GB2351666A

GB2351666A - Autoclave having a water level sensor

Info

Publication number: GB2351666A
Application number: GB0005297A
Authority: GB
Inventors: Patrick Brian Clayton
Original assignee: Smiths Group PLC
Current assignee: Smiths Group PLC
Priority date: 1999-03-24
Filing date: 2000-03-07
Publication date: 2001-01-10
Anticipated expiration: 2020-03-07
Also published as: GB0005298D0; GB2351669B; GB2351666B; GB0005302D0; GB2351668B; GB2351668A; GB9906654D0; GB0005297D0; GB0005304D0; GB2351667A; GB2351669A

Abstract

An autoclave has a chamber 1 closed by a hinged door 3. Two water sensor electrodes 61 and 62 project though the door 3 at the same height towards its lower end so that they are exposed to water in the chamber 1. It is easier to make effective seals with the flat surface of the door 3 than with the curved surface of the chamber 1 itself, where conventional water level sensors are located.

Description

2351666 1 AUTOCLAVES This invention relates to autoclaves.

Autoclaves are used to treat articles with steam at elevated pressure and temperature, such as to effect sterilization. The autoclave chamber is closed by a door through which articles are placed in and removed ftorn the chamber. The door seal usually comprises a flexible gasket bearing on the inside of the door and on the outside of a flange formed around the chamber. The door is locked by a catch mechanism, which should prevent opening during certain parts of the treatment cycle. The autoclave usually has various sensors and various pipe connections to the chamber, which are closed or opened by means of solenoid valves.

It is an object of the present invention to provide an alternative autoclave.

According to the present invention there is provided an autoclave having a chamber with an opening, a door closing the opening and a water level sensor, the water level sensor being mounted on the door to be exposed on the inner surface of the door to water in the chamber.

The water level sensor preferably includes two electrodes spaced from one another and projecting through the door where they are exposed at one end on the inside surface of the door. The electrodes may be located at the same height towards the lower end of the door.

2 An autoclave according to the present invention will now be described, by way of example, with reference to the following drawings, in which:

Figure 1 is a perspective view of the autoclave from one side, without its outer housing and door cover plate; Figure 2 is a perspective view of the autoclave from the same side with the door open and with some components omitted; Figure 3 is a perspective view of the autoclave from the opposite side with the door closed and with some components omitted; Figure 4 is an enlarged cross-sectional view of the autoclave door seal; Figure 5 is an enlarged perspective view of the autoclave door catch; Figure 6 is a perspective view from below showing the mounting of the door cover plate; and Figure 7 is and enlarged view of a part of Figure 7.

With reference first to Figures 1 to 3, the autoclave has a pressure chamber 1 with an open end 2, which can be closed by means of a door 3. The chamber 1 has a heating element.4 at its lower end, which in use is submerged in water supplied to the chamber from a 3 reservoir 5 by piping, not shown. The pipework of the autoclave has been omitted from the drawings to prevent obscuring other parts of the apparatus, the pipework not being important to an understanding of the various aspects of the invention. Articles to be sterilized are placed on racks (not shown) in the chamber 1 above the water level, the door 3 is closed and the heating element 4 is energized in the usual way to raise temperature and pressure in the chamber.

The chamber 1 is formed in two parts, the first being a deepdrawn steel cylinder 10 closed at its rear, domed end 11. The second part is a cast iron neck ring 12 joined to the forward, open end of the cylinder 10 by electron beam welding. The neck ring 12 provides the open end 2 of the chamber 1. The neck ring 12 is formed with various mounts and passages by which fluid connection is made to the chamber. In particular, at the upper part of the neck ring 12 there are three, parallel, outwardly projecting mounting studs 13 to 15, each having a passage 16 extending through the neck ring and opening on the inside of the chamber 1. The studs 13 to 15 have flat end surfaces 17 shaped to receive respective T- piece couplings 18 to 20. A rearwardly extending spigot 21 on each coupling 18 to 20 is connected to piping by which fluid can be supplied to or from the chamber. The couplings 18 to 20 open at their upper end in a threaded bore into which is screwed a respective solenoid valve 22 to 24, which are electrically connected to an autoclave control unit (not shown). Actuation of the solenoid valves 22 to 24 controls flow of fluid along the passages 16 to the spigots 21.

