U.S. patent number 3,675,900 [Application Number 05/019,582] was granted by the patent office on 1972-07-11 for motion compensating hoist.
This patent grant is currently assigned to Byron Jackson, Inc.. Invention is credited to Charles D. Barron, Earl A. Peterson, Gary K. Stark, Carl A. Wilms.
United States Patent |
3,675,900 |
Barron , et al. |
July 11, 1972 |
**Please see images for:
( Certificate of Correction ) ** |
MOTION COMPENSATING HOIST
Abstract
A motion compensating hoist for moving a load between relatively
vertically movable points, in which a cable from a tensioning hoist
is interconnected between the two points, and the cable from a load
hoist is connected to the load, and the tensioning hoist and the
load hoist are cooperable to establish movement of the load
corresponding to the relative movement between the two points and
to cause further movement of the load between the two points.
Inventors: |
Barron; Charles D. (Huntington
Beach, CA), Peterson; Earl A. (Long Beach, CA), Stark;
Gary K. (Buena Park, CA), Wilms; Carl A. (La Habra,
CA) |
Assignee: |
Byron Jackson, Inc. (Long
Beach, CA)
|
Family
ID: |
21793965 |
Appl.
No.: |
05/019,582 |
Filed: |
March 16, 1970 |
Current U.S.
Class: |
254/270; 254/273;
254/361; 254/900; 414/139.6; 254/340; 254/375; 254/903 |
Current CPC
Class: |
B66D
1/48 (20130101); Y10S 254/903 (20130101); Y10S
254/90 (20130101); B66D 2700/0108 (20130101) |
Current International
Class: |
B66D
1/48 (20060101); B66D 1/28 (20060101); B65g
067/58 () |
Field of
Search: |
;214/13-15
;254/172,173,174,175 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Makay; Albert J.
Assistant Examiner: Werner; Frank E.
Claims
We claim:
1. A motion compensating hoist including hoist means for moving a
load between relatively vertically movable locations comprising:
load hoist means mounted at one of said locations and having a load
line connectable to a load, tensioning hoist means mounted at one
of said locations and having a tension line connectable at the
other of said locations, a source of power, slip clutch means for
connecting said source of power to said hoist means to apply
tension to said tension line, motion compensating drive means for
connecting said load hoist means to said tensioning hoist means for
moving said load line and said tension line synchronously with the
relative movement between said locations, and means for
superimposing on said synchronous movement further movement of said
load line to move said load relative to said locations.
2. A motion compensating hoist as defined in claim 1, including
releasable drive means in said motion compensating drive means, and
a separate source of power for said load hoist means operable when
said releasable drive means is released to drive said load hoist
means.
3. A motion compensating hoist as defined in claim 2, wherein said
separate source of power is also operable when said releasable
drive means is engaged to superimpose said further movement of said
load line on said synchronous movement.
4. A motion compensating hoist as defined in claim 1, wherein said
slip clutch means is operable by fluid pressure to transmit torque
at a value which varies with the applied fluid pressure, and
including means for supplying pressure fluid to said slip clutch
means.
5. A motion compensating hoist as defined in claim 4, wherein said
means for supplying pressure fluid to said slip clutch means
includes tension responsive means operable by said tension line for
varying the pressure applied to said fluid pressure operated means
to vary the torque transmitting capacity of said slip clutch
means.
6. A motion compensating hoist as defined in claim 4, wherein said
means for supplying pressure fluid to said slip clutch means
includes tension responsive means operable by said tension line for
varying the pressure applied to said fluid pressure operated means
to vary the torque transmitting capacity of said slip clutch means,
said tension responsive means including a hydraulic load cell
operable by said tension line, and pressure controller means
connected to said load cell and responsive to changes in load on
the latter to vary the pressure of pressure fluid supplied to said
slip clutch means.
7. A motion compensating hoist as defined in claim 4, wherein said
means for supplying pressure fluid to said slip clutch means
includes means for supplying a selected pressure proportionate to
the load to be moved, and means responsive to tension on said
tension line to vary the pressure supplied to said slip clutch
means, whereby the tension on said tension line remains
substantially constant when said load hoist line is supporting said
load and said motion compensating drive means connects said
tensioning hoist means to said load hoist means and releases said
tensioning hoist means from said load hoist means.
8. A motion compensating hoist as defined in claim 4, wherein said
means for supplying pressure fluid to said slip clutch means
includes pressure control means for applying pressure to said slip
clutch means at a value determined by the tension on said tension
line.
9. A motion compensating hoist as defined in claim 1, wherein said
load hoist means includes a drive shaft drivable by said motion
compensating drive means, and a drum revolvable about said shaft,
and including a separate source of power for driving said drum
relative to said shaft.
