US3431065A - Autoclave - Google Patents

Description

March 4, 1969 E. R. SCHIPANSKI AUTOCLAVE Sheet Filed April 6. 1965 j $163 m. we m4 m5 ASJEMBLY 501.. F0? @EF/LL VAL VE IN VENTOR. [M/L 5cH/ 4A/5z/ ,W and United States Patent 5 Claims ABSTRACT OF THE DISCLOSURE An autoclave comprising: (a) a sterilization chamber having an outer pressure wall and an inner liner spaced therefrom and having a top steam port at one end and a bottom condensate port at the other end, both ports communicating with the interior of the liner; (b) a steam "boiler which is in contact with a limited area of the pressure wall of the sterilization chamber so that some heat passes from the boiler into the sterilization chamber whether steam flows from the boiler to the sterilization chamber or not; a condenser vented to atmosphere and communicating with both the steam and condensate ports; a thermostatic control valve regulating flow of steam and air through the condensate port; and a twoposition control valve for passing steam from the boiler through the steam port when in one position and for exhausting steam through the steam port to atmosphere through the condenser when in a second, normal position.

The present invention relates to apparatus for sterilizing surgical gowns, dressings, instruments, liquids, and the like, and more particularly to an improved autoclave wherein such sterilization is accomplished by the use of steam under pressure.

Autocla-ves for the above purposes may be of a single or double jacket type. Single jacket autoclaves generally include a pressure-tight outer shell in communication with an inner liner forming an inner chamber receiving the material to be sterilized. The space between the outer shell and the liner is partially filled with water which is heated by electrical elements to produce steam. The steam is forced through an opening, usually in the top rear of the liner, into the chamber to sterilize material stored therein. After sterilization has occurred, air, condensate and steam are discharged from the chamber and shell through a relatively small bottom opening and steam trap to a condenser.

Although single jacket autoclaves are relatively simple in design and inexpensive to manufacture, they suffer from many inherent practical problems which to date have severly limited their use. First of all, even though steam is discharged from the inner liner after sterilizing, the sterilized material is still subject to boiling temperatures and steam formed from the water located between the liner and the shell. Therefore, the sterile material is initially too Wet to use and is too hot to safely remove from the autoclave, For this reason, the electrical heaters for boiling the water are shut off and the door of the autoclave opened to cool off and dry the material prior to removal from the liner. Even so, an appreciable length of time elapses before the sterile material may be safely removed from the autoclave. Also, the cool air may contaminate the sterile material.

All in all the inefficient sterilizing and drying operations of single jacket autoclaves render them unsuited to sterilizing surgical gowns, towels, dressings and other linen or fabric articles which must be both sterile and dry before use.

Furthermore, the shutdown of the autoclave after each sterilizing cycle requires that the single jacket autoclave be reactivated for each separate sterlilizing operation. This is very time consuming particularly when a number of different articles require sterilization.

Double jacket autoclaves, on the other hand, provide much faster sterilization and produce substantially dry dressings, gowns and the like. Unfortunately, however, double jacket autoclaves are appreciably more expensive to manufacture and are of a more complex design than single jacket autoclaves. Further, commercially available double jacket autoclaves possess numerous practical disadvantages.

Briefly, double jacket autoclaves are structurally similar to a single jacket autoclaves with the exception that the inner liner is a separate sealed unit and communication between the outer shell and inner liner is through a hand or solenoid operated valve.

As with the single jacket autoclave, water is stored in the space between the outer shell and inner liner and is heated to form steam by electrical heating units either stationed in the spaced or attached to the outside of the shell. The steam completely surrounds the inner liner and continuously transfers heat therethrough to the sterilization chamber defined by the liner. Although this arrangement relies upon opening of the valve for rapid sterilization of the contents of the chamber, the continuous radiation of heat to the chamber event after valve shutoff and separate exhaust make it mandatory that the sterilized material be removed quickly from the chamber to avoid damage caused by high temperature dry air within the chamber.

The steam storage arrangement completely surrounding the chamber also continuously transmits heat to the open frontal portion of the autoclave, rendering the frontal portion too hot to be touched by the human hand without burning.

Furthermore, while well saturated steam is initially supplied to the sterilization chamber after turn on of the autoclave, the steam becomes increasingly drier as the surfaces of the sterilization chamber heat up. Dry steam will not penetrate or sterilize dressings and the like and is capable of damaging and dulling instruments. To counteract this, the pressure of the steam must be increased. Therefore, the double jacket autoclave requires close attendance of an operator, particularly if uniform, high quality ster iliziation is to be achieved from batch to batch.

