Tank cover access hatch with safety barrier

A tank cover, especially a cover on a sewage treatment tank, is provided with an access opening with a liftable hatch cover. Along with the hatch cover is a safety barrier or grate, either connected directly to the hatch cover or to structure surrounding the hatch opening. When the hatch is opened the barrier is deployed to prevent a worker from accidentally falling through the opening. In one form the barrier is pivotally attached to the bottom side of the hatch cover, and can be swung out as the hatch is opened to form an “A” shaped or roof shaped barrier, with the hatch cover and the barrier both inclined and essentially forming a roof over the opening. Braces or struts hold these components in the erected position and provide barriers from the sides. For entry of a person through the opening, the barrier or grate can be retained against the bottom of the hatch cover as the cover is swung fully open, through 180°. In another form the barrier is secured to tank cover structure just below the hatch cover and can be left in place as a horizontal barrier when the cover is fully opened. For access into the tank the barrier/grate can be swung back in the same direction as the access cover and stacked on the opened access cover.

BACKGROUND OF THE INVENTION

The invention concerns liftable hatch covers for decks or tank cover structures, especially for covers over tanks in sewage treatment plants. In particular the invention encompasses a safety barrier or grate that cooperates with the hatch cover and prevents service personnel from falling through an open hatch of such a tank cover.

Tank covers, particularly for sewage treatment tanks, are shown in U.S. Pat. Nos. 6,151,835, 6,012,259 and 5,941,027 of Hallsten Corporation. The tank covers, as well as liftable hatches for incorporation in the tank covers, are typically formed of interconnected extruded aluminum components, as shown in each of the above-listed patents.

The prior Hallsten patents, especially U.S. Pat. No. 5,941,027, show tank access hatches that hinge back a full 180° when fully opened, and this can be achieved via a special hinge, essentially a “gear hinge”.

Such tank access covers, especially for sewage treatment tanks, are opened for several reasons: to enable a worker actually to enter the tank for servicing, or to extend a servicing implement into the tank; or simply to admit a flow of air into the tank for aeration, the air being drawn by a fan located elsewhere in or on the tank. The open hatches present a problem of a worker accidentally falling through the opening.

This problem of open hatches, whether over a hatch opening in a public sidewalk, a floor access hatch, or a roof access opening or skylight, has been addressed previously. For example, see the “Hatch Safety Net”, marketed by Safe Approach of Poland, Me., comprising a polyester net that attaches to hook anchors on an aluminum frame that supports a hinged, solid hatch cover. The safety net can be removed from the hook anchors for access into the space below. The hatch with safety net is described as capable of being retrofitted in floor access hatches, roof scuttles, automatic fire vents or skylights. Also, USF Fabrication of Hialeah, Fla. produces a sidewalk hatch with hatch panels hinged on a frame, and one or more safety grate sections separately hinged along an edge of the frame which is perpendicular to the hinged edges of the hatch covers. The apparatus is described as “Double Safety Grate” or “Hinged Hatch Safety Grate”. The hatch/grate apparatus is typically used for public sidewalk access openings.

Another safety grate product, called “RETROGRATE SERIES X”, is produced by Halliday Products Inc. of Orlando, Fla. An aluminum double-door hatch cover is combined with a grate just below the doors, the grate being swingable upwardly for full access into the space below. Like the previously described product, the grate is pivoted on an axis perpendicular to the pivot axes of the hatch covers themselves.

The above safety grate devices are not directed to tank covers in sewage treatment applications, nor do they exhibit the efficient construction, operation and safety features of the invention described below.

SUMMARY OF THE INVENTION

The invention encompasses several different forms of combined hatch cover and safety grate or barrier, as applied to a tank cover particularly of a sewage treatment plant. The tank cover is formed of assembled plank, edge connector and beam components, primarily aluminum extrusions, as described in the previous Hallsten patents noted above. The access cover for the hatch can advantageously be produced from the same aluminum extrusions, especially the planks and edge connectors (interlocking deck channels).

In a first embodiment the hatch cover/grate configuration of the invention forms a “A” shape when raised to the open position with the barrier deployed.

