Patent Publication Number: US-7216459-B1

Title: Access hatch cover assembly with lift-assist assembly and method therefor

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to a cover for hatches, manholes and the like, and more particularly to a hatch cover with a spring assembly to assist in lifting the hatch cover lid. A method of assembling the spring assembly is also disclosed. 
     Today, sewers, subway systems, electrical wiring, plumbing, and a host of other modern necessities are located underground. These necessities require the capability of being accessed. As such, openings large enough to accommodate individuals, equipment, pallets of material or the like are commonplace. These openings generally take the form of manholes or hatches. 
     Many manholes or hatches must be covered because they are needed in places where they are crossed over by pedestrians, cars, trucks, and even aircraft. The covers on the manholes or hatches must be heavy enough so that the air or water pressure inside the cavity beneath them will not lift the cover off the opening. More important, covers need to have sufficient structural integrity so that they will not be compromised under the weight of vehicles passing over them. 
     Covers for openings along streets, roadways, runways, and the like are constructed of iron, steel, aluminum, concrete, plastic or other strong materials. Such covers may weigh several hundred pounds depending on the size of the opening needed to access the cavity. Periodically, covers are lifted so that the cavity can be accessed. Due to the weight of the covers, service personnel must normally work in pairs or use additional equipment to ensure safe handling of the covers. 
     Attempts have been made to solve the problem of safely and easily opening and closing the covers of the underground openings. These attempts involve using covers with spring-biased assemblies to assist in the lifting of the covers. For example, in U.S. Pat. No. 5,788,406, issued to Hernandez on Aug. 4, 1998 shows a device to assist in the opening of a manhole cover. In Hernandez, a spring and pivot rods are attached to both a cover and a stepped skirt that is seated into the opening. The cover may be lifted so that a worker may access the opening. However, the diameter of the stepped skirt is much larger than the actual opening diameter, and the biasing mechanism appears somewhat complex. Both characteristics add to the expense of the entire cover. 
     A simpler prior art device is shown in  FIG. 1 . The biasing assembly “B” is connected to the wall “W” defining the opening, and to the cover “C.” Walls are commonly constructed from concrete, see partial wall “W” shown by way of example. These hinged covers have a spring “S” mounted to the wall of the structure and/or frame. However, there are several disadvantages with this particular design. First, the biasing assembly B encroaches into the opening, which requires workers to negotiate the assembly when entering or exiting the openings. Such negotiation is made more difficult if the opening is small and the worker is carrying tools and equipment. Second, this post construction modification can place a stress concentration at or near the attachment site. Over time, material fatigue may cause failure of the spring mounting assembly and/or failure of the fasteners used to connect it to the wall. In addition, the pressure from the spring can cause the frame to break free form the surrounding concrete. 
     Other prior art spring assemblies are often post construction modifications for existing hatches or manholes. However, it is more complicated to retrofit a spring assembly onto an existing hatch or manhole that one that is already in existence. Further, spring-biased assemblies such as that shown in  FIG. 1  can be difficult to service because the spring is connected to the wall W and cannot be practically removed from the opening without damage. 
     Accordingly, a need exists for a spring assembly for lifting lids of hatch or manhole covers, such assembly containing a minimal number of parts to reduce complexity and/or costs associated with manufacturing and servicing of the assembly. Further, a need exists for a spring assembly that does not significantly impede workers, equipment and other items from entering and exiting the opening. 
     SUMMARY OF THE INVENTION 
     The present invention provides for a spring assembly for a hatch cover that is cost-effective, does not substantially interfere with the opening of the cover, and solves the problems raised or not solved by existing designs. 
     The invention generally comprises a hatch cover with a lid that is hinged to a frame. Generally, a spring assembly is attached to the underside of the lid so that it only makes sliding contact with the frame. One advantage of this construction is that the spring assembly can be removed or replaced with speed and ease. Another advantage is that by attaching the spring to the lid, the spring body moves out of the way of the opening as the lid opens, making it easier for people or objects to move through the hatch. 
     In one aspect of the invention, the lid has several rings aligned across a rear edge of the underside of the lid, near the hinged connection. A torsion spring, with a clip arm and a spring arm extending from opposite ends of the spring body, is attached to the underside of the lid so that the spring body is aligned with the rings. The clip arm is selectively connected to the underside of the lid, and the spring arm extends outwardly so that when the lid is in a resting open position, the spring arm makes contact with the frame. A spring support extends through the spring and rings to keep the spring in place with respect to the lid. Closing the lid winds the spring. Thus, the spring biases the lid toward an open position to assist a person in opening the lid. Multiple springs may be used rather than a single spring. 
