costly and necessitates specialist maintenance, which can often lead to extended periods when the apparatus can not be used.

In addition to a compressed elastomeric seal which is used in some devices, a 'blow out' seal is used in other devices in which the seal is expanded by injecting pressurised air to form an airtight seal between the door and the chamber opening. These require that the air pressure be maintained in order to maintain the seal. The safety of operatives of autoclaves and those in proximity to a working autoclave is paramount when the autoclave is in operation due to the high temperature and pressure within the chamber of the autoclave. Failure of an autoclave door can have catastrophic consequences. Therefore it is necessary to employ various safety mechanisms to prevent operation of the autoclave when the chamber is not sealed and to prevent the door of the autoclave opening when the chamber is pressurised or at a high temperature.

Therefore it is a first object of this invention to provide a means for automatically closing and locking the door of an autoclave which does not require the physical exertion of an operative. A further object of the present invention is to provide a means to repeatably lock the door of the chamber of an autoclave, whereby a predetermined and limited force is exerted on the seal of the chamber, reducing the wear on the seal and extending its life. Yet a further object of the current invention is to provide safety mechanisms to be used with an autoclave to prevent injury to individuals or damage to property near the autoclave when it is in operation.

One aspect of the present invention provides an autoclave, comprising a chamber with a vertically oriented opening, a door for closing the opening, elevation means for raising the door from a first position below the opening to a second position opposite the opening, a seal which is positioned between the chamber and the door when the door is in the second position, the seal forming an airtight seal between the door and the chamber when the door is closed, and locking means for holding the door against the opening to seal the chamber, wherein control means are provided to electrically operate the elevation means and the locking means. As the locking means and elevation means are electrically operated, no physical exertion is required on the part of the operative, which enhances the consistency of the force applied to repeatably lock the door of the chamber.

Preferably the locking means comprises a plurality of cams, each cam being mounted in a cam housing which is attached to the wall of the chamber, wherein the cams, when actuated, bear upon the door when the door is in the second position, to move the door towards the opening of the chamber. The design of the cam can be chosen to limit the extent of movement of the door upon which it bears, thereby providing the desired consistency when repeatably closing the door. Preferably four cams are provided and preferably two cams are disposed opposite each side of the door and the cams on each side of the door are disposed one above the other, which allows a uniform locking force to be applied to the door.

Preferably the cams are rotatably mounted.

Preferably a piston and cylinder are provided to actuate the cams.

In one embodiment the elevation means comprises a motor driven belt for raising and lowering the door.

Another aspect of the present invention provides an autoclave comprising, a chamber having an opening, a door for closing the opening, means for translating the door from a position clear of the opening to a position opposite the opening, locking means for locking the door in a closed position, closing the opening, wherein the locking means comprises a plurality of cams which are movable to a closing position in which the cams bear on the door to hold it against the chamber.

Preferably the cams are rotatably mounted.

In one embodiment, the cams are mounted on the chamber and bear on the door.

Another aspect of the present invention provides an autoclave comprising, a chamber having an opening, a door for closing the opening, locking means for locking the door in a closed position, closing the opening, wherein the locking means comprises a plurality of rotatable cams which are rotated, in use, to a closing position in which the cams bear on the door to hold it against the chamber.

Preferably the door is translated from a position clear of the opening to a position opposite the opening.

Preferably the door moves vertically to efficiently use the available space by allowing other apparatus to be placed opposite and next to the autoclave.

In one embodiment a seal is provided around the chamber opening, and the door is suspended clear of the seal when translated to opposite the opening. This reduces the wear on the seal.

In another embodiment cams are mounted on the chamber housing and the door moves between the cams and the chamber housing.

Another aspect of the present invention provides a cam assembly for closing an autoclave door, the cam assembly comprising a shaft which is rotatably mounted in a housing and a cam mounted on the shaft, the cam urging the door to a closed position when the cam shaft is rotated, in Use, to a closing position. Preferably the cam is electrically controlled.

Preferably the cam shaft is coupled to an electrically controlled piston for rotating the cam shaft.

Preferably the piston is pneumatically operated and rotates the cam between two end positions.

