Cargo hatch cover mechanism

A cargo hatch cover actuation mechanism. At least one fixed unilateral mechanical actuator is mounted on a cargo hatch cover panel. The actuator is driven by an electric motor, and controlled by a hand controller, attached to the end of a flexible electrical cable which can be moved about to any suitable position near the hatch.

BACKGROUND OF THE INVENTION 
This invention relates to the field of ship cargo hatch covers, and 
mechanisms for opening and closing such covers. 
It is impossible to exaggerate the importance of cargo hatch covers to the 
safety, watertight integrity and operability of a ship. Crew safety and 
ship survival may depend on how well hatch covers operate. 
Hatch Cover actuation mechanisms fall into the category of cargo access 
equipment. Such actuators are shown in, for example: 
U.S. Pat. No. 3,211,122 to Barlow discloses a power operated hatch cover 
mechanism in which a spaced pair of rotary hydraulic actuators pivot cargo 
hatch panels through gears. 
U.S. Pat. No. 3,104,643 to Vallet discloses a hydraulic cylinder system for 
opening or locking a closed hatch cover. The hydraulic cylinder is 
suspended between two pivot points under one of two opposed hatch covers. 
U.S. Pat. No. 3,077,225 to Aarvold, in disclosing a design for the hinges 
of a cargo hatch cover, shows the use of a hydraulic motor for opening and 
closing the hatch cover. 
U.S. Pat. No. 3,050,026 to Ligh shows an opening system involving two 
coordinated hydraulic actuators. 
U.S. Pat. No. 2,891,500 to Appleton shows a combined hydraulic and cable 
system to open the hatch covers. This system results in extensive cable 
runs across the cargo deck. 
U.S. Pat. No. 2,737,919 to McRae discloses a system having a multiplicity 
of relatively narrow hatch covers which individually can be rotated to a 
vertical or horizontal position and, in a vertical position, may be moved 
along the hatch by motors and gears. 
German patent 1,506,251 discloses a hydraulic hatch cover with self 
contained hydraulics beneath the hatch cover. 
Swedish patent 221194 discloses a mechanical, gear driven on track hatch 
cover actuator which appears to be a variant on a "single pull MacGregor" 
system, a cable pull system in which a cable is reeved through all the 
wheels supporting all the hatch cover panels, and used to pull the covers 
to a removed position. 
Belgian patent 644496 appears to discloses a cargo hatch cover actuation 
mechanism comprising a belt driven gear, affixed to hinges to fold 
adjacent covers about said hinges. 
Japanese patent 199789 appears to disclose a hydraulically actuated cargo 
hatch cover mechanism 
Australian patent 241030 discloses a hydraulic hatch cover actuating 
mechanism, with hinging to maximize closing force near the cover closed 
position. 
Danish patent 97330 discloses an actuating mechanism in which a freely 
pivoted hydraulic cylinder bears on a link, which is pivotally attached to 
two interlocked gears, each fixed to a hatch cover section, causing the 
gear to pivot around each other as a hinge. 
The principal objection to the use of exposed hydraulic is the possible 
contamination of bulk cargos, especially grains, from hydraulic fluid 
leakage. Since hydraulic systems are uncommon aboard ship, few ships have 
on board maintenance capabilities for such systems, and such leaks and 
failures become increasingly common as ship systems age. 
An equally serious objection is the consequences of system failure; loss of 
hydraulic pressure can result in a sudden fall of the hatch covers. Since 
a hatch cover is a large, heavy metal object, damage by a falling hatch 
cover can be severe, and may result in structural damage to the ship hull 
if the cover falls into the hold. Cable driven systems likewise can 
collapse if the cable snaps. Such failure additionally can result in cable 
whiplash, which endangers all crew. 
SUMMARY OF THE INVENTION 
This invention pertains to cargo hatch opening mechanisms for ship board 
use, and shows a cargo hatch actuating mechanism that avoids the principal 
problems of the prior art mechanisms by avoiding any use of hydraulic, 
cable and chain driven systems. At least one fixed unilateral mechanical 
actuator is mounted on a cargo hatch cover panel. The actuator is driven 
by an electric motor, and controlled by a hand controller, attached to the 
end of a flexible electrical cable which can be moved about to any 
suitable position near the hatch. This permits local operation of the 
hatch covers by an operator having direct view of all aspects of the 
motion of the hatch cover. 
