U.S. patent number 3,612,486 [Application Number 04/867,277] was granted by the patent office on 1971-10-12 for vertical load transfer.
Invention is credited to Gerald Joseph Martin, John Murray Vines.
United States Patent |
3,612,486 |
Martin , et al. |
October 12, 1971 |
VERTICAL LOAD TRANSFER
Abstract
This application discloses a system for lowering a delicate load
to the d of a ship from a helicopter. A first cable maintained at
constant tension extends up from the ship, round a pulley or drum
carried by the helicopter and down to the said load. This provides
support which is substantially constant for the load. A second
cable extends down from the load to the ship, and is used to winch
the load down to the ship. The system can be used to raise loads
from the ship to the helicopter, and can be used for other similar
load transfer situations.
Inventors: |
Martin; Gerald Joseph (Bedford,
Nova Scotia, CA), Vines; John Murray (Bedford, Nova
Scotia, CA) |
Assignee: |
|
Family
ID: |
25349478 |
Appl.
No.: |
04/867,277 |
Filed: |
October 17, 1969 |
Current U.S.
Class: |
254/267; 254/270;
254/275; 254/277; 254/318; 254/386; 254/900 |
Current CPC
Class: |
B66D
1/48 (20130101); B64D 1/22 (20130101); B66D
2700/0108 (20130101); Y10S 254/90 (20130101) |
Current International
Class: |
B64D
1/22 (20060101); B64D 1/00 (20060101); B66D
1/48 (20060101); B66D 1/28 (20060101); B66d
001/50 (); B66d 001/48 () |
Field of
Search: |
;254/144,147,172,173,186
;187/20,27 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Hornsby; Harvey C.
Assistant Examiner: Maffei; Merle F.
Claims
We claim:
1. Means suitable for effecting the vertical or substantially
vertical transfer of objects between an upper station and a lower
station subject to unpredictable but limited relative vertical
movements, comprising:
a. constant tension winch means carried by said lower station;
b. pulley means carried by said upper station;
c. first cable means having a first end and a second end;
d. a first connection between said first end of said first cable
means and said winch means;
e. a second connection between said second end of said cable means
and said object;
f. an intermediate part of said cable means extending from said
first end to said pulley means and thence to said second end;
g. further cable means having a first end and a second end;
h. a third connection between said first end of said further cable
means and said object;
i. haul down winch means carried by said lower station;
j. a connection between said second end of said further cable means
and said haul down winch means;
k. readily releasable means which serve as said third connection
between said first end of said further cable means and said
object;
l. messenger winch means provided at said upper station; and
m. said messenger winch means being adapted when operated to raise
said second end of said further cable means from said lower station
to said upper station;
whereby said object is supported by said first cable means with a
substantially constant force, and said load is forcibly drawn from
said upper station to said lower station by the force in said
further cable means.
2. Transfer means according to claim 1, and in which:
a. said first cable means include a first cable and a second
cable;
b. said pulley means are in the form of a drum;
c. said drum is adapted to accommodate several turns of said first
cable and several turns of said second cable;
d. a first end of said first cable constitutes said first end of
the cable means;
e. a second end of said first cable is connected to said drum;
f. a first end of said second cable is connected to said drum;
and
g. a second end of said second cable constitutes said second end of
said cable means.
3. Transfer means according to claim 2, and in which:
a. said drum is mounted in a freely rotatable manner; and
b. a brake is associated with said drum and is effective to hold
the drum in a desired position.
4. Transfer means according to claim 3, and in which motor means
are provided operatively connected to said drum, and effective when
activated to drive said drum in either direction as desired.
5. Transfer means according to claim 1, and in which;
a. a snatch absorbing device is provided; and
b. said further cable means during vertical transfer of said object
extend from said object to said snatch absorbing device and then to
the haul down winch.
6. Transfer means according to claim 5, and including;
a. a first set of pulleys;
b. a second set of pulleys;
c. biasing means arranged to bias the two sets of pulleys apart by
a force which increases as said sets of pulleys approach one
another;
said sets of pulleys and said biasing means with part of a cable of
said further cable means forming a cable accumulator which serves
as said snatch absorbing device.