In one embodiment the cam bears on a hardened cam follower to reduce wear on the door as the cam rubs the surface of the door as the cam bears on the surface of the door to close it and to reduce indentation which may occur when the autoclave chamber is pressurised.

In another embodiment the assembly is mounted on a housing of a chamber of the autoclave.

Yet another aspect of the present invention provides an autoclave comprising, a chamber having an opening, a door for closing the opening, means for translating the door between a first position, clear of the opening for loading and unloading the autoclave, and a second position opposite the opening, and a third position bearing against the chamber to seal the opening, sterilizing means for increasing the pressure and/or temperature in the chamber, control means controlling the movement of the door between the second and third positions and for controlling the operation of the sterilizing means, and sensor means for outputting a signal to the control means to indicate that the door is in the third position, wherein the control means inhibits operation of the sterilizing means when the sensor means indicates that the door is not in the third position, and inhibits operation of the translating means when the sensor means indicates that the pressure and/or temperature in the chamber is above a predetermined level.

Preferably the sensor includes a pin which is movable between extended and retracted positions, movement of the pin into the extended position being inhibited when the door is not in the third position. This ensures that the door must be properly closed on the seal before operation of the autoclave can commence.

Preferably when in the extended position the pin inhibits physical movement of the door relative to the chamber, so that if the cams were unintentionally removed from the door the pins would provide some resistance to movement of the door.

Preferably the pin is moved towards the extended position as the pressure and/or temperature in the autoclave chamber rises above a predetermined level. Movement of the pins to the extended position is preferably mechanically controlled by the pressure or temperature in the chamber and independent of the autoclave controller, so that this safety mechanism would still operate in the event of malfunction of the autoclave controller.

Preferably means is provided to detect whether the pin moves fully into the extended position and to prevent a further increase in temperature and/or pressure if the pin has not moved into the fully extended position. As the pins are triggered by increased pressure and temperature, which has an associated increased risk, further increases are prevented unless the door is properly locked closed.

In another embodiment the pin is prevented from moving to the retracted position while the temperature and/or pressure in the chamber are above a predetermined level. This is required when the sterilisation cycle is complete and the pressure and temperature in the autoclave have not yet reduced to safe levels.

Other aspects and preferred features of the invention will be apparent from the accompanying claims. The invention will be further described by way of example with reference to the accompanying drawings in which:

Figure 1 is a schematic perspective view of an autoclave, forming an embodiment of the invention, with the door lowered.

Figure 2 is a schematic perspective view of the autoclave of figure 1 with the door raised.

Figure 3 is a perspective view of a cam and cam housing before the door has been locked.

Figure 4 is a perspective view of the cam and cam housing after the door has been locked.

Figure 5 is a cross-sectional view of the edge of the door and cam mechanism.

Figure 6 is a schematic view of safety devices that are deployed in the autoclave..

In Figure 1, various cover plates have been removed to show the operation of the door closing and opening mechanism.

An autoclave 1 comprises a chamber 3, in a housing 79, in which equipment and materials can be sterilised. The housing 79 is a heavy duty structure as well known in the art in order to withstand the high temperatures and pressures used in sterilising procedures. The chamber 3 may be heated directly and/or may be cooled. Steam may be supplied to the chamber under pressure. Typically the housing 79 is supported on a framework carrying other equipment for the autoclave, such as a boiler, compressed air supply, and the like. Here the chamber 3 is simply shown supported on a stand 80. The chamber 3 has a vertically oriented opening 5 through which equipment and materials to be sterilised can be passed. Shelves can be provided in the chamber 3 to provide additional room to place equipment and materials to be sterilised.

The door 7 is shown in a lower position, whereby the opening of the chamber 3 is not obstructed by the door 7. The door 7 is supported by two belts 9, 11, here in the form of chains. One end 13 of one chain 9 is attached towards one end 15 of the upper face 17 of the door 7. The chain 9 then goes upwards and passes over a cog (not shown in the drawings) and descends in front of the outer face 19 of the door 7 to the base 21 of the autoclave 1 where it passes under a second cog 23 and runs up to meet the lower face 25 of the door 7 where it is attached towards the same end 15 of the lower face 25 of the door 7. The second chain 11 is attached at the other side 29 of the door 7 and passes around an upper cog (not shown in the drawings) and a lower cog 31 in a similar manner. The two upper cogs are mounted on the same shaft (not shown in the drawings) which is driven by a motor (not shown in the drawings). The door 7 is raised and lowered by operating the motor, being translated in a plane extending parallel to the plane of the opening 5. As the door 7 is suspended on belts 9, 11 slight horizontal movement is possible, which allows the door 7 to be pushed towards the opening 5 of the chamber 3, as will be explained below.

