Abstract:
Improved manhole cover locks are disclosed that fit into existing access recesses in the covers and engage the rim of the manhole cover housing at one end thereof and latchingly engage the underside of the manhole cover thereof. A tamper proof bolt provides adjustability to the latch from the top of the lock.

Description:
This invention relates to locks and locking devices and, more particularly, to locking devices for securing several manhole covers in their respective housings, when each manhole may have a differing size access hole adjacent the outer edge thereof. 
     BACKGROUND OF THE INVENTION 
     Manholes and manhole covers are everywhere that civilization has infrastructure. They are basic to both storm sewer and sewage structure. Additionally, underground utility lines of all sorts are accessed for maintenance, repair and replacement by the use of manholes topped by metal or concrete rings or housings on which a manhole cover is mounted. 
     Traditionally, the weight of a manhole cover has been considered sufficient to maintain them on their mountings. However, in many parts of the world, the metal content of the manhole cover is considered worth stealing by the locals. Further, in this age of terrorism, improvised explosive devices (IED) planted by the side of a road are a main weapon of a lawless group. The positioning of manholes and their covers along roadways would provide such groups with an unwarranted convenience if the manhole covers were not locked down. 
     Through the years, manhole covers and their mounting rings have been generally cylindrical or rectangular in nature, with cylindrical being the preferred shape. While the design patterns of the tops of manhole covers may vary, as with vent holes, cross bars, or the like, a substantial number of manhole covers have a U-shaped access hole adjacent the outer circumference of the manhole cover in a large access hole, or about ⅞×¾ inch in a smaller access hole of a “concealed pickhole” manhole cover. These holes, due to casting, generally have a slight draft or acute angle from the horizontal, as does an inner lip of a cast manhole cover housing. 
     Patents that require a specially made manhole cover or rim that includes a locking apparatus include U.S. Pat. Nos. 1,473,986; 4,964,755; 5,082,392; 5,324,135; 6,199,414; and 6,854,922. Lock mechanisms that may work with standard manhole covers include U.S. Pat. Nos. 3,980,329; 6,881,007; and Publication 2007/0081856. 
     A need has developed for a less expensive, more generally useful manhole cover lock that is usable on existing designed manhole covers of differing general configurations. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention, generally stated, to provide a new and improved manhole cover lock usable on existing designs of manhole covers. Another object of the present invention is the provision of a manhole cover lock assembly that is capable of being utilized on opposing sides of a “concealed pickhole” manhole cover. 
     The invention resides in a manhole cover lock that comprises a body positionable in an access recess of a manhole cover. The body engages a rim of housing for the manhole cover, and further includes a latch pivotally mounted on the body for moving from a retracted position to an extended position engaging an underside of the manhole cover. The invention further resides in a tamper proof fastener that comprises an elongate shaft having an enlarged head at the top thereof, the head includes at least two recesses formed along a periphery thereof inwardly extending from a side and a top thereof, the angular relation between the recesses around the head is changeable between respective ones of the bolts for preventing unwarranted turning of the fastener. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The invention may best be understood from the following detailed description of currently preferred embodiments thereof taken in conjunction with the accompanying drawings wherein like numerals refer to like parts, and in which: 
         FIG. 1  is a vertical sectional view of a manhole cover and its associated housing including a manhole cover lock constructed in accordance with the present invention; 
         FIG. 2  is an enlarged fragmentary vertical sectional view of a second embodiment of the present invention fitted into a manhole cover and housing of smaller access opening dimensions than that of the first embodiment shown in  FIG. 1 ; 
         FIG. 3  is a top ¾ perspective view of the first embodiment of the present invention; 
         FIG. 3   a  is a top plan view of the bolt shown in  FIG. 3 ; 
         FIG. 3   b  is a top plan view of a wrench for the bolt shown in  FIGS. 3 and 3   a;    
         FIG. 4  is a bottom ¾ perspective view of the first embodiment of the present invention; 
         FIG. 5  is an end elevational view of the first embodiment of the present invention; 
         FIG. 6  is a top ¼ perspective view of the second embodiment of the present invention; 
         FIG. 7  is a bottom ¾ perspective view of the second embodiment of the present invention; 
         FIG. 8  is an end elevational view of the second embodiment of the present invention; 
         FIG. 9  is a bottom plan view of the second embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIG. 1 , a standardized manhole cover and rim or housing assembly, generally indicated at  10 , includes an annular rim, generally indicated at  11 , on which a circular manhole cover, generally indicated at  12 , is matingly mounted. Typically, they are made of cast iron. The circumferential edge  13  of the manhole cover  12  matingly engages a hollow L-shaped rim  14  at the top of housing  11 . A first embodiment of a manhole cover lock assembly constructed in accordance with the invention, generally indicated at  15 , fits in a U-shape recess  16 , about 2½ inches by 2½ inches adjacent the circumferential edge of the manhole cover and fits between that recess  16  and the L-shape rim  14  of the housing  11 . 
