Abstract:
A manhole cover includes a cylindrical manhole including manhole lugs, wherein the manhole lugs extend around the upper outer periphery of the manhole; the cover includes cover lugs, the cover lugs extend around the outer periphery of the cover. The cover co-operatively mates with and closes off the manhole. A strap also extends around the cover and manhole lugs such that applying tension to the strap assembly forceably urges together the cover and manhole lugs wherein the strap for clamping together the manhole lugs to the cover lugs thereby placing cover into a sealed position.

Description:
FIELD OF THE INVENTION 
   The present invention relates to manhole covers for pressure vessels and in particular relates to a manhole cover for a railway car pressure vessel. 
   BACKGROUND OF THE INVENTION 
   Currently manhole covers on railway pressure vessels are large, heavy steel plate circular covers which are bolted down with six to eight large eye bolts. The eye bolts that are used are a source of maintenance in that the bolts often break, the threads wearing, the nuts seize. In addition the installation and removal of the cover with the eye bolts is labour intensive, requiring a substantial amount of time in order to open and close the existing manhole covers. 
   Furthermore, the eye bolts securing the man whole cover are normally standing straight up with the threads exposed to the impact from tools, loading equipment and possible contact with the ground and other obstacles in the event of derailment of the rail car should the vessel overturn. Leaking of the pressure vessel can occur when an eye bolt is damaged or missing or the cover is incorrectly tightened or when the cover is permanently deformed from over tightening. 
   All of the above deficiencies in the existing manhole cover designs are the leading cause of commodity leaks in the north American rail car fleet. 
   Therefore, there is a need for a new and improved manhole cover locking system which overcomes the deficiencies of the current manhole cover designs and in particularly eliminates the need for six to eight large eye bolts which are positioned vertically upward from the cover. 
   SUMMARY OF THE INVENTION 
   A manhole cover comprising:
         (a) a manhole including manhole lugs;   (b) a cover including cover lugs, said cover co-operatively mating with said manhole;   (c) a strap means for clamping together said manhole lugs and cover lugs, by applying tension to said strap means.       

   Preferably wherein said clamping means including a strap which extends around said cover and manhole lugs such that applying tension to said strap forceably urges together said cover and manhole lugs thereby placing cover into a sealed position. 
   Preferably wherein said clamping means including a strap assembly having a left and right strap, each strap pivotally connected at one end to a hinge means for pivotally connecting said left and right strap, and each strap connected at the other end to a tightening means for applying tension to said straps for forceably urging together said cover and manhole lugs thereby placing cover into a sealed position and straps in a locked position, and by releasing said tightening means for releasing tension on said straps such that they can pivot freely away from each other into an unlocked position. 
   Preferably wherein said hinge means including a strap hinge pin operatively connected to each strap for pivotally connecting said straps. 
   Preferably wherein said hinge means includes a strap hinge assembly including a left hinge bracket attached to one end of said left strap, and a right hinge bracket attached to one end of said right strap, and further including a strap hinge pin pivotally connecting said hinge brackets. 
   Preferably wherein said tightening means including a bolt and nut operatively connected to said straps for applying tension to said straps when said nut is tightened onto said bolt. 
   Preferably wherein said tightening means including a bolt bracket assembly including a bolt left bracket attached to said left strap and a bolt right bracket attached to said right strap and a bolt and nut for applying tension to said straps when said nut is tightened onto said bolt. 
   Preferably, wherein said bolt left bracket including a T bolt saddle for receiving a T bolt therein. 
   Preferably wherein said cover lugs and manhole lug each including a chamfered surface corresponding to a V shaped strap chamfered portion such that applying tension to said straps imparts compressive forces urging together said cover and manhole lugs. 
   Preferably further including a pivoting means for pivoting of said cover between a sealed position and an open position. 
   Preferably wherein said pivoting means including a cover hinge pin operably pivotally connecting said cover to said manhole. 
   Preferably wherein said pivoting means including a cover hinge flange connected to said cover and at least one cover hinge bracket connected to said manhole, and a cover hinge pin operably pivotally connecting said cover hinge flange to said hinge brackets. 
   Preferably further including a means for longitudinally sliding said clamping means away from said manhole when said straps in said unlocked position. 
   Preferably wherein said sliding means including a slot defined in a spacer plate which is attached to said manhole such that said hinge pin is slidably received within said longitudinally oriented slot thereby allowing said clamping means to be moved longitudinally to a cleared position. 
