Abstract:
The hatch of a lading container, such as the hopper of a covered hopper car, is sealed by a hatch cover having a locking arrangement which prevents the hatch cover from being blown open by pressure within the hopper when the locking arrangement is unlocked. An over-center locking arm has two spaced catches which co-act with two latches on a latching arrangement to selectively provide a sealed, a pressure blow-off, and a hatch open position. A rotative adjustment is provided to enable adjustment of the sealing pressure of the hatch cover on the hatch.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to hatch covers for cargo carrying vessels such as the hopper of a railway covered hopper car. 
     2. Description of the Prior Art 
     Locking arrangements for lockingly sealing a hatch cover to a hatch opening or coaming of a vessel such as a lading hopper of a railway covered hopper car are old and well known. The lading in a given vessel may have properties such that excess pressure builds up inside the vessel. When the locking arrangement is released, the excess pressure may swing the hatch cover open with considerable force, endangering human operators and potentially damaging the apparatus. To prevent this, the locking arrangement may be designed to retain the hatch cover in an intermediate &#34;blow-off&#34; position where the hatch cover is free to move enough to vent pressure but restrained against larger movement. 
     U.S. Pat. Nos. 4,157,146, 4,388,873, and 4,441,431 show various arrangements for sealing a hatch cover and retaining it in a blow-off position. U.S. Pat. No. 4,157,146 discloses a plurality of clamps mounted about the hatch circumference, requiring a plurality of repeated operator functions to open the hatch. U.S. Pat. Nos. 4,388,873 and 4,441,431 disclose a hatch cover securable by a single cam lock in both sealed and blow-off positions, but the latch structure is relatively weak and in the event of mechanical failure, the hatch cover might blow open. 
     SUMMARY OF THE INVENTION 
     It is an object of this invention to provide a hatch cover lock which is selectively engageable with a hatch cover in three positions: the first being a tightly sealed position, the second an unsealed intermediate or pressure blow-off position, and the third being the fully disengaged or wide open position. 
     A hatch cover locking bar having two vertically spaced catches at the locking end co-acts with a latching member having two latch means. The first latch means is a rotatable, pivotally-mounted cam lock member engageable with the upper catch to cause the cover to be in the tightly sealed position with respect to the hatch. The second latch means is a horizontal bar member engageable with the lower catch to retain the cover in the unsealed or pressure blow-off position. Both latch means may be withdrawn from the catches, thereby allowing the hatch cover to be pivotally removed from the hatch and into a disengaged fully unlatched position. A rotative pressure adjustment structure of the locking member is provided to enable selective control of the sealing pressure of the hatch cover on the hatch. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top plan view of a hatch cover having the locking structure of this invention. 
     FIG. 2 is a full section view of FIG. 1 as indicated by the section line 2--2, showing the latch arrangement completely disengaged from the hatch cover. 
     FIG. 3 is an enlarged detailed view showing the hatch cover lock in the locked and sealed position. 
     FIG. 4 is an enlarged detailed view showing the hatch cover lock in the unsealed or blow-off position. 
     FIG. 5 is an enlarged detailed view of the adjustment means for the latch, showing several adjustment positions. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As best shown in FIG. 2, a railway hopper car has an upper deck surface 9. A hatch ring or annular coaming 10 extends vertically upward from this surface providing a hatch opening in the deck surface. This opening is closed by a hatch cover 11. A seal is maintained by a hatch cover gasket 12 held between hatch cover 11 and coaming 10. 
     In order to rotate the hatch cover 11 away from the coaming 10, a hinged deck bracket 13 is attached to coaming 10. A hatch cover locking bar or lever 14 is pivotally attached to the hinged bracket 13 by a hatch cover bolt 15. The hatch cover locking bar 14 is equipped with a cover abutment surface indicated at 16 which abuts the top deck surface 9 of the hopper car when the hatch cover 11 is in a wide open position. Hatch cover 11 is attached to hatch cover locking bar 14 at the hatch cover&#39;s approximate center point where a pair of center mount flanges 18 extend upward from the hatch cover 11. The hatch cover locking bar 14 is pivotally connected to the center mount flanges 18 by a center mount bolt 17. 
     At the distal end of the hatch cover locking bar 14 are two hatch cover catches, or latch engagement portions, an upper hatch cover catch 19 and a lower hatch cover catch 20. 
     A latch structure 14a is located at the opposite side of the coaming 10 from the hinge deck bracket 13, where a latch mounting bracket 21 is affixed to the coaming 10. As best shown in FIG. 5, a die or locator 22 having a hexagonal cross-section passes through a matching hexagonal cross-section bore or aperture 22a in bracket 21 and the latch plate pivot 23 passes through one of the eccentric bores or receiving means 23a in the hexagonal die 22 forming an arrangement which allows adjustment of the height of the pivot 23. The pivot 23 pivotally mounts the link means or latch plates 24 to the latch mounting bracket 21. 