Each such actuator drives a cam actuated hinge connecting the panel to an 
adjacent panel, and, through the action of the cam actuated hinge, folds 
the pair of panels up into a vertical stowed position, opening the hatch, 
or extends the pair panels flat covering the hatch opening. Adjacent pairs 
of panels may be similarly equipped, providing a multi-panel system. 
Throughout the motion of the unilateral mechanical actuator, the covers are 
positively supported; failure of a unilateral mechanical actuator simply 
results in no further motion of the covers. Since a unilateral mechanical 
actuator is positively and mechanically fixed in position at any 
extension, and since such a mechanism cannot be driven backwards, that is, 
no force exerted at the actuator end will cause the unilateral mechanical 
actuator to retract or extend, the cargo hatch covers are at all times 
positively supported. 
To insure uniform lifting force on the cargo hatch hinges, if more than one 
unilateral mechanical actuator is used for a panel pair, all are driven by 
a single electric motor, through a reduction gear, driving each unilateral 
mechanical actuator through direct drive shafts. All driving motions on 
the unilateral mechanical actuators are thus identical, and the extension 
of each actuator is uniform. 
The preferred motive power source is an electric motor mounted on the same 
cargo hatch cover panel as the unilateral mechanical actuator. This 
permits controlled opening and closing of a cargo hatch by direct control 
by individual hand controllers connected to the motor control by a 
flexible electrical cable. No central hydraulic or fluid power generation 
and distribution is required, and there is no possibility of fluid leaks 
into the cargo, nor is there any failure mode involving chains or cables 
which would result in the un-commanded fall of an unsupported hatch cover, 
as can happen with failures in hydraulic, chain or cable systems. Further, 
a manually powered crank can be used to raise or lower the covers in an 
emergency, by providing a mechanical drive coupling through the motor, for 
use during power failure or in the event of motor failure. 
It is thus an object of the invention to disclose a ship cargo hatch cover 
actuation system which avoids the use of hydraulic piping or chain or 
cable mechanisms within the cargo holds. 
It is a further object of the invention to disclose a ship cargo hatch 
cover actuation system in which there is no possibility of contamination 
of ship cargos from hydraulic fluids. 
It is a further object of the invention to disclose a ship cargo hatch 
cover actuation system which provides a positive mechanical lock of the 
hatch cover position at any point in raising or lowering same. 
It is a further object of the invention to disclose a ship cargo hatch 
cover actuation system which does not require central fluid poser 
generation or piping for motive power. 
It is a further object of the invention to disclose a ship cargo hatch 
cover actuation system which is capable of manual activation in an 
emergency situation. 
These and further objects of the invention will be apparent from the 
detailed embodiment disclosed below.

DETAILED DESCRIPTION OF THE INVENTION 
In a typical ship cargo hold 2, cargo access is provided through one or 
more hatch openings 4, usually set above deck level by a hatch coaming 6 
rising from the ship's deck 8. This coaming 6 protects the hold 4 from the 
easy ingress of foreign objects or sea water when the hatch is open. The 
cargo hold 2 is closed by a hatch cover 10, made of a series of panels 12, 
fitted over the hatch opening, which form a closed upper cover 10 for the 
cargo hold 2. Seals are maintained between the cover panel and the hatch 
coaming when closed, to prevent water leaks into the hold. 
Since a cargo hatch cover 10 must have sufficient strength to resist the 
actions of the sea on the vessel, including the force of breaking seas, 
the covers are made of heavy steel panels 12, well reinforced by internal 
flanges 13 and internal cross beams 14. Opening and closing such cover 
panels safely and effectively is not trivial. The invention is a mechanism 
which provides positive positioning of hatch cover panels in all positions 
from closed, through intermediate to the open position, with positive 
locking of the panel position and without the use of hydraulic, chain or 
cable systems. 
The invention is illustrated and described here in the form of a panel 
opening mechanism for two adjoining cargo hatch cover panels over a cargo 
hold. This exemplar embodiment may be extended to form a multi panel, end 
folding cover 10B. Since it is known how multi-panel assemblies may be 
generalized from a two panel configuration, the example here given is, for 
simplicity, shown as a two panel configuration. It will be apparent to 
those skilled in the art how equivalent structures may be constructed for 
multi panels as well as side opening panels. It should be apparent that 
the disclosed invention is applicable to any number of folding hatch cover 
panels, whether mounted along the length-wise axis of the vessel or 
mounted to be opened from side to side. 