     In another aspect of the invention, the spring is attached to the lid with a different structure. Either one or a pair of spring receptors are attached to the underside of the lid near the hinge, instead of having rings attached to the lid underside, and having a separate spring support that extends through the rings. The spring receptors are shaped so that the spring body can slide thereon and be held selectively in place by securing the clip arm to the lid. As in the previous embodiment, the spring biases the lid toward an open position. 
     In yet another aspect of the invention, the structure to which the spring is attached encloses the spring coil. 
     In any of the above embodiments, the hatch may include a latch to keep the lid shut, and a safety arm to keep the lid open. In addition, the lid to which the spring or springs may be attached may be made in various shapes. 
     The method of assembling the hatch is as follows. The underside of the lid is made accessible. If a ring/spring support attachment is used, the clip arm of each spring is attached to the lid underside so that each spring body is aligned with the rings. The spring support is slid through each spring body and the rings. The spring support is selectively locked into position. The spring arm is in a position so that it can slidingly engage the frame as the lid opens and closes. 
     If the spring receptor(s) are used, each spring is slidingly placed onto a spring receptor and the clip arms selectively locked to the lid underside so that each spring will not slide out of place. As described above, each spring arm is in a position so that it can slidingly engage the frame as the lid opens and closes. 
     If the spring receptor encloses the spring, each spring is inserted into the spring receptor. The clip arm extends through an aperture in the spring receptor and secured so that it will not slide out of place. Each spring arm is positioned to extend from the spring receptor and slidingly engage the frame. 
     While one possible application of the present invention is in connection with airport hatches and hatch covers, many other applications are possible and references to use in connection with airport hatches and hatch covers should not be deemed to limit the scope of the present invention. For example, the invention could be used for manholes, and may be used in city streets, subways, industrial plants, ports or the like. The terms “cover,” “rim,” “lid,” “spring,” “safety arm,” “opening,” “base,” or “hatch” as used herein should not be interpreted as being limited to specific forms of a cover, rim, lid, spring, safety arm, opening, base, or hatch. Rather, these elements may have a wide variety of shapes and structures. 
     These and other objects and advantages of the present invention will become apparent from the detailed description, claims, and accompanying drawings. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional side elevation of a prior art hatch cover with a spring assembly in a closed position; 
         FIG. 2  is a front perspective view of one embodiment of a hatch cover secured in an open state by an optional safety arm, showing a lid, a rim, and a spring assembly of the present invention; 
         FIG. 3  is sectional side-elevation view of the hatch cover of  FIG. 2  taken in the plane of line  6 — 6 , with the cover in a partially closed state, and showing an optional safety arm in a removed position; 
         FIG. 4  is sectional side-elevation view of the hatch cover of  FIG. 2 , with the cover in a fully closed state, without the optional safety arm; 
         FIG. 5  sectional rear-elevation view of the hatch cover of  FIG. 4  taken in the plane of line  5 — 5 ; 
         FIG. 6  sectional side-elevation view of the hatch cover shown in  FIG. 2  taken in the plane of lines  6 — 6 ; 
         FIG. 7  is an exploded view of the hatch cover shown in  FIG. 2 , with the addition of an optional latch mechanism; 
         FIG. 8  is a top plan view of the hatch cover shown in  FIG. 7 , minus the optional safety arm; 
         FIG. 9  is a side elevational view of the hatch shown in  FIG. 8 , taken in the plane of lines  9 — 9 , and showing a pry bar in a position prior to disengagement of the latch; mechanism. 