10. A motion compensating hoist as defined in claim 1, wherein said
load hoist means includes a drive shaft drivable by said motion
compensating drive means, a drum revolvable about said shaft, and
including a separate source of power for driving said drum relative
to said shaft, and releasable means normally connecting said drum
to said shaft for rotation as a unit, and means for releasing said
releasable means upon operation of said separate source of power to
drive said drum relative to said shaft.
11. A motion compensating hoist as defined in claim 1, wherein said
load hoist means includes a drive shaft, said motion compensating
drive means including a clutch interposed between said tensioning
hoist and said shaft, and actuator means for engaging said
last-mentioned clutch.
12. A motion compensating hoist as defined in claim 1, wherein said
load hoist means includes a drive shaft, said motion compensating
drive means including a clutch interposed between said tensioning
hoist and said shaft, actuator means for engaging said
last-mentioned clutch, brake means for said shaft, and actuator
means for releasing said brake means when said last-mentioned
clutch is engaged.
13. A motion compensating hoist as defined in claim 1, wherein said
load hoist means includes a drive shaft drivable by said motion
compensating drive means, a drum revolvable about said shaft, and
including a motor for driving said drum relative to said shaft,
said motion compensating drive means including a clutch interposed
between said tensioning hoist and said shaft, actuator means for
engaging said last-mentioned clutch means, brake means for said
shaft, and actuator means for releasing said brake means when said
last-mentioned clutch is engaged.
14. Drum apparatus for a load line comprising: a drum shaft, a drum
revolvably mounted on said shaft for relative rotation, a support
fixed on said shaft for rotation therewith, reversible motor means
carried by said support and engaged with said drum to rotate the
latter in either direction, releasable means carried by said
support and engageable with said drum to lock said drum to said
shaft, means for driving said motor in either direction and
releasing said releasable means, and drive means for rotating said
shaft in either direction.
15. Drum apparatus as defined in claim 14, including brake means
for said shaft, and means for releasing said brake means when said
drive means is operative to rotate said shaft.
16. Drum apparatus as defined in claim 14, wherein said drive means
includes slip clutch means having a pressure responsive actuator
for varying the torque transmitting capacity of said slip clutch
means.
17. Drum apparatus as defined in claim 14, wherein said drive means
includes another drum and shaft connected for rotation with one
another and having a line, releasable means driven by said another
drum and shaft and connectable to said shaft of the first-mentioned
drum to drive both of said drums in unison, and variable slip
clutch means for driving said another drum and shaft to apply
tension to the line thereon.
Description
BACKGROUND OF THE INVENTION
In the transfer of a load between two relatively movable points,
such as the transfer of cargo or personnel between a well drilling
platform or barge which is located in a body of water and a vessel
floating in the water along side the platform or barge, problems
are encountered caused by the rise and fall of the vessel on the
surface of the water. When the water is rough, the problem is
aggravated. Essentially, the problem involves the difficulty
encountered in moving the load, such as the cargo or personnel,
through a comparatively short distance to and from the rising and
falling deck of the vessel. In many instances, the transfer of
equipment or personnel between a floating vessel and a stationary
platform or larger floating vessel in the water has heretofore been
practically impossible to accomplish in the presence of large
waves, particularly when the waves occur at rapid intervals.
SUMMARY OF THE INVENTION
The present invention provides a motion compensating hoist system
which obviates the difficulties heretofore encountered in the
movement of cargo or personnel between a platform or barge or large
floating vessel and a smaller floating vessel or boat.
More particularly, the invention provides a motion compensating
hoist system whereby a load to be transferred between the platform
and the boat is caused to move synchronously with the boat during
the period that the load is being initially moved from or finally
placed upon the boat. In accomplishing the foregoing, synchronous
movement of the load with the boat is accomplished by a unique
combination of a tensioning hoist coupled to a load hoist.
More particularly, an elevator device adapted to be connected to
the load or to contain the load is carried by the load hoist line
or cable and a tensioning hoist line or cable is connected to the
boat. The tensioning hoist is driven through a clutch which is
adapted to constantly slip with a given variable torque output so
as to maintain a substantially constant tension on the tensioning
hoist line extending between the boat and the platform. Load
sensing means are responsive to the tension on the tensioning hoist
line to provide a continuous signal which is compared to a preset
load value to automatically adjust the torque capacity of the
clutch and thereby maintain tension on the hoist line at
substantially the preset value. The load hoist is connected by
drive means to the tensioning hoist and such drive means are
selectively operable to establish unitized drive of the tension
hoist and the load hoist, resulting in the synchronous movement of
the load with the boat, and means are provided to super-impose on
the synchronous movement controlled raising or lowering of the load
from or to the deck of the vessel.
