US3488142A - Autoclaves - Google Patents

Description

Jan. 6, 1970 w. c. COOPER 3,43J

AUTOCLAVES Filed July 14. 1965 w 5 Sheets-Sheet 2 AIR/WE? Jan. 6, 1970 w. c. COOPER 3,488,142

AUTOCLAVES Filed July 14. 1965 5 Sheets-Sheet 3 Jan. 6, 1970 w. c. COOPER 3,488,142

AUTOCLAVES Filed July 14. 1965 5 SheetsSheet 4 W. C. COOPER Jan. 6, 1970 AUTOCLAVES 5 Sheets-Sheet 5 Filed July 14, 1965 United States Patent 3,488,142 AUTOCLAVES William Charles Cooper, Nottingham, England, assiguor to Manlove, Alliott, & Co. Limited, Nottingham, England Filed July 14, 1965, Ser. No. 471,894 Claims priority, application Great Britain, July 14, 1964,

Int. Cl. A611 3/02 US. Cl. 21-93 12 Claims ABSTRACT OF THE DISCLOSURE A sterilizing autoclave having a power-operated vertically sliding door plate to open and close an opening giving access to the sterilizing chamber at one end of the autoclave body. The operation of the door is interlocked with an automatic steam sterilizing cycle within the chamber so that the door cannot be unlocked and opened when the chamber is at other than atmospheric pressure, nor can sterilizing steam be admitted until the door is locked closed and sealed. The door has an air pressure-operated seal which is also interlocked with the sterilizing cycle so that it cannot be pressurized until the door is closed, nor can it be de-pressurized until the chamber is at atmospheric pressure. Vertical guide flanges sustain the door against the outward pressure of the seal and the sterilizing steam in the chamber.

This invention relates to autoclaves. More particularly, it is concerned with the closing and sealing arrangements of autoclaves.

The conventional way of locking an autoclave door is by means of a door mechanism of the central closing type embodying a centre screw, capstan handwheel and radial locking bolts. The door can be manually or power operated but in either case it is ordinarily of heavy construction and carried on side hinges. A hinged door of this type constitutes something of an impediment to loading and unloading of the autoclave and this disadvantage becomes particularly acute when it is desired to use mechanical handling equipment for loading and unloading. It is therefore an object of the invention to provide a door arrangement that is more convenient in this respect.

According to the present invention, an autoclave is provided with a sliding door which is sealed when closed by means of an inflatable seal to which internal fluid pressure is applied, and the guides for the sliding door incorporate flanges that overlie the margins of the outer face of the door so as to sustain the door against the internal pressure when the autoclave is in operation. Thus the door may slide freely into place when the seal is deflated but will become locked in the guides when fluid pressure is admitted to the seal, the door being even more firmly locked when the autoclave chamber is under pressure.

While a vertically-sliding door will normally be the most convenient, a laterally sliding door, or a door sliding in a substantially horizontal plane to cover and uncover a top opening in a vertical autoclave, are further useful possibilities.

The fluid for pressurising the door seal may be any pressure fluid that can be used satisfactorily at the elevated temperature to which it will be subjected while the autoclave is in operation. These include high temperature oils, steam, air and even water if the pressure is sufficient to prevent boiling at the working temperature. But an arrangement that has particular merit is one in which the fluid is the same as the working fluid employed in other equipment associated with the autoclave. In particular, the pressure fluid may be air from the same comice pressed air system as is connected to a pneumatic piston and cylinder unit or ram that opens and closes the door. And this can be extended to the case in which the autoclave is arranged to perform part or the whole of its cycle of operations automatically under the command of pneumatic control equipment, there then being a comprehensive air pressure system involving the control equipment, the pneumatic door operator and the door seal.

One autoclave construction in accordance with the invention will now be described by way of example and with reference to the accompanying drawings, in which:

FIGURE 1 is a side elevation, in section, of the autoclave,

FIGURE 2 is a front elevation with parts broken away,

FIGURE 3 illustrates the door seal,

FIGURE 4 illustrates a safety switch flap at the top of the door,

FIGURE 5 is a steam piping diagram of the autoclave, and

FIGURE 6 is a pneumatic circuit diagram.