         FIG. 10  is an exploded view of a further embodiment of the hatch cover, showing an alternative spring attachment along with an optional latch; 
         FIG. 11  is a top plan view of the hatch cover shown in  FIG. 10 , showing the latch in a locked position; 
         FIG. 12  is sectional side-elevation view of the hatch cover of  FIG. 11 , taken in the plane of lines  12 — 12 ; 
         FIG. 13  sectional rear-elevation view of the hatch cover of  FIG. 1  taken in the plane of lines  13 — 13 ; 
         FIG. 13A  is a sectional rear-elevation of the lid shown in  FIG. 13 , without a spring attached thereto; 
         FIG. 14  sectional side-elevation view of the hatch cover shown in  FIG. 11 , shown in an open position; 
         FIG. 15  is a perspective view of the optional latch shown in  FIGS. 8–14 ; 
         FIG. 16  is a plan view of another embodiment of the hatch showing a swivel safety arm; 
         FIG. 17  is a sectional side-elevation view of the hatch shown in  FIG. 16 , taken in the plane of lines  17 — 17 , except shown with the lid open; 
         FIG. 18  is a top plan view of another embodiment of the hatch having a different spring receptor; 
         FIG. 19  is a sectional side-elevation view of the hatch shown in  FIG. 18 , taken in the plane of lines  18 — 18 ; 
         FIG. 20  is another embodiment of the hatch having with a different shape lid and location of the spring assembly; 
         FIG. 21  is a sectional rear-elevation of the hatch shown in  FIG. 20 , taken in the plane of lines  20 — 20 ; 
         FIG. 22  is a sectional side-elevation of the hatch shown in  FIG. 20 , taken in the plane of lines  22 — 22 ; and 
         FIG. 23  is a sectional side-elevation of the hatch shown in  FIG. 22  with the lid in an open position, having the optional safety arm removed. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Illustrative embodiments of a hatch cover (identified generally as  30 ) in accordance with the present invention are shown in  FIGS. 1 through 23 . While the invention may be susceptible to embodiment in different forms, there are shown in the drawings, and herein described in detail, certain illustrative embodiments with the understanding that the present disclosure is to be considered an exemplification of the principles of the invention. This specification is not intended to limit the invention to those embodiments illustrated and described herein. Additionally, features illustrated and described with respect to one embodiment could be used in connection with other embodiments. 
     In general for all embodiments, the hatch cover  30  generally comprises a frame  32 , a lid  34  hinged to the frame, and a spring assembly  36  connected to the lid. Frame  32  is adapted to be seated into a cavity opening. For example, the opening may allow access to a sewer or utility tunnel in a public street, or may allow access to a tunnel located in an airport tarmac or hangar. Such openings are typically defined by a concrete wall  38  or the like, as shown by example in  FIG. 4 . It is not essential to the present invention that hatch cover  30  is set into concrete on site, or set into a concrete frame which is later set into a particular site. The frame  32  and lid  34  may be formed of any durable material such as metal. Preferably, the frame  32  and lid  34  are formed of iron, steel, aluminum, or the like and most preferably of gray, ductile, or austempered ductile iron. The frame  32  and lid  34  may be manufactured by casting, molding, or any other appropriate method. 
     Referring to the embodiment shown in  FIGS. 2 through 9 , frame  32  is most preferably rectangular in shape, and generally constructed from two pairs of opposite and upright side-walls  40   a  and  40   b  connected together to form four corners  42 . Of course, the side-walls  40   a  and  40   b  are may be curved rather than straight, and are not necessarily equal in length. Alternative frame shapes include, but are not limited to, trapezoids, truncated circles or squares. The only limit to the shape of frame  32  is to any shape that allows the spring assembly  36  to function as described below. 
     Referring to  FIGS. 2 and 4 , a flange or lip  44  extends at least outwardly from the top edge of each side-wall  40   a ,  40   b . Lip  44  may be positioned not only at the top edge of the side-walls, but at the bottom edge or anywhere between. Vertical gussets  46  may be used to support lip  44  at each frame coiner  42  for added structural integrity. In addition to lip  44 , a seat  48  extends inward around the inner perimeter of the side-walls  40   a ,  40   b . Seat  48  supports the weight of lid  34  and any added loads thereto when lid  34  is in a closed position. Most preferably, horizontal fillets  50  are located at each corner of the seat for ease of manufacture, structural stability of the overall frame, and reduction of stress concentrations. As seen in  FIG. 4 , seat  48  is most preferably recessed below the top surface  51  of lip  44 . Recessing seat  48  by a distance equal to the thickness of lid  34  will allow the lid to be flush with lip  44  when in a closed position. Though this arrangement is desirable in most hatch/manhole cover applications, the present invention is not limited to lids  34  having a flush fit with respect to frame  32 . 