A flexible seal 33 is fitted continuously around the opening 5 in a channel in the housing 79, so that when the door 7 is pushed towards the opening 5, an airtight seal is formed between the door 7 and the chamber 3. In order to reduce wear on the seal 33, the distance that the door 7 moves towards the opening 5 of the chamber 3 is controlled so that the seal 33 is compressed by a known amount and is not over-distorted. Also, there is no substantial sliding movement of the door 7 on the seal 33.

A microprocessor controlled controller is deployed in the autoclave 1 to control the operation of the autoclave 1. The user interface to the controller is a control panel 35 with switches for the operative to control the operation of the autoclave 1. Common autoclave cycles are pre-programmed into the memory of the controller so that the operative can easily select a desired program. An LCD display in the control panel 35 can provide information about the temperature, pressure and cycle progress. The operative controls the operation of the autoclave 1 entirely from the control panel 35. For example, if the operative wishes to close and lock the door 7 of the autoclave 1 a switch on the control panel 35 is pressed and the closing and locking operation takes place. Similarly, when the operative selects a sterilisation cycle, a switch is pressed to begin that cycle.

In Figure 2, the door 7 of the autoclave 1 has been raised so that it is in its second position, opposite the opening 5 of the chamber 3. In this position the chamber 3 is not sealed until a locking mechanism 37 is activated.

The locking mechanism 37 comprises two sets of the following components, namely two cam assemblies 39, two cam housings 47, two arms 55, a coupling member 63, a piston 67, and a piston housing 71, one set of components being at each side 75, 77 of the opening 5 of the chamber 3. Each cam assembly 39 comprises a cam 91 and a cam shaft 93, which are cylinders of different diameter. The cam 91 is of smaller diameter and is eccentrically fixed to the end 95 of the cam shaft 93 which is pivotally mounted in the cam housing 47. The cam assembly 39 may be integrally formed.

The arrangement on one side 75 of the opening 5 will be described and it will be understood by those skilled in the art that a similar mirror-image arrangement exists on the other side 77 of the opening 5.

One cam housing 47, is disposed above the other cam housing 49. The cam housings 47 are securely attached to the chamber housing 79 by high tensile bolts so that when the chamber 3 of the autoclave 1 is pressurised, the cam housings 47 are able to withstand the force which is exerted on the door 7 of the autoclave 1, which is transferred to the cam housings 47 via the cams 91.

An arm 55 is attached to each cam shaft 93 and the coupling member 63 is pivotally attached at its ends 81 to the two arms 55 in order to rotate the two cam assemblies 39 in unison. In use, the coupling member 63 is vertically oriented. The end 83 of the piston 67 is pivotally attached to the lower end 81 of the coupling member 63 and the piston housing 71 is pivotally mounted on a flange 87 which is attached to the stand 80. The pistons 67 here are pneumatically driven, but other types of piston drives can be used.

As stated above, similar niirror-image arrangements exist on both sides 75, 77 of the opening 5, so that balanced forces are applied to the door 7 when it is closed and locked. The pneumatically driven pistons 67 here are connected to the same valve (not shown) so that they are both propelled simultaneously. When the door 7 is translated from the lower position (Figure 1) to the upper position (Figure 2), the door 7 passes between the four cams 91 and the opening 5 of the chamber 3.

The locking mechanism 37 is activated by propelling the pistons 67 out of the piston housings 71, so that the pistons 67 move upwards. The coupling members 63 in turn move upwards which causes the cam assemblies 39 to rotate. The cams 91 are arranged so that when the coupling members 63 are in their lower position, there is sufficient clearance between the cams 91 and the opening 5 of the chamber 3 to allow unhindered vertical movement of the door 7, as can be seen from Figure 3 which shows a cam 91 on the left hand side of the door 7, as viewed in Figure 1.