Double jacket autoclaves also include separate valves to control steam supply, exhaust and venting, respectively. The valves are separately controlled and are normally closed. Therefore, to operate the autoclave, the steam supply valve must be actuated for a predetermined time, followed by a similar but separate actuation of the exhaust valve. Such multiple valving is relatively expensive and requires preadjustment and attention of an operator.

Further, in the case of a power failure either during sterilization or exhaust, all valves close thereby capturing steam within the sterilization chamber. The only way to relieve pressure within the chamber is to open the front door of the autoclave, which presents a great risk of physical harm to the operator, particularly when the captured steam is under high pressure. This safety problem is also present in commercially available single jacket autoclaves.

A further shortcoming of double jacket autoclaves which is also present in single jacket autoclaves is that of liquid loss during liquid sterilization. Such losses are considered unavoidable in presently existing autoclaves and are at best reduced somewhat by utilizing a slow, long exhaust, usually of 15 to 45 minutes duration.

Additional shortcomings common to single and dou- 3 ble shell autoclaves lie in the placement and struction of their steam trap and condenser, respectively.

To prevent heat damage to the steam trap, the trap is usually located some distance from the autoclave exhaust outlet. From a functional standpoint, this is a very unsatisfactory arrangement for the steam trap which blocks the exhaust outlet when steam within the inner liner reaches a predetermined temperature. To function at maximum efiiciency, the steam reaching the trap should be at the same temperature as the steam within the liner. Unfortunately, this is prevented by heat losses which occur in the tubing or long passages connecting the exhaust outlet to the steam trap. Also, variations in such heat losses make it diflicult to adjust the steam trap to compensate for the heat loss.

As to the steam condenser, it usually includes a coil of tubing immersed in a coolant. Unfortunately, such a condenser is susceptible to tube clogging by lint and other foreign matter exhausted from the autoclave after sterilization. Conventional condensers for autoclaves therefore require periodic servicing if uniform overall operating efficiency is to be achieved.

In view of the shortcomings of presently available autoclaves, it is a general object of the persent invention to provide an autoclave which combines the advantages of the single and double jacket autoclaves Without including any of their inherent disadvantages.

Another object of this invention is to provide an improved, single jacket-type autoclave which is capable of producing high quality, rapid sterilization of surgical gowns, dressings, instruments and the like, and which leaves the sterilized material completely dry and ready for use.

A further object of this invention is to provide an autoclave which will sterilize liquids without any appreciable loss of liquid.

Still another object of this invention is to provide an autoclave which is capable of storing sterilized material in its closed sterilization chamber until needed and without damaging the material.

A still further object of this invention is to provide an autoclave having uniform sterilizing characteristics from batch to batch.

It is another object of this invent-ion to provide an autoclave which in case of power failure automatically exhausts its sterilization chamber to atmosphere.

It is a further object of this invention to provide an autoclave which allows a steam trap to be directly connected to its bottom condensate removal port to sense steam temperature in the sterilization chamber of the autoclave.

It is still another object of this invention to provide an autoclave which includes a tubeless condenser requiring a minimum amount of water to condense steam and which is essentially clogproof.

It is still a further object of this invention to provide an autoclave which includes a single valve for passing steam to and exhausting steam from the sterilization chamber of the autoclave.

An additional object of this invention is to provide an autoclave having the foregoing features which is simple in design, inexpensive to manufacture, readily assembled and disassembled for service and replacement of parts, and which is highly efficient and safe in its operation.

The foregoing as well as other objects and advantages of this invention may be more clearly understood by reference to the following detailed description when taken with the drawings which, by way of example, illustrate one form of autoclave embodying the features of the present invention.

In the drawings:

FIGURE 1 is a perspective view of the autoclave with the outer casing thereof shown in phantom lines and the wiring associated therewith removed for clarity;

FIGURE 2 is a cross-sectional side view of the autoclave of FIGURE 1, illustrating the inner structure thereof;

FIGURE 3 is a sectional view taken along the line 33 in FIGURE 1, illustrating the internal construction of the steam trap included in the autoclave;

FIGURE 4 is a sectional view taken along the line 4-4 in FIGURE 1, illustrating the inner construction of a vacuum relief valve for the boiler of the autoclave;

FIGURE 5 is a sectional top view taken along the line 44 in FIGURE 1, illustrating a water level gauge and mirror combination associated with the boiler of the autoclave;

FIGURE 6 is a schematic wiring diagram of the electrical circuitry associated with the autoclave;

FIGURE 7 is an enlarged sectional side view of the valve assembly for the autoclave illustrated in FIGURE 2;

FIGURE 8 is a sectional view taken along the line 8-8 in FIGURE 1, illustrating the inner construction of a refill valve for controlling the refill of water into the boiler of the autoclave; and

FIGURE 9 is a top view of the condenser of the autoclave, portions of the top of the condenser being broken away to illustrate the inner construction of the bottom of the condsenser.