     Approximately 180 degrees around the circumference  13  of manhole cover  12  is positioned an S-shape foot, generally indicated at  17 , that is preferably bolted and also bonded to the underside of the manhole cover  12  with a resin/catalyst type adhesive  18 . The manhole cover may be drilled and threaded at  17   a  from the bottom of the cover upward to provide a mounting for threaded bolt  17 . The distal end of foot  17  provides securement of the distal end of foot  17  around the lip  14  of the housing  11 . 
     Referring to FIGS.  1  and  3 - 5 , the latch portion of the manhole cover lock  15  includes a substantially flat thin top  20  made of hardened or spring steel and having a beveled edge  21  therearound to prevent prying. Subjacent the generally flat top is a body portion, generally indicated at  22 , the top segment of which is shaped similarly to the U-shape recess  16  adjacent the perimeter of the manhole cover  12  with its outermost edge generally matingly engaging the rim  13  immediately outwardly adjacent the U-shape recess  16 . While the body  22  of the lock assembly  15  may be made of differing hard materials suitable for locks, we have found that, in operation, a very tough molded part may be made of polytetrafluoroethylene (PTFE). While the top portion  23  of body  22  includes a generally rectangular cutout  24  is defined by top surface  25  vertical flat surface  26  and beveled lip  27  that fits around the bottom portion of the L-shape rim  14  as shown most clearly in  FIGS. 3 and 4 . The body portion, generally indicated at  22 , includes a pair of vertical bores  30  and  31  therethrough that are aligned with apertures  19   a - 19   b  in the top plate  20  such that ⅜ inch rivets  32  and  33  securely affix the top beveled plate  20  to the body  22 . A small recess  37  in the beveled foot  28  provides access for an installer to spread the end of the rivet. 
     Semicircular recess  30  forms a part and portion of a larger recess  40  opposite the lower portion of body  24  from the generally rectangular recess defined by sides  25 ,  26  and  27 . The recess  40  provides a swivelable home for latch  42  that is threadedly engaged on hardened bolt  43 . A third vertical bore  44  in the upper portion of body  22  ( FIG. 1 ) provides a rotatable mounting for bolt  43  with the top or head  43   a  thereof maintained at the top of body  22  subjacent the third bore  19   c  in top cover  20 . Elongate latch  42  includes a threaded bore  42   a  therethrough in which bolt  43  is threaded. The bottom  43   b  of bolt  43  has its threads interrupted such that latch  42  may not be removed from its threaded mounting in bolt  43 . Also, the interrupted threads at the bottom  43   b  of bolt  43  assure that the latch will turn when desired by rotating the head  43   a  of bolt  43 . 
     With the latch in its retracted position within the outline of recess  40 , the body  22  of the manhole cover lock  15  may be moved downwardly through the U-shaped recess  16  adjacent the perimeter of manhole cover  12  and through the hole therebelow such that the foot  28  of the recess  24   a  in lower body portion  24  may be positioned around the foot of the L-shape rim  14 . With the top plate flat on top of the manhole cover, the latch  42  may then be rotated outwardly of its recess  40  to engage the bottom side of manhole cover  12  to fully engage the latch thereunder and lock the lock  15  to prevent removal of the manhole cover  12  from its housing  11  on both sides of the housing. Once the latch is moved outwardly, its position is restricted by the vertical wall of recess  40  as the latch  42  is drawn upwardly until it meets the top wall  40   a  of recess  40  which should approximate the thickness of the manhole cover  12  to engage the distal end of lock  42  against the bottom of manhole cover  12 . 
     Thereafter, the aperture  19   c  of top plate  20  may be potted with a hardenable material to prevent access to the head  43   a  of bolt  43 . Also, the head  43   a  may have a proprietary or non-standard recess therein that would prevent turning the bolt by unauthorized personnel even if the potted material were removed from recess  19   c.    
     Referring to  FIGS. 3   a  and  3   b , top views of the head  43   a  of bolt  43  is shown as having three equally spaced semicircular recesses  43   b ,  43   c ,  43   d .  FIG. 3   b  shows the top of a wrench  45  suitable for tightening and loosening the bolt  43 . A round metal bar having the outer circumference  45  which is a slip fit into aperture  19   c  or aperture  64  is drilled for positioning smaller bars  46 ,  47 ,  48  respectively, in the holes drilled therein so as to extend from the top thereof approximately the depth of recesses  43   c ,  43   d  and  43   e . The combination is then turned, in this embodiment, in a lathe so as to remove the outer portions of smaller bars  46 ,  47  and  48  until the diameter of the tool is that shown at  49 , which is substantially identical to the outer circumference  43   b  of bolt head  43 . 