   Preferably wherein said slot oriented such that when said clamping means urged longitudinally backwards along said slot said straps clear said manhole and cover lugs to a cleared position, permitting said cover to be pivoted to an open position. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described by way of example only with reference to the following drawings in which: 
       FIG. 1  is a left side, side elevational view of the manhole cover shown in  FIG. 2 . 
       FIG. 2  is a top plan view of the manhole cover. 
       FIG. 3  is a right side, side elevational view of the manhole covers shown in  FIG. 2 . 
       FIG. 4  is a front side, side elevational view of the manhole cover shown in  FIG. 2 . 
       FIG. 5  is a cross sectional schematic view of the manhole cover fastened down to a manhole. 
       FIG. 6  is a top plan schematic view of the locking strap together with the hinge assembly as well as the bolt bracket assembly wherein the strap is shown in an open position in dashed lines and in the closed position in solid lines. 
       FIG. 7  is a side elevational view of the locking strap shown in  FIG. 6 . 
       FIG. 8  is a cross sectional view of the locking strap taken along the lines  8 — 8  of  FIG. 6 . 
       FIG. 9  is a top schematic perspective view of the locking strap together with the strap hinge assembly and the bolt bracket assembly. 
       FIG. 10  is an exploded schematic assembly view of the manhole together with portions of the cover hinge assembly, the cover plate handle and handle flange. 
       FIG. 11  is a top schematic perspective view of the manhole cover in its assembled condition showing the strap in the locked position. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   The present invention, a manhole cover shown generally as  20  includes the following major components namely, cover plate  22 , strap assembly  24 , cover hinge assembly  26  bolt bracket assembly  46  and manhole walls  28 . 
   Manhole walls  28  includes manhole lugs  30  extending around the upper outer periphery  53  of manhole  93 , and having a manhole chamfered surface  32  for engaging with strap assembly  24 . 
   Cover plate  22  includes cover lug  34  extending around an outer periphery  53  of cover plate  22 , having a cover chamfered surface  36  for engaging with strap assembly  24 . 
   Referring now particularly to  FIG. 9  showing strap assembly  24 , includes a right strap  40 , a left strap  42 , a strap hinge assembly  44  and a bolt bracket assembly  46 . Right strap  40  and left strap  42  are hingeably connected at one end with strap hinge assembly  44  which includes a right hinge bracket  48 , a left hinge bracket  50  and a strap hinge pin  52 . Right strap  40  and left strap  42  are rigidly connected to right hinge bracket  48  and left hinge bracket  50  respectively in any manner known in the art including welding, rivetting, bolting etc. 
   Strap assemble  24  can be tightened together with bolt bracket assembly  46  which includes bolt left bracket  54 , bolt right bracket  56 , T-bolt  60 , bolt nut  58 , and sleeve  62 . 
   Referring to  FIGS. 6 ,  7  and  8 , right strap  40  and left strap  42  include a vertical strap portion  64  and an upper and lower chamfered portion  66  creating V shaped chamfered. surfaces. 
   Referring now to  FIG. 10  which shows the details of cover hinge assembly  26 . Cover hinge assembly  26  includes two cover hinge brackets  70 , separated by spacer plate  71 , a cover hinge  72  and a cover hinge flange  74  which is rigidly connected at one end to cover plate  22 . 
   The other end of cover plate  22  includes a handle flange  80  having a handle  82  mounted rigidly thereon. Spacer plate  71  also includes a slot  84  for receiving strap hinge pin  52  there through, such that strap hinge pin  52  can slideably move along slot  84  when opening and closing strap assembly  24 , thereby allowing the opening and closure of cover plate  22  of manhole cover  20 . 
   Further referring now to  FIG. 5 , manhole cover  20  includes a cover gasket  90  which fits in between manhole walls  28  and cover plate  22 , therefore providing an air and liquid tight seal once cover plate  22  is securely fastened down onto manhole walls  28 . Gasket  90  seals onto sealing surface  51  of manhole walls  28 . 
   In Use 
   Manhole cover  20  is used as follows: 
   Manhole cover  20  is shown in  FIGS. 1 through 5  and also in  FIG. 11  is shown in the closed position or sealed position  57 . In  FIG. 5  for example, cover plate  22  is shown seated against manhole walls  28  and sealed with a cover gasket  90 . Sealing between cover plate  22  and manhole wall  28  is accomplished with either a hard gasket and/or an elastomeric gasket which fits in gasket groove  91  defined in cover plate  22 . Other sealing means can be used as known in the art. 