In the arrangement shown in FIGURES 1 and 2 the autoclave 11 stands up above the floor on a frame 12, and the door 13 associated with the front access opening 14 of the autoclave opens by sliding vertically downward. The door is essentially a robust flat mild steel plate stiffened on the outer face and having a protective coat ing of phenolic resin on the inner face. A long stroke pneumatic cylinder 15 raises and lowers the door. Vertical machined door guides 16 are provided at each side of the autoclave on the front end of the body thereof; these guides have flanges 17 that overlie the side margins of the outer face of the door 13. A bar 18 across the top of the autoclave front has a depending flange 19 behind which the upper edge of the door 13 enters when the door is closed. A bar 20 across the inner face of the door at the bottom thereof has a shallow upturned flange 21 that engages behind a bar 22 across the underside of the front of the autoclave body when the door is closed. Thus, by reason of the flanges 17, 19 and 21 the door 13, when closed, is sustained along all four sides against internal pressure of the autoclave, and the pressure of the door seal to be hereinafter described.

In the forward face 24 of the front end of the autoclave body, that is the face across which the door plate 13 slides, there is a continuous channel 25- in which lies a hollow joint ring or gasket 26 of flexible material, as shown best in FIGURE 3. The natural size of this ring and the depth of the channel 25' are such that the ring does not protrude from the channel when it is not subjected to internal pressure. But when a suitable liquid or gaseous medium under pressure is admitted to its interior 27 by way of a pressurizing connection (not shown) it is expanded into contact with the inner face of the door plate, all around the margin thereof, to effect a pressure and vacuum tight seal.

Interlocks are required to prevent the joint ring 26 being pressurised before the door is fully closed, to prevent the autoclave chamber having its pressure raised before the joint ring is pressurised, and to prevent the joint pressure being released or the door opened before the autoclave chamber pressure has been exhausted. This being so, it is convenient to employ the same fluid pressure medium in the door-operating cylinder and the joint ring, i.e. air, and, in the case of an automatic autoclave with which there is associated process control equipment to carry through the desired autoclave cycle of operations, to make the control system a pneumatic system using the same compressed air supply as the door operator and the joint ring.

To prevent the door 13 from opening when there is pressure in the joint ring 26, a safety catch 30 is provided at the underside of the autoclave. The safety catch comprises a pivotally mounted spring-urged latch member 31 which automatically latches under the bar 20 at the bottom of the door as the door closes and which is retractable to unlock the door by means of an air cylinder 32.

At the top of the door is a movable safety flap 33 (FIGURE 4) for operating an air valve to trip the doorclosing cylinder if there should be anything in the path of the door, for example the operators hand or arm, as it rises. The flap 33 overlies the upper end of a door cover 34 which encloses the front face of the door plate proper, and the rod 35 of the door-operating cylinder 15, and rises and descends with the door. The safety flap valve is sensitive so that only very light pressure on the safety flap 33 will suffice to check the closing of the door.

FIGURES and 6 show the steam piping and pneumatic control circuit arrangements, and the normal automatic cycle of operation of the autoclave will be described with particular reference thereto.

As shown in FIGURE 5, the steam supply to the autoclave 11 passes via a separator 50, fitted with a steam pressure gauge 51, a reducing valve 52 and connections 53, 55 into the autoclave jacket 54 and the autoclave chamber there being an air-operated steam valve 56 in the steam line to the chamber. A safety valve 57, an air-operated air admission valve 58, a jacket pressure gauge 59, and chamber pressure and vacuum gauges 60- and 61 are also provided. The separator 50 and the jacket 54 have steam traps 62 leading to a condensate line 63. The autoclave chamber has an outlet line 64 leading to an airoperated exhaust valve 47 and an air-operated drain valve 66, the line connection to the drain valve having a thermocouple fitting 67. The exhaust valve 47 opens to the air/ steam side .of a condenser 68; the drain valve 66 also leads to the condenser via a drain regulator valve 69. An air ejector 70 and a liquid ring vacuum pump 49 are coupled to the condenser '68. Cooling water from a mains line 71' is supplied to the condenser 68 via an air-operated water valve 48 and is discharged into a drain tundish 73. The vacuum pump 49 also draws cold water from a storage tank 74.

The air supply to the pneumatic system (FIGURE 6) is provided by a compressor 75 delivering through a nonreturn valve 76 to an air receiver 77 fitted with a relief valve 78 and pressure gauge 79. A switch 80 responsive to the pressure in the receiver 77 controls the operation of the compressor. The control system obtains its air from the receiver through an assembly comprising a pressure regulating circuit 81 and pressure gauge 90, a filter 91 and a lubricator 92.

On pressing a start button 36 on a spool valve 37 a pilot air supply is passed to an air valve 38 delivering air under pressure to the bottom of the door cylinder 15. Cylinder 15 then extends and lifts the door into the closed position. As the door reaches the fully closed position a trip valve 39 is actuated by the door thereby passing air to the left hand end connection of a delay cylinder 40. Delay cylinder 40 extends and engages -with a seal valve 41 to cause air to be supplied to the door seal 26. If movement of the door into the closed position is interrupted by pressure on the door flap valve 42 then this passes air pressure back to the cylinder control valve 38 so as to switch it back to its original setting and thereby reverse the motion of the cylinder 15 opening the door.

