US3351422A

US3351422A - Sterilizer

Info

Publication number: US3351422A
Application number: US172208A
Authority: US
Inventors: Arthur L Jones; Jr Eugene J Neal
Original assignee: Pelton and Crane Co
Current assignee: Pelton and Crane Co
Priority date: 1962-02-09
Filing date: 1962-02-09
Publication date: 1967-11-07
Anticipated expiration: 1984-11-07

Description

A. L. JONES ET AL 3,351,422

STERILIZER Filed Feb. 9, 1962 4 Sheets-Sheet 1 INVENTORS ARTHUR LJoNE-s and EUGENE J. NEALJJR.

ATTORNEYS Nov. 7, 11967 A. L. JONES ET AL STERILIZER 4 Sheets-Sheet Filed Feb. 9, 1962 New, 7, W7

STERILIZER Filed Feb. 9

4 Sheets-Sheet 5 S m E 9 m s w 8 V 35 m m K E A W. P LT 1 T 3 5 TG R U I AE 7Q n a n 1- 0 l O :L 2

BY WWW ATTO EYS A. L. JONES ET AL Nov. 7,1967

STERILIZER 4 Sheets-Sheet 4' Filed Feb. 9, 1962 ARTHUR. LJoNEs and. EuqENE J. NEAL,J2., INVENTORS ATTOR N E Y5 United States Patent Otitice 3,351,422 Patented Nov. 7, 1967 3,351,422 STERELHZER Arthur L. Jones and Eugene J. Neal, Jr., Charlotte, N.C., assignors to The Pelton & Crane Company, Charlotte, NAB a corporation of North Carolina Filed Feb. 9, N62, Ser. No. 172,208 5 Claims. (Cl. 21-94) The present invention relates generally to an apparatus for sterilizing dental and medical articles and supplies, such as instruments, glassware, dressings and the like. More particularly, the persent invention is directed to a sterilizer having a sterilizing chamber in which sterilization of such articles and supplies can be accomplished by utilizing either steam under pressure or dry heat as a sterilizing agent.

Heretofore, two different types of apparatuses have been employed for respectively sterilizing objects by steam under pressure and by sustained dry heat at high temperatures. As between these two modes of sterilizing procedure, it is generally agreed that steam under pressure is to be preferred as a sterilizing agent, because sterilization by steam under pressure can be accomplished at lower temperatures and in a shorter period of time than is required to effect sterilization by dry heat. However, in certain instances, dry heat sterilization offers advantages over steam sterilization, such as in the sterilization of metallic instruments, glassware, and other heatresistant articles which must be completely dry during the sterilization. Metallic instruments are commonly made of carbon steel which will corrode to some extent when contacted by steam. Where the carbon steel instrument is of a type used for cutting, its blade must be kept in an extremely sharp condition-a condition difficult to maintain if the instrument is sterilized by steam which has a tendency to cause the blade to be dulled because of the corrosive effect of the steam. Sterilization of glassware by steam under pressure frequently results in objectionable etching of the glassware. Thus, dry heat sterilization has been found to be more practical and desirable than sterilization by steam under pressure in instances where the articles to be sterilized are of a type likely to be adversely affected by the steam even though dry heat sterilization requires dry heat at a high temperature sustained over a comparatively long period of time. Thus, separate and distinct sterilizers respectively relying upon steam under pressure and dry heat as a sterilizing agent are common among the medical or dental equipment found in hospitals, clinics and individual offices of doctors and dentists.

A single dual-purpose sterilizing apparatus equipped for either steam sterilization or dry heat sterilization treatments of articles to be sterilized has been previously regarded as being impractical. In the latter respect, heretofore an efficient control system for synchronizing the variable factors involved in utilizing steam pressure or dry heat as a sterilizing agent in a single dual-purpose sterilizer and having the virtues of simplicity of construction, ease of operation, and rapid response has not been devised.

Moreover, the problem of obtaining rapid response toward achieving a minimum sterilizing pressure and/ or temperature in a single sterilizer regardless of Whether the sterilizing medium may be steam under pressure or sustained dry heat has not been satisfactorily resolved. Rapid response toward raising the temperature and pressure within a sterilizing chamber partially filled with Water to satisfactory levels for achieving steam sterilization can best be accomplished by applying concentrated heat capable of producing extremely high temperatures to the water within the sterilizing chamber. On the other hand, concentrated heat capable of producing extremely high temperatures is likely to overheat the sterilizing chamber and the articles therein to be sterilized to a harmful degree when the sterilizing chamber is emptied of water and steam in an instance where dry heat is to be employed as the sterilizing medium. Rapid response in achieving a minimum dry heat sterilizing temperature as quickly as possible must therefore be: conditioned upon certain limitations imposed by safety factors on the concentration and quantity of heat supplied to the sterilizing chamber to avoid harmful overheating of the sterilizing chamber and the artic1:s therein to be sterilzed.

It s also important to provide a hermetically sealed sterilizing chamber in accomplished steam sterilization for permitting a pressure build-up in the chamber upon the admission of steam thereto or the generation of steam therein. A relatively massive pressure door is therefore normally employed to hermetically seal the opening to the chamber through which articles to be sterilized are admitted into the chamebr when steam under pressure is employed as the sterilizing medium to withstand the superamospheric pressure developed in the chamber. The use of a relatively massive door for hermetically closing the sterilizing chamber, considered desirable from a safety standpoint in sterilizers employing steam under pressure as a sterilizing medium, detracts from the rapidity at which the temperature in the interior of the sterilizing chamber will rise to a degree suflicient to effect sterilization by dry heat. In this respect, the mass of the door absorbs heat from the chamber walls and the interior of the chamber to significantly slow down the rate of temperature rise within the interior of the chamber. Each of the above-mentioned factors have contributed to the general belief that separate sterilizers for steam and dry heat sterilization are necessary, if it is desired to elficiently accomplish sterilization treatments by relying upon either steam under pressure or dry heat as a sterilizing agent.

Accordingly, it is a primary object of this invention to provide an improved dual-purpose sterilizer having a chamber in which sterilization can be accomplished by utilizing either steam under pressure or dry heat as a sterilizing agent, thereby eliminating the added expense of equipping medical and dental facilities with separate sterilizer units for respectively performing sterilization procedures by steam under pressure and dry heat.