7. Transfer means according to claim 1, and in which:
a. a snatch absorbing device is provided;
b. the first cable means pass through the snatch absorbing device;
and
c. the snatch absorbing device is positioned close to the constant
tension winch means.
8. Transfer means according to claim 7, and including:
a. a first set of pulleys;
b. a second set of pulleys;
c. biasing means arranged to bias the two sets of pulleys apart by
a force which increases as the sets of pulleys approach one
another;
said sets of pulleys and said biasing means with part of a cable of
said first cable means forming a cable accumulator which serves as
said snatch absorbing device.
9. Transfer means according to claim 8 and including:
a. a first transducer providing an output indicative of the speed
of said first cable means at said winch side of said cable
accumulator;
b. a second transducer providing an output indicative of said speed
of said first cable means at said load side of said cable
accumulator;
c. sensitive means arranged to received these two outputs; and
d. a control system including said first and second transducers and
said sensitive means and arranged to control said constant tension
winch means; said control system being arranged in accordance with
the output from said sensitive means to provide an anticipatory
control of said winch means tending to keep the cable tension
constant.
10. Transfer means according to claim 1, and including:
a. a transducer providing an output indicative of the speed of said
second cable means;
b. a control providing an output indicative of a desired speed for
said second cable means;
c. sensitive means to which these two outputs are applied; and
d. a control system including said transducer, said control and
said sensitive means, and arranged to control the operation of said
haul down winch means, and arranged to control said winch means to
keep the speed of the second cable means constant.
11. Transfer means according to claim 1, and in which said object
includes a C-shaped load support frame adapted to accommodate and
support the weight of a load to be transferred between said upper
and lower stations.
12. Transfer means according to claim 11, and in which said
C-shaped load support frame is provided at its top with a buffer by
which upward movement of the frame is checked when it reaches said
upper station.
13. Transfer means according to claim 1, and in which said further
cable means are coupled to the bottom of said object through a
remotely releasable shackle.
14. Means suitable for effecting the vertical or substantially
vertical transfer of objects between an upper station and a lower
station subject to unpredictable but limited vertical movements,
comprising:
a. constant tension winch means carried by the lower station;
b. first cable means including a first cable and a second cable and
having a first end and a second end;
c. drum pulley means carried by the upper station adapted to
accommodate several turns of the first cable and several turns of
the second cable;
d. a connection between the first end of the first cable and the
winch means;
e. a connection between the second end of said first cable and the
said object;
f. said first end of the first cable connected to the drum by a
readily detachable coupling;
g. a first end of the second cable connected to the drum;
h. a second end of the second cable constituting the said second
end of the cable means;
i. an intermediate part of the cable means extending from the said
first end of said first cable to the pulley means and thence to the
second end;
j. further cable means having a first end and a second end;
k. a connection between the first end of the further cable means
and the said object;
l. haul down winch means carried by the lower station;
m. a connection between the second end of the further cable means
and the said haul down winch means; whereby the said object is
supported by the first cable means with a substantially constant
force, and the load is forcibly drawn from the upper station to the
lower station by the force in the further cable means;
n. readily releasable means serve as the said connection between
the first end of the further cable means and the said object;
o. messenger winch means provided at the upper station; and
p. said messenger winch means are adapted when operated to raise
the said second end of the further cable means from the lower
station to the upper station.
Description
This invention relates to the provision of a system which will
enable a delicate load to be lowered to the deck of a ship from a
helicopter with minimum possibility of damage to that load. It will
be appreciated that when the ship is pitching, the load is liable
to impact the deck violently, and it is important to lower the load
onto the deck of the ship with minimum practical acceleration with
respect to the ship's . deck.
According to the present invention, means suitable for effecting
the vertical or substantially vertical transfer of objects between
an upper station and a lower station subject to unpredictable but
limited relative vertical movements, comprise constant tension
winch means carried by the lower station, pulley means carried by
the upper station, first cable means connected at a first end to
the winch means and extending from the winch means to the pulley
means carried by the upper station and attached at their second end
to a load to be lowered from the upper station, and further cable
means extending downwardly from the said load to haul down winch
means also carried by the second station, whereby the load is
supported by the first cable means with a substantially constant
force, and the load is forcibly drawn from the upper station to the
lower station by the force in the further cable means.
