Abstract:
A closure assembly ( 20 ) for engaging a door ( 14 ) across the opening ( 16 ) of a chamber ( 12 ) includes first and second triangular plates ( 28 ) and ( 30 ) which are pivotally connected to opposite corners of a front face ( 32 ) of the door. The plates face each other at the longest sides of the triangles. The remaining sides of the triangles define engagement portions ( 72, 74, 76, 78 ). To restrain the door, the plates are pivoted ( 50, 52 ) until the engagement portions engage flanges ( 80, 82, 84, 86 ) situated around the perimeter of the opening. A seal ( 96 ) is then activated to seal the door around the opening. Preferably, a coupling member ( 33 ) is coupled to the plates to coordinate their pivoting. Cam slots ( 114, 116 ), defined in the coupling member, receive followers ( 118, 120 ) connected to the two plates. An operator rotates the coupling member, the followers are cammed or permitted to move by gravity as the plates are pivoted apart and together.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to the door closure arts. It finds particular application in connection with restraining a door across an opening to a steam sterilization chamber, and will be described with particular reference thereto. It should be appreciated, however, that the invention is also applicable to a wide variety of doors which are to be securely fastened to a pressure vessel or which are to be secured on four sides, such as vault doors or ship doors. 
     Conventionally, steam sterilizers are operated at high internal pressures and temperatures. To maintain these temperatures and pressures, the door of the sterilizer is generally clamped in position across an opening to the sterilization chamber by a closure assembly. Typically, a sterilization chamber door must be sealed to approximately 15 to 20 Kilograms force to prevent the door from leaking. A gasket or other flexible member is sealed between the door and the chamber. The closure assembly inhibits the ingress of air around the seal and also prevents hazards arising from accidental opening of the door during a sterilization cycle. 
     U.S. Pat. Nos. 4,756,123 and 4,891,910 disclose examples of closures for sealingly engaging a door across the opening to a sterilization chamber. U.S. Pat. No. 4,891,910 discloses a motorized closure assembly which drives a central locking wheel. A plurality of arms are connected to the locking wheel. The arms move upon rotation of the locking wheel until outer ends of the arms engage a plurality of apertures positioned along the perimeter of the opening to the chamber. Such closure assemblies are often complex, requiring a number of moving parts. 
     The present invention provides for a new and improved closure assembly for restraining a sterilizer door which overcomes the above-referenced problems and others. 
     SUMMARY OF THE INVENTION 
     In accordance with one aspect of the present invention, a steam sterilizer apparatus is provided. The apparatus includes a pressure chamber with a door frame which defines an opening into the chamber. A door is connected to the door frame and is sized to cover the opening. A plurality of flanges are connected with the door frame, at least one flange being adjacent each of opposite edges of the door. A closure assembly selectively maintains the door in a proximate relationship to the frame. The closure assembly includes first and second plates. The first plate has an uppermost portion which is pivotally connected to the door and an engagement portion which is pivoted into and out of engagement with one of the flanges. The second plate has a lowermost portion which is pivotally connected to the door and an engagement portion which is pivoted into and out of engagement with another of the flanges. 
     In accordance with another aspect of the present invention, a closure assembly f or selectively maintaining a door in sealing engagement around an opening in a cabinet is provided. Flanges extend from a front face of the cabinet. The assembly includes first and second plates, pivotally connected adjacent first and second sides of the door, respectively. The first and second plates each define two engagement portions for selectively engaging two of the flanges. A coupling member couples the first plate to the second plate for selectively rotating them from a disengaged position, in which the engagement portions are displaced from the flanges, to an engagement position, in which the engagement portions engage the flanges. 
     In accordance with yet another aspect of the present embodiment, a method of selectively restraining a door across an opening is provided. The method includes pivoting first and second plates which each define two engagement portions until the engagement portions engage corresponding flanges. The two plates are pivotally connected to the door. 
     One advantage of the present invention is that it requires few moving parts. 
     Another advantage of the present invention is that the closure may be operated with application of minimum operator effort and a minimum of articulation. 
     Another advantage of the present is that the closure is self-locking in the engaged position. 
     Still further advantages of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description of the preferred embodiments. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention may take form in various components and arrangements of components, and in various steps and arrangements of steps. The drawings are only for purposes of illustrating a preferred embodiment and are not to be construed as limiting the invention. 