It is another object of this invention to provide an improved dual-purpose sterilizer having a sterilizing chamber for accomplishing sterilization of dental and medical articles and supplies by employing either steam under pressure or dry heat as the sterilizing agent depending upon the circumstances, wherein a plurality of heating elements are arranged in proximity to the chamber walls for heating the chamber walls with energization of the heating elements being regulated by a Selective heater control means operative to energize a single heating element of the plurality of heating elements during a steam sterilization cycle, while energizing the plurality of heating elements under a reduced power input for each heating element during a dry heat sterilization cycle as compared to the power input selectively directed into the single heating element so as to substantially eliminate any possibility of damage to the sterilizer caused by overheating of the chamber walls or other components of the sterilizer when the chamber contains no water or an insignificant amount thereof. In this way, the dual-purpose sterilizer responds rapidly in producing pressures and/ or temperatures within its sterilizing chamber at levels sulficient to effect sterilization by steam or dry heat, while maintaining a safe restriction on the concentration and quantity of heat developed by the plurality of heating elements during a dry heat sterilization cycle.

It is another object of this invention to provide an improved dual-purpose sterilizer having a chamber in which dental and medical articles and supplies may be placed for sterilization by steam under pressure or by dry heat depending upon the circumstances, wherein the opening into the chamber through which the articles and supplies to be sterilized are inserted is adapted to be closed by interchangeable closures subject to the mode of sterilization employed. In the latter connection, a relatively massive pressure door is employed as a closure to hermetically seal the chamber against pressure leakage when steam under pressure is employed as the sterilizing agent, while an auxiliary closure is provided in the form of a lightweight door of limited mass which can be quickly heated when employed as a closure for the chamber during a dry heat sterilizing cycle to speed up the response of the sterilizer in attaining a temperature within the chamber of sufficient magnitude to effect sterilization by dry heat.

Some of the objects of the invention having been stated, other objects will appear as the description proceeds when taken in connection with the accompanying drawings, in which:

FIGURE 1 is a perspective view of the improved sterilizer in accordance with the present invention, and showing a closure in the form of a relatively massive pressure door hermetically sealing the opening into the sterilizing chamber for performing a sterilizing treatment with steam under pressure as the sterilizing agent;

FIGURE 2 is a perspective view similar to FIGURE 1, but showing an auxiliary closure in the form of a lightweight lid or door of limited mass covering the opening into the sterilizing chamber with the hermetic door closure of FIGURE 1 being disposed in an open position for performing a sterilizing treatment with dry heat as the sterilizing agent;

FIGURE 3 is an enlarged perspective view of the auxiliary lightweight lid or door shown in FIGURE 2, looking at the inwardly disposed side thereof hidden from view in FIGURE 2;

FIGURE 4 is an enlarged plan view of the sterilizer as shown in FIGURE 1 with the top wall of the outer housing or cabinet being removed for purposes of clarity;

FIGURE 5 is an enlarged elevational view of the sterilizer as shown in FIGURE 1, looking at the right side thereof and with the hermetic door closure and the right side wall of the outer housing or cabinet being removed for purposes of clarity;

FIGURE 6 is an enlarged vertical sectional view taken along the line 6-6 in FIGURE 1;

FIGURE 7 is a schematic wiring diagram illustrating the selective heater control means for the electrical circuits energizing the heating elements employed in the sterilizer; and

FIGURE 8 is a schematic view illustrating the piping system interconnecting various components of the sterilizer for transmitting fluid to and from the sterilizing chamber.

Referring more specifically to the drawings, the sterilizer has an outer casing or housing forming a cabinet 10 in which a sterilizing chamber 11 is received. The bottom of the cabinet 10 is provided with four supporting feet 18 which are preferably made adjustable as to their length by suitable means (not shown) for raising and lowering the sterilizer cabinet 10 as may be required to tilt the sterilizing chamber 11 as desired or to accommodate the cabinet 10 in a particular location. Provision may also be made for adjusting the front pair of feet 18 longitudinally along the bottom of the cabinet 10 by means (not shown) to accommodate the cabinet 10 in locations of varying depth. The chamber 11 is generally cylindrical and includes an integral rear end closure, access to the chamber 11 being afforded through its open front end. The chamber 1 11 is mounted within the cabinet 10 so that its open front end coincides with a circular opening provided in the front wall of the cabinet 10 to which the open front end of the chamber 11 is connected. An annular liner 12 (FIGURE 6) is suitably secured to the open front end of the chamber 11, as by welding, the annular liner 12 being frictionally received within the opening provided in the front wall of the cabinet 10. A door 13 of generally circular configuration conforming to the shape of the opening through the front wall of the cabinet 10 and the open front end of the chamber 11 is mounted on the front wall of the cabinet 10 by means of an integral bar 20 hingedly connected to the cabinet 10 for pivotal movement of the door 13 between positions opening and closing the chamber 11. It will be understood that the door 13 is a relatively massive pressure door of a type regarded as a suitable closure for a sterilizing chamber in which sterilization by steam under pressure will be employed. The door 13 is provided with a resilient pressure-responsive annular sealing gasket 14 made of suitable heat-resistant material, such as silicone rubber. The gasket 14 is adapted to sealingly engage the liner 12 when the door 13 is in closed position, thereby cooperating with the door 13 to provide a hermetic pressure-tight closure for the open front end of the chamber 11. When steam sterilization is in progress within the chamber 11, the door 13 is latched in closing relation to the front end of the chamber 11 for hermetically sealing the chamber 11 by means of a bolt 15 slidably mounted within the bar 20 of the door 13 and receivable by a keeper 16 mounted on the front wall of the cabinet 10 (FIGURES 1 and 2). The bolt 15 is manipulated between positions latching and unlatching the door 13 by a handle 17 afiixed thereto, the handle 17 being readily grasped for sliding the bolt 15 into and out of reception with the keeper 16. In this respect, it will be observed that the bar 20 is suitably slotted for slidable movement of the bolt 15 and its attached handle 17, there being a depending slotted section for reception of the handle 17 when the free end of the bolt 15 has been moved within the keeper 16. It will be understood that the handle 17 when disposed in vertical alinement with the depending slotted section in the bar 20 may be drawn downwardly in an arcuate movement rotating the bolt 15, wherein the handle 17 will be retained Within the depending slotted section against inadvertent movement sliding the bolt 15 out of the keeper 16 to unlatch the door 13.