Briefly, the illustrated form of the autoclave is represented in the drawings by the numeral 10 and is of a single jacket type having a sterilization chamber 12 for receiving the material to be sterilized. A steam producing boiler 14 is stationed directly behind the sterilization chamber and communicates with a well 16 extending under the rear portion of the bottom wall 18 of the chamber. The combination of the well 16 and the front wall of the boiler 14 forms a preheater 20 for driving cold air and moisture from the sterilization chamber 12 through a bottom port 22, and for preheating the walls of the chamber prior to the start of the sterilization cycle. The preheater thus readies the sterilization chamber 12- for steam, and ensures a minimum heat loss in the steam initially entering the chamber and a minimum formation of condensate during the sterilization cycle.

In the present invention, the passage of steam to the sterilization chamber 12 is under the selective control of a single valve assembly 24. The valve assembly 24 (see FIGURES 2 and 7) is stationed atop the boiler 14 and opens directly to a top port 26 near the back of the sterilization chamber 12 to normally vent the chamber to atmosphere through a tubeless steam condenser 28, via tubing 160. The valve assembly 24 is selectively operated by an electric timer circut to close the vent to atmosphere and pass steam from the boiler to the chamber 12, also through the top port 26. Thus, in a single structure, the valve assembly 24 performs the multiple functions of (1) passing steam to the sterilization chamber, (2) automatically exhausting steam from the chamber, and (3) venting the chamber to atmosphere at the end of the sterilization cycle determined by the timer circuit. Furthermore, should power to the autoclave fail for any reason, the valve assembly rapidly and automatically exhausts and vents the chamber to atmosphere, thereby preventing high pressure steam from being captured within the sterilization chamber.

In the present invention, the exhaust of steam through top port 26, valve assembly 24, and tubeless condenser 28 is extremely rapid. In this regard, it should be noted that the condenser 28 does not present an appreciable back pressure to exhaust flow, as is common in conventional condensers where steam flow is restircted to relatively small tubes immersed in a coolant.

The rapid exhaust means a rapid equalization of sterilization chamber pressure toward atmospheric pressure and combines with the operation of the preheater 20 to leave the chamber 12 free of steam and the sterilized material therein dry for immediate use. In particular, the preheater 20 maintains the temperature in the sterilization chamber 12 just above 200 F. both during and after exhaust. This aids in forcing steam upward and out of the chamber during exhaust. After exhaust, the preheater continues to heat the chamber 12, evaporates any residual condensate to further dry the sterile material, and maintains a slight positive pressure within the chamber to prevent cool air from entering the chamber through the atmospheric vent system provided by the condenser 28 and the valve assembly 24.

In this manner, the exhaust operation assures dry material without requiring separate drying procedures and provides a sterile and safe storage place for the sterile material since chamber temperatures of 200 F. to 212 F. will not injure any heat sensitive materials such as surgical gloves or instruments.

Further, the foregoing combination comprising the autoclave achieves controlled steam temperature and saturation which provides for uniform, rapid and safe sterilization from one batch to the next.

Moreover, it has been found that the rapid exhaust of steam through the top port 26 and the valve assembly 24 at the rear of the sterilization chamber allows the autoclave 10 to sterilize liquids without any appreciable liquid loss. This is directly contrary to liquid sterilization techniques employed with presently available autoclaves which utilize long and slow exhausts.

Referring more specifically to FIGURES l and 2, the sterilization chamber 12 is inclined slightly downward toward the front of the autoclave 10, and is illustrated as being formed in a hollow rectangular body 30 having open front and back ends 32 and 34. A rectangular collar 36 tightly surrounds the front end 32 of the body and secures a sheet metal liner 38 within the sterilization chamber 12 to receive the material to be sterilized. To this end, the liner 38 includes a flange 40 surrounding its open front end. The flange is captured between the back of the collar 36 and the front end of the body 30 around four sides of the body. The bottom of the flange 40 extends into the center of a series of bottom ports 22, here defined by separable recesses in the back of the collar and corresponding relieved front edges of the bottom wall 18.

The collar 36 also supports a rectangular front panel 42 having an upper instrument section 44 with meters 46 and 48 for indicating steam temperature in the sterilization chamber and steam pressure in the boiler, and control iknobs 45 and 47 for a variable thermostat 50 and electric timer 52 (see FIGURE 6) for presetting the temperature of the heat applied to the boiler and the duration of the sterilization cycle.