     Referring now to  FIGS. 2–4 , a pair of lugs  54  extend oppositely from seat  48  at side-walls  40   a . Each of the lugs  54  functions as a bearing surface and guide for the spring assembly  36 . As will be described more fully herein, a pair of spring arms  68  extend from spring assembly  36  and each bear against a corresponding lug  54  whether the lid  34  is in an open or closed position. Preferably, as seen in  FIG. 2 , a ridge  59  extends upwardly from the end of each lug  54  so that spring arms  68  do not slip off of lug  54 . 
     Referring now to  FIGS. 6 and 7 , each of a pair of hinges  60  extends from the rear side-wall  40   b . Lid  34  pivots from an open position to a closed position about hinges  60 . Preferably, hinges  60  are constructed from a female hinge portion  62 , a male hinge portion  64  and a hinge pin  66 . The female hinge portion  62  may extend from the rear side-wall  40   b , and the male hinge portion  64  may extend from the corresponding rear edge of lid  34 . A hinge pin connects the hinge portions  62  and  64 . Other types or arrangements of hinges may be used. The type of hinge shown in the  FIGS. 2–7  is commonly used for cast, fabricated or molded components. 
     Lid  34  may have a grid of ridges or ribs  70  on its underside. Ribs  70  may increase the stiffness of the lid  34 , and may be formed in various configurations other than that shown. Lift handles  73  may be located on the top surface of lid  34  as shown in  FIG. 8 , but are not essential to the present invention. If lift handles are used, there may be handle indents  76  visible from the underside of lid  34 , as seen in  FIG. 7 . 
     In one embodiment of the present invention as shown in  FIGS. 7 and 8 , lid lift assistance is provided by a spring  90  and the means used to selectively attach spring  90  to lid  34 . Spring  90  is a torsion spring, and is preferably made from stainless steel. Other materials such as spring steel or the like may be used. On the underside of lid  34 , adjacent the edge where hinge portions  64  are located, is a series of rings  72  formed integrally with ribs  70  and lid  34 . Preferably, three rings  72   a ,  72   b  and  72   c  are used, but this number may vary. 
     In some instances, only one spring  90  is used. In this case, one of the springs  90  is simply omitted. This is true regardless of which embodiment of lid  34  is used. The number of springs used is generally dependent upon the weight of lid  34 , the amount of force required to lift lid  34 , and the amount of spring force provided by spring  90 . 
     In the first embodiment shown in  FIGS. 2–9 , the spring will be designated as spring  90   a . Spring  90   a  has two arms extending therefrom. The first is a spring arm  68  which extends outwardly from the spring body. The second is a clip arm  94  tangentially extending from the spring body in straight torsion. Preferably, the angle between the spring arm  68  and the clip arm  94  ranges between about 90 to about 130 degrees in a free or equilibrium position. In this embodiment the spring  90  is in a free position when lid  34  is completely open. Spring  90  may have a stiffness such that lid  34  does not shut completely when the only force acting upon the spring is the weight of lid  34 . That is, preferably, a force in addition to the weight of lid  34  will be required to shut the lid completely. A person standing on lid  34  may provide adequate force to shut the lid and employ a latch, bolt, lock or other fastener to keep the lid in a closed position. In addition, the stiffness of spring  90  may be selected so that the force of closing the lid  34  shut will enable a latch or other fastener to keep lid  34  in a closed position. 
     Referring still to the embodiments shown in  FIGS. 2–9 , a spring support is used to connect spring  90  to lid  34 . In the preferred embodiment shown, the spring support takes the form of a cylinder  98  or hollow tube, but other forms, such as a simple bar of any cross section, may also be provided. Cylinder  98  slidably attaches to lid  34  by sliding axially through rings  72 , and is held into place with a set screw  99 . Preferably, the outer diameter of cylinder  98  is slightly less than the inner diameter of spring  90  when lid  34  is in a closed position. The spring support may be made of any durable material, preferably a metal such as iron, steel, aluminum, or the like, and most preferably galvanized steel. 