In the inventive mechanism, a first cargo hatch cover panel 12A is mounted 
on the stowage end 16 of the hold 2, the end where the open hatch cover 
panels are to be stowed. This first panel 12A is attached to the hatch 
coaming 6 or deck 8 by hinges 18 so that the first panel 12A can be 
pivoted from a lowered closed position to a vertically raised open 
position. In general, for all hatch covers, an end panel is hinged, on a 
stowage end of the hatch, usually to the coaming of the hatch or deck, and 
all other panels 12B, each connected by hinges to its adjacent panel 12A, 
are supported by wheels 20 on both sides, the wheels riding on or in 
tracks 22. In this example, the second panel 12B is supported by wheels 20 
which ride on wheel tracks 22 which extend along each side of the hatch 
coaming 6. Both tracks 22 have an upper wheel supporting edge 24 which is 
substantially horizontal. In the example here shown, the track smoothly 
descends near the end of the hatch to a lower step level 26. Depending on 
the configuration of a specific hatch cover panel, the wheel tracks may be 
raised, or flat or integral with the hatch coaming sides. 
The second hatch cover panel 12B is mounted over the coaming 6 adjacent the 
first cover panel 12A. At least one cam actuated hinge 30, and sufficient 
secondary hinges for support, connect adjacent ends 32 of the second and 
first cover panels 12, so that they fold with respect to one another. For 
each such cam actuated hinge 30, a unilateral mechanical actuator 40 is 
mounted on one panel 12, and drives its respective cam actuated hinge 30 
so that the two adjacent panels 12 fold up into a stowed position at the 
stowage end 16 of the hatch, or extend flat to a position covering the 
hatch opening. 
The usual hatch cover has two or three cam actuated hinges 30 connecting 
adjacent panels 12. In addition to these hinges 30, secondary hinges (not 
shown) may also be provided for strength or stability. The number of cam 
actuated hinges and secondary hinges depends upon the weight and 
configuration of the hatch cover 10. 
As previously stated the first driven panel 12A is supported at the stowage 
end 16 of the hatch by support hinges 18. The remaining panels 12 are 
supported by wheels 20 which ride on wheel tracks 22 running along the top 
of the coaming 6. In this two panel example, the wheels 20 are mounted on 
the sides 50 of the second panel 12B, near the end opposite the support 
hinges 18. These wheels 20 may have flanges to prevent the wheels from 
derailing. 
It is an essential element of the invention that a mechanical actuator 
having a unilateral positioning mechanism 40 acts on the cam actuated 
hinge 30 to fold the panels 12, without the use of hydraulic fluid, chain 
or cable systems. Since all vessels have trained electrical personnel to 
service ship systems, this mechanical actuator 40 is powered by electric 
motor 42, so that the entire mechanism is within the maintenance 
capability of on board personnel and equipment. 
The phrase unilateral mechanical actuator 40 means a mechanically driven 
positioning actuator having a drive input 44 where mechanical motion is 
applied to position the actuator and a driven output 46, here a driven 
extension output, which is positioned in response to the input motion, but 
where mechanical force applied to the output does not result in motion of 
or change the position of the actuator extension. Such actuators typically 
involve a worm screw 48 and gear drive 52, where the worm 48 will rotate 
the gear 52 cannot turn the worm 48. 
The preferred form of unilateral mechanical actuator 40 is a worm driven 
screw mechanism. In the example embodiment, for each cam actuated hinge 
30, there is mounted to the underside of the first hatch cover panel 12A 
such a worm driven mechanism 40, fixed to the hatch cover panel 12A at 
right angles to the axis 54 of the hinge and aligned with the hinge 30. 
This actuator 40 is mounted to the panel 12A through a clevis fitting 56 
at its base, and is attached to the cam actuated hinge 30 by a upper yoke 
58 on its extension shaft. 