The door 13 defines a hermetic closure for the open front end of the chamber 11 and is complemented by a non-hermetic auxiliary closure in the form of a lightweight lid or auxiliary door 21 which is utilized to close the chamber 11 when dry heat sterilization is in progress Within the chamber 11 rather than steam sterilization. The auxiliary door 21 is of limited mass as compared to the relatively massive pressure door 13 and can be quickly heated to speed up the response of the sterilizer in attaining a temperature within the chamber 11 of sufficient magnitude to effect sterilization by dry heat. As shown best in FIGURE 3, the auxiliary door 21 comprises inner and outer

circular discs

22, 23 respectively, the inner disc 22 having a diameter substantially greater than the outer disc 23. The outer disc 23 is secured to the inner disc 22 in superimposed spaced relationship over the central portion thereof by suitable fastener means, such as

studs

24, 24 extending therebetween. The diameter of the inner disc 22 is slightly greater in size than the opening through the front cabinet wall and the open front end of the chamber 11 to provide a marginal portion on the auxiliary door 21 overlying the portion of the front cabinet wall defining the boundary of the circular opening therethrough. The auxiliary door 21 is releasably mounted in a position closing the open front end of the chamber 11 with the larger inner disc 22 thereof covering the open front end of the chamber 11 and loosely held in place by means of a plurality of holding brackets 25 secured to the inwardly disposed surface of the inner disc 22. Each of the holding brackets 25 includes a lip extending transversely from the inner surface of the inner disc 22 and adapted to be loosely received within the annular liner 12 forming the mouth of the opening in the front end of the chamber 11.

It will be observed that one of the holding brackets 25 also has an integral retainer tab member 26 connected to the lip thereof and extending in spaced generally parallel relation to the inner surface of the inner disc 22. In closing the open front end of the chamber 11, the auxiliary door 21 is initially arranged with respect to the chamber opening so as to admit the portion of its inner disc 22 carrying the holding bracket 25 provided with the tab member 26 within the chamber 11. The tab member 26 is disposed behind the annular liner 12 and together with the lips on the other holding brackets 25 which are adapted to loosely bear against the inner periphery of the annular liner 12 retains the auxiliary door 21 in a position closing the chamber 11. A thermometer 27 for measuring the temperature attained in the chamber 11 during a dry heat sterilization cycle is carried by the inner disc 22 of the auxiliary door 21, the opposite ends of the thermometer 27 protruding outwardly and inwardly of the auxiliary door 21, respectively. The exposed portion of the thermometer 27 extending outwardly of the auxiliary door 21 permits visual observation of the dry heat temperature within the chamber 11. The bulb end of the thermometer 27 which protrudes within the chamber 11 is preferably shielded from damage by a perforated guard or cage 28. The cage 28 is afiixed to the inner surface of the inner disc 22 and encircles the inwardly protruding portion of the thermometer 27 in spaced relationship therewith to permit free flow of air about the thermometer 27 for obtaining reliable measurements of temperature within the chamber 11. In instances where the case 28 may be responsible for absorbing some of the heat from the interior of the chamber 11 and allowing heat dissipation through the inner disc 22 to cause a temperature reduction in the space between the thermometer 27 and the cage 28, it has been found practical to employ a calibrated thermometer with an offset graduated scale compensating for the heat loss caused by the protective cage 28 for the thermometer 27. Thus, the temperature reading registered on such a calibrated thermometer will coincide with the actual temperature within the chamber 11 even though the heated air in direct contact with the bulb of the thermometer 27 is at a lower temperature than the actual temperature within the chamber 11 because of the heat loss caused by the cage 28. For convenience in mounting and removing the auxiliary door 21, a handle 29 (FIGURE 2) is provided on the outer disc 23 of the auxiliary door 21. Heat is transmitted to the inner disc 22 of the auxiliary door 21 from the rising heat of the chamber walls and the rising heat within the chamber 11 in attaining a high temperature within the chamber 11 during dry heat sterilization. However, the outer disc 23 and the handle 29 afiixed thereto will remain relatively cool because of the spaced relationship between the inner and

outer discs

22, 23 of the auxiliary door 21 which effectively thermally isolates the outer disc 23 and the handle 29 from the inner disc 22. This thermal isolation of the outer disc 23 and the handle 29 allows the auxiliary door 21 to be immediately removed from the front cabinet wall to open the chamber 11 following a dry heat sterilization cycle without danger of personal injury from burns due to the high temperature employed in this mode of sterilization. The chamber 11 is thereby permitted to cool more readily by exposing its interior to ambient temperature conditions in the vicinity of the sterilizer soon after the dry heat sterilization cycle has been completed.

Means are provided to heat the chamber walls for raising the temperature therewithin in processing the sterilization of articles disposed Within the chamber 11 by steam under pressure or by dry heat. In this c0nnection, the heating means comprises a plurality of electric heating elements 30 (FIGURES 6 and 7). The heating elements 30 are disposed beneath the bottom portion of the cylindrical chamber 11 in clamped engagement therewith, as will be herein-after described. Referring to FIG- URE 7, it will be observed that each of the heating elements 30 comprises an elongated curved plate having electrical resistance wiring embedded therein and conforming to the cylindrical shape of the chamber walls, there being a centrally disposed heating element 30 and a pair of side heating elements 30, 3t] flanking the centrally disposed heating element 30. As will be described hereinafter, the plurality of heating elements 30 are thermostatically controlled and in addition are adapted to be energized by manually-controlled electric heating circuits so as to provide for selective energization of the centrally disposed heating element 30 at an increased power input while the

side heating elements

30, 30 remain inactive during a steam sterilization cycle and to provide for simultaneous energization of the plurality of heating elements 30 at a reduced power input during certain time intervals preceding and following the steam sterilization cycle and during a dry heat sterilization cycle. Thus, it is contemplated that the

side heating elements

30, 30 will operate only under a reduced power input, while the cetnrally disposed heating element 30 will be selectively energized under high and reduced power inputs. Heating element-s of the electrical resistance wire type may develop one or more hot spots along the length of the wire. Since the central heating element 30 is intended to be selectively energized under a high power input during the steam sterilization cycle, any such hot spots developed in the electrical resistance wiring thereof may be capable of creating suflicient-ly large heat differentials along certain areas of the chamber walls when the central heating element 39 is energized under a high power input to cause buckling of the chamber walls. This problem of buckling is accentuated in instances where the chamber 11 is in a tilted position during a steam sterilization cycle so as to cause any water therein to collect at one end or the other, and a hot spot on the central heating element 30 happens to occur in proximity to a portion of the bottom chamber wall above the water level in the chamber 11. For this reason, a heat equalizer plate 30a is preferably sandwiched between the cent-rally disposed heating element 3t} and the bottom wall of the chamber 11 to evenly distribute heat emanating from the central heating element 30 along the bottom wall of the chamber 11. The heat equalizer plate 30a is appropriately curved to correspond to the curvature of the central heating element 30 and the cylindrical shape of the bottom wall of the chamber 11 and is made of a material possessing excellent heat conductivity, such as aluminum, to enable it to disperse the effect of any hot spots on the central heating element 30 throughout its surface area adjoining the bottom wall of the chamber 11, thereby avoiding the troublesome consequences associated with such hot spots.