     In any of the embodiments as shown in  FIGS. 2–9 , hatch cover  30  may have a safety arm  110 . The purpose of safety arm  110  is to selectively prevent lid  34  from closing. Safety arm  10  is selectively connected to lid  34  either in a stored position as seen in  FIG. 9  or in a deployed position as shown in  FIG. 6 . In the most preferred embodiment, safety arm  110  is J-shaped, made from a bent rod having a first end  112  with two bends and a second end  114  with a single right-angle bend or an acute-angle bend. In the most preferred embodiment the two bends of first end  112  total about 180 degrees. The distal portion of first end  112  may be inserted into an aperture  116   a  or  116   b  located in one of the ribs  70 , or the like. Aperture  116   a  is located on the underside of lid  34 , far enough from hinges  60  so that lid  34  may completely close when end  112  of safety arm  110  is placed within aperture  116   a . Aperture  116   b  is located on the underside of lid  34 , close enough to hinges  60  so that, when the first end  112  of arm  110  is inserted therein, second end  114  extends downward past the seat  48  and contacts the wall (not shown) of the opening. In use, the user of the hatch  30  may open lid  34 , remove first end  112  of arm  110  from aperture  116   a , and place the first end of the arm into aperture  116   b , thus permitting second end  114  to contact the wall and by that means secure and support lid  34  in an open position. 
     To assemble spring  90   a  onto the lid  34  shown in  FIGS. 2–9 , the following procedure is preferred. Lid  34  is either resting on hinge  62  in an open position or completely detached from the frame. As can be seen by comparing  FIG. 2  with  FIG. 7 , the clip arm  94  of spring  90   a  is placed into aperture  101  located in the rib  70  of lid  34 , and the spring arm  68  is in contact with lug  54 . This step is repeated if two springs  90   a  are used. Cylinder  98  is slid through the body of each spring  90 , and through rings  72   a ,  72   b  and  72   c , so that it is about centered with respect to lid  34 . Cylinder  98  may be kept in place by any suitable means, most preferably with a set screw  99  threaded through one of the rings, central ring  72   b , and at least into contact with the surface of the cylinder. The set screw  99  may even penetrate into the surface of the cylinder  99 . To replace a spring  90   a , this procedure is reversed and repeated. 
     Referring now to  FIGS. 10–14 , a different embodiment of the invention includes spring receptors  80  to connect springs to the lid. In this embodiment, ribs  70  may be present at least to the extent necessary, and configured so as, to support the spring assembly  36 . Preferably in this embodiment, two sets of ribs  70  are formed on or attached to the underside of lid  34 , a longitudinal set  70   a  and a transverse set  70   b . The length of ribs  70   a  and  70   b  are such that they fit within the inner perimeter of seat  48 . Each spring receptor  80  extends outwardly substantially perpendicular from one or both of the longitudinal ribs  70   a  adjacent the hinges  64 . As seen in  FIG. 12 , in this embodiment a lateral cross-section of spring receptor  80  reveals a profile that is formed in a hemi-cylindrical shape. Preferably the outer surface of receptor  80  has a radius that is the same as, or just less than, the inner radius of the spring  90 . 
     Referring still to the embodiment shown in  FIGS. 10–14 , spring  90  differs in only one respect, and will be designated as spring  90   b . Referring to  FIGS. 11 and 13 , the difference is that the clip arm, designated here as clip arm  95 , does not tangentially extend from the spring body in straight torsion, but rather extends away from the spring body generally in the direction of the spring-body axis. The length of clip arm  95  is such that it extends through and beyond an aperture  103  provided for that purpose in the adjacent rib  70   a . Spring  90   b  is fastened in place, preferably with a cotter pin (not shown) that extends through an aperture located in the distal end of clip arm  95 . The cotter pin or other means of fastening substantially prevents clip arm  95  from sliding out of aperture  103 , thereby keeping the spring body from moving along the axis of spring receptor  80 . 
     To assemble spring  90   b  onto the lid  34  shown in  FIGS. 10–14 , the following procedure is used. With lid  34  resting on hinges  62  in an open position, the spring  90   b  is slid onto spring receptor  80  so that clip arm  95  is placed into aperture  103  located in the rib  70  of lid  34 , and the spring arm  68  is in contact with or slidingly retained by lug  54 . If the spring arm rests atop lug  54 , a cotter pin or other fastener is placed on the clip arm  95  of spring  90   b  so that the spring cannot slide off from the spring receptor  80 . If lug  54  is designed to slidingly retain spring arm  68 , the spring  90  will stay in place without any cotter pin or other fastener. To replace a spring  90   b , this procedure is reversed and repeated. 
