Abstract:
A vacuum oven for decontaminating items, a system incorporating multiple such vacuum ovens and a method of operating such system are provided. The ovens are portable. They can have a vacuum drawn in them and can be heated by being coupled to a vacuum and a power source, respectively at a first location and then be decoupled from the vacuum and power sources and moved to a second location such as a glove box or clean room while still maintaining a vacuum.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application is based and claims priority on Provisional Application Ser. No. 60/329,190, filed on Oct. 12, 2001, the contents of which are fully incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   The present invention relates to a vacuum oven, to a system incorporating the same, and to a method of using the same, and more specifically to a vacuum oven that is portable and that can be moved while maintaining vacuum and to a modular system incorporating the same. 
   Chips and sensitive electronic components many times need to be worked on in an inert clean environment. To accomplish this, glove box/oven systems have been developed. Typically a glove box is a fully enclosed hermetically sealed box. An operator accesses the inside of the box through gloves attached to a side of the box. 
   An oven is attached to an end of the box. The interface between the oven and the box is also hermetically sealed to ensure an air tight seal. The oven can be opened at opposite ends. In this regard, the oven can be opened at its end attached to the glove box and at its opposite end. 
   Sensitive electronic equipment or items, as for example pacemakers, have to be sealed or welded in an inert environment. To accomplish this, the item is placed into the oven by opening the end of the oven not attached to the box. The oven is then closed and the item is heated under a predetermined vacuum i.e., it undergoes a vacuum bake cycle to get rid of moisture and impurities. Once the vacuum bake cycle is completed, the vacuum oven is back filled from the glove box and the end of the oven interfacing with the glove box is opened. The item is then moved into the glove box where the operator can work on it, as for example weld it. 
   The problem with current glove box/oven systems is that while the item is undergoing a vacuum bake cycle, other items cannot be brought into the glove box for processing. As such, use of the glove box is dependent on whether or not the oven is being used. Consequently, in a manufacturing setting, multiple glove box/oven systems are required to increase productivity. As a result, the manufacturing costs of the products processed through such glove box/oven systems are increased. 
   As such, an oven and a system are required that will allow the vacuum bake of items in locations away from the glove box or other clean air space and which can then be transported while maintaining vacuum into the glove box. In this regard, multiple items may be baked in one or more ovens and can be operated on using a single glove box or a single clean air space. 
   SUMMARY OF THE INVENTION 
   A vacuum oven for decontaminating items, a system incorporation multiple such vacuum ovens and a method of operating such system are provided. The ovens are portable. They can have a vacuum drawn in them and can be heated by being coupled to a vacuum and a power source, respectively at a first location and then be decoupled from the vacuum and power sources and moved to a second location such as a glove box or clean room while still maintaining a vacuum. 
   An exemplary embodiment oven includes a hollow body having an opening providing access to an interior of the body and at least one removable shelf fitted in the body. A heater such as a heating pad is coupled to the shelf. A power interface is coupled to the heater and is releasably coupled to an external power source separate from the body. A vacuum valve is coupled to the body and releasably couples to an external vacuum source. A door is coupled to the body for covering the opening and sealing against the body by vacuum. The exemplary embodiment oven can be incorporated in a system. 
   An exemplary embodiment system includes a rack having at least a bay for receiving a vacuum oven in each bay. Each bay has a vacuum valve and a power interface mounted therein. The vacuum valve controls the vacuum being drawn from a vacuum source. A vacuum oven is slidably fitted in the bay and is releaseably coupled to the rack, the power interface and vacuum source. 
   An exemplary method for decontaminating items using the exemplary oven of the present invention includes placing the items to be decontaminated in the interior of the oven and coupling the oven to a vacuum source for drawing vacuum in the oven. The oven interior is heated heating the items to a predetermined temperature for decontaminating. The oven is then decoupled from the vacuum source and moved to a work area where the vacuum in the oven is released and the oven door is opened providing access to the decontaminated items. 