When the door seal 26 is pressurised air is fed also to a cylinder 43 which provides a slight time lag before striking a micro switch 44 that supplies an electrical impulse to a solenoid valve 45. Solenoid valve 45 opens and closes giving an air pulse to an indexing'cylinder 89 to operate a 30 position electrical rotary switch in a timer unit. This is the commencement of the sterilising programme and each time a pulse is supplied via a solenoid valve 45 to this electrical switch the programme moves on to a fur: the: s ag Th e are ge her fi e i a ole o d valves 45, 46, 82, 83, each associated with a respective spool valve 93, 9-4, 95, 96, 97.

Vacuum pump 49 is started up at the commencement of the sterilizing cycle and runs continuously throughout the entire process. Solenoid valve 46 opens passing operating air to the autoclave exhaust valve 47 and to the cold water valve 48 opening both these valves. Air is evacuated from the autoclave chamber down to a vacuum of 25" Hg at which point a vacuum switch is made and the chamber is given a pulse of steam which causes the pressure in the chamber to rise to a slight positive pressure. Evacuation is then repeated down to 25" Hg and the pulse of steam is repeated twice more. Then the rotary switch in the timer unit moves to the sterilizing stage. The solenoid valve 46 closes and solenoid valve 82 opens passing air to the steam valve 56 and the drain valve 66. Steam is admitted to the chamber via the reducing valve 52 allowing a set pressure of 32 lbs. p.s.i. When the sterilizing temperature of 134 F. is reached this is registered by the drain Line thermocouple 67. A temperature control switch makes contact and the sterilizing holding time begins. This time will normally be set at 3 minutes but a switch on the timer unit enables this time to be adjusted from /2 minute to 5 minutes in /2-minute stages.

A monitor timer is set to allow two minutes in which to reach sterilizing temperature during the sterilizing stage and if the sterilizing temperature is still low at the end of this time a flashing warning indicator comes on and remains on to the end of the process.

After sterilization the rotary switch in the timer unit moves on to the drying stage. Solenoid valve 82 closes and solenoid valve 46 opens passing air to the exhaust valve 47 and cold water valve 48 opening both these valves. Chamber pressure is rapidly reduced and the duration of this drying vacuum may be adjusted for a period of between /2 minute and 5 minutes, the time being normally in the region of 3-4 minutes.

At the end of the drying stage the rotary switch in the timer unit moves on to the release stage. Solenoid valve 46 closes and solenoid valve 83 opens allowing air to pass to the release valve 58 which opens and admits filtered air to the chamber. At the same time the process counter unit 84 is moved on by one unit to record the completed operation. As air fills the chamber and the chamber is restored to atmospheric pressure, a switch is made which signals the timer unit on to the door release position and a lamp indicating cycle complete comes on. Solenoid valve 85 opens passing air to cylinder control valve 39 which switches over and supplies air to the right hand end of delay cylinder 40 and to the door safety catch cylinder 86 causing it to be withdrawn. Delay cylinder 40 withdraws from seal valve 41 which is spring-loaded to return to the exhaust position. Air pressure is relieved from the quick exhaust valve 87 which immediately allows the escape of air pressure from the door seal 26.

The delay cylinder 40 in retracting strikes a cylinder reverse valve 88 passing air to the cylinder control valve 38 which switches over and passes an air supply to the top end of the main door cylinder 15 bringing the door down into the open position.

It will be noted that an automatic interlock is provided between the steam valve 56 and the exhaust valve 47 by means of a spool valve 99. If the door seal pressure should fail this is sensed by a microswitch 98 that can be employed to initiate the necessary precautionary measures.

The arrangement described is particularly suited for use. in an installation, for example a hospital sterilising plant, in which the autoclave is loaded and unloaded by means of a conveyor since the sliding door does not require the same clearance volume in front of the autoclave in which to operate as does a hinged door and it is easier to bring the conveyor up to the autoclave. If there is to be, in eifect, a conveyor line passing right through the autoclave then a similar sliding door is needed at the, th end.

Modifications of the arrangement described are possible without departing from the scope of the invention. For instance, instead of being operated by a long stroke cylinder at the front of the autoclave the door could be opened and closed by a short stroke cylinder situated elsewhere and coupled thereto by a system of levers. While in the drawing the channel housing the sealing gasket is shown to be in a separate ring member bolted on to the autoclave end ring it is to be understood that there will ordinarily be only a single integral end ring.

