Abstract:
A hatch useful for forming a portal to a sub-surface facility has a cover plate with a plurality of fasteners around its perimeter. These fasteners apply an adjustable compressive force on the cover plate. A compressible material is affixed to the cover plate inward from the perimeter adjacent to the fasteners. A first vertical portion of a rectangular channel has a first end penetrating the compressive material to form a water barrier with the penetration distance being determined by the compressive force. A mechanical stop determines a maximum penetration depth.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     N.A. 
     U.S. GOVERNMENT RIGHTS 
     N.A. 
     BACKGROUND 
     1. Field 
     This invention relates to a hatch that provides access to a sub-surface facility, such a utility space. More particularly, the hatch includes a watertight seal that is precisely controlled to prevent leakage through the seal due to under-tightening and damage to the seal due to over-tightening. 
     2. Description of the Related Art 
     There are numerous hatches having a top surface flush with another surface, such as a sidewalk or roadway. These hatches provide access to an underlying sub-surface facility. The subsurface facilities frequently contain utility lines, such as power lines or communication lines. It is desirable to prevent the ingress of water, such as during a rainstorm or flood. In the manufacture of hatches, it is known to include a compressible material, such as a gasket, in the assembly to provide a watertight seal. The hatch may be sealed with a plurality of fasteners. As these fasteners are tightened, a penetration force is applied to the compressible material. If the penetration force is too low, a watertight seal is not achieved. If the penetration force is too high, the compressible material is permanently deformed causing a failure in the watertight seal. 
     An accurate penetration force may be achieved by use of a torque wrench or by accurate measurement of the penetration depth. However, it is desirable to minimize the tools carried by a worker and maximize worker efficiency and these options are not ideal. 
     U.S. Pat. No. 4,441,724 to Taylor discloses a threaded post that extends through a gasket to prevent undue crushing of gasket. U.S. Pat. No. 4,768,684 to Dugge discloses and I-shaped metallic spacer that controls the deformation of two gaskets located along the narrowed central portion of the spacer. The disclosed systems are not intended for repeated opening and closing. They require a skilled person utilizing tools, gages and specialized fixtures to install. Both U.S. Pat. No. 4,441,724 and U.S. Pat. No. 7,768,684 are incorporated by reference herein in their entireties. 
     In both disclosures above, spacer accuracy must be carefully controlled and the seal is not intended for frequent opening and closing. There remains, therefore, a need for a watertight seal for a hatch that is frequently opened and closed that is not subject to the above disadvantages. 
     BRIEF SUMMARY OF THE DISCLOSURE 
     Disclosed herein is a hatch useful for forming a portal to a sub-surface facility. The hatch has a cover plate with a plurality of fasteners around its perimeter. These fasteners apply an adjustable compressive force on the cover plate. A compressible material is affixed to the cover plate inward from the perimeter adjacent to the fasteners. A first vertical portion of a rectangular channel has a first end penetrating the compressive material to form a water barrier with the penetration distance being determined by the compressive force. A mechanical stop then determines a maximum penetration depth. 
     A first feature of this hatch is that it forms a watertight seal to keep water such as from rain or flooding out of the sub-surface facility. 
     A second feature is that the penetration depth is kept within predefined tolerances to prevent under penetration of the compressible material, leading to water leakage, and to prevent over penetration of the compressible material that could cause material deformation, again leading to leakage. 
     A third feature is that the dimensional aspects are prepared to insure that over-tightening and under-tightening do not occur. This enables an unskilled operator to accurately seal the hatch and to effectively open and close the hatch using conventional tools. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top view of a watertight hatch as disclosed herein. 
         FIG. 2  is a partial cross-sectional view of the watertight hatch of  FIG. 1 . 
         FIG. 3  is a top view of a portion of the watertight hatch of  FIG. 1  with underlying structure shown in phantom. 
         FIG. 4  is a partial cross-sectional view of an alternative watertight hatch. 
     
    
    
     Like reference numbers and designations in the various drawings indicated like elements. 