A door 54 is adapted to close and seal the opening in the collar 36 and hence the front of the sterilization chamber 12. To this end, the door 54 is carried by a strong back-type door latch 56. The strong back door latch 56 is of conventional design and may be of the type described in detail in the copending patent application Serial No. 708,824, filed Jan. 14, 1958, including a strong back 58 hinged at one end to the front panel 42 and carrying a locking nut type safety latch 60 at its opposite end for locking the door closed over the opening in the collar 36.

To complete the enclosure of the sterilization chamber 12, the open back 34 of the body 30 is sealed by the front wall 62 of the boiler 14, the boiler 14 being connected to the body 30 by a plurality of screws 64 passing through a flange 65 surrounding the open back of the body, a sealing gasket 66, and into the front wall of the boiler.

As illustrated most clearly in FIGURE 2, the front wall 62 of the boiler 14 includes a front port 67 communicating with the well 16, here formed by a horizontal recess in the back end of the bottom wall 18 extending substantially the width of the bottom wall and forward under the middle of the sterilization chamber. Boiling water from the boiler 14 passes into the well 16 which, in turn, transfers heat to the bottom Wall 18 of the body 30. As previously indicated, the combination of the well 16 and the front wall 62 of the boiler 14 comprises the preheater 20-.

In particular, heat radiates from the front wall 62 and from the well 16 to drive cold air and any condensate in or surrounding the liner 38 forward and out of the sterilization chamber 12 through bottom ports 22. From the bottom ports 22, the cold air and condensate pass into a hollow 68 in the front edge of the bottom wall 18 and through a steam trap 70 upwardly through tubing 72 into the bottom of the condenser 28. In this manner, the preheater 20 readies the sterilization chamber for steam, and ensures a minimum heat loss in the steam initially entering the chamber and a minimum formation of condensate during the sterilization cycle.

The steam trap 70 is of a conventional design and includes a sump 74 having a side port 76 leading through an insulator 78 directly to the hollow 68 in the bottom wall of the body 30. The sump 74 also has a bottom port 78 connecting to the tubing 72 for passing fluid to the condenser 28. Mounted Within the sump 74 is a thermostatic valve means which includes a valve needle 80 and a thermostatic bellows 82 of conventional design. The bellows S2 is conveniently mounted within the sump by means of a threaded shaft 84 passing upward through a threaded hole 86 in an upper cap 88 covering and sealing the sump. By turning the shaft 84, the vertical position of the bellows within the sump may be controlled to preadjust the operating temperature of the steam trap.

Since the steam trap 70 is directly connected to the body 30, it senses and responds to the temperature in the sterilization chamber to initially allow cold air and condensate to pass through the sump 74 and upward through the tubing 72 into the bottom of the condenser. However, as the temperature of the steam in the sterilization chamber, and hence the temperature of the fluid passing through the sump increases, the bellows 82 expands. When steam within the sterilization chamber 12 reaches a predetermined sterilization temperature, the bellows expands to close valve needle 80 against a seat 90 in the top of the port 78. Thereafter, during the sterilization cycle, the valve remains closed but may open intermittently to exhaust any air and condensate which falls below the fixed trap operating temperature. In this manner the steam trap 7 0 responds directly and rapidly to temperature variations in sterilization chamber 12 to ensure that the steam within the chamber remains at the predetermined sterilization temperature during the entire sterilization cycle.

The apparatus for heating water within the boiler 14 and for controlling the temperature thereof is of a conventional design, including a pair of electrical heating elements 92 and 94 connected to an electrical circuit including a pair of thermostats 50 and 96. The thermostats are mounted within the boiler immediately adjacent the heaters to automatically control the on-oif operation of the heaters and thereby maintain the water and steam within the boiler at a predetermined temperature. As illustrated in FIGURE 6, the thermostat 50 is adjustable between 0 and 300 F. while the thermostat 96 is fixed at 300 F. The electrical circuit to the heaters 92 and 94 is through the thermostats. Therefore, if the operating temperature of either thermostat is exceeded, the circuit is opened and the heaters shut off. In this regard, the thermostat 50 may be preset by adjusting the control knob 45 on the panel 42, and the thermostat 96 acts as a safety device preventing the boiler temperature from exceeding 300 F. in case of a failure in the thermostat 50.

