GB2104995A - Pressure chamber with power-operated door - Google Patents

Abstract

A pressure chamber, especially a steam sterilizer, with a front head ring 2 and opening 3, has a power- operated door 4 opened and closed by bodily vertical movement through motor drive of a vertical lead screw 10 and drive nut 17 on which the door 4 is pivotally mounted and biased so that the door constantly tends to rock away from the head ring. Co-operating wedge surfaces 31, 32, and 33, 34 are provided on the door and head ring to guide the door into sealed closure and allow the door to rock open slightly, for venting, as opening of the door begins. <IMAGE>

Description

SPECIFICATION Pressure chamber with power-operated door This invention relates to a pressure chamber with a power-operated door particularly, but not exclusively, a steam sterilizer for sterilization of the chamber contents. The invention will be described as applied to a steam sterilizer.

Various kinds of steam sterilizers with manual or power-operated doors are known but there is a standard safety requirement that the chamber shall effectively vent to atmosphere before the door-opening mechanism is fully released.

To meet this requirement for a manual or power-operated door has involved somewhat elaborate and costly constructions, such as radial locking arms with central operation, to give two-stage operation, first venting and then opening of the door.

The present invention provides a pressure chamber with a power-operated door of simple construction and operation which automatically provides for safety venting at the commencement of simple opening movement.

The invention is applied to a known kind of pressure chamber having, extending vertically at one end, a head ring, defining a front opening, and a power-operated door which can be moved bodily substantially in its own plane to and from a closed position in which it covers the opening and seals fluid-tight against the head ring. According to the invention, the door is pivotally mounted on its power-operating means and biased with respect to the head ring so that the door constantly tends to rock forwardly, away from the opening, and co-operating wedge surfaces are provided, on the door and head ring respectively, to guide the door rearwardly into sealed engagement with the head ring as the door is closed and to allow limited forward movement of the door, away from the head ring, during an initial part of opening movement of the door.

Such pivotal mounting of the door, to rock away from the head ring, provides two major advantages. In closing movement, the door remains clear from its head ring sealing means until brought into contact by the action of the wedge surfaces at the end of the closing movement. In opening movement, as soon as initial door movement provides some clearance at the wedge surfaces, the door moves slightly away from the head ring and permits venting past the sealing means while the door is still held, by the wedge surfaces, against release from the head ring. Biasing of the door away from the head ring may be effected by gravity or spring-loading or both.

In a preferred embodiment, the wedge surfaces are provided by hooks on the head ring and door respectively, the power-operating means comprises a reversible, motor-driven lead screw with a nut on which the door is pivoted, the door is arranged to move vertically across the head ring, being raised and lowered by the lead screw and nut arranged below the chamber, and the sealing means is a rubber or like ring seated in a dovetailsection groove around the face of the head ring.

A further feature of the invention is that a manually-movable safety screen is arranged to operate a switch in a control circuit of the door-operating means so that the door cannot be closed by power operation except when the screen is in closed position covering the chamber opening.

The above and other features of the invention are set out in the appended claims and the preferred embodiment is somewhat diagrammatically illustrated, by way of example, on the accompanying drawings, in which: Figure 1 is a front elevation of the vertically movable door, of a steam sterilizing chamber, and its operating means, the door and a safety screen being shown partly lowered in opening, Fig. 2 is a part-sectional side elevation thereof, Figure 3 is a fragmentary elevation similar to Fig. 2 but showing the door and safety screen partly lowered as in Fig. 1, and Figure 4 is a fragmentary detail view on a larger scale.

Only part of the front end of a rectangular sterilizer chamber 1 is shown by the drawings, the remaining body of the chamber and its support not forming part of the invention and being of any conventional construction.

At the front, the chamber 1 has a head ring 2 which defines a front opening 3 through which the sterilizer is loaded and unloaded with articles to be sterilized by steam admitted to the chamber during an automatic evacuation and steam supply cycle.

During the sterilizing cycle, the opening 3 is hermetically closed by a door 4 which seals by its inner surface against a rubber or like elastomeric sealing ring 5 seated in a dovetail cross-section groove 6 in the face of the head ring 2, around the opening 3. The ring 5 fits in the groove so that it holds in place and projects slightly to be contacted by and seal against the inner surface of the door 4.

The door 4 is carried at the mid-length of its lower edge by an L-shaped carrier block 7 which is fast with the door by one limb 8 and has its other limb 9 forked to straddle a vertical lead screw 10 rotatably mounted captive in top and bottom bearings 11 and 1 2.

The carrier block limb 9 is trunnionmounted between a pair of cheek plates 1 3 to which it is pivotally connected by pivot stubs 14.

The cheek plates are each pivotally mounted, with spring-loaded freedom of small angular movement, by a pivot stud 1 5 and a stop stud 1 6 on a drive nut 1 7 threaded on to the lead screw 1 0. The stop stud 1 6 enters a small recess 18, in the nut 17, so that it has a small freedom of movement under the thrust, towards the door 4, of a spring 1 9.

The cheek plates 1 3 are tied, to move together, by a cross bar 36.

The door 4 is thus pivotally mounted on the drive nut and, being located forwardly of the pivot stubs 14, is biased so that it tends constantly to rock under gravity, as well as under the thrust of the springs 19, away from the head ring opening 3, in the direction indicated by the arrow in Fig. 3. The angle through which the door can rock open is in fact very small, being limited by the studs 1 6 in the recesses 18, the angle being sufficient however for the door to move away from contact with the sealing ring 5 and give an effective opening for venting of the chamber at the end of a sterilizing cycle.