   Closing Manhole Cover 
   In order to close manhole cover  20 , onto manhole  93 , cover plate  22  is rotated about cover hinge pin  72  until it makes contact with the top of manhole walls  28 . Lying between cover plate  22  and manhole walls  28  is a cover gasket  90  fitted within a gasket groove  91  and is adapted to be retained within gasket groove  91  upon opening of cover plate  22 . 
   Cover plate  22  has a cover hinge flange  74 , rigidly connected to cover plate  22  at one end and is hinged onto cover hinge brackets  70 , via cover hinge pin  72 . On the other end of cover plate  22  is a handle flange  80  which is rigidly connected to cover plate  22 , having a handle  82  mounted thereon. Urging handle  82  upwardly, one can open cover plate  22  removing it from manhole wall  28  and by pivoting cover plate  22  about cover hinge pin  72 . One can lower cover plate  22  onto manhole wall  28 , thereby creating a seal with cover gasket  90  between cover plate  22  and manhole  93 . 
   Once cover plate  22  is in the closed or sealed position  57  as shown in  FIG. 5 , a strap assembly  24  is mounted in position around manhole lugs  30  as well as cover lugs  34 . 
   Strap assembly  24  is best shown in  FIG. 9 , and includes a right strap  40  and left strap  42  which are hingeably connected at strap hinge assembly  44  which includes a left hinge bracket  50  and right hinge bracket  48 , such that the left and right straps  42  and  40  respectively pivot about strap hinge pin  52 . 
   Referring now specifically to  FIGS. 6 ,  7  and  8 , one will see that right strap  40  and left strap  42  have a vertical strap portion  64  and two chamfered strap portions  66 . The chamfered portions  66  register and co-operatively make contact with chamfered surface  32  and cover camfered surface  36 . This modified V configuration allows one to forceably compress cover plate  22  onto manhole walls  28  by constricting right strap  40  and left strap  42  around the outer circumference of cover lugs  34  and manhole lugs  30 . 
   On the end distal from strap hinge assembly  44  is a bolt bracket assembly  46  which includes a bolt right bracket  56  for right strap  40  and bolt left bracket  54  for left strap  42 . Bolt left bracket  54  also defines a T bolt saddle  97  which receives T bolt  60  and bolt right bracket  56  receives bolt nut  58  and a sleeve  62  wherein sleeve  62  covers over any exposed threads of T bolt  60 . T bolt  60  preferably has acme threads defined thereon which cooperatively engage with bolt nut  58 . Any excessive length of T bolt  60  is covered with a sleeve  62 , thereby protecting any exposed threads from damage. Tightening bolt nut  58 , forceably urges bolt left bracket  54  together with bolt right bracket  56 , thereby imparting constrictive forces on right strap  40  and left strap  42 , thereby forceably urging cover plate  22  onto cover gasket  90  which applies increasing pressure onto manhole walls  28 , thereby providing a fluid proof seal. 
   In this manner by simply tightening one bolt, namely bolt nut  58 , the entire closing and sealing mechanism is accomplished. 
   Opening Cover Plate  22   
   In order to open cover plate  22 , from the locked position  81  shown in dark lines in  FIG. 6  the reverse procedure of the above described is carried out. Firstly, bolt nut  58  is loosened off, thereby loosening the tension in right strap  40  and left strap  42 . Right strap  40  and left strap  42  pivot away from each other about strap hinge pin  52 . When bolt nut  58  is eased off far enough, it is possible to dislodge T bolt  60  from T bolt saddle  97  which is defined in bolt left bracket  54 . 
   As shown in  FIG. 6 , T bolt  60  is dislodged from T bolt saddle  97  allowing further pivoting of right strap  40  from left strap  42  to the position as shown in dotted lines in  FIG. 6  which is the unlocked position  83 . Further to ensure that right strap  40  and left strap  42  completely clear manhole lugs  30  and cover lugs  34 , one can then forceably urge the entire strap assembly  24  rearwardly towards cover hinge assembly  26  by slideably urging strap hinge pin  52  longitudinally backwards along slot  84  along longitudinal direction  77  to a cleared position not shown. Once right strap  40  and left strap  42  have cleared manhole lugs  30  and cover lugs  34  completely, it is possible to hingeable lift cover plate  22  about cover hinge pin  72 , thereby pivoting manhole cover  20  from the sealed position  57  to an open position not shown. 
   It should be apparent to persons skilled in the arts that various modifications and adaptation of this structure described above are possible without departure from the spirit of the invention the scope of which defined in the appended claim.