     Referring now to  FIGS. 16 and 17 , an alternative embodiment for a safety arm is shown. In this embodiment, safety arm  170  is rotatably connected to the inside surface of frame  32 , preferably between hinges  62 . Specifically, safety arm  170  is connected to a bracket  172  by extending a hinge pin  174  through the bracket and a slot  176  in the proximal end  178  of safety arm  170 . By positioning pin  174  in the most inner end of slot  176 , the safety arm is positioned so that lid  34  cannot inadvertently fall closed. By positioning pin  174  in the opposite end of slot  176 , the safety arm  170  may be rotated to lie in horizontally in the plane of the frame opening to allow lid  34  to close, or could hang straight down into the opening. The length of safety arm  170  is such that it can be aligned with latch  120 . The edge  180  of proximal end  178  is contoured so that it does not interfere with the frame when safety arm  170  is rotated to the horizontal position shown in  FIG. 16 . 
     Referring now to  FIGS. 18 and 19 , another embodiment of the hatch is shown. The only substantive difference between the hatch of  FIGS. 18 and 19  and the hatch of previously described embodiments is that spring receptors  200  are provided, for the purpose of receiving a spring in the interior thereof. That is, spring receptors  200  replace rings  72  ( a–c ) and cylinder  98  of the embodiment shown in  FIGS. 2 through 9 , and also replace the spring receptors  80  of the embodiment shown in  FIGS. 10 through 14 . Spring receptors  200  are preferably cast integrally with lid, and have a hemi-cylindrical cross section so that the curved portion  202  substantially corresponds with the shape of spring  90   c . The side walls  204  extending from the curved portion  202  may extend between a rib  70  and the spring arm  68  extending from spring  90   c . Spring  90   c  is substantially the same as spring  90   b  shown in  FIG. 10 . Spring receptors  200  may be used with differently shaped lids  34 . 
     To assemble spring  90   c  onto the lid  34  shown in  FIGS. 18 and 19 , the following procedure is used. Lid  34  is set up in hinge  62  in an open position. The spring  90   c  is slid into spring receptor  200  so that clip arm  95  is placed into aperture  103  located in the rib  70  of lid  34 , and the spring arm  68  is in contact with or slidingly retained by lug  54 . If the spring arm rests atop lug  54 , a cotter pin or other fastener is placed on the clip arm  95  of spring  90   b  so that the spring cannot slide off from the spring receptor  80 . If lug  54  is designed to slidingly retain spring arm  68 , the spring  90  will stay in place without the cotter pin or fastener. To replace a spring  90   c , this procedure is reversed and repeated. 
     Yet another embodiment of the invention is shown in  FIGS. 20–23 . Here the hatch cover  30  generally comprises a lid  210 , a frame  212  and a spring assembly  214 . Lid  210  is attached to frame  212  at hinges  215 . Lid  210  is similar in construction to lid  34 , except that is circular in shape and has radial ribs  216 . Spring assembly  214  is located near the edge of lid  210 . The spring assembly  210  shown is very much like that shown in  FIG. 10  except that the springs may be smaller in length. That is, in this embodiment spring receptor  221  is constructed similarly to spring receptors  80 . However, the spring receptors could be adapted so that they work similarly to those shown in  FIG. 7  or  18 . 
     The spring arm  220  is preferably oriented so that it slides against the inner wall of frame  212  when the lid is positioned from an open to a closed position. Specifically, as seen in  FIG. 22 , spring arm  220  rests against the edge  222  of frame  212  when in a closed position. In the alternative, spring arm  220  rests against edge  224  when in an open position. Most preferably, the angle between the spring arm  220  and lid  210  is about 80 degrees when the lid is closed, and about 22 degrees when the lid is open. These angles are indicated in  FIGS. 22 and 23  as D′ and D″ respectively. 
     To assemble spring  90   d  onto the lid shown in  FIGS. 20–23 , the spring  90   d  is slid onto spring receptor  221  so that clip arm  223  extends therethrough where it is subsequently locked or secured. Spring arm  221  is oriented so that it is in contact with frame  212 . To replace a spring  90   d , this procedure is reversed and repeated. 
