Road structure – process – or apparatus – Pavement – Vault cover-closure
Reexamination Certificate
2000-09-15
2003-07-22
Pezzuto, Robert E. (Department: 3671)
Road structure, process, or apparatus
Pavement
Vault cover-closure
C052S020000
Reexamination Certificate
active
06595716
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to manholes in large container vehicles for dry bulk products. In particular, the present invention relates to locking levers and sealing gaskets for securing the cover on such manholes.
Container vehicles such as railcars and truck trailers used for transporting dry bulk products such as grains or powdered cement typically have manhole access ports on their top sides which allow workers to climb into the container vehicle and inspect or clean the interior of the container. Normally to unload a container vehicle, pressurized air is applied to the interior of the container and the products are carried by the escaping air through an outlet located near the bottom of the container. Naturally, the manholes must be sealed while the container vehicle is being unloaded to prevent air from exiting the manhole cover rather than the intended container outlet. Also, when transporting cargo, it is desirable to maintain an air tight seal in order to prevent contamination of the cargo by outside elements and moisture. A typical system for covering and sealing the manhole is seen in
FIGS. 1-3
.
FIG. 1
illustrates a typical dry bulk container vehicle
100
.
FIG. 1
shows how container vehicle
100
will have one or more manholes
1
.
FIG. 2A
illustrates prior art manhole
1
in greater detail. A cylindrical weld ring
3
will surround the opening in the container vehicle and be welded to the body of the vehicle. A cover
2
will be attached to weld ring
3
by way of hinge
4
as best seen in the side view of FIG.
2
B. It can be seen in
FIG. 2B
that a gasket
6
is positioned around an underside perimeter of cover
2
and will rest on the upper edge of weld ring
3
. It will be understood that gasket
6
forms a seal between the upper edge of weld ring
3
and cover
2
.
FIG. 3
shows how gasket
6
will be position in a gasket channel
7
with inwardly sloping sidewalls
8
.
FIG. 2A
illustrates how a series of cam lever assemblies
10
will be positioned around the outside perimeter of cover
2
. Each cam lever assembly
10
will have a cam handle
11
and a forked end
17
opposite handle
11
. Each prong of forked end
17
will have a pin aperture
22
formed therein and will also include a cam surface
18
formed on the lower portion of the prong. As best seen in the cross-section view of
FIG. 3
, an adjusting screw
12
is pinned between the prongs by a pivot pin
13
. Adjusting screw
12
extends through cover
2
and engages jam nut
14
and connector
15
. It will be understood that jam nut
14
acts as a locking mechanism and will not allow downward travel of screw
12
when jam nut
14
is positioned against connector
15
.
FIG. 2A
illustrates how connector
15
will be connected to weld plate
3
by way of brackets
25
and clevis pin
20
. Returning to
FIG. 3
, it can be visualized how the rotation of adjusting screw
16
will raise or lower cam surface
18
and cause cam surface
18
to place either more or less pressure on cover
2
. Typically, a wear plate
19
is positioned on cover
2
and provides the actual surface which cam surface
18
engages. Wear plate
19
may be constructed of a wear resistant and rust resistant material such as stainless steel and operates to prevent the frictional force of cam surface
18
from damaging cover
2
. Wear plate
19
may be screwed to cover
2
(see
FIG. 2A
) in order that it may be easily replaced when it becomes excessively worn.
FIG. 2A
best illustrates how locking lever assembly
10
operates to hold cover
2
tightly closed against weld ring
3
. One lever handle
11
A is shown rotated back and completely removed from engagement with cover
2
. When it is desired to place pressure on cover
2
, the cam lever handle is placed in the upper position as shown by lever handle
11
C. At this point, cam surface
18
has not engaged wear plate
19
and forced cover
2
downward. As cam handle
11
C is rotated forward, cam surface
18
begins to engage wear plate
19
and exert a downward force on cover
2
. When cam lever handle
11
C is rotated fully forward as shown by cam lever handle
11
B, a flat portion of cam surface
18
rests upon wear plate
19
and tends to resist upward rotation of cam lever handle
11
. Over time, wear plate
19
and gasket
6
may become worn. To maintain a proper seal between weld ring
3
and gasket
6
, it will be necessary to press cover
2
further downward or in other words, bring cam surface
18
closer to connector
15
. This may be accomplished by positioning the cam lever handles as seen for handle
11
C. Handle
11
C may then be rotated which will cause adjusting screw
12
to travel further down the threaded surface of connector
15
. This results in cam surfaces
18
being moved correspondingly closer to connector
15
. Therefore, when handle
11
C is rotated forward in the closed position, cam surface
18
will apply a greater downward force to wear plate
19
and thus press gasket
6
more firmly onto weld ring
3
.
FIG. 2A
also shows safety catch
23
. Safety catch
23
rotates over wear plate
19
as suggested by viewing the safety catch
25
shown on handles
11
A and
11
B. The purpose of safety catch
23
is to prevent cover
2
from being “blown” open if the container is pressurized when all cam handles
11
are released. If air pressure is pushing cover
2
upward, safety catch
23
is engaged by wear plate
19
and cannot be rotated backwards. It is necessary for pressure to bleed off and cover
2
to rest on weld ring
3
before safety catch
23
may rotate backwards. Normally, only one cam lever assembly
10
will have a safety catch
23
.
FIG. 2A
illustrates two safety catches
23
in order to show one in the rotated backwards (open) position and one in the rotated forward (closed) position. There are several disadvantages to the prior art cam lever assembly
10
. First, adjusting screw
12
may only be rotated when handle
11
is not in the forward or locked position. Thus, to adjust screw
12
, handle
11
must be lifted and the downward force on wear plate
19
released. If cover
2
is forming a pressure seal with weld ring
3
, releasing force on wear plate
19
may undesirably allow gases within the container vehicle to escape. Second, when handle
11
is rotated, it must be rotated in complete revolutions in order for handle
11
to be able to rotate forward to the locked position. Thus, if the desired adjustment is ½ a turn of adjustment screw
12
or 1½ turns, this cannot be achieved. Adjustment screw
12
must be turned in increments of 360 degrees, even if this causes cam surface
18
to place more or less force on wear plate
19
than is desired. Placing to little force prevents the formation of an effective pressure seal. On the other hand, placing too much tends to damage and shorten the life of gasket
6
.
Other problems also arise with the prior art gasket
6
. As gaskets become old, they tend to stick to the rim of weld ring
3
and are too easily pulled out of gasket channel
7
. Attempts have been made to fix gasket
6
in channel
7
with an adhesive, but this creates its own set of problems. For example, adhesives which are not evenly applied may form lumps under gasket
6
, lessening the gasket's ability to seal uniformly. Moreover, when it becomes necessary to replace gasket
6
, gasket
6
may tear and leave segments of the gasket still glued within channel
7
. This necessitates the time consuming task of clearing out all the small bits of the old gasket remaining in channel
7
before the new gasket may be inserted. It would be a significant advance in the art to provide a cam lever assembly and gasket which overcomes the above described disadvantages.
SUMMARY OF THE INVENTION
The present invention provides a sealable manhole system having a weld ring, a cover with a gasket shaped to engage said weld ring, and a cam lever assembly. The cam lever assembly comprising includes a cam lever having a cam surface and a pivot aperture. A pivot pin is sized to engage th
Knaack, Jr. Henry
VanDeVyvere Bryan
Delaware Capital Formation Inc.
Jones, Walker, Waechter, Poitevent, Carrere & Denegre, L.L.P.
Pechhold Alexandra K.
Pezzuto Robert E.
LandOfFree
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