The plurality of heating elements 3 0 are releasably clamped against the chamber walls (with the heat equalizer plate 30a interposed between the central heating element 30 and the bottom portion of the chamber walls) by a clamping plate 301; (FIGURE 6) overlying the heating elements 30 and a plurality of suitably adjustable straps 31 (FIGURE 4) encircling the chamber 11 and the clamping plate 3% to firmly hold the heating elements 30 in place about the lower opposite side portions and bottom portion of the chamber walls for transmitting heat thereto.

A water supply for the chamber 11 from which steam is to be generated in eifecting the sterilization of objects placed in the chamber 11 by steam under pressure is obtained from a reservoir tank 32 (FIGURES 4, 5 and 8). The reservoir tank 32 is mounted Within the cabinet 16 to one side of the chamber ill, the reservoir tank 32 being cylindrical and extending vertically upward from the bottom wall of the cabinet 10. Within the reservoir tank 32, there is a coiled condenser tube 331 for condensing steam discharged from the chamber 11 at the conclusion of a steam sterilization cycle to replenish the water supply in the reservoir tank 32. A drain plug 34 is provided in the bottom wall of the reservoir tank 32 and is accessible from the bottom wall of the cabinet 10 (FIGURE to drain water from the reservoir tank 32 when it is desired to clean the interior of the reservoir tank 32 and the condenser tube 33 contained therein. It will be noted that the top wall of the cabinet includes a circular aperture in vertical alinement with the reservoir tank 32 to permit filling of the reservoir tank 32 to a graduated fill line 35 (FIGURE 5) for replenishing water in the tank 32 lost by evaporation. The reservoir tank 32 is provided with a ventilated cover 36 (FIGURES 1 and 2) loosely received within the aperture formed in the top wall of the cabinet 10 and mounted atop the reservoir tank 32.

It will be observed that a tray 37 is mounted within the chamber 11 so as to extend lengthwise in spaced relation above the bottom thereof. In this respect, the tray 37 is fastened to an upright support member 38 projecting from the bottom wall of the chamber 11 adjacent the mouth thereof defined by the annular liner 12 by suitable means, such as screw 39, and is further supported above the bottom wall of the chamber 11 by a transverse band 3% extending between the side walls of the chamber 11 and beneath the rear portion of the tray 37 (FIGURE 6). The tray 37 has an indicator bracket 40 afiixed therebeneath. The indicator bracket 40 is disposed at the forward end of the tray 37 and is provided with a fill plate 41 integral therewiththe fill plate 41 being horizontally arranged in spaced relation between the tray 37 and the bottom of the chamber 11. As shown in FIGURE 8, the tray 37 has a plurality of perforations therein to allow steam generated from Water in the chamber 11 below the tray 37 to pass upwardly through the perforations in the tray 37, and the forward end of the tray 37 is recessed to expose the fill plate 41 which is visible through the open front end of the chamber 11.

Referring now to the piping system in the sterilizer for admitting water into the sterilizing chamber 11 and thereafter discharging steam from the chamber 11 following the conclusion of a steam sterilization cycle as schematically illustrated in FIGURE 8, the passage of fluid to and from the chamber 11 is manually regulated by a rotatable control knob 42 which also simultaneously regulates the energization of the heating elements 30 as will be subsequently described. The control knob 42 is mounted on a control panel 43 forming a part of the front wall of cabinet 10, the control knob 42 being the lower knob in a vertical row of three knobs disposed on the control panel 43, as shown in FIGURE 1. The control knob 42 has a spindle 44 extending through the control panel 43, and the spindle 44 carries a pair of spaced apart cam members 45, 46 which are adapted to actuate a valve control mechanism 47 regulating fluid flow in the piping system, while also actuating a pair of switches in regulating energization of the heating elements 30. In this respect, it will be observed that each of the cam members 45, 46 has a blunt protrusion for depressing respective flexible follower members 50, 51 associated therewith. The valve control mechanism 47 comprises plunger-operated valve members A and B mounted within a valve housing 52, each of the valve members A, B being selectively actuated by means of the cam members 45, 46 and the flexible follower members 50, 51the cam member and follower member 50 being effective to depress a plunger moving valve member A to an open position and the cam member 46 and follower member 51 similarly depressing a plunger to move valve member B to an open position when the control knob 42 is disposed in selected position. Ports 53, 54, and are provided in the valve housing 52-port 53 communicating with the valve chamber corresponding to valve member B at a point above valve member B, port 54 communicating with the valve chambers corresponding to both valve members A, B at points below the valve members A, B, and port 55 communicating with the valve chamber corresponding to valve member A at a point above valve member A.

When the control knob 42 is in the off position illustrated in FIGURE 8, both valve members A, B will be in closed positions to block communication between the chamber 11 and the reservoir tank 32. Upon rotating the control knob 42 in a counter-clockwise direction to the fill position, the cam member 46 will be arranged so as to depress the follower member 51 associated therewith for moving the valve member B to an open position which connects ports 53 and 54 through the unblocking of the valve chamber containing valve member B. Water is thereby allowed to flow from the reservoir tank 32 through a delivery tube 56 extending from the reservoir tank 32 near the bottom thereof, into port 53, past the open valve member B into port 54, and a conduit 57 which leads to the bottom of chamber 11 adjacent the front end thereof at a point disposed beneath the fill plate 41. Water from the reservoir tank 32 is admitted to the chamber 11 through the conduit 57 until the fill plate 41 is covered by the water.

When the water within the chamber 11 has reached a level covering the fill plate 41, the control knob 41 is then turned to sterilize position which causes valve 1 member B to return to closed position by movement of the cam member 46 so as to discontinue its depressing action on the follower member 51. Valve member A is also in closed position at the sterilize position of the control knob 42 which isolates the chamber 11 from the reservoir tank 32 during a steam sterilization cycle and stops the flow of water into the chamber 11. Upon rotating the control knob 42 to the vent position, the cam member 45 will be arranged so as to depress the follower member 50 for moving the valve member A to an open position, while valve member B remains in a closed position. The movement of valve member A to an open position connects