The worm driven screw 48 is mechanically driven through a right angle drive 
shaft, and provides a considerable mechanical advantage to its extension 
shaft 46, which extends or retracts as the drive shaft 44 turns. The 
example unilateral mechanical actuator is driven by rotating a worm 48 
against a gear 52, which in turn rotates a second screw 46, which forms 
the extension shaft. The application of driving forces in such a device is 
unilateral; rotation of the drive shaft 44 results in movement of the 
extension shaft 46, but no force on the extension shaft 46 will move the 
extension shaft 46 or rotate the input drive mechanism 44. As a result, 
the unilateral mechanical actuator 40 is positively mechanically locked in 
any position against compressive or tension forces along the extension 
shaft 46. 
It will be understood that such worm driven mechanical actuators 40 may be 
of many various configurations, although a worm and gear mechanism is 
preferred for both its mechanical advantage, and its strength of 
resistance against reverse motion. 
The cover panels 12 are lowered by retracting the extension shaft 46 of the 
unilateral mechanical actuator 40, which pulls the cam actuated hinge 30 
to a flat position. Throughout, the position of the cam actuated hinges 
30, and thus of the cover panels 12, is positively maintained by the 
extended position of the unilateral mechanical actuator 40. Since the 
unilateral mechanical actuator 40 is a mechanically positioned unit 
without susceptibility to back movement from the weight of the covers 10, 
any interruption of power merely stops the covers 10 in their travel; 
there is no possibility of the covers falling. Further the mechanical 
advantage of a unilateral mechanical actuator 40 is such that it is easily 
possible that one unilateral mechanical actuator 40 would be sufficient to 
move the covers 10. Usually more than one unilateral mechanical actuator 
40 and cam actuated hinge 30 is used. When a plurality of actuators 40 
exist, it is possible to overcome the failure of one actuator 40 by 
disconnecting the failed actuator 12 from its cover panel 12 and continue 
to operate the covers 10 using the remaining actuator(s) 40. 
The actuators 40 are driven by an input rotating shaft 44, which is driven 
by a worm gear reducer 60, which in turn is driven by an electric motor 
42. This ability to use electric power for positioning the hatch covers 10 
is a major strength of this invention. It eliminates the need for any 
hydraulic fluid, chain or cable drive on ship or near the cargo hold. This 
both secures the cargo against the possibility of contamination from 
hydraulic leaks, and simplifies shipboard maintenance. 
The embodiment example shows two mechanical actuators 40 driving two cam 
actuated hinges 30. The usual installation will have two actuators 40, 
while it is possible that some applications will have one actuator 40 and 
others may have three or more per panel, depending on panel weight and 
configuration. The two actuator system illustrates the principal features 
of the motor drive. One electric motor 42 is provided per driven panel 
12A, mounted on the panel 12A which supports the actuators 40, centrally 
between the actuators 40, or at any convenient point adjacent to the 
actuators 40. The motor 42 drives a worm gear reduction box 60 through a 
shaft and shaft coupler 62. The gear box 60 drives two shafts 64, each 
connected to an actuator 40. Each shaft 64 is provided with universal 
joints 66 to eliminate binding as the actuator 40 pivots about its 
mounting clevis 56. The use of a single motor 42 and gear box 60 insures 
that all actuators 40 are synchronously driven, and thus the movement of 
each cam actuated hinge 30 is identical across the panel 12. An additional 
advantage of the use of unilateral mechanical actuators 40 in the 
inventive apparatus is that mechanical overloads may be corrected by 
providing mechanical disconnects 66a on the shafts 64, to shear if any 
excessive binding occurs. Since the actuator 40 maintains its last 
position when drive rotation stops, no possibility of undesired hatch 
cover panel motion exists, and the panels 12 will not fall if the 
disconnect 66a shears. This provides a simple protection against 
mechanical binding or jams, with a desirable outcome that motion of the 
covers 10 stops until the source of the problem is found and corrected. 
The actuators 40 will act as locks, holding their position safely. 
The electric drive motor 42 is controlled through a master controller 70 
which receives power from ship's power main. The motor controller 42 
contains a relay, which is controlled by a control switch 72, mounted on a 
flexible cable 74 which may be plugged into an outlet 76 provided on the 
hatch cover panel side 50. This permits the operator to move around 
hatches 4, and directly control the opening and closing of each from a 
position where he can directly see and control the hatch covers 10. Limit 
switches 78 are provided to cut off motor motion when the cover panels 12 
are in the maximum open or closed position. These limit switches 78 may be 
set to sense the position of the panels, or, they may count the rotation 
of the drive shaft 64. Since the mechanical actuator 40 is precisely and 
repeatably positioned in response to the rotation of its drive shaft 64, 
basing hatch panel 12 positioning on the rotation limits of the drive 
shaft 64 is sufficiently accurate and precise. 