     Referring to  FIGS. 7 ,  8 ,  10 ,  11 ,  15 ,  18  and  20 , this invention provides for an optional latch  120 . The purpose of latch  120  is to lock or keep lid  34  in a closed position. Latch  120  may be incorporated into any of the embodiments discussed supra. Referring to the embodiment shown in  FIG. 15 , latch  120  preferably has a body  122  with a curved or wedge-shaped leading edge  124  and a means for removable attachment  126 , such as a threaded rod, extending from a rear edge  128 . Referring to  FIGS. 8 and 9 , as an example, latch  120  is attached to lid  34  at an aperture  132 . A slot  134  is preferably located in the adjacent structure of the lid  34 , namely in rib  136 . A latch receptor  138  is thereby formed. The latch is assembled by placing a compression spring  140  onto rod  126 , and then placing rod  126  into the aperture  132  located in rib  136 . Latch  120  is fastened to lid  34 , with a nut  127  if the attachment means is a threaded rod, and otherwise by other removable means. In any event, the components are assembled so that compression spring  140  is in a compressed state. Whenever latch  120  is activated during the opening or closing of lid  34 , spring  140  biases the latch toward the front edge  142  of lid  34 . The body  122  of latch  120  extends through the slot  134  located in rib  138 . 
     The operation of the latch  120  can be described with reference to  FIG. 9 . As can there be seen, the top surface  146  of body  122  engages the underside of seat  48  when lid  34  in a closed position. An indent  144  is located on the top surface  146 . A pry bar  150  may be inserted through an aperture  152  located in the indent  144  to move the top surface  146  out of contact with seat  48 . This will release latch  120  and allow lid  34  to open. Preferably, lid aperture  152  is offset within detent  144  so that pry bar  150  can pivot toward the front edge  142  of lid  34  at aperture  152 . Regardless of embodiment, latch  120  is operated in a similar manner. Further, in alternative embodiments, latch  34  may instead take the form of a locking mechanism operated by use of a key (not shown), or the like. To operate a lid  34  that does not include latch  120  as shown herein, the user first disengages the lock or other fastener (not shown) keeping lid  34  in a closed position, and reengages this lock or fastener once the lid  34  is ready to be closed and locked down. 
     The operation all of the embodiments of hatch  30  that include a latch  120  is as follows. First, a user inserts the pry bar  150  into a lid aperture  152 , as seen in  FIG. 9  or  12 . The user pulls the pry bar  150  toward the front edge  142  of lid  34  to release latch  120 . Lid  34  will pop open to a position that depends on the stiffness of the spring or springs  90  and the weight of lid  34 . Lid  34  is pulled back so that it rests against hinges  62 . The optional safety arm  110 , if present, may then be removed from aperture  116   a  and placed into aperture  116   b  to prevent lid  34  from being knocked from its resting position, as seen in  FIG. 2 . 
     To close lid  34 , safety arm  110 , if present, is first removed from aperture  116   b  and replaced into aperture  116   a . Lid  34  is rotated on hinges  60  toward a closed position. The user may stand on lid  34  or apply other force to lid  34  so that it closes completely. As lid  34  is closing, the curved or wedged leading edge  124  of latch  120  makes contact with seat  48 . This causes latch body  122  to slide away from seat  48  until body  122  is located below seat  48 , thereby further compressing the spring  140 . When the leading edge  124  clears the seat  48 , the spring  140  moves latch body  122  forward so that the latch upper surface  146  is securely located under the seat. 
     It should be understood that the ribs  70  are not essential to the present invention. Though ribs  70  are described in both embodiments as being used for the connection of items including the clip arm  94 , latch  120 , safety arm  110 , cylinder  98 , etc., ribs  70  can be replaced by individual brackets (not shown) that are attached to the underside of the lid and adapted to receive such items. The term “bracket” is used in a general sense to mean a structure for holding or attaching another structure to the lid  34 . Preferably, the individual brackets would be integrally connected to the lid. For example, in the case where ribs  70  are not present in the first embodiment, rings  72 , which are in effect brackets, could be attached to or integrally connected with lid  34 . 
     From the foregoing description, it can be seen that the hatch cover  30  provided by the invention is simply constructed. It has a minimum number of parts, especially moving parts. It can be made from relatively inexpensive but durable materials such as steel and iron by molding, casting, or other conventional methods. It allows for easy replacement of the spring. It can assist and support the opening of heavy lids and covers. 
     The spring assist for lifting lids of the present invention may have other applications aside from use in connection with hatches and manholes. Although the invention has been herein shown and described in what is perceived to be the most practical and preferred embodiments, it is to be understood that the invention is not intended to be limited to the specific embodiments set forth above. Rather, it is recognized that modifications may be made by one of skill in the art of the invention without departing from the spirit or intent of the invention and, therefore, the invention is to be taken as including all reasonable equivalents to the subject matter of the appended claims.