A hatch cover, preferably with a gear hinge on one edge that allows the hatch to fold completely back onto the deck (through) 180°, has a safety grate attached to its bottom side by a grate hinge. The grate hinge pivots at the forward, free end of the hatch cover, bottom side. Thus, when the hatch cover is opened, the grate structure will hang freely down from the hatch cover, unless latched back to the cover. For access of a person down into the tank, the grate can be held or latched back against the bottom of the hatch cover, to swing the two components back against the deck, stacked together. For using the opening as an air intake vent, the grate can be spread outwardly from the hatch cover, swung about the gear hinge, to the point that the bottom edge of the grate can be engaged against the deck at the edge of the opening, at the opposite side of the opening from the hatch cover hinge. Braces or struts are included as a limiting device, similar to those employed in a step ladder, on both sides, so that an “A” shape is formed. This sets the angle of the grate and cover and allows the hatch opening to serve as a ventilation opening, for admitting air into the tank, and there can be a series of these openings set up for ventilation (one or more fans exhaust the air at points on the tank distant from the hatch openings).

With the struts extended, holding the grate at its fixed position to form an “A”, the struts, the grate and the hatch cover form safety barriers around the opening at all four sides.

Thus, this form of hatch cover/grate serves the dual purpose of (a) allowing full access into the tank when needed; and (b) serving as a ventilation opening when needed, with safety barriers surrounding the hole.

In a second form of the invention the hatch cover can be essentially the same as in the first form, and the grate can also be similar. The grate has a pair of hinge legs extending upwardly (perpendicular to the grate) at its back end. When lying horizontally in the normal position of the grate, the grate will be pivotally connected to a beam or other fixed structure via the vertical legs, lying, for example, a few inches below the deck of the tank cover. The pivot point for the legs preferably is just below and inward of the opening, relative to the hatch cover hinge. Once the hatch cover is opened fully, through 180°, and folded back onto the deck, the grate will provide a protective barrier, lying horizontally across the opening, to prevent fall-through accidents. If access is needed for a person to enter the tank, the grate is simply pulled up and hinged about the pivot points of the legs, to swing the grate back, upside down and stacked against the opened hatch cover. The length of the hinge legs is such as to allow the opened safety grate to lie essentially flatly against the opened hatch cover.

A third form of safety grate arrangement is similar to the second form described above, except that the grate, again with hinge legs at one edge, is hinged at the opposite side of the opening from the hatch cover hinge. The hinge legs allow the grate to sit a selected distance below the closed hatch cover. When the hatch cover is opened, both the hatch and the grate can be fully opened to 180° so that each lies flatly on the deck, on opposed ends of the opening. Alternatively, the hatch can be opened, e.g. to a vertical position, and the grate can be opened at the opposite side of the access hole, also to a vertical position, for ventilation or to allow access into the tank. The system includes some form of hold open device for each of the hatch cover and the grate, such as foldable struts or a telescoping locking strut device, which will stow beneath the deck when the grate and the hatch cover are both closed.

This forms a pair of safety barriers, one at each side of the opening. Flexible lines, such as chains or cords, can be connected from the hatch cover to the grate, spanning across the side spaces that would otherwise be vulnerable to personnel falling into the tank. This provides a four-sided safety barrier around the access hole. If access through the hole is needed, the safety chains or cords at one side can be removed.

A variation of the above embodiment is to have the same hatch cover and grate opened into an “A” configuration, as in the first form described above. The free end of the grate can simply engage into a space at the bottom of the hatch cover, near its free end, and a latch can be provided to retain the two together at this point. A flexible line or chain can be put in place at each open side of the “A” configuration, so that the hatch opening will be protected by a barrier at all four sides.

The grate when in place on the opening can be supported on all four sides, if a typical extruded component as in Hallsten Corporation tank covers or decking is welded to or otherwise fixed to a beam tube at the lateral sides of the hatch opening. These are the sides of the opening that extend at right angles from the hatch hinge. Supporting the grate at all four sides allows the grate to be of lighter materials, for less total weight. The grate in this case could be a lifted-out grate, without hinges, or it could be hinged at one edge.

Essentially the same configuration could be used for another purpose, with a solid inner layer rather than a grate. This is essentially another piece of decking beneath the hatch cover. Such an inner layer can be repeated under all deck or tank cover sections, not only at hatch covers, for providing an insulation layer in the case of a high-temperature sewage treatment process. The system called ATAD (auto thermophilic aerobic digestion) is operated at 180° F., and must be well insulated, up to R-20 insulative value. The deck panels of the invention are essentially all lift-out panels, and the lower panels can also be liftable, so that each panel can provide access.