The upper part of the neck ring 12 is also formed with two short tubes 25 and 26 projecting upwardly and formed with a threaded bore 27 by which piping, a temperature sensor 28 or a pressure relief valve 6 can be connected to the inside of the chamber.

4 The lower part of the neck ring 12 is formed on its external surface with a manifold 29 having horizontally-extending passages opening at opposite ends 30 and 3 1. T-piece couplings 32 and 33 are mounted at the ends of the manifold 29 and these receive respective solenoid valves 34 and 35. The passages along the manifold 29 open on the inside of the neck ring 12 through openings 36, only one of which is shown. Water is supplied to or from the chamber through the openings 36 by controlling the solenoids 34 and 35.

The passages to the inside of the chamber 1 through the neck ring 12 avoid the need to make openings in, or fluid connections to, the main body 10 of the chamber, which can be more difficult to seal and require additional manufacturing time. The neck ring 12 enables the solenoid valves 22, 23, 24, 34 and 35 to be mounted very close to the chamber 1, with a very short passage between the chamber and the solenoid. By reducing the deadspace between the chamber and the valves, there is a lower volume of space that may be at a reduced temperature, compared with conventional autoclaves where the solenoid valves are connected by lengths of piping to the chamber. This is important in that it ensures there are no regions of the autoclave that are not fully sterilized.

With reference now also to Figure 4, the neck ring 12 has an inner, forwardly-facing annular end surface 40 surrounded by a recess 4 1, which faces axially outwardly towards the door 3. The recess 41 is surrounded by an outer lip 42, which projects forwardly beyond the end surface 40 to provide an annular shoulder 43. The shoulder 43 forms a continuation of the radially outer side 44 of the recess 41. The radially inner side 45 of the recess 41 has an undercut inner part 46 so that the inner end 47 of the recess is wider than the outer end 48. The recess 41 serves to locate and retain a sealing ring 50.

The sealing ring 50 is an annular ring of a rubber or similar resilient material moulded with two ribs 51 and 52, which project radially inwardly and diverge away from one another axially. Figure 4 shows the inner rib 52 in its natural, undeflected state. The outer rib 51 is slightly longer that the inner rib 52 and is located to be contacted by an inner surface of the door 3, when this is closed. The inner rib 52 is slightly shorter and resiliently bears against the annular end surface 40 of the neck ring. The sealing ring 50 also includes a locating member 53 in the form of a rearwardly-projecting collar. The collar 53 has an enlarged lip 54 projecting radially inwardly at its end and, on its opposite, outer surface has a shallow taper 55. The shape and location of the lip 54 is such that it locates in the undercut part 46 of the recess 4 1. The taper 5 5 leaves a small gap with the outer side 44 of the recess 41 so that the locating collar 53 can flex outwardly by a small distance to enable the lip 54 to clear the ledge between the inner and outer parts of the recess. The sealing ring 50 is located by pushing the locating collar 53 into the recess 41 until the lip 54 engages the undercut part 46. When fully inserted, in this way, the inner rib 52 is flexed to lie flat against the end surface 40 of the neck ring 12, the radially outer surface of the sealing ring 50 abutting the shoulder 43. When the door 3 is closed, the outer rib 51 is flattened against the door but leaves a small gap between the two ribs 51 and 52 so that pressure in the chamber I forces the ribs outwardly into better sealing contact with the respective surfaces.

The door 3 supports water-level sensors 60 in the form of two electrodes 61 and 62 spaced a short distance apart from one another at the same height, towards the lower end of 6 the door where they are exposed on the inner surface of the door, The electrodes 61 and 62 project through the door 3 to its outer surface where they are connected by wires, not shown, to the autoclave control unit. By measuring the resistance between the two electrodes 61 and 62 and the chamber it is possible to determine whether or not they are submerged in water and hence whether the water level has reached a certain height. The output from the waterlevel sensors 60 are used to control the solenoids 34 and 35 so that flow of water from the reservoir 5 into the chamber 1 is stopped once the correct height of water has been reached. Conventional water level sensor electrodes are mounted on the wall of the cylindrical chamber itself but it is more difficult to form a seal with this curved surface than with the flat surface of the door.