ports

54 and 55 through the unblocking of the valve chamber containing valve member A. Steam and water within the chamber 11 are thereby allowed to be discharged from the chamber 11 through the conduit 57, into port 54, past the opened valve member A into port 55, and to a discharge tube 6%) which leads back into the reservoir tank 32 through the condenser tube 33, the upper end of the condenser tube 33 being connected to the discharge tube 60. A suitable thermostatic air valve 61 is associated with the discharge tube 60 adjacent the connection between the discharge tube 60 and the condenser tube 33. The thermostatic air valve 61 is intended to release air having a relatively low temperature from the chamber 11 into the condenser tube 33 by allowing the low-temperature air from the chamber 11 to be passed into the portion of the discharge tube 60 linking the thermostatic air valve 61 with the condenser tube 33 in a manner to be presently described. A safety relief valve 62 is associated with the thermostatic air valve 61 by a connecting conduit 63 so as to protect the chamber 11 against an excessive pressure build-up therein, the pressure relief valve 62 being of a type which may be adjustably set to open when a predetermined excessive pressure exists in the chamber 11 for exhausting the excessive pressure into the reservoir tank 32 through an exhaust tube 64 providing communication between the safety relief valve 62 and the upper portion of the reservoir tank 32. The chamber 11 communicates with the thermostatic air valve 61 and the safety relief valve 62 through an air tap line 65 which is connected at one end to the rear wall of the chamber 11 at a point beneath the tray 37 (FIGURE 6) and at its other end to the connecting conduit 63 extending between the thermostatic air valve 61 and the safety valve 62. It will be understood that the thermostatic air valve 61 may be adjusted so as to automatically close whenever a predetermined temperature is attained in the chamber 11 during a steam sterilization cycle. Until the predetermined temperature is attained in the chamber S 11, the thermostatic air valve 61 remains open to allow relatively low-temperature air to be forced out of the chamber 11 as steam is being generated therein through the air tap line 65, the portion of the connecting cnduit 63 linking the air tap line 65 to the thermostatic air valve 61, through the open thermostatic air valve 61 and into the condenser tube 33 via the portion of the discharge tube 60 linking the thermostatic air valve 61 to the condenser tube 33. In this way, the predetermined steam sterilizing pressure will not begin to build up in the chamber 11 to an appreciable extent until the chamber 11 is filled with relatively high temperature steam which assures that proper steam sterilizing temperatures will be quickly obtained in the chamber 11. In practice, the thermostatic air valve 61 will open and close intermittently throughout the duration of a steam sterilization cycle even after the predetermined temperature at which the thermostatic air valve 61 has been set to close has been attained in the chamber 11 because of the heat loss eventually sustained by the mixture of air and steam temporarily trapped in the air tap line 65 and the portion of the connecting conduit 63 linking the air tap line 65 to the thermostatic air valve 61 when the thermostatic air valve 61 is closed. The cooling of this trapped air-steam mixture below the predetermined temperature causes the thermostatic air valve 61 to open, but soon after the thermostatic air valve 61 has opened to bleed off the cooled air-steam mixture, it closes upon being subjected to a fresh air-steam mixture issuing from the chamber 11 which is at or above the predetermined temperature required to close the thermostatic air valve 61. Any excessive pressure build-up in the chamber 11 over the predetermined superatmospheric pressure desired will be exhausted from the chamber 11 through the air tap line 65 and the conduit 63 into the reservoir tank 32 by the opening of the safety relief valve 62 in the manner previously described.

A thermometer 66 is installed in the air tap line 65 for measuring the steam temperature within the chamber 11, the thermometer 66 being connected to a temperature gauge 67 for visibly registering the steam temperature within the chamber. The steam pressure within the chamber 11 is visibly indicated on a pressure gauge 70, the steam pressure within the chamber 11 being communicated to the pressure gauge 76 by means of the air tap line 65 and a branch pressure line '71 connected to the pressure gauge 70 and the air tap line 65. The temperature gauge 67 and the pressure gauge 76 are mounted in the front wall of the cabinet so as to be readily observed, as shown in FIGURES 1 and 2.

Referring now to FIGURE 7, which schematically illustrates the electric heating circuits and the control means for selectively directing electric current to the plurality of heating elements 30, it will be observed that the control knob 42 and the cam members 45, 46 instrumental in regulating the flow of fluid between the reservoir tank 32 and the chamber 11 also simultaneously effect the selective energization and the de-energization of the heating elements 30. It will become ap parent as the description proceeds that each of the plurality of heating elements 30 is energized under a low power input when the knob 42 is located in the full and vent positions, while the centrally disposed heating element 30 is selectively energized under an increased power input with the

side heating elements

36, 30 being inactive when the control knob 42 is located in the sterilize position. A pair of

flexible follower elements

72, 73, separate and distinct from the flexible follower members 50, 51 previously discussed in connection with the regulation of the passage of fluid in the piping system of the sterilizer, are respectively associated with the cam members 45, 46 for effecting the operation of

switches

74 and 75. Switch 74 is a primary heating circuit switch comprising a pivotal arm movable between a circuitbreaking position in which the delivery of electric current to the three heating elements 30 is cut off and a position in engagement with a fixed contact 76 in which the delivery of electric current to all three of the heating elements 36 or to only the centrally disposed heating element 30 is assured, subject to the operation of a modulation thermostat as will be later described. Switch 75 is a selective secondary heating circuit switch determining whether all three of the heating elements 30 or only the centrally disposed heating element 30 will be energized when the primary heating circuit switch 74 is closed to engage the fixed contact 76. The selective secondary heating circuit switch 75 comprises a pivotal arm movable between a position in engagement with a fixed contact 77 in which electric current will be directed to all three of the heating elements 30 and a position in engagement with a fixed contact 78 in which electric current will be selectively directed to the centrally disposed heating element 30. It will be understood that the blunt protrusions on the cam members 45 and 46 depress the

fiexible follower elements

72 and 73 in a predetermined sequence depending upon the position of the control knob 42 for operating the

switches

74 and 75. As illustrated diagrammatically in FIGURE 7, each of the pivotal arms of the

switches

74, 75 is provided with a button intermediate its ends against which the

follower elements

72, 73 correspondingly bear, the switch arms pivoting in response to appropriate movement of the cam members 45, 46 either disposing the blunt protrusions thereon in contact or out of contact with the

follower elements

72, 73. Suitable means, such as springs (not shown) bias the pivotal arm of switch 74 into engagement with the fixed contact 76 and the pivotal arm of switch 75 into engagement with the fixed contact 77 on occasions when the blunt protrusions of the cam members 45, 46 are out of contact with the follower elements 72, '73.

Current to the heating elements 30 is also controlled by means of a modulating thermostat 86 which is ar ranged in series with the primary heating circuit switch 74. The thermostat 80 comprises an elongated temperature-sensing bulb 81 disposed within the chamber 11 beneath the tray 37 and the level of the fill plate 41 depending therefrom so as to be normally immersed in Water received in the chamber 11 (FIGURE 6). The temperature-sensing bulb 81 is connected to a rotatable control knob 82 mounted on the control panel 43 of the cabinet 10 above the control knob 42. The control knob 82 may be rotated to adjust the thermostat 86 for cutting off and turning on the electric current to the heating ele ments 36 when the temperature within the chamber 11 cycles above and below a desired level. In the latter connection, when the temperature within the chamber 11 is at or below the level determined by a particular setting of the control knob 82, electric current is allowed to pass bet-ween spaced

terminals

83 and 84 of the thermostat 80 completing a primary heating circuit including the closed switch '74. Should a temperature build-up above the predetermined level occur in the chamber 11, no electric current will pass between the

thermostat terminals

83, 84 while this excessive temperature condition is present, thereby breaking the primary heating circuit and interrupting the delivery of electric current to the heating elements 30. The control knob 82 may be rotated in either a clockwise or counterclockwise direction for adjusting the thermostat 80 to operate during a dry heat sterilization cycle or a steam sterilization cycle, respectivelythere being suitable indicia on the control panel 43 behind the control knob 82 divided into dry heat sterilization and steam sterilization sectors for identifyinig where an indicator mark on the control knob 82 should be located to correspond with the mode of sterilization employed.