     DETAILED DESCRIPTION 
       FIG. 1  is a top view of a hatch  10  having an upper surface that is flush with a surface  12 , such as a sidewalk. The same hatch  10  may be installed flush with other surfaces, such as a roadway, town square, subway platform, or any other relatively flat surface used for pedestrian or vehicle transit. Typically the hatch  10  provides access to subsurface utilities such as power or signal lines. The hatch is formed from a suitable material such as aluminum, stainless steel or steel and may be coated to provide weatherproofing, by preventing damage from heat, sun, water, ice melting chemicals, and the like. The hatch  10  has a channel frame  14 , typically formed from aluminum, circumscribing a cover plate  16 . The cover plate  16  is attached to a hinge  18  at one end allowing it to swing open from the other end  19 . To hold the hatch in place and to compress the gasket, a plurality of fasteners  20  are located around the perimeter of the cover plate  16 . To enable easy opening and closing of the cover plate  16 , a small gap  22 , typically with a width of about 3/16 inch, exists between the channel frame  14  and cover plate  16 . When water flows over the cover plate, such as in rain or flood conditions, the water flows into the small gap  22 . As described below, the hatch  10  is waterproof and effectively prevents the water from contacting the subsurface utilities or other features isolated by the hatch. 
       FIG. 2  is a cross-sectional view of the hatch  10  showing a watertight seal  21 . The channel frame  14  has a partial square or rectangle shape with a first horizontal portion  24  that defines a distance between the edge of the hatch  10  and the cover plate  16 . A first vertical portion  26  extends the entire length of the channel frame. A second horizontal portion  28  has a top surface  30  that is flush with both a top surface  32  of the cover plate  16  and a top surface  34  of the fasteners  20 . This second horizontal portion  28  extends for a portion of the length of the first horizontal portion enabling the cover plate  16  to extend over, and be supported by, a second vertical portion  36  of the channel frame  14 . In addition, a combination of the edge  38  of the cover plate  14  and the shorter length of the second horizontal portion  28  define the gap  22 . 
     Referring to  FIGS. 2 and 3 , the edge  38  includes countersunk portions  40  enabling the head  42  of the fastener  20  to be recessed in the cover plate  16  so that top surface  34  of the fastener  20  is flush with the top surface  32  of the cover plated  16  when the hatch  10  is closed. 
     Referring back to  FIG. 2 , when the hatch  10  is closed, a free end  44  of the second vertical portion  36  penetrates a compressible material  46  to form a waterproof seal. The compressible material is fanned from a material that is not porous to water and that resiliently returns to its original shape when penetration by the second vertical portion terminates by raising the cover plate  16 . A suitable material for the compressible material  46  is neoprene. Other compressible materials that are resilient and weatherproof, such as urethane, may also be used for the gasket. Notwithstanding the resiliency of the compressible material  46 , if penetration is too deep, multiple insertions and removals will permanently deform the compressible material and the material will not return elastically to its original shape. If the fastener is under-tightened and there is inadequate penetration, the seal will not be watertight. To maintain both a watertight seal and elasticity, the penetration is limited to from 15% to 35%, in length, of the thickness, t, of the compressible material and most preferably limited to a penetration of from 23%-27%, in length, of the thickness. 
     The fastener  20  is typically a bolt that is secured to a base  48 , such as by the engagement of threads  50 . The further the fastener  20  is secured into the base  28 , the greater the penetration of the free end  44  into the compressive material  46 . To prevent over-tightening of the fastener  20  and the resultant excessive penetration of the compressive material  46 , a stop  52  is supported by a top surface  54  of the base  48 . When the stop  52  contacts a bottom surface  56  of the countersunk portion  40 , the fastener  20  may not be tightened further and the depth of penetration of the free end  44  is controlled. By accurately controlling the thickness of the stop  52 , the depth of penetration is accurately controlled. 
     To prevent movement of the stop  52 , the stop is preferably affixed to the top surface  54  of the base  48 , such as by welding. As shown in  FIG. 3 , the stop  52  (shown in phantom under the cover plate  16 ) has a width effective to extend from a shaft  58  of the fastener  20  to the edge of the countersunk portion  40 . The stop may extend for essentially the entire length of the base  48  and underlie a row of fasteners (as seen in  FIG. 1 ) or a separate stop  52  may be associated with each fastener  20 . An exemplary stop is formed from a corrosion resistant material such as an aluminum alloy, for example, 6063 aluminum. Exemplary nominal dimensions for the stop  52  are 7/16 inch× 7/16 inch×1.75 inches. 
     Alternatively, as shown in  FIG. 4 , the stop  52  may be omitted and housing  60  for the compressible material  46  has sides  62 , some of which, or portions of which, contact top surface  54  the base  48  when the depth of penetration of the free end  44  is at the proper distance. 
     One or more embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.