The hatch cover/safety grate system of the invention is of simple and lightweight construction, is highly compatible with a tank cover of extruded aluminum components, is easily operated, and is effective to prevent fall-through accidents. These and other objects, advantages and features of the invention will be apparent from the following description of a preferred embodiment, considered along with the accompanying drawings.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIGS. 1A-1Cshow a deck or tank cover10, formed almost entirely of interconnected aluminum extrusions, essentially as in the patents of Hallsten Corporation referenced above, as well as other Hallsten patents. The deck or tank cover includes an access opening with a hatch12, openable via a hinge14which, as noted above, can be as described as in Hallsten U.S. Pat. No. 5,941,027. The hatch12includes a handle16which is incorporated in one of the extruded aluminum planks18,18athat form the hatch cover (“hatch”). As explained above, the hatch/safety barrier of the invention is advantageously used in sewage treatment tank covers.

FIG. 2shows the hatch opening closed, with the hatch cover12supported by the hinge14at the left of the drawing, and with a free end20formed as a lip that resides on a flange22which can be part of an extrusion24at the edge of the hatch opening, i.e. fixed structure. A barrier or grate26is shown suspended below the closed hatch12. In this embodiment the grate26is secured by a grate hinge28to the outer extrusion18aof the hatch cover.FIG. 2shows the grate substantially fully engaged against the bottom of the hatch cover, and this configuration can be retained by an appropriate form of latch if desired, such as a simple hook and eye or a slide bolt (not shown).

As shown inFIG. 3, for access the hatch12is swung upwardly about the hinge14, with the grate26retained against the bottom of the hatch cover. InFIG. 4the cover12has been raised sufficiently to deploy the grate26as a safety barrier, spreading it outwardly via the grate hinge28to a fully extended position, shown inFIG. 5. As shown in these views, the pivoted brace30opens in the manner of a stepladder brace, fully extended in the erected position ofFIG. 5. The opened brace30may be permitted to travel slightly over-center to form the locked position. In this configuration the assembly makes an “A” shape, the brace30being repeated at both sides. The grate (barrier)26when deployed engages its foot end against the edge of the access opening, at the extrusion24. This is preferably via an elastomeric end piece, such as a D-seal32as shown.

In the example shown, the access opening has a width (as viewed inFIG. 5) of about two feet eight inches to two feet ten inches, with the hatch12angled upwardly at about 35° (or 25° to 45°). The length of the grate26, i.e. the dimension shown inFIG. 5, can be about 14 inches, or about 13 inches to 18 inches. The dimensions and angles can be selected as desired, and suited to the size of the access opening.

With the braces30, the structure shown inFIG. 5provides a barrier on all sides of the access opening.

FIG. 6is a further illustration of the erected hatch/barrier system shown inFIG. 5. This elevation view is from the right relative toFIG. 5. This view, partially in section, indicates extruded aluminum interlocking beam tubes34that may frame the access opening, these beam tubes34normally being secured to structural aluminum or steel beam tubes36below. The beam tubes34have upwardly hooked flanges at each side as shown. A deck plank38is seen at the far side of the opening inFIG. 6, retained at edges (as with other deck planks) by an extruded aluminum interlocking deck channel or10framing channel40, which has a downwardly hooked flange to be received on the flange. The deck channel40also rests at its bottom side on the beam tube34as shown (on a lateral protrusion34aof the beam tube). This is consistent with typical liftable panels of Hallsten Corporation as seen in previous Hallsten patents.

In the example shown, the spacing from beam to beam (36) can be about three feet, although the dimension can vary as desired. The grate26can have a width of about 24-26 inches, although this, too, can vary. InFIG. 6the grate is seen as a preferably aluminum frame27supporting crossing internal pieces.

The erected configuration shown inFIG. 5is useful when the hatch opening is to used as an aeration vent, as discussed above. When access through the opening into the tank is desired, the hatch hinge14(FIG. 3) allows the hatch12to be completely folded back onto the deck, through 180°. The grate26, preferably latched in place, can remain against the bottom of the hatch, to be stacked on the top of the hatch when the hatch is fully opened.