Upon supplying power to the sterilizer by connecting a suitably grounded electrical plug 96 into a convenient power outlet electric current will be deliverd to all three heaters 30 when the control knob 42 is rotated from the off to the fill position. The fill position of control knob 42 arranges the cam member 45 so as to allow the arm of switch 74 to engage the contact 76, while the arm of switch 75 remains in engagement with the contact 77, thereby completing an electrical circuit passing through each of the three heating elements 39. As shown in FIG- URE 7, this electrical circuit includes the delivery of electric current from one plug terminal through a quick connector junction W, across the pivotal switch arm '74 which is in engagement with the contact 76 in the fill position, across the thermostat terminals 83, 84-, across the pivotal switch arm 75 which is in engagement with the contact 77 in the fill position, through a quick connector junction X, and then proceeding through the three heating elements 30 which are serially connected so as to direct current flow through one of the side heating elements, the other side heating element and finally through the centrally disposed heating element, from where the current is directed through a quick connector junction Y and is returned to the other plug terminal.

The same electrical circuit just described which provides for the energization of all three heating elements 30 will also be completed when the control knob 42 is disposed in the vent position, since the pivotal arm of switch 74 will be in engagement with the contact 76 and the pivotal arm of switch 75 will be in engagement with the contact 77. In the sterilize position of the control knob 42, while the pivotal arm of the primary heating circuit switch 74 engages the contact 76, it will be observed that the blunt protrusion on the cam member 46 will be disposed so as to depress the follower element 73 for moving the pivotal arm of the secondary heating circuit switch 75 away from the contact 77 and into engagement with the contact 78. Thus, when a steam sterilization cycle is in progress within the chamber 11, the central heating element 39 is selectively energized under an increased power input by engagement between the switch arm 75 and the contact 78, while the side heating elements 30 are inactivated. In this respect, the electric circuit which is formed in the sterilize position of the control knob 42 is the same as that previously described which is formed in the fill and vent positions of the control knob 42 except for the portion controlled by the location of the switch arm 75. At sterilize position, the electrical circuit extends across the pivotal switch arm 75 in engagement with the contact 78, through a quick connector junction Z, and then proceeds through the centrally disposed heating element 30 only, the quick connector junction Y, and returns to the other plug terminal.

A safety cut-off thermostat 91 is interposed in the wiring connecting the quick connector junction Z to one terminal of the centrally disposed heating element 30. The safety cut-off thermostat 91 may be adjustably set to cut olf the electric current and break the electrical circuit selectively energizing the centrally disposed heating element 30 should the temperature of the central heating element 39 increase to a predetermined excessive degree when the control knob 42 is located in the sterilize position during a steam sterilization cycle. While the safety cut-off thermostat 91 may be made directly responsive to the temperature of the central heating element 30, it is preferred to make the safety cut-off thermostat 91 directly responsive to the temperature of the heat equalizer plate 300:, in which case the safety cut-off thermostat 91 will be indirectly responsive to the temperature of the central heating element 30. To this end, the heat equalizer plate 39a is provided with an integral depending flange 94 (FIGURE 7) extending below the central heating element 30, and the safety cut-off thermostat 91 includes a thermally-sensitive circuit-breaking arm 95 in association with a pair of switch arms 96, 97 having normally engaging electrical contacts. The switch arms 96, 97 are respectively connected in the wiring leading from the quick connector junction Z to one terminal of the central heating element 30 so as to cut off the electric current selectively energizing the central heating element 30 should their electrical contacts become disengaged. The safety cut-off thermostat 91 is mounted on the depending flange 94 of the heat equalizer plate 30a by suitable means, such as an insulated threaded bolt 98 extending through the switch arms 96, 97 and the circuit-breaking arm 95 of the safety cut-otf thermostat 91 and through the depending flange 94, with the thermally-sensitive circuit-breaking arm 95 being adjacent the depending flange 94. It will be observed that the switch arm 97 is shorter in length as compared to the switch arm 96 and the circuit-breaking arm 95 and is located therebetween, while the circuit-breaking arm 95 carries a non-conductive prong 99 which abuts the switch arm 96 and is disposed beyond the shorter switch arm 97. Thus, when the central heating element 30 acquires a predetermined excessive degree of temperature, this excessive temperature will be transmitted to the heat equalizer plate 390 and its depending flange 94 from where it will be communicated to the thermally-sensitive circuit-breaking arm 95. The circuitbreaking arm 95 is thereby caused to flex toward the switch arm 96 because of its thermal sensitivity, which results in the prong 99 forcing the switch arm 96 to flex rearwardly to disengage its contact from the contact on the switch arm 97. Accordingly, the electrical circuit selectively energizing the central heating element 30 is broken by the disengagement of the electrical contacts on the switch arms 96, 97 in the manner described. Excessive heating of the central heating element 30 actuating the safety cut-off thermostat 91 may occur due to the failure of the modulating thermostat or because the temperature-sensing bulb 81 is unable to sense a rapid temperature build-up in the central heating element 30 fast enough. The latter occurrence is mitigated to a considerable extent by the presence of the heat equalizer plate 30a. Insufficient water in the chamber 11 or excessive pressure in the chamber 11 during a steam sterilization cycle are factors which can contribute to the acquiring of an excessive temperature by the central heating element 30. By breaking the electrical circuit selectively energizing the central heating element 30 when this excessive temperature condition occurs, the safety cut-off thermostat 91 prevents damage to the sterilizer and to dental and medical articles and supplies undergoing steam sterilization in the chamber 11.