   An exemplary method for operating multiple ovens in an exemplary system of the present invention for decontaminating items includes providing a rack having a plurality of bays and coupling a vacuum source and a power source to the plurality of bays. A first vacuum oven having a first items to be decontaminated in it is mounted in a first bay and the vacuum source and power source are coupled to the first vacuum oven. A vacuum is drawn in the interior of the first oven to a predetermined vacuum level and the interior of the first vacuum oven is heated to a predetermined temperature for decontaminating the first set of items. A second vacuum oven having a second set of items to be decontaminated in it is mounted in a second bay and the vacuum source and power source are coupled to the second vacuum oven. A vacuum is drawn in the interior of the second vacuum oven to a predetermined vacuum level and the interior of the second vacuum oven is heated to a predetermined temperature, for decontaminating the second set of items. One or both vacuum ovens may be removed from its corresponding bay while maintaining a vacuum. The second vacuum oven may be mounted in the rack and operated before or after the vacuum and temperature in the first vacuum oven reach their predetermined level and temperature, respectively, or while the vacuum and temperature in the first vacuum oven is ramping up to the predetermined level and temperature, respectively. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective partial cut-away view of an exemplary oven of the present invention. 
       FIG. 2A  is an end view of the exemplary oven shown in FIG.  1 . 
       FIG. 2B  is a partial end side view of the oven shown in FIG.  1 . 
       FIG. 2C  is a perspective cut-away view of a pin with insulator sleeve assembly which extends from the rear wall of the oven shown in FIG.  1 . 
       FIG. 2D  is a partial end assembly view of the oven shown in  FIG. 1  incorporating a keying system. 
       FIG. 3  is a perspective upside-down view of a shelf with heating pad for incorporation in the oven shown in FIG.  1 . 
       FIGS. 4A and 4B  are perspective rear and front views, respectively, of the oven body with rear end wall of the oven shown in FIG.  1 . 
       FIG. 5  is a perspective view of a system having a rack incorporating the oven shown in  FIG. 1 , a controller, and a computer. 
       FIG. 6  is a front view of the system shown in FIG.  5 . 
       FIG. 7  is a partial cut-away perspective view of the rack shown in FIG.  5 . 
       FIG. 8  is a perspective view of a manifold valve assembly incorporated in the rack shown in FIG.  7 . 
   

   DETAILED DESCRIPTION 
   A vacuum oven, a system incorporating one or more of such ovens and a method of operating such ovens and system are provided. In an exemplary embodiment, an oven  10  of the present invention comprises a generally hollow elongated body  12  having four rectangular sides  14 , one end wall  16  fixed to one end of the body and a door  18  at the other end  20  of the body for providing access to the interior of the body, as shown in FIG.  1 . In an exemplary embodiment, the body  12  is extruded from aluminum. The end wall  16  is welded to the body. In alternate embodiments, the body may have other shapes, as for example, it may be a cylindrical. For descriptive purposes, however, the oven of the present invention is described herein in relation with an oven having a hollow body formed by four generally rectangular sides. The exemplary embodiment oven described herein is 6″ wide, by 6″ high by 18″ long. Applicants have discovered that these dimensions provide optimum accommodations for most items typically treated by such ovens. 
   It should be noted that the terms “front,” “rear,” “top,” “bottom,” “upper,” “lower,” “uppermost,” and “lowermost” are used herein for descriptive purposes to recite relative positions of various parts without limiting the location the parts to such positions. 
   The oven is designed to accommodate one or multiple shelves  22  which can be heated. In an exemplary embodiment, the shelves are formed from aluminum. To accommodate the shelves, two opposite side supports  24  are fitted in the oven, each having a slot  26  for accommodating each shelf  22 . The slots are formed on the same location in each support. The supports are placed inside the oven against opposite sidewalls  28  of the oven  10 , such that the slots are facing each other. In the exemplary embodiment, the oven supports are formed from Teflon® for allowing the shelves to slide easily along the slots on the supports. In addition, the oven supports provide thermal insulation to the oven, eliminating the need to insulate the oven from the outside for keeping the outer surface temperature of the oven at a safe level for handling. In an alternate exemplary embodiment, the slots may be formed on the inner surfaces of the sidewalls  28  thus not requiring the supports. In other exemplary embodiments, one or more shelves may be slidably fitted in the oven or may be fixed in the oven. For illustrative purposes, the exemplary oven is described as having three shelves, an upper shelf  22   c  which is fixed in place and two lower removable shelves which are slidably fitted in the oven. The upper shelf  22   c  is used for heating while intermediate shelf  22   b  and lower shelf  22   a  are used for heating and for supporting the items to be heated. Use of the upper shelf  22   c  allows for similar heating of space  23   b  between the upper shelf  22   c  and intermediate shelf  22   b  as of space  23   a  between the intermediate shelf and the lower shelf oven. Similar heating control is possible since both spaces  23   a  and  23   b  are bounded by two heating shelves. 
