Abstract:
A sliding hatch cover unit for a pressurizable tanker, that carries a dry granular material that is pneumatically discharged, the sliding hatch cover unit having a track mounted hatch cover that can be displaced from a position of safety and a circular hatch port gate that is internally mounted on a hinge within the tank of the tanker through a port in the tank before installation of a port sleeve having a seal engageable with the circular gate in order to use the internal pressure of the tank when pressurized to seal the tank, the gate being hinged and connected to the hatch cover for opening and closing along with the sliding hatch cover.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This invention is an improved slide hatch for bulk carriers and in particular comprises a sliding hatch cover unit with internal seal for pressurizable tanks of the type used for cement tankers. The sliding hatch cover unit includes an actuator system that has an external actuator that displaces both an outside hatch cover and an inside sealing gate. In particular, this invention relates to a hatch cover kit that can be incorporated into a bulk carrier container at the time of manufacture or adapted as a replacement cover system for an after market carrier having a top loading port. 
         [0002]    The slide unit hatch can be used on any bulk carrier vehicle of the type used for transport of dry powdered or granular material that is free flowing in a hopper style container. This description utilizes a cement carrier as a preferred example of the transport carrier contemplated. Bulk transport of dry cement is accomplished utilizing a gondola-style trailer that is loaded with cement from a top port by means of a hose or chute. Typically, the gondola has a tank with sloping sides that converge to a bottom discharge for gravity feed of the cement to a discharge hose that is used to pneumatically deliver the bulk cement to a destination for storage or mixing. To assist in the discharge of the fine powder cement, the gondola tank is pressurized to both compensate for volumetric displacement by the discharging cement and to assist in moving the cement to the discharge pump. 
         [0003]    To maintain a pressure within the gondola tank, the hatch cover must have a sealed engagement with the hatch port at the top of the tank. Typically, the hatch cover is connected to the tank with a hinge and a series of threaded dogs mounted around the hatch cover. When the tank is refilled, the hatch cover must be opened which has customarily required that the driver or assistant climb to the top of the trailer and manually disengage the tie-down dogs to open the hatch. Not only is this task time consuming, but because of the configuration of the tank and carrier trailer the task is dangerous as well. 
         [0004]    The sliding hatch cover unit of this invention relates to my U.S. Pat. No. 6,196,590, entitled “Slide Hatch for Bulk Carrier”, issued Mar. 6, 2001. In the referenced patent, a hatch cover is designed to slide over a hatch port on a track that by cam action forces the cover onto a seat around the port. 
         [0005]    A considerable force is applied to the hatch cover when the tank is even moderately pressurized to 15 p.s.i. for fluidizing and pneumatically conveying the tank contents from the tankers. 
         [0006]    When the bulk material is a dry powder such as cement, that tends to build-up on the cover seat, the seal begins to fail after a number of transport operations. A leaking access hatch lowers the internal tank pressure and delays the unloading process. 
         [0007]    Internal sealing has the advantage of utilizing the force developed by the tank pressure to improve the seating and seal. However, locating an actuator assembly within a tank loading and unloading material like cement is preferably to be avoided to prevent frequent servicing in a difficult environment. 
         [0008]    The subject invention avoids this disadvantage by mounting the primary actuator assembly external to the tank. The use of an internal sealing gate and an outside protective cover improves the longevity of the system before maintenance and cleaning is required. 
         [0009]    In the preferred embodiment described, the cover and gate are linked with the external actuator to reciprocally slide the outer cover and raise and lower the inner gate. 
         [0010]    It is to be understood that the sliding hatch cover unit of this invention can be utilized with a cam assisted covering system as described in the referenced patent with the primary function of the hatch cover being to cover and protect with sealing accomplished by the internal gate. 
         [0011]    In the preferred embodiments of this invention the gate is linked to the cover by cables and operated in conjunction with the sliding of the cover as further described in the summary and detailed description of this invention. 