A pressure sensitive device (not shown is also included in the boiler and connects to the pressure gauge 46 on the front panel 42 of the autoclave to provide an indication of steam pressure within the boiler. A vacuum relief valve 98 protects the pressure gauge 46 from damage caused by the development of vacuum pressures within the boiler 14. To this end, and as most clearly illustrated in FIGURE 4, the relief valve 98 includes a valve block 100 having a threaded lower end received by a threaded hole 102 in the top of the boiler 14. A vertical bore 104 extends through the valve block and receives a valve stem 106 having an enlarged lower end 108. The upper end of the valve stem is threaded and receives an adjusting nut 110 for controlling the tension in a coil spring 112 extending around the stem. The coil spring is captured between the valve block and the nut 11%] and presses upward on the bottom of the nut to normally urge the bottom of the valve stem upward toward the bottom of the valve block. An O-ring 114 seated in the upper surface of the enlarged head of the valve stem is therefore normally pressed against the bottom of the valve block to create an airtight seal between the valve 98 and the boiler 14. However, if for any reason a vacuum pressure is created within the boiler 14, as after the shutdown of the heaters in the boiler, the valve stem 106 is drawn down within the boiler breaking the seal between the O- ring 114 and the valve block 100 and providing passage for air into the boiler to equalize the pressure therein.

Another safety factor associated with the boiler 14 is a water level gauge 116 connected to the right side of the boiler. The Water level gauge is of conventional design and includes therein a colored fluid for clearly indicating the water level within the boiler. In order to provide a clear viewing of the water level when the autoclave is against a wall, a mirror 118 is connected to the side of the housing surrounding the boiler and aligned such that the level of the water is reflected forward along the side of the autoclave.

As previously indicated, the supply of steam from the boiler 14 to the sterilization chamber 12 is under the selective control of the valve assembly 24. As illustrated most clearly in FIGURES 2 and 7, the valve assembly 24 is supported on top of a mounting bracket 120 connected to and resting directly on top of the boiler 14. The boiler 14 communicates with the valve assembly 24 through a top port 122 in the boiler, and opening 124 in the mounting bracket and a bottom port 126 in the valve block 128 of the valve assembly.

The valve block 128 is carried by the mounting bracket 120 and in addition to the bottom port 126 includes a horizontal bore 130 and a vertical top port 132 from the bore 130. An elongated valve stem 134 is supported for sliding movement within the horizontal bore 130 and includes an enlarged, hollow front end portion 136 with two pair of vertically aligned top and bottom ports 138 and 140 and relatively small rear end portion 142 extending from the valve block 128. A coil spring 144 passes around the rear end portion 142 of the stem and is compressed between the back of the enlarged front end portion of the stem and plug 146 in the open rear end of the horizontal bore 130. In this manner, the spring 144 normally urges the valve stem forward against a connecting block 148 stationed atop the body 30 and against the front of the valve block 128.

In this normal position, the hollow front end 136 of the valve stem communicates directly with a horizontal bore 150 in the connecting block 148 which in turn leads through an intersecting vertical bore 152 to a tube 154. The tube 154 extends downward into the top port 26 in the sterilization chamber-passing through a hole 156 into the liner 38. Also, the top and bottom ports 138 in the valve stem communicate with the top port 132 in the valve block, which here receives a threaded connector 158 for the end of a tube 160 leading from the valve assembly to the condenser. Since the condenser includes an open vent to atmosphere, this means that the valve assembly 24 normally vents the sterilization chamber 12 to atmosphere.

To operate the valve assembly 24, a solenoid 164 is connected to the rear end of the valve stem 134 and is mounted atop the bracket. The series electrical circuit for energizing the solenoid is illustrated in FIGURE 6 and includes the electric timer 52 and a three-position switch 166 connected to a source of electrical power. When it is desired to sterilize material in the sterilization chamber, the switch 166 is first set in its down or heat boiler position and the control knob 47 on the front of the instrument panel 42 then is set to any desired time interval. In the down position, the switch 166 completes the series circuit to the heaters 92 and 94 to heat the water in the boiler 14. As the water heats, the preheater 20 functions to drive cold air from the sterilizaiton chamber and ready the chamber for steam. When the steam in the boiler is up to temperature, the timer 52 is set. This completes a series circuit from the source through the timer 52, solenoid 164 and a light 168 indicating that the timer is working. The solenoid 164 functions in a conventional manner to hold the valve stem 134 in a rearward position. In this position, the valve stem closes the top port 132 in the valve block, thereby blocking the vent to atmosphere and the top and bottom ports 140 open to the boiler through the opening 124 in the bracket and the top port 120 in the boiler. Steam immediately rushes through the valve assembly 24 downward through the vertical tube 154 into the liner 38 and circulates forward through the sterilization chamber 12. Air and condensate from the sterilizing chamber are forced ahead and downward and escape through the multiple bottom ports 22 into the steam trap and upward into the condenser 28. As the air and condensate is replaced by steam, the steam will enter the steam trap at a temperature well above 212 F. and force the bellow assembly 82 to ex-' pand and close the line 78. The saturated steam then functions to sterilize the contents of the chamber for a. period of time determined by the setting of the timer 52.