     A lower latch bar 25 (See FIG. 1) extends between the two latch plates 24 at a point roughly midway along the length of the latch plates 24. As best shown in FIG. 4, at the further end of the latch plates 24 a cam lock member pivot 26 pivotally connects a cam lock member 27 to the latch plates 24. The cam lock member 27 has a cam lock member engaging surface 28 which engages the upper hatch cover catch 19 at the catch engaging surface 29. 
     To facilitate manual contact by the operator, the cam lock member 27 has a handle 30. When the cam lock member is rotated to the position for tightly sealing the hatch cover, the handle 30 abuts a spacer stop 31 on the locking bar 14 which maintains a space between the cam lock member handle 30 and the main portion of the locking bar 14 (See FIG. 3). 
     For pilferage prevention, as best shown in FIG. 4, a security seal 32 may be engaged with the cam lock member 27 and the hatch cover locking bar 14. The security seal 32 passes through the security seal bore 33 in hatch cover locking bar 14. 
     DESCRIPTION OF OPERATION 
     The position of the hatch cover 11 relative to the coaming 10 may essentially be one of three positions: (1) tightly closed, (2) partially open in a pressure blow-off position, or (3) wide open. 
     To place the hatch cover 11 in a tightly closed position as shown in FIG. 3, the hatch cover 11 is allowed to rest against the upper end of coaming 10. The latch plates assembly 24 is then rotated about pivot 23 to allow cam lock member 27 to engage upper hatch cover catch 19. The cam lock member engaging surface 28 engages the catch engaging surface 29 and the cam lock member 27 is rotated until the handle 30 abuts the spacer stop 31. This rotation causes a camming interaction of the cam lock member 27 and the upper hatch cover catch 19, which results in a downward force being applied on the hatch cover locking bar 14 and transmitted to the hatch cover 11 via the center mount flanges 18. 
     Frequently the lading in a hopper car is of a nature to impose an upward or unsealing gas pressure on the underside of the hatch cover 11. These forces may be of sufficient magnitude to cause a hatch cover to be forced to swing completely open when an ordinary locking mechanism is unlatched. Consequently, it is desirable to restrict such movement. To that end, in this invention there is a secondary release position, or pressure blow-off position, for the latching arrangement. To remove the hatch cover 11 when it is sealed, the cam lock member 27 is rotated away from the spacer stop 31, disengaging the cam lock member engaging surface 28 from the catch engaging surface 29. Any pressure directed upward below the hatch cover 11 will cause the hatch cover 11 to rise and, as a consequence, cause the hatch cover locking bar 14 to rotate about the hatch cover bolt 15. This rotation will continue up to the point where the lower hatch cover catch 20 will meet lower latch bar 25. At this point, the hatch cover will be restrained from further upward movement but adequate space will be present between the hatch cover 11, the sealing gasket 12, and the top of the coaming 10 to allow pressure present in the hopper car to dissipate. Once this pressure has dissipated, the hatch cover 11 will settle to rest against the coaming 10 and the latch plates 24 may be pivoted so as to disengage the lower latch bar 25 from the lower hatch cover catch 20. The cover 11 and the hatch cover locking bar 14 will then be free to pivot into the wide open position. 
     To reach the wide open position, the hatch cover 11 is pivoted about hatch cover hinge pivot 15 to uncover completely the opening into the hopper car. When the cover 11 is pivoted in this fashion, at the furthest range of its movement the cover abutment surface 16 on the hatch cover locking bar 14 will abut the deck surface of the hopper car 9 supporting the cover 11 in its widest open position. 
     It is possible to adjust the downward pressure imposed by the latch structure 14a on the hatch cover locking bar 14. As best shown in FIG. 5, the hexagonal die 22 is equipped with eccentric bores 23a which are sized to accomodate the latch plate pivot 23. When the latch plate pivot 23 is removed from the die 22, the die 22 may be removed from its matching hexagonal bore 22a in latch mounting bracket 21. After removal of the die from the bore 22a, the die 22 may be rotated to one of a plurality of positions wherein the die 22 fits into the hexagonal bore 22a and reinserted, altering the vertical height of the bores 23a in the die 22. The latch plate pivot 23 may then be reinserted in the bore 23a in the die 22 having the vertical height desired. The adjustment in the vertical location of the latch plate pivot 23 adjusts the vertical location of the cam lock member 27 when in the lock position and, as a consequence, alters the pressure applied via hatch cover locking bar 14 to the hatch cover 11. 
     When the latch arrangement 14a is in the tightly sealed position, as shown in FIG. 3, it is possible to lock the latch mechanism by passing a suitable lock through the security seal bore 33 which will restrain the cam lock member handle 30 from being moved to release the hatch cover 11. Also a tamper-indicating seal 32 may be used to connect the cam lock member handle 30 to the hatch cover locking bar 14 by running security seal 32 through the security seal bore 33 and securing it around the handle 30. 
     While the present invention has been described with reference to a particular embodiment, it is not intended to illustrate or describe herein all of the equivalent forms or ramifications thereof. The words used are words of description rather than limitation, and various changes may be made without departing from the scope or spirit of the invention disclosed herein.