The invention will now be described, by way of example, with
reference to the accompanying drawings, in which:
FIG. 1 is a diagrammatic side elevation of a helicopter and of a
ship-borne haul-down system for that helicopter, and is included to
show the form of a constant tension haul-down winching system
utilized in the carrying out of the present invention.
FIG. 2 is a diagrammatic representation of the arrangement of
tackle between a helicopter and a ship during the transfer of loads
between the helicopter and the ship;
FIG. 2A is a diagram in the form of a sectional end elevation taken
on the line II--II of FIG. 2;
FIG. 3 is a force diagram showing how forces acting on a load
during lowering are balanced; and
FIG. 4 is a circuit diagram indicating the control of a tension
winch and a velocity winch shown in FIG. 2.
Referring first to FIG. 1, it has been proposed in copending
Canadian Pat. application Ser. Nos. 887,011 and 914,140 that a
helicopter 1 shall be hauled down onto the deck 3 of a ship at sea
by a cable 5 acting against the lift produced by the helicopter
rotor. This enables the helicopter to land safely despite pitching
of the ship and despite the action of wind on the aircraft. In
those proposals, a probe 7 carried by the helicopter 1 is seized in
a trap 9 carried by the ship so that once the helicopter has landed
it is held firmly against movement relative to the ship, and
eventually the trap is used to transport the helicopter bodily into
a hanger in which the helicopter is stored.
As described in those earlier patent applications, an electric
motor (not shown) is coupled to the driving shaft of a variable
displacement hydraulic pump, connected in closed circuit to a fixed
displacement hydraulic motor. Such an arrangement is well known in
the art, and commonly makes use of a pump with a tiltable
swashplate or a pump with a fixed swashplate but an adjustable tilt
head. The output shaft of this hydraulic motor is connected through
a gearbox alternatively either to a drum 15 of haul down winch or
to a drum 21 of a trap traversing winch. The cable 5 has one end
wound on the drum 15 and extends from the winch drum first over
pulleys of a rope accumulator 23 and then round a guide sheave 25
and finally over a sheave 27 before passing upwardly through the
deck 3 to the helicopter 1. The rope accumulator includes a first
set of pulleys and a second set of pulleys, the two sets being
biased apart by a pneumatic cylinder device 29 which has a
force/displacement characteristic such that the force biasing the
two sets of pulleys apart increases progressively as the two sets
are forced closer together by the tension in the cable 5.
The present invention does not relate to the probe 7 or the trap 9
or the trap traversing winch associated with drum 21. However it
does make use of the cable 5 and the associated drum 15 and rope
accumulator 23.
As shown in FIG. 2, mounted inside the fuselage of the helicopter 1
is a winch drum 41 arranged with its axis horizontal and provided
at one end with a drum brake 43. This drum 41 is free to rotate in
each direction when not held by brake 43. At its end remote from
brake 43, drum 41 is provided with an eye bolt 45 to which a cable
5 can be connected by a shackle 47. Near the brake 43, the drum 41
is provided with an anchor 49 to which one end of a load cable 51
is connected by a suitable shackle. Load cable 51 is long enough to
reach from the helicopter to the ship deck 3 during a load-lowering
operation, but as shown is normally wrapped round the drum 41 and
has its other end connected to the upper end of a C-shaped load
support frame 53. This frame 53 is big enough to extend round a
load 55 to be lowered from the helicopter to the ship deck, and
carries in its upper part a suitable support by which the load 55
can be suspended. If desired, the load 55 can be supported on the
lower part of the frame 53.
Fitted to the underside of the frame 53 is an electrically
releasable shackle 57, and an actuating electrical cable 59 for
this shackle extends from the shackle up round the frame 53 to an
electric cable reel 61 carried by the helicopter. The reel 61 is
provided with a reversible driving motor, by means of which an
operator can pay out or reeve in cable 59 as he deems necessary. A
load transfer winching cable 65 is connected at one end to the
frame 53 in a readily detachable manner through the shackle 57, the
cable 65 extending up past the frame 53 and being stored as a loose
coil at 65A on the floor of the helicopter.