With reference now also to Figure 5, the door 3 is held closed by means of a catch mechanism 70, which locks closed automatically when the door is pushed closed. At the end of the sterilization cycle, the catch mechanism 70 releases the door 3 to a partially opened, preliminary position from which the user can manually open the door fully after releasing the catch. The door 3 has a lateral support beam 71 hinged at its left-hand end 72 with a hinge 73 formed as a part of the neck ring 12. At its right-hand end 74, the beam 71 is divided into two parallel fingers 75 which carry a hook arm 76 hinged by a pivot 77 about a vertical axis. The hook arm 76 has two parallel limbs 78 extending horizontally on one side of the pivot 77 and each terminated by hook 79. The limbs 78 are linked on the opposite side of the pivot 77 by a vertical bar 80 by which the user can move the arm about its axis. A spring, not shown, urges the arm 76 in an anti-clockwise sense when viewed ftorn above so that the limbs 78 are urged against two respective, rearwardly-facing catches 81 formed from the neck ring 12. The upper one of the end fingers 75 on the door beam 71 also supports a closure-sensing 7 microswitch 82, which faces rearwardly and is positioned to be actuated by contact with the door cover plate 110 (Figure 6) when the door is closed. A short plate 83 projects between the two fingers 78, in parallel with them and spaced from the fingers to form two small gaps. The plate 83 supports a second, lock-sensing microswitch 84.

The two catches 81 support a right-angled locking yoke 90 pivoted with the catches about a vertical axis. One arm 91 of the yoke projects forwardly between the fingers 75 of the door beam, the arm being formed by two parallel, horizontal members 92 and 93 bridged at their outer end by a vertical locking beam 94. The locking beam 94 can be swung in front of the plate 83 on the door beam 71 when the locking beam is displaced to the left. The other arm 95 of the yoke 90 projects at right-angles laterally outwardly and is coupled by a rotatable joint 96 at its outer end to an actuating arm 97 extending horizontally forwardly from two solenoids 100 and 112 (Figure 1). When the solenoid 112 is unpowered, the actuating arm 97 may be in a rearward position, thereby holding the arm 95 of the yoke 90 back and the locking beam 94 to the right, unlocked position. This position is also obtained when the solenoid 100 is powered, the actuating arm 97 being pulled rearwardly by the solenoid, thereby rotating the yoke 90 in an anticlockwise sense (when viewed from above) and pulling the locking beam 94 to the right-hand, unlocked position.

With the autoclave on and the door 3 open, the solenoid 100 is not powered, the yoke 90 being maintained in the open position by an overcentre device, not shown. When the door 3 is pushed closed, the hook arm 76 rides over the catches 81 and the closure-sensing microswitch 82 is triggered causing the solenoid 112 to be powered and the yoke 90 to swing to its locking position. In its locking position, the locking beam 94 contacts the lock-sensing 8 microswitch 83 confirming that the door 3 is fully locked. If the microswitch 83 is not actuated, the control unit supplies power to the solenoid 100 to open the catch mechanism 70. At the end of a sterilization cycle, when pressure has fallen to a safe level inside the chamber 1, the door 3 can be opened by pressing a button (not shown) on the front of the autoclave. This powers the solenoid 100 to release the catch mechanism 70 enabling the door 3 to open. The door 3, however, only opens to a preliminary, venting position as limited by engagement of the hooked arm 76 with the catches 8 1. This allows any residual steam to escape and promotes cooling inside the chamber 1. The user fully opens the door 3 when desired by pushing the bar 80 on the hook arm 76 to the left so that the hooks 79 clear the catches 8 1.

With reference now to Figures 6 and 7, the cover plate 110 extends over the front surface of the door 3, the plate being hinged about a vertical axis 111 on a front cover 113 of the autoclave. The cover plate 110 is retained with the door 3 by means of a vertical pin 114 spring-mounted on the cover plate and projecting into a slot 115 on the underside of the door beam 7 1. The cover plate 110 can be readily swung back by a maintenance engineer so that sensors or other parts on the door 3 can be accessed. This is done by introducing a tool, such as a screwdriver into a slot 116 in the cover plate 110 to depress the pin 114 so that it clears the slot 115 in the door beam.

9

Claims

1. An autoclave having a chamber with an opening, a door closing the opening and a water level sensor, wherein the water level sensor is mounted on the door to be exposed on the inner surface of the door to water in the chamber.

2. An autoclave according to Claim 1, wherein the water level sensor includes two electrodes spaced ftom one another and projecting through the door where they are exposed at one end on the inside surface of the door.

3. An autoclave according to Claim 2, wherein the electrodes are located at the same height towards the lower end of the door.