Since the preheater 20 has preheated the walls of the sterilization chamber and driven cold air and condensate therefrom, the steam initially entering the chamber from the boiler is subject to a minimum heat loss. Therefore, a minimum time elapses before steam in the chamber is up to the desired sterilization temperature and a minimum amount of condensate is initially formed in the chamberthat being driven from the chamber with the initial passage of steam through the steam trap to the condenser.

During sterilization, the material to be sterilized heats up and a certain amount of condensate is formed within the chamber. This condensate flows by gravity along the downwardly sloping bottom wall of the liner 38 and drops through the bottom ports 22 into the hollow front end of the bottom wall 18. Most of this condensate is expelled from the hollow by momentary openings of the steam trap. A certain amount of the condensate, however, is carried with steam around the liner 38 within the body 30.

At the end of the sterilization cycle, the electrical circuit to the valve assembly 24 is automatically opened. The spring then rapidly returns the valve stem 134 to its normal position providing an exhaust path for steam from the chamber 12 to the condenser 28 through the vertical tube 154, top port 26, valve assembly 24 and tube 160. The exhaust path presents a minimum back pressure to the steam in the chamber 12, and, as will be described more fully, provides a vent to the atmosphere. Therefore, the steam exhausts from the chamber rapidly through the top port 26 to the condenser 28. The rapid exhaust of steam, which is accompanied by a rapid drop in chamber temperature and a rapid equalization of chamber and atmospheric pressures, completely extracts all condensate forming vapors from the chamber 12 leaving the sterile material dry and ready for use.

After exhaust, heat continues to be radiated into the chamber 12 at a uniform rate from the preheater 20. In fact, the preheater 20 maintains a chamber temperature of about 210 F. This produces a slight positive pressure in the chamber 12 to prevent cool air from entering through the exhaust and vent system including the condenser 28, valve assembly 24 and to port 26. Also, condensate between the liner 38 and the body 30 evaporates on the superheated surfaces 18 of the preheater and is driven from the chamber 12 through the top port 26. In this manner, a completely dry, safe, and sterile storage place is provided for the material in the chamber 12.

From the foregoing, it should be particularly noted that since the valve assembly 24 normally vents the sterilization chamber to the condenser 28, the valve assembly automatically exhausts steam from the sterilization chamber whenever it is deenergized. This, of course, occurs at the end of the sterilization cycle. This also occurs if power to the autoclave should fail. The valve assembly 24, therefore, prevents steam from being captured within the chamber 12 and allows the contents thereof to be removed without endangering the operator of the autoclave.

As previously indicated, all condensate and steam is exhausted from the sterilization chamber 12 to the condenser 28. As can be seen most clearly in FIGURES 2 and 9, the condenser 28 is of a tubeless type. This means that the condenser will not clog with lint and other foreign matter exhausted with the condensate and steam to the condenser and therefore requires little if any servicing. Also, the relatively open, tubeless design presents a minimum back pressure to steam exhaust, thereby materially aiding in the rapid exhaust of steam from the chamber 12.

More particularly, the condenser 28 is formed in three parts, a bottom portion 170, a separator plate 172, and a top portion 174. The bottom portion 17.0 is carried by the top of the body 30 and connected thereto by a plurality of screws 176 passing into upwardly extending H flanges 178 of the body. The bottom portion is generally of a rectangular cup shape and includes a vertical rib extending rearward from the front wall of the condenser and curling inwardly toward the center of the bottom portion. In this manner, the ridge defines a generally horizontal, inwardly curling, channel 180. The channel 180 slopes slightly downwardly as it curls toward the center of the condenser. Also various sections of the channel are divided by vertical partitions 182 of decreasing height toward the center of the condenser.

The separator plate 172 covers the top of the bottom portion 170 and carries a vertical tube 188 which opens into the bottom portion 170 through a tube 190 and which extends upwardly and opens into the top portion 174 of the condenser through downwardly inclined side ports 192 and 194. Vertically spaced side pins 196 and 198 extend from the vertical tube 188 to provide an indication of water level within the top portion 174 of the condenser by viewing through an opening 200 in the top of the condenser, the top portion resting on the separator plate and the combination being secured to the bottom portion by a plurality of screws 202. The top opening 200 also provides a vent for the condenser to atmosphere and an opening for adding water to the upper portion of the condenser.

In addition to the foregoing, the condenser 28 includes a small tube 203 which extends from bottom portion 170 to the top portion 174 as illustrated in FIGURES 2 and 9. The tube 203 allows the condenser to breathe if the channel 180 should become clogged. The tube 203 also acts as a small condenser for the small amounts of fluid passing therethrough in that it is partially immersed in cool water.