Additional equipment provided on the deck 3 of the ship includes
another rope accumulator 71 generally similar to the rope
accumulator 29. Accumulator 71 includes an hydraulic cylinder 73
connected through a pipe 75 to a hydropneumatic accumulator 77
having a diaphragm 79 separating a gas under pressure from the
liquid used in the cylinder 73. The pipe 75 includes a flow
restricting orifice 81 shunted by a nonreturn valve 83 which
permits free flow of liquid during inward movement of piston 85 in
the cylinder 73. Thus inward movement is not seriously impeded but
outward movement is seriously dampened. Associated with accumulator
71 is a deck wince 87 provided with a clutch 89 which can be
operated to cause the winch drum to freewheel. A messenger winch 91
driven by a reversible electric motor is provided in the
helicopter, but if desired this can be omitted and a messenger
winch of the haul-down system used in its place.
The floor of the helicopter is provided with an aperture 95 through
which the various cables can extend, and this aperture is of such
size that the upper part of the load support frame 53 can be drawn
up into the helicopter body. The top of the frame 53 is provided
with a spring-loaded buffer 97, and a slidable shutter 99 can be
moved from the position shown, in which a stop 101 on the shutter
99 engages the buffer when the frame 53 is raised excessively, to
an open position in which the upper part of frame 53 is free to
rise into the body of the helicopter. Respectively adjacent
aperture 95 and on shutter 99 are provided first and second power
operable guillotines 103 and 105. These are arranged when actuated
(the frame 53 being below the helicopter) to sever respectively the
cable 5 and the cable 51.
Turning now to the use of the load handling system of FIGS. 2, 2A
and 3, the two winches 15 and 87 are required to operate the load
handling system of the present invention. The primary winch 15 is
used to provide a constant tension in cable 5, which during loading
and unloading is shackled to the drum 41 and thus is effectively
connected through the cable 51 to the load support frame 53 as if
cables 5 and 51 were a single length of cable. The tension during
use in cables 5 and 51 must exceed the cable tension necessary to
support the weight of the load 55. The secondary deck winch 87 is
used to control the rate of descent of the load 55 onto the deck 3
of the ship, and cable 65 at this time is connected (see dotted
line in FIG. 2) at one end to the winch 87 and at the other end to
the shackle 57 of the load support frame 53.
SEQUENCE OF OPERATION
To raise the load 55 from the deck of a supply ship to the
helicopter, the helicopter 1 hovers over the supply ship at a
height of about 50 feet and lowers a light messenger cable to the
deck crew by means of the messenger winch 91. The deck crew attach
the shackle 47 on cable 5 to the messenger cable, and the
helicopter crew then winches the messenger cable with the free end
of the cable 5 up to the helicopter. Once cable 5 is inside the
helicopter, the shackle 47 is transferred to the eyebolt 45. At
this time, the helicopter will be about 50 feet above the ship and
slightly aft of the ship, so that the cable 5 will extend upwardly
at a slight inclination to the vertical, as indicated in FIG. 2A,
which is a view of the drum 41 as viewed from one side of the
helicopter and the ship. It is important that the force on cable 5
shall be applied to the helicopter through the axis of drum 41 and
therefore at the time of connection the drum 41 is held by the
brake 43 with the eyebolt 45 in the position shown in FIG. 2A.
The winch 15 is now set by a controller on the ship to produce an
appropriate constant tension to the cable 5, and the helicopter is
then tethered to the ship, the force produced by the helicopter
rotor being sufficient to counter balance both the tension T in the
cable 5 and the weight of the frame 53 and the other downward
forces acting on the helicopter.