Indicator lights 92 and 93 are located on the control panel 43 adjacent the upper margin thereof and are adapted to be illuminated for signalling that electric power is being supplied to the sterilizer and that the electrical heating means is energized, respectively. The power indicator light 92, which may be red, is connected in parallel with the modulating thermostat 80 in an electric power indicator circuit unaffected by the modulation of the thermostat 80 and glows when the control knob 42 is located in fill, sterilize, or vent positions so that the pivotal arm of switch 74 engages the contact 76. The electric power indicator circuit for illuminating the power indicator light 92 extends from one terminal of the plug 90, through the junction W, across the switch arm 74 in engagement with the contact 76, through the terminal 83 of the modulating thermostat 80, through the power indicator light 92, and then proceeds through the junction Y to return to the other terminal of the plug 90. The heat-on indicator light 93, which may be amber, is connected in series with the modulating thermostat 80 and will therefore glow intermittently when the control knob 42 is located in fill, sterilize, or vent positions, the illumination of the heat-on indicator light 93 depending upon the flow of electric current across the

terminals

83, 84 of the thermostat 80 to indicate that the electrical heating means is being energized. The electric heat-on indicator circuit for illuminating the heat-on indicator light 93 is therefore similar to the electric power indicator circuit previously described, except that the electric heat- 13 on indicator circuit extends across the

terminals

83, 84 of 316 thermostat $11 and through the heat-on indicator light As it is necessary to operate the sterilizer during a steam sterilization cycle and a dry heat sterilization cycle for a predetermined period of time in order to effect sterilization of the articles within the chamber 11, a bell timer 160 (FlGURE is located on the inner surface of the front cabinet wall behind the control panel 43, and an adjustable timer control knob 101 is associated therewith for setting the required time to effect sterilization either by utilizing steam or dry heat as the sterilizing agent. The timer control knob 101 is arranged as the uppermost knob on the control panel 43, the bell 1110 sounding when the preset time on the timer control knob 1111 has elapsed to signal the completion of a steam sterilization cycle or a dry heat sterilization cycle.

It will be observed in FIGURE 4 that a partition wall 1112 extends lengthwise within the cabinet 11 between the chamber 11 and the reservoir tank 32, the partition wall 102 segregating the chamber 11 from various components of the piping system and the electrical system for the sterilizer which are grouped on the same side of the partition wall 162 as the reservoir tank 32. The partition wall 102 is suitably apertured to permit the air tap line 65 and the conduit 57 to pass therethrough and may be utilized as a supporting base in which the quick connector junctions W, X, Y, Z of the electrical system may be mounted to extend therethrough and to which other components of the piping system and the electrical system may be attached. Preferably, suitable insulation material, such as fiber glass, rock wool, or the like (not shown) is packed around the chamber 11 within the cabinet to prevent excessive heat loss from the chamber 11.

In operating the improved dual-purpose sterilizer embodying the present invention as a steam sterilizing apparatus, the hermetic closure door 13 is opened and the control knob 42 is turned to the fill position. The fill position of the control knob 42 allows water to enter the chamber 11 from the reservoir tank 32 while causing the three heating elements 30 to be energized. When water within the chamber 11 reaches a level covering the fill plates 41, the control knob 42 is turned to sterilize position. In sterilize position, both valve members A and B are in a closed position and the flow of water from the reservoir tank 32 into the chamber 11 is stopped, while the central heating element 30 is selectively energized under an increased power input and the side heating elements 30 are rendered inactive. At this Point, the chamber 11 is loaded with the articles to be sterilized by steam under pressure, and the closure door 13 is pivoted into a position closing the front end of the chamber 11 with the slidable bolt 15 thereon being moved into reception within the keeper 16, as illustrated in FIGURE 1, to hermetically seal the chamber 11. The middle knob 82 on the control panel 43 controlling the modulating thermostat St) is then turned to a selected steam pressure and temperautre valuation. In adjusting the control knob 82 for the modulating thermostat 80, the control knob 82 is preferably turned through the indicated range of the steam sterilization sector for steam sterilization. The operator then observes the pressure gauge 70 until the desired pressure has been obtained within the chamber 11, whereupon the control knob 82 is rotated in an opposite direction away from the extreme limit of the steam sterilization sector until the heat-on light 93 goes out, thereby setting the modulating thermostat 80 to maintain the desired pressure within the chamber 11. Once this setting of the control knob 82 has been obtained, it is not necessary to adjust the control knob 82 for subsequent steam sterilization cycles unless it is desired to steam sterilize at a difierent pressure. The upper timer control knob 101 is then set to the desired time for the steam sterilization cycle.

When the period of time selected on the timer control knob 101 has expired, the bell 100 will ring to signal that the steam sterilization cycle has been completed. The control knob 42 is then turned from the sterilize position to the vent position, wherein valve member A is moved to an open position while valve member B remains in a closed position, to permit steam and water within the chamber 11 to be discharged through the condenser tube 33 into the reservoir tank 32. The steam discharged from the chamber 11 is converted to water as it passes through the condenser tube 33 which is substantially immersed in relatively cold water contained in the reservoir tank 32. Following the discharge of steam and water from the chamber 11 when the control knob 42 has been moved to vent position, the pressure gauge 70 will drop to register zero pressure and the hermetic closure door 13 is opened to remove the sterilized articles from the chamber 11. If it is desired to dry the sterilized articles before their removal from the chamber 11, the hermetic closure door 13 is opened slightly, and the control knob 42 is left in vent position. As previously de scribed, the plurality of heating elements 311 are energized under a reduced power input when the control knob 42 is in vent position and supply heat for drying moisture from the steam sterilized articles in the chamber 11. This drying cycle following the steam sterilization cycle should not be confused with a dry heat sterilization cycle which must be carried on at a selected high temperature for an extended period of time in order for sterilization to take place.

In utilizing the improved sterilizer for sterilizing ob jects, such as instruments made of heat-resistant material and glassware, by dry heat sterilization, after the objects to be sterilized are loaded into the chamber 11, the auxiliary non-hermetic closure door 21 is inserted within the opening through the front cabinet wall to loosely close the chamber 11, as illustrated in FIGURE 2. The control knob 42 is turned from off position directly to vent position to avoid the filP position. The middle control knob 82 for regulating the modulating thermostat is then adjusted to a selected position within the dry heat sterilization sector. The extreme limit at which the control knob 82 may be set in the dry heat sterilization sector may produce a temperature of 350 Fahrenheit, for example. When the thermometer 27 protruding from the auxiliary non-hermetic closure door 21 registers a temperature within the chamber 11 sufiicient to efiect dry heat sterilization, such as 320 Fahrenheit for example, the timer control knob 101 is then set for the required time period to sterilize the objects within the chamber 11 by dry heat. At the conclusion of the dry heat sterilization cycle, the timer bell will ring, and the auxilary door 21 can be immediately removed for unloading the sterilized objects from the chamber 11.

Electric power for the sterilizer may be supplied from a standard electrical wall socket with the heating elements 30 being energized simultaneously under a total input of 400 watts, or approximately 133 watts for each of the three heating elements, and the centrally disposed heating element being selectively energized under a 1250 watt input.