     FIG. 1 is a front perspective view of a sterilizer with a cosmetic front door surface removed to show a counterbalanced closure assembly according to the present invention; 
     FIG. 2 is schematic front elevational view of a sterilizer door and closure assembly in the disengaged position, in accordance with the present invention; 
     FIG. 3 is an enlarged side sectional view of the door and closure plate of FIG. 2 along Section A—A; 
     FIG. 4 is a front elevational view of the door and closure assembly of FIG. 2 in the engaged position, in accordance with the present invention; and, 
     FIG. 5 is a side sectional view along section A—A of FIG. 4 with the flange engaged; 
     FIG. 6 is a side sectional view along Section A—A of FIG. 4 with the flange engaged and the seal actuated; and, 
     FIG. 7 is a front elevational view of the closure assembly of FIG. 1 in both the engaged (hatched lines) and disengaged (solid lines) positions. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to FIG. 1, a steam sterilization apparatus  1  includes a cabinet  10  which defines an interior chamber  12 . A rectangular door  14  opens and closes to allow items to be sterilized to be loaded and unloaded into the chamber through an opening  16  in the chamber. The door is sized to cover completely the opening and is preferably formed from a material which is resistant to the chemical environment within the chamber, such as a stainless steel plate. When the door is in the closed position, a closure assembly  20  selectively restrains the door. 
     Hinges  22  pivotally connect a first vertical side or edge  24  of the door to a door frame, such as a frame or front wall  26  of the cabinet, which defines the opening. The hinges allow pivotal movement of the door during opening and closing. The hinges also permit a small amount of transverse motion of the door in a direction perpendicular to the front wall of the cabinet to allow a small door movement due to pressure changes within the sterilizer. 
     The closure assembly  20  includes two generally triangular-shaped flat plates of substantially equal weight, namely an upper plate  28  and a lower plate  30 , which are pivotally mounted to a flat exterior face  32  of the door, and a coupling member  33  for articulating the plates from a disengaged position, in which the door  14  can be opened, to an engaged position, in which the door is restrained in position across the opening  16 . 
     The plates  28  and  30  are formed from a rigid material, such as steel, and are of a sufficient thickness, e.g. 1-2 cm, to withstand the pressures exerted on the door from within the chamber  12 . Each of the plates has a generally right-angled corner  34  and  36 , respectively, which is indented, as will be described in further detail hereinafter. The two right-angled corners are positioned adjacent diagonally opposite corners  38  and  40 , respectively, of the door. Specifically, the door first upper corner  38  is defined between the top of the door  41  and a second vertical side or edge  42  of the door that is furthest from the hinges and the first lower door corner  40  is defined between the bottom of the door  43  and the first vertical edge  24  of the door. The upper plate  28  is thus positioned with its right-angled corner  34  adjacent the first upper corner  38  of the door, and the lower plate is positioned with its right-angled corner  36  adjacent the first lower corner  40  of the door. The plates are arranged so that their longest sides  44  and  46 , respectively, lie parallel to each other, in facing opposition and generally diagonally across the door. A gap  48  is preferably defined between the two plates. 
     The plates are pivotally connected to the exterior face  32  of the door of the sterilizer at plate pivot points  50  and  52 , respectively, by any suitable pivoting means, such as a pivot pin. The pivot pins allow the plates to rotate in a plane parallel to the exterior face  32  of the door. The pivot points are located adjacent diagonally opposite corners of the door. Specifically, the pivot point  50  of the upper plate  28  is positioned adjacent a corner of the plate  53  closest to a second lower corner  54  of the door defined between the second edge  42  of the door and the bottom  43  of the door, while the pivot point  52  for the lower plate  30  is positioned adjacent a corner  55  of the plate which is adjacent a second upper corner  56  of the door, defined between the first edge  24  of the door and the top of the door  41 . 
     While the shapes of the two plates  28  and  30  and their respective pivot points  50  and  52  have been described in relation to the first and second edges of the door  24  and  42 , it is to be understood that the positions of the plates could also be flipped  180 ° so that one of the plates is positioned with its right-angled corner adjacent the second upper corner  56  of the first edge of the door and the other plate with its right-angled corner adjacent the lower corner  54  of the second edge of the door. It is to be understood that this alternative arrangement of the plates is also contemplated. Additionally, while FIG. 1 shows the door hinges on the left edge of the door, the door could equally well be hinged on the right of the door, or on the top or bottom of the door, if desired. 