   In an exemplary embodiment, the shelves are heated by incorporating a heating pad  30  adhered to one side of each shelf as shown in FIG.  3 . In other exemplary embodiments, other heaters such as heating elements may be used. In an exemplary embodiment, heating pads are used formed from silicon rubber. The heating pad of each shelf is connected to an interface assembly  32  which provides an interface for providing power for heating the heating pad and thus, the shelf. A thermocouple  37  is incorporated on the heating pad for measuring temperature. The thermocouple  37  is coupled to thermocouple plug  34  which provides an interface for the thermocouple  37 . The heating pad includes an overtemperature thermostatic switch  36 . The overtemperature thermostatic switch shuts off power to the heating pad when the temperature of the heating pad or heater exceeds a predetermined temperature. 
   In alternate exemplary embodiments, a heater such as a heating pad may be mounted on an upper inner surface of the oven such as the oven upper wall, thus not requiring a separate upper shelf just for heating. 
   In an exemplary embodiment oven, when each of the intermediate and lower shelves is completely inserted into the oven along the slots  26  on the supports  24 , each shelf&#39;s thermocouple plug  34  mates with a thermocouple interface  40 . In the exemplary embodiment the thermocouple interface is a thermocouple heavy duty connector made by Omega Engineering, Inc. of Stamford, Conn. Each shelf thermocouple interface  40  is coupled to a thermocouple connector  42 . In the exemplary embodiment shown in  FIG. 1 , the thermocouple connectors are external of the oven and are mounted on a rear top surface of the oven. Morever, in the exemplary embodiment, as each removable shelf is fitted into the oven, the interface assembly  32  of each shelf mates with a connector  47  which is coupled to openings  44  formed on the rear wall  16  of the oven. In the exemplary embodiment oven, each interface assembly  32  comprises two spring loaded conductive pins  49 . Each connector  47  comprises two banana plugs  48  which penetrate openings  44  and interface with the conductive pins  49  ( FIGS. 2A ,  2 C,  2 D and  4 A) when the shelves are pushed into position in the oven. The spring loaded pins provide for a reliable connection between the interface assembly of a shelf and the corresponding banana plugs of the connector  47 . Preferably, the plugs  48  are surrounded by an insulating sleeve  51  as for example shown in FIG.  2 C. The insulating sleeve fits into the openings  44  ( FIG. 4A ) formed on the rear wall of the oven sealing the openings air tight while allowing for penetration by the banana plugs. In an alternate embodiment, instead of banana plugs, the interface assembly may contain sockets that mate against the openings  44 . 
   In the exemplary embodiment, the upper shelf  22   c  which is fixed to the oven is connected to connector  45 . In an alternate exemplary embodiment instead of a connector  45 , an interface assembly  32  is incorporated in the fixed shelf which is connected to a connector  47  as described in relation to the removable shelves. A two-way valve  50  is coupled to a fitting  52  coupled to the rear end wall  16  of the oven as for example shown in  FIGS. 2A and 2B . A disc  54  is coupled to the end of the two-way valve  50  opposite the rear wall. An opening  56  is formed through the disc. The two-way valve  50  and fitting  52  provide access from the opening  56  formed through the disc to the interior of the oven through opening  57  formed on the rear wall  16  (FIG.  4 A). The two-way valve controls the flow through the fitting. The two-way valve is preferably a solenoid type valve and is coupled to a connector  59  which in the exemplary embodiment is external of the oven as shown in FIG.  1 . 
   In the exemplary embodiment shown in  FIG. 1 , a lip  60  extends radially outward from the sides of the oven front end and surrounds the oven front end. The lip defines a flange surface  62  surrounding the front end of the oven. A groove  64  is formed on the upper surface  65  of the lip as shown in  FIGS. 1 ,  4 A and  4 B. The door  18  has sufficient dimensions such that its entire surface proximate its perimeter mates with the flange surface of the lip. 
   A bracket  66  is attached or fastened to the upper end  67  of the door and has a lip portion  68  extending therefrom for mating with the groove  64  formed on the upper surface  65  of the lip as shown in FIG.  1 . In this regard, the door can be hanged at the groove by using the bracket  66 . In an alternate embodiment, the bracket may be integrally formed with the door. By hanging the door to the body, the door may easily be completely removed from the body so as to provide unimpeded access to the oven interior. In a further alternate exemplary embodiment, the door may be hingeably connected to the oven body. 