When the coupling members 63 are raised, the cam assemblies 39 rotate to move the cam 91 towards the opening 5 of the chamber 3, and so bear upon the door 7. As the cam assemblies 39 further rotate, the door 7 is further pushed by the cams 91 towards the opening 5 of the chamber 3 and the door 7 bears upon the seal 33 of the chamber 3 to seal the chamber 3. A metal plate 97 is attached to the door 7 where each cam 91 comes into contact with the door 7. The plate 97 is made from a tough material, for example, hardened steel, so that it is able to withstand the rubbing action to which it is subjected as the cam 91 rotates while bearing on the door 7. The plate 97 is also sufficiently hard so that when the door 7 is closed and the chamber 3 is pressurised, the cams 91 do not dent the plates 97 which bear the force which is exerted on the door 7 from within the chamber 3 while the autoclave 1 is operational.

Figure 4 shows a cam 91 when the door 7 is closed. The cam assembly 39 is oriented so that the axes of the cam 91 and cam shaft 93 lie in the same horizontal plane so that when the chamber 3 is pressurised, the cams 91 bear the major part of the force exerted on the door 7. This cam assembly 39 orientation occurs when the piston 67 is fully extended. If the cams 91 were to be under- or over-centred then when the chamber 3 is pressurised there would be a tendency for the cam assemblies 39 to be rotated and the piston 67 would bear some of the force which is exerted on the door 7, so as to maintain the door 7 in the locked position.

When the cam assemblies 39 rotate from the position shown in Figure 3 to the locked position shown in Figure 4, the cam 91 moves towards the chamber 3 by approximately 4mm. Figure 5 shows a cross sectional view through the edge of the door 7 at the level where the upper right cam 91 bears on the door 7. Two guide rails 101, 103 are attached to the side 105 of the door 7 and an intermediate guide rail 107 is attached to a portion of chamber housing 109 which protrudes in front of the opening 5 of the chamber 3. There is a gap 111 between the intermediate guide rail 107 and the two guide rails 101, 103 mounted on the side 105 of the door 7, to allow the door 7 to move towards the opening 5 of the chamber 3 when the door 7 is closed. There is also a gap 113 between the two guide rails 101, 103 on the side 105 of the door 7 and the portion of the chamber housing 109 which protrudes in front of the opening 5 of the chamber 3 so that when the door 7 is raised and lowered the sides 105 of the door 7 do not rub the portion of the chamber housing 109 which protrudes in front of the opening 5 of the chamber 3.

The front guide rail 103 extends in front of the door 7 and this front portion 97 serves as the plate 97 on which the cam 91 bears when the door 7 is closed.

The cam shaft 93 is mounted in the cam housing 47 which is attached, here by high tensile bolts 115, to the portion of the chamber housing 109 which protrudes in front of the opening 5 of the chamber 3. Arm 57 is attached to the end of the cam shaft 93 and a coupling member 65 is pivotally mounted on the end 117 of the arm 57.

When the coupling member 65 is raised the cam shaft 93 rotates in the cam housing 47 and the cam 91 moves towards the plate 97 which is mounted on the front of the door 7. The cam 91 bears upon the plate 97 to push the door 7 on to the seal 33 which is mounted on the front face 119 of the opening 5 of the chamber 3, to seal the chamber 3.

At the end of the sterilisation cycle and when the pressure and temperature in the chamber 3 have fallen below predetermined levels (see below), the door 7 can be released. This process is controlled by the autoclave controller. To release the door 7, the pistons 67 are withdrawn into the piston housings 71 and the coupling members 63 move down. The cam assemblies 39 rotate and the cams 91 move away from the chamber 3, allowing the door 7 to move away from the opening 5 of the chamber 3. The door 7 tends to move away from the opening 5 of the chamber 3 as the cogs 23, 31 around which the chains 9, 11 which support the door 7 are passed, are set back from the opening 5 of the chamber 3. W en the pistons 67 have been fully withdrawn and the door 7 has moved away from opening 5 of the chamber 3, the door 7 can be lowered by operating the motor and the equipment and materials can be removed from the chamber 3.

