Door latch for a pressure vessel

Abstract

A pressure vessel such as a steam cooker has a novel variably sloped cam arrangement for sealing a warped access door against the inside of an access opening. Such access openings are typically of circular configuration, and the access doors are warped about one axis for insertion therethrough. The latching mechanism of this invention enables the door to be swung from an open position into a first position inside the pressure vessel and then to be moved rapidly into a second position in engagement with an inside rim of the access opening. This rapid movement is accomplished by rotation of an operating handle through a relatively small angle. Thereafter continued rotation of the handle stresses the access door, removing the warp therefrom and sealing the door against the inside rim of the access opening. The latter door stressing rotation produces relatively little motion of the door for a relatively large angular rotation of the operating handle. Thus there is achieved a relatively large mechanical advantage during the actual stressing of the door, while minimizing the amount of operating handle rotation required during that portion of door movement wherein a large mechanical advantage is not necessary. There is further disclosed a novel shift plate arrangement which causes both rectilinear and angular shifting of the access door during movement between the above mentioned first and second positions. This avoids manual shifting of the door and enables door latching by merely swinging the door into the closed position and actuating the operating handle. Door opening is accomplished by a sequence which is the reverse of the latching sequence.

What is claimed is: 
     
       1. In a pressure vessel having a wall provided with an access opening, apparatus for sealing a door against the inside surface of said wall to cover said opening comprising: door support means supported exteriorly adjacent said wall,   door mounting means supported by said door support means and extending inwardly through said opening for pulling said door toward said wall, said door mounting means comprising a cam follower and a cam having a cam surface having adjoining steeply pitched and gradually pitched surface portions for causing door movement along said axis at a relatively rapid rate when said cam follower moves against the steeply pitched portion of said cam surface and at a relatively slow mechanically advantageous rate when said cam follower moves against the gradually pitched portion of said cam surface, and   door operating means connected to said door mounting means for producing relative movement between said cam and cam follower.   
     
     
       2. In a pressure vessel comprising a closable tank, a tank access opening, a normally warped closure door for sealing said opening, and stressing means rotationally operable about a longitudinal axis of said tank for flexing said door against said access opening; the improvement wherein said stressing means comprises cam means having a cam surface which is pitched at a relatively steep first angle for rapidly moving said door longitudinally toward a sealing rim of said opening and pitched at a smaller second angle for providing a large mechanical advantage to flex the door against said rim. 
     
     
       3. Apparatus according to claim 2 said first pitch angle producing in the order of about 0.0138 inches of door movement per degree of rotation of said stressing means and said second pitch angle producing in the order of about 0.0023 inches of movement of the door attachment point per degree of rotation of said stressing means. 
     
     
       4. Apparatus according to claim 2 said cam surface having a third region having substantially no pitch to provide for latching said door in a sealed and stressed position that is non responsive to door and vessel pressure stresses. 
     
     
       5. In a pressure vessel comprising a wall having an access opening, a normally warped closure door which is insertable through said opening, and stressing means .[.fo.]. .Iadd.for .Iaddend.flexing said door against said wall to seal the access opening from the inside, the improvement wherein said stressing means comprises: a door support arm mounted exteriorly of said wall and extending across said access opening from a fixed hinge located at one side thereof,   door operating means mounted on said arm for rotation about a longitudinal axis and slidable laterally along the arm,   a hollow cylindrical cam member mounted with its longitudinal axis coincident with the rotational axis of said door operating means, said cam member being provided with a radially extending projection reaching outwardly from the surface thereof, and a longitudinally extending helical slot,   a cylindrical stem slidable longitudinally within said cam member and provided with a radially extending projection for mating engagement with said slot, said stem being secured to the exterior surface of said door so that when the door has been inserted through the access opening and centered therein, rotation of said door operating means rotates said cam member, pulls said stem outwardly and flexes said door against the inside surface of said wall to seal the access opening, and   a shift plate mounted in fixed relation with said door support arm and cooperative with the projection of said cam member to cause lateral shifting of said cam member, said stem, and said door, when the door operating means are rotated as aforesaid.   
     
     
       6. The improvement of claim 5 wherein said helical slot has a first pitch angle for pulling said door from an initial position inside said pressure vessel outwardly for contact against the inside surface of said wall, a second pitch angle for flexing said door against said wall to seal said access opening, and a third pitch angle for latching said door in the sealed position. .[.7. In a pressure vessel comprising a wall having an access opening, a normally warped closure door which is insertable through said opening, and stressing means for flexing said door against said wall to seal the access opening from the inside, the improvement wherein said stressing means comprises a door support arm mounted exteriorly of said wall and extending across said access opening from a hinge line at one side of the opening to an attachment point on the opposite side thereof, and means for securing said door on said arm movably both longitudinally 
     
     
        and laterally relative thereto..]. 8. .[.Apparatus according to claim 7 wherein.]. .Iadd.In a pressure vessel comprising a wall having an access opening, a normally warped closure door which is insertable through said opening, and stressing means for flexing said door against said wall to seal the access opening from the inside, the improvement wherein said stressing means comprises a door support arm mounted exteriorly of said wall and extending across said access opening from a hinge line at one side of the opening to an attachment point on the opposite side thereof, and means for securing said door on said arm movably both longitudinally and laterally relative thereto; and .Iaddend.said stressing means further comprises operating means for producing said longitudinal movement and 
     
     
        said lateral movement by rotation about a longitudinal axis. 9. Apparatus according to claim 8 wherein said stressing means further comprises means for causing the rate of said longitudinal movement to be dependent upon 
     