       SUMMARY OF THE INVENTION 
       [0012]    The sliding hatch cover unit of this invention is designed for a pressurizable tanker, which carries a dry granular material that is pneumatically discharged. The sliding hatch cover unit has a track mounted hatch cover that can be displaced from a position of safety. In the embodiment disclosed, the hatch cover unit includes a hatch port gate that is internally mounted within the tank of the tanker in order to use the internal pressure of the tank when pressurized to seal the tank. 
         [0013]    In the embodiments of the sliding hatch cover unit described, the actuator mechanism that slides the hatch cover to an open position and a closed position also actuates the internal hatch port gate. In the preferred embodiment, a piston and rod actuator mechanism is connected to the hatch cover to open and close the hatch cover. The actuator mechanism preferably utilizes a pair of compact hydraulic actuators arranged on each side of the sliding hatch cover. It is to be understood that a single rod and piston actuator that may be air driven may be utilized instead of the preferred dual actuator system. Alternately, a mechanical winch and spring return system may be employed. 
         [0014]    In order to overcome the problem of pressure leakage around the closed hatch cover during the process of pressurizing the tank for discharge of the contents, the sealing is accomplished from the inside the tank. In this manner, the force of the internal air pressure against the closure member aids in sealing the tank. The closure member comprises a hinged flap plate that engages a gate seat on the inside of the tank port to seal the tank chamber. 
         [0015]    The flap plate is hinged at one side to an internal mount on a cylindrical sleeve that is a component of the hatch cover kit. The plate is actuated by a cable that connects the plate to the sliding hatch cover in a manner that closes the flap plate against the gate seat when the cover is closed. When the cover is opened, the plate drops open by force of gravity. 
         [0016]    Whether the sliding hatch cover is actuated by action of a manually operated cable system or by action of a rod in a pneumatic cylinder actuator, the displacement of the hatch cover is translated to the displacement of the hinged plate for sealing the hatch port. 
         [0017]    In order to adapt the hatch cover kit to an existing bulk carrier tank, the adaptation must be easily accomplished with minimal modification to the existing cover system. Of primary concern is the ability to install a rugged system that will withstand the abuse of the loading mechanism and wear from often abrasive material. 
         [0018]    Additionally, key components, such as the flap plate, must be installed through the loading port of the carrier tank. Repair and replacement of the components must be easily accomplished and, preferably, the cover system should be removable and usable as a unit on another bulk carrier tank. 
         [0019]    These and other features will become apparent on considering the preferred embodiment described in the detailed specification that follows. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1  is a perspective view of a bulk carrier tanker with a sliding hatch cover unit, with piston and rod actuator units arranged on each side of one of the top hatches. 
           [0021]      FIG. 2  is perspective view of a portion of the tank of the bulk carrier and a part of the sliding hatch cover unit without the actuator system. 
           [0022]      FIG. 3  is a top plan view of the sliding hatch cover unit with the cover in the open position and with portions of the cover unit broken away to reveal underlying components. 
           [0023]      FIG. 4  is an end view of the sliding hatch cover unit with part of the tank of the bulk carrier shown in cross section. 
           [0024]      FIG. 5  is a side elevational view of the hatch cover unit of  FIG. 4  partially in cross section with the internal flap plate in an open position. 
           [0025]      FIG. 6  is a side elevational view of the hatch cover unit of  FIG. 4  partially in cross section with the internal flap plate in a closed position. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0026]    Referring to  FIG. 1 , the sliding hatch cover unit of this invention is designated by the reference numeral  10  and is incorporated onto a bulk carrier  12  in the form of a cement tanker  14 . The cement tanker  14  has a trailer carriage  16  with wheels  18  and a frame  20  that supports and contains a pressurizable tank  22 . 
         [0027]    The tank  22  typically has one or more hatches  24  with hatch covers  26  and  28  covering an opening or port  30  for filling the tanker with dry granular powdered material such as bulk cement. 