Thus, it will be seen that we have disclosed an improved dual-purpose sterilizer which may be employed in processing articles to be sterilized by either steam sterilization or dry heat sterilization, depending upon the nature of the articles to be sterilized and other circumstances which may be involved. The operation of our improved sterilizer through the various cycles involved in a sterilization process requires only simple manipulation of the three

control knobs

42, 82, and 101 on the control panel 13 of the cabinet 10 and observation of the temperature and

pressure gauges

67, 70 and power and heat-on

lights

92, 93 to effect sterilization by employing either steam under pressure or sustained dry heat as a sterilization agent.

In the drawings and specification there has been set 15 forth a preferred embodiment of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being defined in the claims.

We claim:

1. A dual purpose sterilizer for dental and medical articles and supplies or the like and adapted for selectively sterilizing by steam under pressure or by sustained dry heat at high temperatures; said sterilizer comprising:

(a) enclosed sterilizing chamber means including means for permitting access thereto for receiving articles and supplies to be sterilized and adapted to contain water when sterilizing by steam and pressure is selected;

(b) electric heating means disposed in close proximity to said chamber means and adapted to be selectively energized to heat said chamber means under an increased power input for generating steam and pressure therein when sterilizing by same is selected or to heat said chamber means under a reduced power input for producing sustained dry heat at high temperatures when sterilizing by same is selected;

(c) discharge means communicating with said chamber means and adapted to be selectively opened for discharging steam, water or air therefrom and closed for preventing discharge therefrom; and

((1) control means operatively associated with said heating means and said discharge means, said control means being adapted to energize said electric heating means under the increased power input and to maintain said discharge means closed for generating steam and pressure in said chamber means when sterilizing by same is selected and being adapted to energize said electric heating means under the reduced power input and to open said discharge means for producing sustained dry heat at high temperatures in said chamber means when sterilizing by same is selected.

2. A dual purpose sterilizer, as set forth in claim 1, including a reservoir means adapted to contain a supply of water and communicating with said chamber means for supplying water thereto when sterilizing by steam and pressure is selected, and in which said discharge means communicates with said reservoir means for discharging steam and water from said chamber means to said reservoir means after a sterilizing cycle by steam and pressure has been completed.

3. A dual purpose sterilizer, as set forth in claim 1, in which said electric heating means comprises a plurality of heating elements, and in which said control means is adapted to energize a single heating element under the increased power input when sterilizing by steam and pressure is selected and is adapted to energize all of said heating elements under the reduced power input when sterilizing by sustained dry heat at high temperatures is selected.

4. A dual purpose sterilizer, as set forth in claim 1, in which said means for permitting access to said chamber means comprises a primary closure means of high mass adapted to hermetically close said chamber means when sterilizing by steam and pressure is selected, and a secondary closure means of limited mass adapted to be used in lieu of said primary closure means when sterilizing by sustained dry heat at high temperatures is selected to facilitate attaining high temperatures within said chamber means.

5. In a sterilizer,

(a) a sterilizing chamber,

(b) a reservoir tank adapted to contain water,

(c) piping means providing communication between said sterilizing chamber and said reservoir tank,

16 (d) a plurality of electric heating elements in proximity to the chamber walls for increasing the temperature within the chamber and for generating steam when water is contained in the chamber to 5 originate a steam sterilizing cycle,

(e) a pair of valve members alternately disposable in open positions for regulating fluid flow in said piping means between said chamber and said tank to admit water from said tank into said chamber in beginning a sterilization treatment by steam under pressure when one of said valve members is in open position and to discharge steam and water from said chamber into said tank at the end of a steam sterilizing cycle when the other valve member is in open position, each of said valve members being closed during a steam sterilizing cycle to block communication between said chamber and said tank,

(f) means operable conjointly with said valve members for selectively energizing one of said heating elements under a power input when said valve members are closed during a steam sterilizing cycle and energizing all of said heaitng elements under a reduced power input when either of said valve members is in open position,

( g) manually operable means movable between a plurality of positions for simultaneously controlling said valve members and said heater energizing means to close said valve members while actuating said heater energizing means for selectively energizing said one heating element during a steam sterilizing cycle and to alternately open each of said valve members in beginning and ending a steam sterilization treatment while actuating said heater energizing means for energizing all of said heating elements under a reduced power input, and

(h) said manually operable means being movable directly to the position for simultaneously controlling said other valve member and said heater energizing means to selectively open said other valve member while actuating said heater energizing means for energizing all of said electrical heating elements under said reduced power input to obtain a dry heat sterilizing temperature within the chamber when said chamber is empty of steam and water to provide a dry heat sterilizing cycle in response to the disposition of said manually operable means in said position.

References Cited UNITED STATES PATENTS OTHER REFERENCES Reddish: Antiseptics, Disinfectants, Fungicides and Sterilization; Second Edition, 1957, pp. 810-818.

MORRIS O. WOLK, Primary Examiner.

E. SZOKE, J. ZATARGA, Assistant Examiners.

Claims

1. A DUAL PURPOSE STERILIZER FOR DENTAL AND MEDICAL ARTICLES AND SUPPLIES OR THE LIKE AND ADAPTED FOR SELECTIVELY STERILIZING BY STEAM UNDER PRESSURE OR Y SUSTAINED DRY HEAT AT HIGH TEMPERATURES; SAID STERILIZER COMPRISING: (A) ENCLOSED TERILIZING CHAMBER MEANS INCLUDING MEANS FOR PERMITTING ACCESS THERETO FOR RECEIVING ARTICLES AND SUPPLIES TO BE STERILIZED AND ADAPTED TO CONTAIN WATER WHEN STERILIZING BY STEAM AND PRESSURE IS SELECTED; (B) ELECTRIC HEATING MEANS DISPOSED IN CLOSE PROXIMITY TO SAID CHAMBER MEANS AND ADPATED TO BE SELECTIVELY ENERGIZED TO HEAT SAID CHAMBER MEANS UNDER AN INCREASED POWER INPUT FOR GENERATING STEAM AND PRESSURE THEREIN WHEN STERILIZING BY SAME IS SELECTED OR TO HEAT SAID CHAMBER MEANS UNDER A REDUCED POWER INPUT FOR PRODUCING SUSTAINED DRY HEAT AT HIGH TEMPERATURES WHEN STERILIZING BY SAME IS SELECTED; (C) DISHCARGE MEANS OMMUNICATING WITH SAID CHAMBER MEANS AND ADAPTED TO BE SELECTIVELY OPENED FRO DISCHARGING STEAM, WATER OR AIR THEREFROM AND CLOSED FOR PREVENTING DISCHARGE THEREFROM; AND