In operation, steam, condensate and air (collectively referred to as exhaust) passing from the sterilization chamber either through the bottom port 22 or through the top port 26 and valve assembly 24, enters the bottom portion 170 of the condenser through side ports 184 and 186 as illustrated in FIGURE 9. The exhaust travels along the channel 180 spiralling inward toward the center of the bottom portion 174. In so doing, it passes over the large surfaces of the channel and engages the water cooled separator plate 172. Therefore, as the exhaust travels along the channel, it condenses to water. Upon reaching the center of the bottom portion, the liquid, together with any remaining steam and hot air, passes upward through the vertical tube 188 and outward through the side ports 192 and 194. The liquid drains onto the separator plate 172 while any remaining vapors or hot air pass outwardly from the condenser through the top opening 200 to atmosphere.

Any condensate remaining in the bottom portion 170 is blocked from returning to the sterilization chamber 12 through lines 168 and 72 by the partitions 182. In fact, in practice the partitions 182 prevent water backflow into the compartment of the channel including the side ports 184 and 186 to thereby create a water-free space Within the condenser 28. The tube 203 communicating with the atmosphere is therefore added assurance of an open vent between the chamber 12 and atmosphere independent of the condenser 28.

Because of the lage cool surfaces contacted by the exhaust, the condenser possesses a high operating efficiency and due to its tubeless design, is essentially clog-free requiring a minimum of servicing.

The condenser also acts as a source of water for refilling the boiler. To this end, a tube 204 extends between the top portion 174 of the condenser and the boiler 14 through a normally closed refill valve 206.

As illustrated most clearly in FIGURES l and 8, the refill valve 206 is connected directly to the right side of the boiler and includes a valve block 208 having a vertical bore 210 and a connecting horizontal bore 212 communicating with the boiler through a side port 214. The bottom of the vertical bore receives a tube connector 216 connecting the tube 204 to the bottom of the valve block.

A valve stem 218 is supported within the vertical bore 210 to normally close the path to the condenser. To this end, an O-ring 220 is seated in an annular groove 221 in the lower end of the valve stem and engages the inclined surfaces of the vertical bore adjacent its lower end. The upper end valve stem passes through a ring 222 threadedly engaging the internal bore 224 of a hollow plug member 226. The plug member, in turn, is stationed within the top end of the vertical bore 210 and tightly compresses an O-ring 228 to create an airtight seal between the plug and the valve block. The lower end of the plug 226 rests upon an annular separator 230 which surrounds the valve stem and prevents fluid from entering the area of the plug. The valve stem 218 also carries an annular collar 232. A coil spring 234 extends around the valve stem and presses against the top of the collar and the bottom of the ring 222. In this manner, the spring normally urges the valve stem 218 downward to seal the bottom of the vertical bore 210.

To operate the refill valve, the top of the valve stem 218 is connected to a solenoid 236 which forms a part of the circuitry for the autoclave illustrated in FIGURE 6. Referring specifically to FIGURE 6, the solenoid 236 is actuated by moving the switch 166 to its upper or refill position. This simultaneously disconnects the boiler heaters from the power source and completes a series circuit through the solenoid 236 to the source. The energizing of the solenoid 236 causes the valve stem 218 to move upward away from the bottom of the valve block 208 and allows water to pass from the top portion of the condenser 28 downward to the valve block and into the boiler through the side port 214. In order that the flow of liquid may be more rapid, the timer 52 should also be energized. This opens the top port in the boiler 14 to atmosphere through the valve assembly 24 and condenser 28 and allows the added liquid to displace air within the boiler. When sufficient water is in the boiler, the switch is returned to its normal position and the refill valve 206 again blocks liquid flow from the condenser to the boiler.

From the foregoing, it is appreciated that the autoclave of the present invention combines the advantages of single jacket and double jacket autoclaves without their inherent disadvantages. This, the present invention accomplishes, employing a single jacket design in combination with a preheater and single valve assembly. Furthermore, the operation of the autoclave is extremely rapid and provides completely dry dressings which are ready for use or which may be stored in the sterilization chamber until required for use. Moreover, the autoclave provides uniform high quality sterilization from batch to batch and is capable of sterilizing liquids without liquid loss.

Also, the autoclave allows the steam trap to be connected directly to the bottom condensate removal port for directly sensing the temperature of steam in the sterilization chamber and includes a tubeless condenser which is highly efficient in its operation and essentially clog-free. All of this, the present invention accomplishes with a simple, relatively inexpensive design.

In the foregoing, a particular form of the present invention has been described in some detail. Changes and modifications, however, may occur to those skilled in the art without departing from the spirit of the present invention. It is therefore intended that the invention be limited in scope only by the following claims.