         [0028]    A conventional hatch cover  26  has a series of perimeter bolts  32  which secure the cover  26  to an elevated rim  34 , which allows the tank to be pressurized for discharge of the contents of the tank  22 . Typically a discharge hose or pipe (not shown) is connected to a discharge unit  36  at the bottom of the tank  22 . The released pressurized air fluidizes the contents during the discharge and pneumatically conveys the fluidized powder material to a delivery terminal. 
         [0029]    Climbing to the top of the tank  22  on the ladder  38  at one end of the tanker  14  to undo the bolts  32  is a danger and inconvenience to an operator. To remedy this situation at least one hatch cover  28  can be removed from a position of safety. Referring to  FIG. 1 , the hatch cover  28  is part of the sliding hatch cover unit  10  which includes, in addition, a pair of slide tracks  40  adjacent each side of the rectangular or square hatch cover  28  and an actuator assembly  42 . The actuator assembly  42 , as shown in  FIG. 1 , schematically comprises a pair of piston and rod units  46  as shown in greater detail in  FIG. 3 . Preferably, the piston and rod actuator assembly  42  can be actuated from inside the vehicle cab (not shown) or by the controls at the side of the tanker. 
         [0030]    In addition, the sliding hatch cover unit  10  includes an internal gate  48  that is preferably actuated by the actuator assembly  42  to seal the tank  22  when the hatch cover  28  is positioned over the port  30 . Preferably, the hatch cover unit  10  is in the form of a compact kit that can easily be installed on an existing bulk carrier with minimal modification. 
         [0031]    In the embodiment of  FIGS. 2-6 , the gate  48  is in the form of a circular flap plate  50 . In the process of pressurizing the tank  22 , the internal pressure will force the plate  50  against an internal gate seat  54  and seal the tank  22 . 
         [0032]    In the preferred embodiment, the gate seat  54  is located at the end of a cylindrical guide sleeve  56  installed within the tank  22 . In the preferred embodiment shown, the sliding hatch cover unit  10  is incorporated onto an existing tanker  14  with minimal modification, using the installation method disclosed. A typical tanker  14  has one or more hatches  24  with elevated rims  34 , having a flange  60  around the circular port  30  for attachment of a cover. 
         [0033]    In the preferred embodiment, the sliding hatch cover unit  10  is connected to the port flange  60  and is supported in part on the top surface of the typical tank  22  of a bulk carrier  12  as an integrated assembly kit. The compact actuator assembly  42  includes a conventional hydraulic system  62 , indicated schematically, that includes the hydraulic and electronic controls (not shown) for remote actuation by a driver in the cab of the carrier and/or at the side of the tanker  14 . 
         [0034]    To install the hatch cover unit  10 , a notch  64  is cut into the lower portion of the original cylindrical port wall  66  that downwardly projects into the interior of the tank  22  to guide the hose or chute during the filling operation. This notch  64  allows a clevis bracket  68  to connect to the lower edge of the guide sleeve  56  without having to extend the guide sleeve  56  beyond the lower edge of the original port wall  66 . The clevis bracket  68  is hingedly attached by a pin  70  to a projecting bifurcated tongue  72 , extending from the underside of the circular flap plate  50 . The circular flap plate  50  is sized with an outer diameter substantially equal to the inside diameter of the port  30  to enable the flap plate  50  to be inserted into the tank  22  through the port  30  before the guide sleeve  56  is inserted, which thereafter reduces the effective diameter of the port  30 . The flap plate  50  has a handle bracket  74  on its upper surface that includes a hole  76  for an anchor pin  77  for anchoring a closure cable  78 . The closure cable  78  and handle bracket  74  provide a convenient means to retrieve the suspended flap plate  50  for fastening after the guide sleeve  56  is inserted into the port  30  and the attached bib plate  58  is seated and bolted onto the existing flange  60  of the rim  30 . In many instances, the existing dog bolt brackets  80  can be fitted with bolt sockets  82  to connect the bib plate  58  to the rim flange  60  with a series of spaced bolts  84  without substantial modification. After seating and securing the bib plate  58  and depending guide sleeve  56  to the port flange  60 , the clevis bracket  68  can be attached to the guide sleeve  56 . If the flap plate  50  is not already connected to the clevis bracket  68 , then the plate is connected to the bracket  68  with the pin  70 . 