The bottom bearing 1 2 for the lead screw 10 is mounted in the sterilizer base 20 and, closely above the bearing 12, the screw 10 carries fast thereon a toothed pulley 21 engaged by a toothed driving belt 22 driven by a reversible electric motor 23 with a smaller pulley 24 to give an appropriate reduction drive ratio for rotation of the screw 10 to raise or positively lower the door, with the drive nut 17, according to the direction of rotation of the screw 1 0.

In the control circuit of the motor 23 there is included a master switch 25, at the top of the head ring 2, to be closed, to allow operation of the motor to close the door, only when contacted by the upper border of a manuallyoperable vertical safety screen 26 which slides outside the door 4 in guides 27 at either side of the front of the sterilizer chamber. The screen 26 has a handle 28 by which it may be raised and lowered and is restrained by friction guide ways or is counterweighted so that it requires positive manual effort for any movement.

The upper border of the screen 26 is inclined towards the head ring 2 so that its upper edge 29 just clears the projection of the sealing ring 5. When the screen is raised, as an essential preliminary to closing of the door 4, the screen edge 29 sweeps upwardly across the chamber opening 3 and enables the operator, manually raising the screen, to detect any obstructing projection of chamber contents from the opening 3.

When the screen 26 has been fully raised and has closed the master switch 25, the motor 1 3 can be operated to turn the screw 10 to raise the door.

At the top of the head ring 2 there is provided a pair of spaced-apart fixed clamping hooks 30 each with an inclined wedge surface 31 to be encountered by a coacting wedge surface 32 on the leading edge of the door 4 as the door completes its upward closing movement. The wedge surfaces 31 and 32 co-operate to guide the door into sealing contact of its inner surface against the sealing ring.

Similarly, the bottom of the head ring 2 is formed with an inclined wedge surface 33 to be encountered by coacting wedge surfaces 34 of a pair of hooks 35 on the lower edge of the door 4. The wedge surfaces 33 and 34 co-operate, simultaneously with the wedge surfaces 31 and 32, to guide the door into sealed closure against the sealing ring 5. The pivotal mounting of the door, by the studs 14 and 15, permits the small bodily movement of the door necessary for this purpose.

Limit switches (not shown) are included in the motor control circuit to stop the drive when the door is fully closed.

For opening the door 4, the motor is reversed to turn the screw 10 to drive the nut 1 7 and door 4 downward. As soon as a clearance exists between the wedge surfaces 31, 32, and 33, 34, the door 4 rocks outwardly, under its own weight and the thrust of the springs 19, and this movement allows venting of the chamber, to balance its internal pressure with atmosphere, while the door 4 is still held close to the head ring 2 by the hooks 30 and 35.

To provide adequate venting time, the motor control may include a dwell period before continued rotation of the screw 10 drives the door 4 downwards to a fully open position at which limit switches are operated to stop the motor.

After venting, the door and screen can be lowered and this can be arranged for automatic operation, as known for sterilizers, opening of the door entraining in its movement lowering of the screen. It will be appreciated that any attempt to lower the screen 26 before the door is open will be limited by the upper border of the screen encountering the top of the door.

A power-operated door as described may be provided at each end of a steam sterilizer chamber.

Other power means than a lead screw and nut could be used, for example a hydraulic or pneumatic ram, and the direction of movement of the door could be any direction across the face of the head ring.

Claims (9)

1. A pressure chamber, for steam sterilization or the like, having extending vertically at one end a head ring, defining a front opening, and a power-operated door which can be moved bodily substantially in its own plane to and from a closed position in which it covers the opening and seals fluid-tight against the head ring, characterised thereby that the door is pivotally mounted in its power-operating means and biased with respect to the head ring so that the door tends constantly to rock forwardly, away from the opening, and cooperating wedge surfaces are provided on the door and head ring respectively to guide the door rearwardly into sealed engagement with the head ring as the door is closed and to allow limited forward movement of the door, away from the head ring, during an initial part of opening movement of the door.

2. A pressure chamber according to claim 1, in which the wedge surfaces are coacting surfaces of hooks provided respectively on the head ring, to be encountered each by a coacting abutment on the door, and on the door, to encounter a coacting abutment on the head ring, at the end of the closing movement of the door.

3. A pressure chamber according to claim 1 or 2, in which the power-operating means for the door comprises a reversible, motordriven lead screw and a nut, on which the door is pivotally mounted, engaged with the lead screw to be driven by rotation of the lead screw to move the door across the head ring in closing and opening of the door.

4. A pressure chamber according to any of claims 1 to 3, in which the door is arranged to move vertically across the head ring in opening and closing.

5. A pressure chamber according to claim 4, in which the power-operating means for the door is arranged below the chamber to raise and lower the door to close and open respectively.

6. A pressure chamber according to claims 2 and 5, in which the hooks on the head ring are arranged at the top thereof, to be encountered by the upper, leading, edge of the door, and hooks on the door are arranged on the lower, trailing, edge thereof, to encounter an abutment at the bottom of the head ring.

7. A pressure chamber according to any of the foregoing claims, in which a manuallymovable safety screen is arranged, outside the door, to be moved across the chamber opening in advance of the door, to ensure that the path of the door is clear, and to remain covering the opening until opening movement of the door, the safety screen being arranged to operate a switch in a control circuit of the door-operating means so that the door cannot be power-operated to close except when the screen is in closed position covering the chamber opening.

8. A pressure chamber according to any of the foregoing claims in which sealing means, for the door when closed against the head ring, comprises a ring of rubber or like elastomeric material seated in a groove, of dovetail cross-section, around the face of the head ring and projecting from the mouth of the groove to be encountered by and seal against the inner surface of the door as the door completes its closing movement.

9. A steam sterilizer substantially as described with reference to the accompanying drawings.