     With reference also to FIGS. 2 and 3, the plates  28  and  30  are shaped and positioned so that in the disengaged position the periphery of the plates does not extend beyond the periphery of the door. As seen from FIGS. 1 and 2, in the disengaged position, the horizontal and vertical edges of the two plates are not aligned in parallel with the adjacent vertical and horizontal edges of the door, but rather are offset by a few degrees, preferably from about 5-15°. Specifically, the gap between a side edge  60  of the upper plate  28  and the adjacent second edge of the door  42  narrows from top to bottom of the door, while the gap between a side edge  62  of the lower plate  30  and the adjacent first edge  24  of the door widens from top to bottom of the door. Similarly, the gap between an upper edge  64  of the upper plate  28  and the adjacent horizontal top  41  of the door narrows from the first edge  24  of the door to the second edge  42  of the door, while the gap between a bottom  68  of the lower plate  30  and the adjacent horizontal bottom  43  of the door widens from the first to the second edge. 
     With reference also to FIG. 4, which shows the plates in the engaged position, the upper and lower and side edges of the two plates  64 ,  68 ,  60  and  66 , respectively, define engagement portions. Specifically, a first engagement portion  72  is defined by the upper edge  64  of the upper plate  28 , a second engagement portion  74  is defined by the lower edge  68  of the lower plate  30 , a third engagement portion  76  is defined by the side edge  60  of the upper plate and a fourth engagement portion  78  is defined by the side edge  62  of the lower plate. 
     Four over-hanging retaining members or bars  80 ,  82 ,  84 , and  86  are positioned around the perimeter of the opening  16 . The retaining bars are rigidly connected with the front face  26 , or structural frame of the sterilizer, adjacent to the corresponding four engagement portions  72 ,  74 ,  76 , and  78 . With reference also to FIGS. 3 and 5, each of the retaining bars  80 ,  82 ,  84 , and  86  extends parallel to, and slightly spaced from, the adjacent edge of the door  41 ,  43 ,  42  and  44 , respectively, so that the bars do not interfere with the opening and closing of the door. Each of the retaining bars includes a spacer portion  90  which extends beyond the exterior face  32  of the door to a position which is slightly forward of the corresponding plate engagement portion  72 ,  74 ,  76 , and  78 . (See FIG. 4.) On each bar, a flange  92  extends perpendicularly from the forward end of the spacer portion. The flange on the bar  80  also extends parallel to the top  41  of the door, while the flanges on the bars  82 ,  84 , and  86  also run parallel to their respective edges  43 ,  42  and  24  of the door. The flange overlaps the corresponding engagement portion when the closure assembly  20  is in the engaged position, as shown in FIG.  5 . Accordingly, each plate is engaged by two perpendicularly positioned flanges. 
     With particular reference to FIGS. 3,  5 , and  6 , a door seal, such as a gasket  96 , is housed in a channel  98  which is defined in the front surface  26  of the cabinet and which extends around the perimeter of the opening  16 . FIGS. 3 and 5 show the seal prior to activation. To activate the seal, the channel is supplied with steam, or other pressurizing fluid while the plates  28 ,  30  are in the engaged position. The seal moves outwardly from the channel, compressing the door  14  and the plate engagement portions  72 ,  74 ,  76 , and  78  against an interior sealing face  100  on the corresponding flange  92 , as shown in FIG. 6. A leak-tight seal is thus formed between an interior surface  102  of the door and the front surface  26  of the cabinet, thus sealing the opening to the chamber  12 . The flanges  92  and engagement portions  72 ,  74 ,  76 , and  78  cooperate to prevent the door from opening in response to a pressure from within the chamber. 