         [0035]    This design and method of installing the flap plate  50  and guide sleeve  56  enables the diameter of the hatch opening to be reduced only by the thickness of the guide sleeve  56  and allows the internal flap plate to be mounted as high as possible within the tank  22 . In this manner, the customary loading systems can be used and the downward swing of the cover is minimized. Care must be taken in order not to overfill the tank  22 , making it difficult to swing the flap plate  50  to the closed position. 
         [0036]    The flap plate  50  has a perimeter seal  86  on the upper or top surface that contacts the gate seat  54  to seal the tank  22 , particularly when the tank  22  is pressurized, forcing the flap plate  50  against the gate seat  54  of the guide sleeve  56 . Between the flange  60  of the rim  34  of the tank port  30  and the underside of the bib plate  58  is a seal  88  which becomes air tight when the guide sleeve  56  and bib plate  58  are installed and secured by the perimeter bolts  84 . In this manner, the sliding hatch cover  28  is not required to provide an air tight seal, but merely covers the port  30  to prevent debris or water from entering that portion of the guide sleeve  56  between the closed flap plate  50  and the upper rim  89  of the guide sleeve  56  which projects above the bib plate  58 . 
         [0037]    To displace the sliding hatch cover  28  and swing the hinged flap plate  50 , the actuator assembly  42  is actuated. The actuator assembly can be a simple mechanical system with a crank and spring return, as proposed in my earlier application, or a single or double piston and rod unit. Preferably, the actuator assembly  42  is a hydraulic system with two piston and rod units  46  mounted on each side of the tank port  30  for simultaneous operation. 
         [0038]    The bib plate  58  is generally rectangular and extends over a portion of the top of the tank  22 . The bib plate  58  is supported at the far end by a shell bracket  90  that seats on the top of the tank  22  as shown in  FIG. 2 . The side edges  92  of the bib plate  58  have U-shaped side channels  94  that form tracks  40  for side rollers  96  on downwardly directed cover guides  98  that comprise the sides of the hatch cover  28 . The heavier cylinder piston component  100  of each piston and rod unit  46  are mounted to support brackets  102  extending from the underside of the bib plate  58  on each side of the port  30 . The lighter rod component  104  of the piston and rod unit  46  projects from the piston cylinder component  100  and connects to the outwardly extending end  106  of a cross member  108  at one edge of the sliding hatch cover  28  by pin  110 . In this manner, actuation and extension of the rod component  104  displaces the cover  28  exposing the port  30 . 
         [0039]    The closure cable  78 , which is attached to the anchor pin  77  of the flap plate  50  at one end, is anchored to a cable retainer  112  on the top side of the bib plate  58  at its other end. When the cover  28  is displaced, the closure cable  78  simultaneously slackens and lowers the flap plate  50 , thereby opening the port for filling. The closure cable  78  is carried over a pulley assembly  114  mounted on the underside of the cover  28  and through a notch  115  in the upper rim  89  of the guide sleeve  56  and causes the flap plate  50  to lift when the rod component  104  is retracted and the cover  28  displaced to the closed position, stretching the closure cable  78  over the port opening. As apparent, the cable  78  in the open position is out of the way and does not interfere with the filling of the tank  22 . The bib plate  58  has a cross seal  116  that provides a cover stop and front cover seal on closure, and a cross seal  118  mounted under the cover adjacent the cross member  108  that connects to the piston and rod units  46 . In this manner, with only minor modification to the existing hatch, a sliding hatch cover  28  can be installed as a unit to an existing port  30 . 
         [0040]    While, in the foregoing, embodiments of the present invention have been set forth in considerable detail for the purposes of making a complete disclosure of the invention, it may be apparent to those of skill in the art that numerous changes may be made in such detail without departing from the spirit and principles of the invention.