The free end of the load transfer winching cable 65 (i.e. the part
of that cable in coil 65A) is now lowered by the helicopter crew to
the ship deck. This cable can be dropped, but usually it will be
thought better to lower it by the messenger cable of messenger
winch 91. The crew of the ship reeve the free end of the cable 65
round the pulleys of the accumulator 71 and attach the free end to
the drum of winch 87. With the cable 65 slack, the helicopter crew
slacken the brake 43 so that the drum 41 revolves until the
clockwise and anticlockwise torques on it, produced by cables 5 and
51, are balanced. It is to be noted that the total force in cable
51 is less than the total force in cable 5, and this must be so if
the frame 53 is not to descend unchecked. However, initially the
line of action of cable 5 is through the axis of drum 41, so that
it produces zero torque, and the position of rest will be reached
in less than a quarter turn of the drum 41, which in the worst
initial case of cable 5 being vertical would bring cable 5 into
tangential position relative to the drum.
The controller on the ship now operates deck winch 89 to take in
the slack on the cable 65 and to apply a tension to the cable. This
will increase the load in cable 51 and thus the torque applied by
that cable on drum 41. The drum will change its angular position to
maintain the two torques on it equal, but since the torque which
cable 5 can produce is limited by the (constant) tension in this
cable, once the torque produced by cable 51 rises above the
limiting value for cable 5, the load frame 53 will commence to
descend.
During descent, the forces acting on the frame 53 and the drum 41
will be as shown in FIG. 3. For non accelerating transfer of the
frame 53, the force T in cable 5 and the equal force T in cable 51
will set up a downward force of 2T on the drum 41 which will be
balanced by the reaction of the drum bearings. The force T in cable
51 will set up an upward force T on the frame 53, and this will be
balanced by the sum of the downward force W produced by the weight
of frame 53 and the downward force T0 produced by the tension TO in
the cable 65. For the sake of simplicity, the weights of the cables
5, 51 and 65 are ignored in the present discussion, but in practice
these would need to be considered if cables 5 and 65 had a
different "weight per foot length." During descent, any change in
the relative positions of the helicopter and the ship are
accommodated by the action winch the winch 15, which operates
automatically to keep the tension in cable 5 constant. Ideally, a
change in the distance of the helicopter from the ship would not
cause any change in the effective length of cable 65, so that the
load supporting frame 53 would remain at a constant distance from
the ship. This means that the distance of the frame 53 from the
helicopter would vary, and this is compensated for automatically by
the control system for the winch 15. Changes which are too fast for
the winch 87 to follow would be accommodated by the taking-in or
the paying-out of cable 5 at the accumulator 23. In practice, the
accumulator 71 would operate to smooth out snatch loadings such as
would arise if the ship drops suddenly in the trough of two waves.
The speed of descent is controlled by the speed of winch 87.
When the load frame 53 is settled on the deck of the ship, the ship
crew attach the load 55 to the frame 53. This causes no upset in
the force system, since the force T0 falls to such a level that the
force TO plus the weight of the frame 53 and the weight of load 55
together equal force T in cable 51. The deck winch 87 is now
operated to pay out cable 65 so that the frame 53 with the load 55
rises towards the helicopter. The frame 53 is drawn up until the
buffer 97 engages the stop 101, and the brake 43 is then applied.
Care is taken that the drum 41 is locked in the position shown in
FIG. 2A. The clutch 89 is now released so that the force T0 falls
to zero (apart from the weight of the cable). The helicopter winch
91 is used to lower the messenger cable, the lower end of cable 65
is freed from winch 87 and accumulator 71, and this end of cable 65
is drawn up by the messenger cable and stored in the helicopter at
65A. The controller on the ship progressively reduces the tension
in the tethering cable 5 and when this tension is zero (apart from
the weight of the cable) the shackle 47 is released from the winch
eyebolt 45 and this end of cable 5 lowered to the ship. It may be
dropped, or it may be lowered by the messenger cable of winch 91,
as desired.
The helicopter is now free to fly to the ship to which the stores,
represented by load 55, are to be transferred. The procedure
described above, as used at the supply ship, will be repeated,
except that of course during the lowering of frame 53 it will
contain the load 55 and during raising it will be free of the
load.
Also shown in FIG. 2 is a hydraulic motor-and-clutch unit 201 which
can be supplied if desired. This motor-and-clutch unit 201 is
normally disconnected by its clutch from the drum 41, but when
desired the clutch can be engaged and, with the brake 43 released,
the motor used to drive the drum 41 to raise or lower the frame 53.