   To provide a seal between the door and the lip, in the exemplary embodiment, a groove  70  is formed on the flange surface of the lip extending around the entire perimeter of the oven end (FIGS.  1  and  4 B). An O-ring seal (not shown) is fitted within the groove. In an alternate embodiment, the groove for accommodating the O-ring seal may be formed on the surface of the door mating with the flange surface of the lip. 
   In the exemplary embodiment, a handle  72  is formed on the door to allow for easy installation (i.e., hanging) and removal of the door from the oven. A valve  74  is also fitted through the door extending outward to relieve vacuum and provides access to the interior of the oven through the door. 
   A carrying handle  76  is coupled to the oven body and preferably an upper side of the body to facilitate the carrying the transportation of the oven. 
   In an exemplary embodiment, the oven is mounted on a rack  80  as for example shown in FIG.  5 . The rack may accommodate one or multiple ovens forming a system. For descriptive purposes, a rack that can accommodate six ovens is described herein. Each oven is slid into an opening  82  formed on the rack (FIG.  6 ). The rack comprises rails  84  which extend from each opening and define bays, as for example bays  86 , to support the ovens (FIG.  7 ). Each rail defines a corner of a bay  86  into which the oven is slid for mounting. To reduce the friction between an oven and the rails when sliding, low coefficient of friction nylon feet  88  may be mounted on either side of the lower surface of the oven for interfacing with the two lower rails of a bay (FIG.  1 ). In an alternate exemplary embodiment, low friction members such as feet may be mounted on the racks. Alternatively, the racks may be made from a low friction material. 
   At its rear end, each bay includes appropriate connectors for connecting with the various connectors of the oven such as the thermocouple connectors, the connector  45 , the two way valve connector and the interface assembly. In the exemplary embodiment, a connector  90  is located at the rear end of each bay for connecting with the thermocouple connectors  42 , the two-way valve connector  59  and the connector  45 . The connector  90  is connected to a controller  91  which is controlled by a processor such as a computer  93  (FIG.  5 ). The connector  90  provides paths for receiving temperature indicative signals from the thermocouples  37  of each shelf and provides paths for providing power to the two-way valve connector  59  for controlling the two-way valve  50  and to the heating pad of the upper shelf  22   c  for heating the upper shelf. A shelf connector  92  is also located on the rear of each bay to connect with the interface assemblies  32 . The shelf connector  92  is also connected to the controller  91  and provides a path for providing power to the heating pad of each shelf via the interface assemblies  32 . All of the connectors allow for quick connection and disconnection with their corresponding connectors and assemblies on the oven. 
   In the exemplary system, a manifold valve assembly  94  is also located on the end of each bay (FIGS.  7  and  8 ). An exemplary manifold valve assembly is shown in FIG.  8  and comprises a manifold  96 . A three-way valve  98  is mounted on one end of the manifold via a fitting  100 . A suction cup  102  is mounted on another end of the manifold via a fitting  104 . A passage  106  provides a path from the suction cup to the three-way valve. 
   The suction cup is positioned on a bay to engage the disc  54  extending from the rear wall of an oven such that the passage  106  extending to the suction cup communicates with the opening  56  formed through the disc when the oven is mounted in the bay. 
   The three-way valve has a port  108  which is connected to a vacuum source  110  and a relief port  112  for relieving vacuum. The three-way valve may also be a solenoid valve and is also coupled to the controller  91 . An exemplary three-way solenoid valve is manufactured by ASCO (Automatic Switch Co.). 
   Once the oven is mounted within its bay, the disc  56  mates with the suction cup  102  and a vacuum may be applied to the oven via the three-way and two-way valves. The two-way and three-way valves are controlled by the controller. The controller also individually controls the amount of power available to each of the interface assemblies for heating each of the shelves. The controller control of the valves and power may be manual through the use of the computer or may be automated. For example, the controller may be programmed to control temperature and vacuum ramp up and to maintain the temperature and vacuum in the oven at preselected levels. The temperature of each shelf is ascertained by the controller from signals received from the thermocouples and registered on the computer. 
   Once the oven is mounted on its appropriate bay and vacuum is applied, the vacuum pulls the door  18  tightly against the oven body  12  compressing the O-ring seal, fitted in the groove  70  on the flange surface, between the door and the flange surface, creating an air tight seal. Consequently, a latch is not required for keeping the door closed. 