FIGS. 7 to 15show another form of the invention. In the plan view ofFIG. 7the hatch is closed, the hatch cover being seen at12. Interlocking beam tubes are seen at34, at opposed non-hinge edges of the access opening. In dashed lines the grate26ais indicated, just below the hatch cover12. The sectional view ofFIG. 8, a lateral view taken along the line8-8inFIG. 7, shows the positions of the hatch12and the grate26a, as well as the surrounding interlocking beam tubes34and structural beam tubes36. The hatch12rests via its side edges on structure of the interlocking deck channels34, or structure attached thereto, in the manner shown for another panel inFIG. 6. The hatch is liftable upwardly at a hinge14which is not seen inFIG. 8but is illustrated inFIG. 9. In this embodiment the grate26ais supported in a different way.FIG. 9shows that the grate has, at its back end adjacent to the hatch hinge14, hinge legs42that serve to space the grate downwardly an appropriate distance. The pivot for the grate is at44, below the hatch hinge14and slightly inward of the opening relative to the hinge14. The pivot44is a hinge that occurs at both sides of the grate, or it could be continuous, and it is supported on fixed structure (i.e. the planks18of a panel to the left as seen in the drawing) by a mounting bracket46.FIG. 9shows the point20at which the free end of the hatch12rests on the surrounding deck structure when closed.

FIG. 10shows the hatch assembly of this embodiment with the hatch cover12fully opened, folded back against the deck. The grate26aprotects against fall-through accidents at the opening. The brackets46that support the grate for pivoting are seen in dashed lines inFIG. 7.

The side elevation views ofFIGS. 11 and 12indicate the opening of the hatch12and its fully opened position. The free end of the grate, at48, rests on fixed structure of the adjacent panel or other structure (not shown), or it can simply be supported fully along the length of the sides, as shown schematically inFIG. 8.

FIGS. 13 to 15show opening of the grate for access of a service person into the tank.FIG. 8shows that, as here, both the hatch and the grate preferably are fully supported along the length of both sides, via engagement of extrusions. The beam tube36, below34, supports fixed structure to receive the grate26a(a ledge49is indicated schematically for support at both sides of the grate). InFIG. 14two different positions of the grate are shown, as it is swung upwardly.FIGS. 14 and 15show the reason for the hinge legs42, the length of which is just enough to allow the grate26ato lie flatly against the opened hatch cover12.

FIGS. 16 to 22show another form of the hatch/grate system of the invention.FIG. 16is a plan view, with the hatch closed and the grate26ain place below. A sectional elevation view looking left would be similar toFIG. 8, in regard to position and supporting of the hatch12and the grate26bbelow. Note that the apex of the triangle indicator in these plan views denotes the hinge side of the hatch.

FIG. 17is a section view looking in the plane17-17inFIG. 6, i.e. a side view. The hatch is at12, with the hinge of the hatch shown at14. The principal difference in this embodiment is that the grate26bis supported at the opposite end as compared to the embodiment ofFIGS. 7 to 15. The grate26bhas hinge legs42, similar to those shown inFIGS. 9-15, establishing a spacing of the grate26bbelow the deck appropriate to allow the grate to be folded back through 180°. In this case the grate will be opened in the opposite direction from that of the hatch, so that when fully opened, the two will lie at opposite ends of the access opening.

FIG. 18shows the hatch both fully opened, lying on the deck at the left side of the access opening as seen in this plan view. The barrier or grate26bis in place, for protection against fall-through accidents. The pivot or hinge support of the grate is indicated at46, and is similar to that shown inFIGS. 11-15, although at the opposite end of the opening. Side support for the grate, at both lateral sides, is not shown but preferred.

The position shown inFIG. 18is appropriate for using the opening as an air intake, as discussed above. The components can assume different positions, as well, for use as an air intake.FIG. 19illustrates the swinging up of the hatch cover12, andFIG. 20shows the upward deployment of the grate, as the hatch12is held in position. Once the components reach the position shown inFIG. 20, they can be secured together as inFIG. 21, in the “A” configuration. For this purpose a bracket50is included on the bottom side of the hatch, near its outer end. This can have pins that couple with structure or openings in the grate, to retain the erected configuration shown inFIG. 21. Also, chains or flexible lines can be included, one at each side of the erected hatch/grate assembly, to provide a form of safety barrier at all four sides, in conformity with safety requirements.

As noted above, if access through the opening is needed, the hatch12and the grate26bcan each be fully swung to 180°, to rest against the deck. The hinge legs42at the hinged end of the grate have length selected for this purpose.