Cam Actuated Hinges 30 convert the motion of the unilateral mechanical 
actuator 40 into a folding motion of the hatch cover panels 12. In the 
example shown here, the cam actuated hinge 30 consists of two meshed hinge 
brackets 80, each rigidly attached to a cover panel 12; this is a strong 
attachment, such that movement of a hinge bracket 80 moves its attached 
panel 12. The brackets 80 are fastened together with, and fold around, 
hinge pins 82, which establish the hinge axis 54 around which the two 
cover panels 12 fold. 
The hinge 30 is designed so that when the driving force of the actuator 40 
is applied to a cam link, the cam link applies a lifting and folding force 
to the hinge 30 to fold the hinges 30. In this example, the cam link is 
two connected links. The first link is a "boomerang" or inverted L shaped 
hinge plate 84. This plate 84 is centered within the hinge 30; it is 
pivotally connected to one hinge bracket at a point 86 below the hinge 
axis 54. The top of the inverted L plate 84 is connected at one end 88 to 
a yoke 58 on the extending shaft 46 of the unilateral mechanical actuator 
40, and at the other end 90 to a second link 92, which in turn is 
connected 94 to the second hinge plate 80. 
Extension of the unilateral mechanical actuator 40 thus pushes the inverted 
L link 84, which, pivoting in an arc 96 above the folding axis 54 of the 
hinges 30, pulls up and lifts the hinge axis 54 and, pushing through the 
second link 92, folds down the second hinge bracket 80 against the first 
bracket 80. Thus when the driving side of the system is in motion, the 
cover panels 12 begin to rise up towards the open or stowed position. 
Retraction of the unilateral mechanical actuator 40 pulls on the inverted L 
link 84 and second link 92, unfolding the hinge 30 and the panels 12. This 
motion reverses the pulling action of the L link 84, pushing down and 
opening the hinge 30, causing the cover 10 to move to the flat or closed 
position. 
It is desirable to lift the hatch cover panels 12 free of the coaming 6 to 
protect the hatch cover seals. The wheel track 22 is shaped with an 
initial step rise 26, so that the motion of the panels 12 during opening 
is initially upwards, lifting the panels 12 sufficiently clear of the 
coaming 6 to prevent seal rub and wear. 
In order that the folded panels 12 clear the open hold 2 to allow full 
access to the cargo storage spaces, the first panel coaming hinges 18 are 
set back so that the opened panels 12 will retract to a space clear of the 
hold 2. Full extension of the mechanical actuator 40 pivots the second 
panel 12B against the first panel 12A, raising both panels 12 into a 
stowed, vertical position clear of the cargo hold 2. 
It can thus be seen that the disclosed electrically driven, unilateral 
mechanical hatch cover actuator, used in lieu of hydraulic, cable or chain 
actuators, provides significant operational advantages. The removal of 
hydraulic systems, with their attendant piping, fittings and leaks, avoids 
a major source of cargo contamination, by eliminating the presence of any 
hydraulic fluid in cargo spaces. Further, the use of a linear mechanical 
drive means which has no appreciable susceptibility to back motion 
eliminates nearly all the disadvantages, ricks to cargo and dangers 
attendant to the prior art hydraulic, chain and cable cover actuators, by 
eliminating the possibility of any mechanical failure which would result 
in the free fall of a hatch cover. 
It can thus be seen that the invention provides for a mechanically simpler 
and safer cargo hatch cover actuation mechanism. While a two cover system 
has been described, it will be apparent to those skilled in the art how 
the system may be generalized to multipanel systems, and how variant power 
drives may be employed. 
It should also be clear that, according to the invention, the unilateral 
mechanical actuator mechanism may be substituted for hydraulic cylinders 
following the structure of many of the prior art hydraulic actuated 
systems, providing many of the advantages shown. The example system with 
worm driven screw actuators mounted to a cover panel has advantages in 
easy mechanical synchronization of the drive to each mechanical actuator, 
and some such synchronization must be provided for all multi actuator 
systems to prevent warping the covers. 
The invention therefore extends beyond the embodiments described to include 
equivalents to the claims.