   As the vacuum is applied, the suction cup engages and seals against the disc  54 . Thus, to remove the oven without losing the vacuum in the oven, the two-way valve is closed while a vacuum is being drawn through the three-way valve. The three-way valve is then closed. Afterwards, the three-way valve relieves the vacuum in the manifold  96  through the relief port  112  so that the vacuum between the suction cup and disc is broken allowing for the withdrawal of the oven from the rack. 
   In an exemplary embodiment, all the ovens mounted into the rack are coupled to the same vacuum source. This alleviates the need to incorporate individual vacuum pumps and/or vacuum sources which are expensive. Consequently, the cost of the system is significantly reduced. Alternatively, multiple vacuum sources may be used. 
   Ovens may be installed into the rack at will and may be started at will. Each newly installed oven, however, may contain an atmosphere that may contaminate the other already installed ovens if they are not isolated when the newly installed oven is connected to the vacuum source. As such, it is necessary to use the three-way and the two-way valves to sequence the operation of the vacuum source to each of the ovens to avoid loss of vacuum in an evacuated oven. 
   In an exemplary operations sequence, the oven is mounted into the appropriate bay in the rack. The items to be decontaminated are placed on the oven shelves as appropriate, and the door is hung on the oven. The items may be placed in the oven prior to mounting or after mounting of the oven in the rack. The bay containing the new oven is selected on the computer. The selection may be made via the keyboard, mouse or touch screen. The operator then sends instructions via the computer to start the oven and may enter a data file name to identify the oven. If the other ovens have not finished the initial heat up and vacuum cycle, the system waits for the other ovens to reach their required temperature and vacuum. Then, the two-way valves on all the other ovens are closed and the three-way valve and then two-way valve on the newly installed oven are opened. Vacuum is spooled on the newly installed oven for a certain period of time and is checked to see if the vacuum level within a predetermined period of time has reached a desired level. For example, a typical value may be one millitor. If the vacuum does not reach the desired level, then an error is flagged and the process is stopped. If the vacuum does reach the desired level, then the two-way valve on the newly installed oven is closed. 
   The two-way valves on the other ovens which are in cycle mode (i.e. are being heated and evacuated) are opened, and heat is applied to the newly installed oven shelves until the temperature of the shelves reaches a desired level. The two-way valves are then closed on the other ovens. The two-way valve is then opened on the newly installed oven until the proper vacuum level is achieved. Once the proper vacuum level is achieved, the two-way valves on the other ovens are opened. When the bake cycle is completed on the newly installed oven, the two-way valve on the newly installed oven is closed and then the three-way valve is closed. This entire process may be automated through programming. An exemplary software that may be used to run the system is LABVIEW by National Instruments. 
   To remove the oven, the three-way valve opens the release port  112  so as to relieve the vacuum between the two-way valve and the three-way valve so as to allow the oven to slide out of the rack. The oven with the items may be then mated with or inserted in glove box, or it may be taken to a clean room where the vacuum oven is back filled with appropriate gas, e.g., the environment found in the glove box or clean room, and the door  18  is opened for removing the items treated by the oven. To back fill the vacuum oven so as to allow the door to open, the valve  74  coupled to the door is opened. 
   If it is desired that a specific oven is always mated with a specific bay in the rack, a key  120  ( FIG. 2D ) may be coupled to the rear of the oven that is accepted by a complementary key in a desired bay. For example, the key may have specific ports  124  arranged in a specific pattern that accommodate specific pins arranged in the same pattern and coupled to the rear and of the desired bay. 
   It should be noted that the exemplary oven, system and method have been described in relation to exemplary embodiments. It should be understood that the inventive oven, system and method are not limited to the exemplary embodiments. For example, other types of connectors and valves then those described may be used. For example, a female connector may be incorporated on the oven and a complementary male connector may be incorporated on the bay to connect with the female connector and vice versa. Moreover, the suction cup may be incorporated on the end of the fitting  52  extending from the oven instead of the disc  54  and the disc may incorporated at the end of the fitting  104  instead of the suction cup  102 . 
   Although the present invention has been described and illustrated to respect the exemplary embodiments thereof, it is to be understood that it is not to be so limited, since changes and modifications may be made therein which are within the full intended scope of this invention as hereinafter claimed.