     
        the rotational position of said operating means. 10. In a pressure vessel comprising a wall having an access opening, a normally warped closure door which is insertable through said opening, and stressing means for flexing said door against said wall to seal the access opening from the inside, improved mounting means for said door comprising a door support arm hinged along a fixed hinge line exteriorly of said opening and configured for extending exteriorly across said opening while supporting said door interiorly thereof, door operating means supported by said door support arm for operating said stressing means, and shifting means actuated by said operating means for shifting said door both laterally and angularly from a position facilitating insertion of said door through said opening to a position in alignment with said opening prior to said door flexing by 
     
     
        said stressing means. 11. The improvement of claim 10 wherein said stressing means comprises a stem attached to said door and connected to said door operating means for longitudinal movement in response to 
     
     
        actuation thereof. 12. The improvement of claim 10 wherein said shifting means comprises an arc-shaped door base provided with an aperture for passage of said stem therethrough and sliding means operable in response to actuation of said door operating means for causing said stem to slide laterally relative to said door and causing the longitudinal axis of said stem to shift angularly in accordance with the curvature of said door 
     
     
        base. 13. The improvement of claim 12 wherein said door base is fixed 
     
     
        relative to said door support arm. 14. The improvement of claim 10 wherein said door operating means comprises a door closer cam provided with a helical slot, means for manually rotating said cam about a longitudinal axis, and a cam follower attached to said stem and fitting within said slot for producing longitudinal movement of said stem in response to 
     
     
        rotation of said cam. 15. The improvement of claim 14 wherein said helical slot is variably pitched for producing a longitudinal movement rate for said stem which varies in accordance with the rotational position of said 
     
     
        cam. 16. The improvement of claim 15 wherein said cam is provided with a lug and said shifting means comprises means cooperative with said lug for causing said sliding of the stem to occur when said cam has been rotated 
     
     
        to a predetermined position. 17. Apparatus for supporting and operating an interiorly fitting door against an entrance aperture in a pressure vessel comprising: means suspended adjacent said aperture for removably mounting said door,   means attached to said door mounting means for supporting said door thereon, said means for supporting including means for both angularly and laterally shifting said door with respect to said mounting means for optimally passing said door through said aperture into the pressure vessel; and   means supported on said door mounting means for engaging and disengaging   
     
     
        said door with the interior side of said aperture. 18. The apparatus of claim 17 wherein said means for angularly and laterally shifting includes a horizontally mounted curved guide member and wherein means connected with said door bears upon said guide member to move said door in a curved arc of lateral displacement while disengaged and within said pressure 
     
     
        vessel. 19. The apparatus of claim 18 wherein said means for engaging and disengaging includes means for urging said door along said curved guide 
     
     
        member as part of the door engaging and disengaging sequences. 20. The apparatus of claim 19 wherein said means for urging includes a cam member operative near one end of an operating stroke of said means for engaging 
     
     
        and disengaging. 21. The apparatus of claim 17 wherein said means for mounting said door include an arm pivotally mounted at a fixed location on 
     
     
        said pressure vessel. 22. The apparatus of claim 17 wherein said means for engaging and disengaging includes a helically slotted rotatable cam member and cam follower means engaged therewith and connected with said door for 
     
     
        stressing said door during engagement with said apparatus. 23. In a pressure vessel comprising a wall having an acess opening, a normally warped closure door which is insertable through said opening, and stressing means for flexing said door against said wall to seal the access opening from the inside, the improvement wherein said stressing means comprises: a door support arm mounted on said pressure vessel exteriorly of said opening,   door operating means mounted on said arm,   cam means including a hollow cylinder provided with a variably pitched helical slot, said cylinder being mounted on said arm for rotation about a generally longitudinal axis in response to actuation of said door operating means, and   door mounting means movably supporting said door along said axis and including a stem which is slidable within said cylinder and which is provided with a projection for mating engagement with said slot whereby operation of said operating means causes movement of said door along said axis at a variable rate corresponding with variations in the pitch of said   
     
     
        helical slot. 24. In a pressure vessel comprising a wall having an access opening, a normally warped closure door which is insertable through said opening, and stressing means for flexing said door against said wall to seal the access opening from the inside, the improvement wherein said stressing means comprises: a door support arm mounted on said pressure vessel exteriorly of said opening,   door operating means mounted on said arm,   cam means provided with a variably pitched cam surface and mounted on said arm for rotation about a generally longitudinal axis in response to actuation of said door operating means,   a shift plate mounted fast to said support arm, said cam means having a projection engageable with said shift plate to cause lateral shifting of said cam in response to rotation thereof, and   door mounting means for supporting said door movably along said axis and cooperating with said cam surface to produce said movement at a variable   
     
     
        rate corresponding with variations in the pitch of the cam surface. 25. Apparatus according to claim 1 wherein said cam comprises a hollow cylinder, said cam surface is a helical slot around said cylinder and said door mounting means comprises a stem slidable within said cylinder and 
     
     
        having a projection for mating engagement with said slot. 26. Apparatus according to claim 25 further comprising a shift plate mounted fast to said door support means, said cam being provided with a projection engageable with said shift plate to cause lateral shifting of said cam in 
     
     
        response to rotation thereof. 27. Apparatus according to claim 26 wherein said support means is an arm hinged to said wall along a fixed hinge line. 
     
     
        8. The improvement of claim 24 wherein said door support arm is hinged to 
     
     
        said wall along a fixed hinge line. 29. The improvement of claim 28 wherein said shift plate has a first lip engageable by said cam projection to cause movement of said door toward said hinge line during door releasing rotation of said operating means and a second lip engageable by said cam projection to cause movement of said door toward the center of said access opening during door engaging rotation of said operating means.