This is a useful ancillary facility, and does enable the helicopter
to dispose of the frame 53 and load 55 when for any reason the
system described above cannot be used.
The helicopter 1 cannot take off or land with the frame 53 in the
position shown in FIG. 2. During landing and takeoff, the frame 53
can be drawn up partly into the helicopter 1 to enable the usual
landing means to be operative. Alternatively, the frame 53 can be
lowered onto the deck of a ship; the brake 43 applied to lock the
drum 41; cables 51 and 59 disconnected from the frame 53; cable 59
reeled in by its winch 61; the brake 43 allowed to slip so that the
tension in cable 5 rotates drum 41 firstly to unwind cable 5 from
that drum and secondly to wind cable 51 back on that drum, the drum
41 finally being braked again in the orientation shown in FIG. 2A;
the tension in cable 5 removed progressively, the shackle 47
disconnected from the eyebolt 45 to free the helicopter from the
ship, and the free end of the cable 5 lowered to the ship.
The following data relate to one embodiment of the invention:
The proposed system has been designed within following
assumptions:
1. The helicopter will lift a load greater than 5,000 lbs. fully
fueled.
2. The maximum load is limited to 3,000 lbs.
3. Maximum velocity between ship and helicopter 20ft./sec.
4. Maximum acceleration between ship and helicopter
20ft./sec.sup.2.
5. The height of the helicopter undercarriage above deck for
transfer is 50 ft. .+-. 30 ft.
6. Maximum velocity of velocity winch 3ft./sec.
7. Maximum tension variation on helicopter: .+-.15 percent of total
load on helicopter.
FIG. 4 illustrates a control system which controls the operation of
the tension winch 15 and the velocity winch 87. As regards the
velocity winch 87, and control 201 operated by the controller of
the transfer operation sets the desired rate of ascent or descent
of the load frame 53. Through an amplifier 203 the signal from
control 201 determines the operation of motor/gear box unit 205
driving the velocity winch 87. A velocity transducer 209 provides
the amplifier 203 with a second input which indicates the actual
speed of operation of the winch and thus the actual velocity of the
cable 65.
As regards the constant tension winch 15, a control 221 operated by
the controller of the transfer operation sets the desired tension
in the cables 5 and 51. The output from control 221 is applied to
an amplifier 223 together with a second input from a tachometer 225
which indicates the actual velocity of the drum of the winch 15 and
a third input from a tachometer 227 which indicates the actual
velocity of the cable 5 at the point where it leaves the ship.
Control of the winch 15 is by adjustment of the "tilt-head" 228 of
the hydraulic drive for the winch, the winch being driven by an
electric motor which drives a hydraulic pump 229 arranged to drive
the hydraulic motor 231 of the winch. A tension transducer 233
associated with a sheave carried by the ship and about which the
cable 5 is wrapped before it extends upwardly to the helicopter,
provides an indication of the actual tension in the cable 5. The
output from this transducer is used during "constant tension"
operation to buck the signal from the control 221 and so provide an
indication of error between desired tension and actual tension in
the cables 5 and 51. It will be noted that in FIG. 4 a switch 241
is provided by which the winch 15 can be changed from "constant
tension" operation to "velocity" operation during taking up of
slack in the cables. The output from tension transducer 233 is
applied to a sensor 243 which is effective when the cable tension
reaches 100 pounds, during "velocity" operation, to change the
setting of the switch 241 and so transform the winch operation
automatically from "velocity" to "constant tension."
It may occasionally be necessary in an emergency to abort a
transfer operation and rapidly to disconnect the helicopter from
the ship. This can be done by activating the guillotine 103 to
sever the cable 5 and by releasing the shackle 57 to release the
cable 65 from the frame 53. The helicopter can then veer away from
the ship. The guillotine 105 is provided so that if necessary the
frame 53 with the load 55 can be jettisoned by cutting the cable
51. However, this would not be done while the helicopter was still
over the stern of the ship.
* * * * *