     As so constructed, with any type of handle on the opposite end of wrench  45 , the wrench may be utilized to tighten, loosen, or turn the bolts  43  and  61  as shown in the present preferred embodiments. In another aspect of the present invention, the location of the recesses  43   c ,  43   d  and  43   e  may be moved around the periphery of the bolt head  43   b  to provide a plurality of unique bolts for each government entities, with each entity having one of the multiple combinations of recess placements. 
     Likewise, the smaller rods  46 ,  47  and  48  may be positioned at differing positions around the wrench head  45  to match the configuration of the recesses in bolt head  43   b . Also, the number of recesses may be diminished to one or two and may be increased to 4, 5, 6 etc. With these combinations, and with changing the bolt head size from that of ¼ inch, 5/16, ⅜ etc. or 10 mm, 12 mm, etc., a myriad of municipality or utility specific bolts may be utilized in a secure fashion. 
     Referring to FIGS.  2  and  6 - 9 , a second embodiment of the sewer cover lock of the present invention, generally indicated at  50 , is used on what is referred to as “concealed pickhole” manhole covers and their housings. Such a manhole cover is shown, generally at  51  and its housing at  52  in  FIG. 2 . On some such covers, a second identical recess (not shown) may be positioned 180 degrees from the recess shown. A U-shape recess  53  inwardly adjacent the circumference of manhole cover  51  approximates 1⅞×1¾ inches. The radial depth of the recess  53  is smaller than the radial length of the inner ledge  54  of housing  52  such that when one looks at the recess  53  one does not see the recess goes completely through the manhole cover and the housing. However, such recesses include an additional internal pocket, shown at  55  which can facilitate the use the curved end of a pry bar (not shown) to lift the manhole cover  51  from its housing  52 . This inner pocket  55  forms at one end thereof a diagonal surface which applicant&#39;s manhole cover lock  50  utilizes to its benefit. 
     Referring to  FIGS. 6-9 , the second embodiment of the manhole cover lock of the invention, generally indicated at  50  includes a body  56  which, in this preferred embodiment, is a generally rectangular metal block wherein two of what would be its side surfaces form a single convex side  57 , to be discussed in more detail below. On top of the body  56  is positioned an enlarged flat cover plate  58  made of hardened or spring steel similar to the cover plate  20  of the first embodiment, with the exception that one end of same is bent downwardly along edge  59  to provide a vertical wall  60 . A pivot bolt  61  is positioned generally centrally through the body  56  and may be fixedly or threadedly attached to L-shape latch  63  positioned below the bottom of body  56 . The head  62  of bolt  61  may be turned through aperture  64  in top plate  58 . The height of side plate  60  approximates the height of the combination of body  53  and the height of latch  63  positioned below the body  53 . As shown most clearly in  FIG. 2 , when the second embodiment of the manhole cover lock  50  of the invention is positioned in recess  53 , the extended foot  63   a  of L-shape latch  63  extends at right angles from the body of latch  63  and may have a curved outer surface. When latch  63  is turned 90 degrees the body is shaped to further turning. A threaded latch bolt, if utilized, will then draw the latch upward to more tightly engage the recess surface  55  of the manhole cover. 
     In operation, as shown in  FIG. 2 , the second embodiment of the invention  50  is positioned as shown in  FIG. 7  with its L-shaped latch  63  positioned parallel to end plate  60 . As such, the lock is positioned in the recess  53  in the “concealed pickhole” manhole cover  51  so that the bottom of the plate  58  rests on the cover and the end plate  60  rests against the inside and bottom of the rim on housing  52 . 
     Next, a wrench is inserted in aperture  64  so as to drivingly engage the bolt head  62 . With the bolt head turned 90 degrees from  FIG. 7 , as shown in  FIGS. 8 and 9 , the upper distal end of the face  63   a  of the foot portion of latch  63  will preferably engage the slanted face  55  of the pocket portion of recess  53 . The latch is then turned so as to tightly engage the pocket surface whereupon the upper corner of face  63   a  will push the lock radially outwardly against the inside edge of the rim of housing  52 . The lock works with radial force against both the cover and the housing. With a pair of such locks in 180 degrees opposing relation on the manhole cover  51 , the cover is securely maintained on the rim. Also, any slack between the rim and manhole cover may be taken up by wedge shape shims, as they are known in the trade, sized about 2 inches by 1 inch, wedged in thickness from about 1/16 to ⅛ inch, both before or after the second embodiment  50  of the lock of the invention is latched into securement. 
     While two embodiments of the present invention has been shown and described, it will be apparent to those skilled in the art that many changes and modifications may be made without departing from the true spirit and scope of the present invention. For example, the computer screen may be utilized for presenting advertising to the customer while waiting for certain of the method steps to be completed. It is the intent of the appended claims to cover all such changes and modifications which fall within the true spirit and scope of the invention.