Figure 6 is a schematic view of safety devices that are incorporated in the autoclave 1 to prevent the autoclave 1 from operating when door 7 is not locked and to prevent the door 7 from opening when the chamber 3 is pressurised or at a high temperature. In Figure 6, sensor devices, here in the form of microswitches, are represented by 'X's. The sensor devices are connected to the autoclave controller which monitors their status and responds appropriately.

A spring mounted bar 121 is located above the door 7 to detect any obstructions as the door 7 is raised. Two position sensors 123 are deployed towards the ends 125, 127 of the bar 121, to determine if the bar 121 encounters an obstacle, if either of these sensors 123 are triggered, the upward movement of the door 7 is stopped.

Two position sensors 129, 131 are provided for each of the coupling members 63. One position sensor 129 is below each coupling member 63 so that it is triggered when the coupling member 63 is in its lower position, when the door 7 is released by the cams 39 and so can be slid up and down. Another position sensor 131 is above each coupling member 63 to detect when the coupling member 63 is raised to close the door 7. Heating and pressurisation of the chamber 3 will not start until the position sensors 131 on both sides 75, 77 of the opening 5 are triggered, to indicate that the door 7 is fully closed.

Two pressure sensors 133 are mounted on the door 7, each controlling a rod 135. The rods 135 are mounted on the door 7 and in holes 137 in the side of the door 105. When the door 7 is locked, the rod 135 is vertically and horizontally aligned with a hole 139 in a portion of the chamber housing 109 which protrudes in front of the opening 5. As the pressure in the chamber 3 increases, the pressure sensors 133 are triggered and the rods 135 are propelled into the holes 139 in the portion of the chamber housing 109 which protrudes in front of the opening 5. Each rod 135 is made of a strong material, here being made of steel.

There are also two temperature sensors 141 mounted on the door 7, each controlling a rod 143. The rods 143 are mounted on the door 7 and in holes 145 in the side of the door 105. When the door 7 is locked, the rods 143 are vertically and horizontally aligned with holes 146 in a portion of the chamber housing 109 which protrudes in front of the opening 5. As the temperature in the chamber 3 increases, the temperature sensors 141 are triggered and the rods 143 are propelled into the holes 146 in the portion of the chamber housing 109 which protrudes in front of the opening 5, in a similar manner to the pressure sensors 133.

Two position sensors 147, 149 are provided for each of the temperature/pressure sensors 133, 141. One position sensor 147 detects when the rod 135, 143 has been inserted through the holes 139, 146 to lock the door 7, and the other position sensor 149 detects when the rod 135, 143 is retracted.

. When the pressure in the chamber 3 increases, the pressure can not increase past a predetermined, low level until both the pressure sensors 133 are triggered to propel the rods 135, which in turn trigger the 'outer' position sensors 147. If, for example, one side of the door 7 has not closed properly, the rod 135 will not be aligned with the holes 139 and will not be able to pass through the holes 139 and the 'outer' position sensor 147 can detect this.

When the sterilisation process is complete, the door 7 can not be opened until the pressure and temperature in the chamber 3 drop below certain levels. These levels are determined by the temperature and pressure sensors 133, 141, and once the temperature and pressure have dropped sufficiently, the sensors 133, 141 allow the rods 135, 143 to be retracted, which triggers the 'inner' position sensors 149. The door 7 unlocking mechanism 37 can not be activated until all four of the 'inner' position sensors 149 are triggered.

Various modifications will be apparent to those in the art and it is desired to include all such modifications as fall within the scope of the accompanying claims.

Claims

CLAIMS:

1. An autoclave, comprising a chamber with a vertically oriented opening, a door for closing the opening, elevation means for raising the door from a first position below the opening to a second position opposite the opening, a seal which is positioned between the chamber and the door when the door is in the second position, the seal forming an airtight seal between the door and the chamber when the door is closed, and locking means for holding the door against the opening to seal the chamber, wherein control means are provided to electrically operate the elevation means and the locking means.

2. An autoclave as claimed in claim 1, wherein the locking means comprises a plurality of cams, each cam being mounted in a cam housing which is attached to the wall of the chamber, wherein the cams, when actuated, bear upon the door when the door is in the second position, to move the door towards the opening of the chamber.