     To move the closure from the disengaged to the engaged position and seal the door  14  across the opening  16 , the door is first pivoted from an open position, shown in FIG. 1, to a closed position, shown in FIG. 2, where the door is positioned generally parallel to the front surface  26  of the cabinet. The two plates  28  and  30  are rotated about their pivot points  50  and  52 , in a clockwise direction. As the plates rotate, the engagement portions  72 ,  74 ,  76 , and  78  of the plates are brought into engagement with the respective flanges  92  of the retainer bars  80 ,  82 ,  84 , and  86 . The plates are then in the positions shown in FIGS. 4 and 5. A cut-out portion  104  in the lower plate  30  is shaped to allow for the protrusion of the hinge  22 . The upper plate  28  may be provided with a similar cut-out portion so that the plates may be operated on either a left opening or a right opening door. Additionally, it is desirable for the plates to be manufactured similarly so that they are of approximately equal or identical weight. Further, eliminating material along the top and bottom edges toward the corners can reduce the distance the plates move between the engaged and disengaged positions. Once the plates  28  and  30  are in position with the engagement portions engaged by the respective retainer bar flanges, the seal  96  is activated, as shown in FIG.  6 . 
     In the engaged position, each edge of the door is restrained from outward movement by the engagement of the corresponding engagement portion and flange. While it is also contemplated that a single engagement portion be provided on each of the plates  28  and  30 , rather than two engagement portions, the use of two engagement portions assists in restraining the door. Specifically, when an outward force is applied adjacent to a first engagement portion, the force will be distributed over the entire plate as the adjacent engagement portion resists pivoting of the plate around the first engagement portion. 
     With reference to FIG. 7, one preferred embodiment of the coupling member  33  is shown. It is to be appreciated, however, that a variety of mechanisms for articulating the plates  28  and  30  to the engaged positions are also contemplated, which may include separate mechanisms for moving each of the plates. The coupling member  33  provides a convenient means for rotating the heavy plates with a minimum of rotational force. The coupling member preferably defines a flat rectangular plate, and may be formed from steel or other rigid material. It is pivotally connected at its center to the front face  32  of the door by an axle or shaft member  108 , such as a central pivot pin. Preferably, the axle member is located in the gap between the two plates, at the geometric center of the assembly. The axle member allows the coupling member to rotate in a plane parallel to the front face  32  of the door. Each of the plates  28 ,  30  may define a semi-circular cut-out portion  109  adjacent the central pivot pin  108  so that the plates do not obstruct rotation of the central pivot pin. 
     A first, or upper portion  110  of the coupling member  33  overlaps the upper plate  28  while a second, or lower portion  112  of the coupling member overlaps the lower plate  30 . First and second curved cam slots  114  and  116  are defined in the first and second portions  110  and  112 , respectively. First and second low friction shafts or pins  118  and  120 , are connected with the plates  28  and  30 , respectively. The shafts extend outwardly from the plates and are received through the cam slots  114  and  116 . In cooperation, the coupling member  33 , the pivot pins  50  and  52 , and the shafts  118  and  120  maintain the plates  28  and  30  in close proximity to the front face  32  of the door, particularly when the plates are in the disengaged position. Other devices may also be added to maintain close proximity. 
     The cam slots  114  and  116  are configured such that, in the disengaged position, the first shaft  118  is located adjacent a lower end of the first cam slot  114  while the second shaft  120  is at an upper end of the second cam slot  116 . The positions of the shafts and the cam slots are reversed in the engaged position, with the first shaft  118  being cammed to the upper end of the first cam slot  114  and the second shaft  120  being cammed to the lower end of the second cam slot  116 . To reduce friction between the shafts  118  and  120 , and resulting wear of the shafts, the shafts optionally include an outer layer of a low friction material, such as a sleeve of TEFLON. Alternatively, the shafts include a rotatable outer portion, such as a sleeve, which is spaced from the shaft by bearings. 
     The coupling member may be moved manually, by an operator, between the disengaged and engaged positions, or be power operated. Preferably, a handle, such as a wheel or crank, is connected to the coupling member  33  to rotate it between its two positions. As the force is applied, the coupling member  33  rotates in a clockwise direction around the central pivot pin  108 , and the two plates  28  and  30  are rotated clockwise around their respective pivot pins So and  52 , into the engagement positions. 
     The plates  28 ,  30  are mutually counterbalanced around the coupling member. Specifically, the upward force required to push the upper plate  28  into the engaged position is generally counterbalanced by the downward force of the lower plate  30  which tends to pull the lower plate to the engaged position. 