FIG. 22shows an alternate erected configuration for the hatch12and grate26bofFIGS. 16-21. In this case each is set to a vertical configuration, with pivot braces30provided at each side of each of the hatch and grate, as schematically shown in the drawing. The lower ends of these foldable braces can be secured to the interlocking beam tube34or structural beam tube36, or to structure supported by those members.

InFIG. 22pairs of chains or cables52are shown at upper and lower locations, extending between the hatch cover12and the grate26b, to provide a four-sided safety closure around the opening. The height of the upper cable52is such as to meet safety handrail requirements.

As explained above, the assembly shown inFIGS. 16 to 22can be modified for a special purpose, such as for ATAD, a sewage treatment system operated at high temperature, e.g. about 180° F. Lower support plates can be placed in a position of the horizontal grate26b, potentially capable of lifting out, but preferably not pivoted. These can provide a means for insulating the space between the deck panels and the barrier plate, and this can occur at every panel of a deck or tank cover.

FIGS. 23 and 24illustrate one implementation of such a system for insulation. InFIG. 23a liftable panel60is shown, broken away at ends (left and right in the drawing) and of any desired length. No hinges are shown in the drawing; the panel60could be hinged at one end, or simply configured as a lift-out panel. As in the other embodiments, interlocking beam tubes34support panels typically at both sides of the beam tube, with the beam tubes34in turn supported by structural (preferably aluminum) beam tubes36. The panel is not affixed to the interlocking beam tubes34, but rests on extruded flanges as explained above and as typical of tank covers of Hallsten Corporation. Note that this detail can be typical for all panels in a tank cover.

Beneath the lift-out panel60is a lower support plate or solid inner layer62which is analogous in some respects to the safety grate discussed above. The support plate62can also be formed of aluminum planks and interlocking deck channels at edges of the series of planks, and it can rest on brackets64secured to the structural beam tubes36, as illustrated. It is thus supported at sides in the same manner as shown inFIG. 8for the illustrated grate discussed above. A section of rigid insulation is shown at65, supported on the removable support plate62. To allow for the insulation section to be installed and removed as needed, it has edges that terminate at a gap66, thus being of less width than the opening formed when the lift-out panel or hatch60is removed. Small end pieces65acan be located to fully extend the insulation to the beams36, resting on the structure64at both sides.

As explained earlier, such insulation can be installed to provide an insulative value up to R-20, for a high-temperature sewage treatment process. In this way, the illustrated assembly allows for full access into the tank by removal of the lift-out panel or hatch60, then the insulation section65, and finally the support plate or solid inner layer62. When all are in place and installed, the solid inner layer62provides an air space below the liftable cover panel60which provides a small degree of thermal barrier. The insulation65and65afills essentially all this space, to result in an effective insulative barrier for the high-temperature process.

FIG. 25shows the system ofFIGS. 23-24but with both the deck panel60and the lower plate62being hinged, as in some of the hatch arrangements discussed above. In the elevational section views ofFIGS. 25-26, seen in the direction perpendicular to that ofFIG. 24, the system functions as a hatch opening with cover, but in this case the lower hinged element62is not a safety grate but an essentially impermeable lower plate or panel. A two-arm brace30can be included, as explained above, to hold the lower plate62in an opened position, and a hinge leg42is included so that the plate62could be folded all the way back, at 180°, if desired. In this case the insulation panel65is secured to the liftable deck panel60, and remains with the deck panel when it is swung open about its hinge14to the folded-back position as shown inFIG. 25. This provides access through the opening.

FIG. 26shows a deck or tank cover opening with the same components as inFIG. 25, but with both the hinged deck panel65and the solid barrier62opened to vertical position, again to allow access into the tank. This is essentially the same as inFIG. 22described above, with foldable braces30for each of the components65and62, but with the insulation panel65attached to the underside of the deck panel60. As inFIG. 22, safety lines or chains52are shown secured between the deck panel and the lower plate62, for safety requirements. These can be released at one side for access.

The assemblies described above are simple in construction and efficiently operated to provide, in main embodiments, safety barriers at tank cover access openings. The barrier or grate is in place for any situation wherein the access opening is to be left open for a period of time, and this can include use of the openings for admission of air for aeration or ventilation of the treatment process in the tank. The system of simple and interconnectable components is more efficient than the previously described safety barriers.

The above described preferred embodiments are intended to illustrate the principles of the invention, but not to limit its scope. Other embodiments and variations to these preferred embodiments will be apparent to those skilled in the art and may be made without departing from the spirit and scope of the invention as defined in the following claims.