3. An autoclave as claimed in claim 2, wherein four cams are provided.

4. An autoclave as claimed in claim 3, wherein two cams are disposed opposite each side of the door and the cams on each side of the door are disposed one above the other.

5. An autoclave as claimed in claim 4, wherein the cams are rotatably mounted.

6. An autoclave as claimed in claim 5, wherein a piston and cylinder are provided to actuate the cams.

7. An autoclave as claimed in any one of the preceding claims, wherein the elevation means comprises a motor driven belt for raising and lowering the door.

8. An autoclave comprising, a chamber having an opening, a door for closing the opening, means for translating the door from a position clear of the opening to a position opposite the opening, locking means for locking the door in a closed position, closing the opening, wherein the locking means comprises a plurality of cams which are movable to a closing position in which the cams bear on the door to hold it against the chamber.

9. An autoclave as claimed in claim 8, wherein the cams are rotatably mounted.

10. An autoclave as claimed in claim 9 or 10, wherein the cams are mounted on the chamber and bear on the door.

11. An autoclave comprising, a chamber having an opening, a door for closing the opening, locking means for locking the door in a closed position, closing the opening, wherein the locking means comprises a plurality of rotatable cams which are rotated, in use, to a closing position in which the cams bear on the door to hold it against the chamber.

12. An autoclave as claimed in claim 11, wherein the door is translated from a position clear of the opening to a position opposite the opening.

13. An autoclave as claimed in claim 12, wherein the door moves vertically.

14. An autoclave as claimed in claim 11, 12 or 13, wherein a seal is provided around the chamber opening, and the door is suspended clear of the seal when translated to opposite the opening.

15. An autoclave as claimed in any one of claims 11 to 14, wherein cams are mounted on the chamber housing and the door moves between the cams and the chamber housing.

16. A cam assembly for closing an autoclave door, the cam assembly comprising a shaft which is rotatably mounted in a housing and a cam mounted on the shaft, the cam urging the door to a closed position when the cam shaft is rotated, in use, to a closing position.

17. A cam assembly as claimed in claim 16, wherein the cam is electrically controlled.

18. A cam assembly as claimed in claim 17, wherein the camshaft is coupled to an electrically controlled piston for rotating the cam shaft.

19. A cam assembly as claimed in claim 18 wherein the piston is pneumatically operated and rotates the cam between two end positions.

20. A cam assembly as claimed in any one of claims 16 to 19, wherein the cam bears on a hardened cam follower.

21. A cam assembly as claimed in any one of claims 16 to 20, wherein the assembly is mounted on a housing of a chamber of the autoclave.

22. An autoclave comprising, a chamber having an opening, a door for closing the opening, means for translating the door between a first position, clear of the opening for loading and unloading the autoclave, and a second position opposite the opening, and a third position bearing against the chamber to seal the opening, sterilizing means for increasing the pressure and/or temperature in the chamber, control means controlling the movement of the door between the second and third positions and for controlling the operation of the sterilizing means, and sensor means for outputting a signal to the control means to indicate that the door is in the third position, wherein the control means inhibits operation of the sterilizing means when the sensor means indicates that the door is not in the third position, and inhibits operation of the translating means when the sensor means indicates that the pressure and/or temperature in the chamber is above a predetermined level.

23. An autoclave as claimed in claim 22, wherein the sensor includes a pin which is movable between extended and retracted positions, movement of the pin into the extended position being inhibited when the door is not in the third position.

24. An autoclave as claimed in claim 23, wherein when in the extended position the pin inhibits physical movement of the door relative to the chamber.

25. An autoclave as claimed in claim 22 or 23, wherein the pin is moved towards the extended position as the pressure and/or temperature in the autoclave chamber rises above a predetermined level.

26. An autoclave as claimed in claim 25, wherein means is provided to detect whether the pin moves fully into the extended position and to prevent a further increase in temperature and/or pressure if the pin has not moved into the fully extended position.

27. An autoclave as claimed in any one of claims 23 to 26, wherein the pin is prevented from moving to the retracted position while the temperature and/or pressure in the chamber are above a predetermined level.