I claim:

1. An autoclave, comprising a body having a sterilizing chamber therein and further having an end wall with an opening in a vertical plane giving access to the chamber at one end thereof, a flat door plate sliding rectilinearly against said end wall in a vertical plane to open and close said access opening, side guides for said door plate on said body and having flanges associated therewith to sustain the door plate against outward pressure thereon, a top flange on said body above the access opening behind which the upper margin of the door plate engages when the door is in closed position, a bottom flange on said door which engages behind a lower portion of said body when the door is in closed position, a fluid-pressure-responsive flexible door seal member carried by said body and extending around said access opening, fluid-pressure applying means operable to force said door seal member by fluid pressure into sealing engagement when the door plate is in the closed position, and power-operated means coupled to said door plate to cause it to slide between the open and closed positions.

2. An autoclave according to claim 1, wherein said door plate is arranged to slide vertically, and said power-operated means comprises a long stroke pneumatic cylinder disposed with its axis vertical.

3. An autoclave according to claim 1, wherein the seal pressurizing fluid is air.

4. An autoclave according to claim 1, further comprising a lock to hold the door plate closed, and automatic interlock means whereby the lock is not released unless the autoclave is open to atmospheric pressure and the door seal is unpressurized.

5. An autoclave according to claim 1, further comprising a movably mounted safety member across the edge of the door plate that leads during closing, and safety control means arranged to respond automatically to light pressure on the safety member by initiating substantially instantaneous reversal of said power-operated door-sliding means.

6. An autoclave according to claim 1, wherein said flexible seal member is lodged in a channel in said end wall surrounding the access opening.

7. An autoclave according to claim 6, wherein said seal member is hollow and inflatable and has internal fluid pressure applied to it for sealing, the seal member protruding outwardly from the channel in which it is lodged when so inflated but lying wholly within the channel when not inflated.

8. A sterilizing autoclave according to claim 1, further comprising valve means to admit and exhaust sterilizing medium to and from said chamber to perform a sterilizing cycle, and fluid-operated control means for said valve means, and wherein the same working fluid is used in said control means and for pressurizing the door seal.

9. An autoclave according to claim 8, wherein said fluid-operated control means is automatic and controls both said valve means and said power-operated door-sliding means.

10. A sterilizing autoclave, comprising a body containing a sterilizing chamber and having an access opening at a front end thereof, a flat door plate arranged to slide vertically against said front end to open and close the access opening, vertical guides on the body guiding the door plate at the side edges thereof, vertical flanges associated with said guides to sustain said door plate against outward pressure thereon, a top flange on said body extending horizontally above the access opening and behind which the top margin of the door plate enters when in the closed position, a bottom bar on said body extending horizontally below the access opening, a flanged bar extending horizontally across the bottom margin of the door plate and the flange of which engages behind said bottom bar when the door plate is in closed position, a channel in the front end of the body extending all around the access opening, a flexible joint ring lodged in the channel, means for applying fluid pressure to the joint ring in the channel thereby to force it into sealing contact with the door plate when the door plate is in the closed position, and poweroperated means for raising and lowering the door plate.

11. An autoclave according to claim 10, further comprising interlock means preventing the door seal from being pressurized when the door plate is not fully closed, and preventing the power operated means from acting to open the door when the door seal is pressurized.

12. A sterilizing autoclave, comprising a body containing a sterilizing chamber, a sliding substantially rectangular door assembly to open and close an access opening to said chamber, door-retaining members on said body extending along four sides of a rectangle containing said access opening and interengaging with portions of said door assembly when closed to sustain said door assembly against pressure within the chamber along all four margins of said door assembly, powered means coupled to operate said door assembly, a fluid-pressure-operated seal member on said body to seal said door assembly when closed, means for applying fluid pressure to said seal to cause it to effect door sealing engagement, and automatic control means controlling both the sterilizing operations in the autoclave chamber and the operation of the door assembly and door seal in an integral cycle of sequential operatrons.

References Cited UNITED STATES PATENTS 1,752,265 3/1930 Schwarzkopf 21-108 XR 2,208,552 7/1940 Walter 2198 3,136,007 6/1964 Maher et al.

3,147,068 9/1964 Castle et al 21-93 XR 3,371,986 3/1968 Brown 21-98 FOREIGN PATENTS 747,356 4/1956 Great Britain.

MORRIS O. WOLK, Primary Examiner B. S. RICHMAN, Assistant Examiner U.S. Cl. X.R.

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