     The two spacer plates  28  and  30  are bound to follow the cam slots  114  and  116  of the rotating coupling member  33 . To maintain counterbalancing, i.e., for the plates to remain at rest in any position, or, alternately, to take zero torque to rotate the coupling member to actuate the plates, the net torque on the coupler should remain zero. Taking moments about the coupling member pivot point  108 , there are only two forces—the contact at the two cam surfaces. In order for them to equal zero, the cross product of the force and location vector for each contact is equal and opposite. 
     By hanging the plates  28  and  30 , with one naturally wanting to rotate to the disengaged position while the other naturally wanting to rotate to the engaged position, by making them identical, so that the weight of each is the same and, just as importantly, the horizontal distance from the plate&#39;s center of gravity to the pivot point of each identical at any position, and by making the cam slots mirrors so that the direction of the force vector to the coupler is identical for each plate, the net torque on the coupler remains zero. It should be appreciated that an equivalent counterbalancing could be achieved by shaping each plate differently or pivoting the plates about non-mirrored points, and maintaining a zero net torque by altering the shape of the cam slots. 
     Additionally, only a small amount of articulation, preferably from about 5-10°, and more preferably about 7°, brings the plates to the engaged position. Accordingly, only a small net force to overcome friction forces is supplied by the operator to move the plates. 
     To return the plates  28  and  30  to the disengaged position, the movements are reversed. The operator applies a small counterclockwise torque on the coupling member  33  camming the shafts  118 ,  120  inward toward each other. 
     The cam slots  114  and  116  are configured to cam the shafts smoothly such that when the plates  28  and  30  are in the engagement position, the plates  28  and  30  cannot be rotated by themselves to the disengaged position without rotating the coupling member  33 . This prevents inadvertent disengagement of the plates by any rotational force which may act on the plates. 
     In the embodiment of FIG. 7, the engagement portions  72  and  74  of the plates  28  and  30  each define a camming surface  122  and  124 , respectively, on a leading portion  126 ,  128 , respectively, of the engagement portion. The camming surfaces are the first parts of the engagement portions to engage the corresponding retainer bars  80 , and  82 , respectively, when the plates are moved towards the engagement position. As the camming surface slides against the inner surface  100  of the retaining bar flange, the plate is smoothly guided into closer proximity with the outer face  32  of the door so that the remainder of the engagement portion engages the flange  92  smoothly. 
     To sterilize or disinfect items, the items are first loaded into the chamber  12  through the opening  16 . The door  14  is then pivoted into a position where it covers the opening. The plates  28  and  30  are pivoted from the disengaged to the engaged position. The seal  96  is activated, pushing the engagement portions  72 ,  74 ,  76 , and  78  into intimate engagement with the corresponding flanges  92  and sealing the interior surface of the door to the door frame  26 . 
     At one or more stages of a sterilization or disinfection cycle, steam is admitted to the chamber under pressure to sterilize the items. The added pressure within the chamber provides an outward force on the door  14  and on the plates  28  and  30 . The flanges  92  resist the outward motion of the door by limiting outward movement of each of the plates along two adjoining edges of the plate. The force on one engagement portion tending to pivot the plate outwardly is thus resisted by an opposing force on the adjacent engagement portion. 
     At various stages of the sterilization or disinfection cycle, the chamber is evacuated by connecting a source of vacuum, such as a vacuum pump, to the chamber. The reduced pressure within the chamber tends to draw the door  14  towards the door frame  26 . The spacer portions  90  provide the door with some freedom of movement, allowing the engagement portions to move inwardly and outwardly a small amount in response to the changing pressure within the chamber. 
     At the end of the sterilization or disinfection cycle, the pressure within the chamber is returned to ambient pressure. The seal is deactivated by venting and/or evacuating the steam from within the seal and the plates  28 ,  30  are pivoted from the engaged to the disengaged position. The door is then opened and the sterilized or disinfected items removed. 
     The closure assembly  20  has been described with reference to a sterilizer door. It should be understood that the closure assembly is equally suited to selectively engaging a variety of doors across an opening to a chamber, in particular, doors which are subjected to high pressures from within the chamber. 
     The invention has been described with reference to the preferred embodiment. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.