I claim:

1. An autoclave comprising:

means defining a sterilization chamber including an outer pressure shell and an inner liner spaced therefrom and having a top steam port adjacent one end of said chamber and a bottom condensate port adjacent the other end of said chamber, said ports communicating with the interior of said liner;

boiler means communicating with said steam port, a

section of said boiler means being in conductive heat transfer relation with a limited portion of said outer shell for heating said sterilization chamber before, during and after passage of steam from said boiler means into said sterilization chamber;

steam condenser means having a vent to atmosphere and communicating with said condensate port and with said steam port;

first control valve means for preventing steam from flowing from said sterilization chamber through said condensate port to said steam condenser means when the temperature of said steam passing through said first control valve means rises above a predetermined temperature; and

second control valve means having a first position for normally venting said sterilization chamber to atmosphere through said steam port and said steam condenser means, and having a second position for passing steam from said boiler means to said sterilization chamber through said steam port, said control valve means automatically returning to said first position when not energized, whereby said sterilization chamber is preheated in the absence of steam to remove air therefrom, sterilized with steam from said boiler means at elevated pressure, and postheated in the absence of steam to dry said sterilization chamber and to substantially prevent flow of air into said sterilization chamber.

2. The autoclave of claim 1 wherein said second control valve means comprises a valve block having a hole therethrough and first and second side ports from said hole to said boiler means and steam condenser means, respectively, a valve stem stationed for sliding movement within said hole with a hollow end communicating with said top steam port in said sterilization chamber and a third side port from said hollow portion of said valve stem for communicating with said second and first side ports in said valve block when in a normal and operating position, respectively, spring means for normally urging said valve stem toward said normal position, and electrical circuit means including a timer for operating said second control valve means for preselected periods of time,

3. The autoclave of claim 1 wherein said steam condenser means comprises a bottom portion having a generally horizontal, spiral-shaped channel extending inwardly and slightly downwardly from the outside to the center of said bottom portion, said bottom portion further including a side port for communicating with said first and said second control valve means, a separator plate over said bottom portion, and a top ortion vented to atmosphere, and a generally vertical tube having its bottom opening to the center of said bottom portion and a top opening spaced above said separator plate in said top portion for venting to atmosphere and for passing water to said top portion.

4. An autoclave comprising:

means defining a sterilization chamber having a top steam port adjacent the rear of said chamber and a bottom steam condensate port adjacent the front of said chamber;

boiler means;

a steam condenser having a vent to atmosphere;

and control valve means normally venting and exhausting said sterilization chamber to atmosphere through said top steam port and said steam condenser and for operating to block said vent to atmosphere and to pass steam from said boiler means through said top steam port to said chamber, said valve means comprising a valve block having a hole therethrough and first and second side ports from said hole to said boiler means and said steam condenser, respectively, a valve stem stationed for sliding movement within said hole with a hollow end communicating with said top steam port in said chamber and a third side port from said hollow portion of said valve stem for communicating with said second and first side ports in said valve block when in a normal and operating position, respectively, spring means for normally urging said valve stem towards said normal position, and electrical circuit means including a timer for operating said valve means for preselected periods of time.

5. An autoclave comprising:

means defining a sterilization chamber having a top steam port adjacent the rear of said chamber and a bottom condensate port adjacent the front of said chamber;

boiler means;

a steam condenser having a vent to atmosphere, said steam condenser comprising a bottom portion having a generally horizontal, spiral-shaped channel extending inwardly and slightly downwardly from the outside to the center of said bottom portion, said bottom portion further including a side port for communicating with said top steam port, a separator plate over said bottom portion, and a top portion vented to atmosphere, and a generally vertical tube having its bottom opening to the center of said bottom portion and a top opening spaced above said separator plate in said top portion for venting to atmosphere and for passing water to said top portion;

and control valve means normally venting and exhausting said chamber to atmosphere through said top steam port and through said condenser and for operating to block said vent to atmosphere and to pass steam from said boiler means through said top steam port to said sterilization chamber.

References Cited UNITED STATES PATENTS 573,273 12/1896 Kellogg 2l98 916,611 3/1909 Schoettl 2l98 2,068,692 1/ 1937 Myron. 2,112,639 3/1938 Underwood 2l98 2,526,974 10/ 1950 Schipanski 2l98 3,065,509 11/1962 Vischer 2l94 XR 3,304,149 2/1967 Pile 21-103 XR FOREIGN PATENTS 235,084 8/ 1961 Australia.

302,177 12/ 1917 Germany.

661,714 4/ 1963 Canada.

MORRIS O. WOLK, Primary Examiner.

I. ZATARGA, Assistant Examiner.

US. Cl. X.R. 2l94, 104

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