Such a motion compensating hoist system enables the effective
transfer of cargo and personnel between a platform and a floating
boat or vessel in a much safer manner than has been heretofore
proposed. Since the load is synchronously moving with the boat, the
load experiences no hard landings or impact with the boat as the
load is moved to or from the boat, and the tensioning line or cable
which connects the boat to the platform is available for use as a
guide for the load to direct the movement of the load to or from a
precise location on the boat, as well as to prevent spinning of the
load.
This invention possesses many other advantages, and has other
purposes which may be made more clearly apparent from a
consideration of a form in which it may be embodied. This form is
shown in the drawings accompanying and forming part of the present
specification. It will now be described in detail, for the purpose
of illustrating the general principles of the invention; but it is
to be understood that such detailed description is not to be taken
in a limiting sense, since the scope of the invention is best
defined by the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective, fragmentary view, showing a platform or
barge above the water and equipped with the invention for moving a
load to or from a boat afloat in the water;
FIG. 2 is an end elevation of the power unit and the hoist and
tension winches;
FIG. 3a is a fragmentary view in side elevation, as taken on the
line 3--3 of FIG. 2, on an enlarged scale, and showing the tension
winch, with parts broken away;
FIG. 3b is a fragmentary view, as taken on the line 3--3 of FIG. 2,
constituting a continuation of FIG. 3a, and showing the hoist winch
and its drive connection to the tension winch; and
FIG. 4 is a diagrammatic illustration of the combined winches and
control means therefor.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring first to FIGS. 1 and 2, there is generally illustrated a
barge or platform P adapted to be supported above the water on a
number of suitably located legs L which extend to the bottom of the
water, and on which the platform or barge P is mounted. In the case
of certain barges, the platform is adapted to be elevated to a
selected height above the water on the legs L, a distance of 80
feet more or less. On the barge or platform may be located the
usual well drilling and/or completion or workover apparatus (not
shown), as is well known in the art. It will also be understood
that the platform P may consist of a large vessel afloat on the
water.
Periodically, the workers on the platform must be transported
between the platform and the shore, and in addition, it becomes
necessary from time to time to move various gear between the shore
and the platform. Thus, a boat or vessel V is in part illustrated,
and such boats or vessels range considerably in size from
comparatively large work boats adapted to move heavy gear and
supplies between the shore and the platform, and small personnel
carrying boats. In either case, problems are experienced in
transferring the gear or personnel between the vessel and the
platform.
When the weather is fair and the water is calm the problem is less
pronounced, but, when the water becomes rough and swells tend to
cause the boat or vessel V to rise and fall relative to the
platform, the problem is more pronounced. The greater the frequency
of the swells the worse the problem, so that under many commonly
encountered conditions, the transfer of equipment or personnel
between the platform and the boat or vessel V is very difficult, if
TH, V and not impossible to accomplish.
The present invention contemplates a motion compensating hoist
system whereby an elevator E or other load support is adapted to be
raised or lowered between the outer extremity of a boom B and the
vessel V, the elevator E being suspended by a load hoist cable or
line 10. A tensioning line or cable 11 extends between the outer
extremity of the boom B and a point of attachment 12 to the deck of
the boat or vessel V. The lines or cables 10 and 11 respectively,
are controlled by load hoist means LH and tensioning hoist means
the whereby during the initial stages of the lifting of the
elevator E from the deck of the vessel Vand during the final stages
of movement of the elevator E onto the deck of the vessel V, the
elevator is caused to move synchronously with the vertical movement
of the vessel V, i.e., the elevator E moves in the same direction
and at the same rate that the vessel V moves, as the vessel V is
subjected to wave action. Superimposed on the synchronous movement
of the elevator E with the vessel V is independent movement of the
elevator E in a controlled manner whereby the elevator E is moved
smoothly and gently to or from the deck of the vessel V by the load
hoist means LH. The load hoist means LH is also operable, when the
elevator E is moving through the portion of its travel safely above
the deck of the vessel V to independently cause vertical traverse
of the elevator E.
More particularly, the boom B is mounted on suitable support
structure 13 which is affixed to a side of the platform P. The boom
comprises in the illustrative embodiment a pair of laterally spaced
outwardly convergent V-shaped arms 14 and 15, which are preferably
fabricated from upper and lower rails 16 and 17 reinforced by
suitable struts 18 for rigidity, the arms 14 and 15 being suitably
connected to the support structure 13. Also supported on the
support structure 13 is a power unit platform 20 on which is
mounted a power source 21 such as an engine adapted through a
suitable reduction gear box 22 and a chain drive 23, by way of
illustration, to drive the hoist means consisting of the tensioning
hoist means TH and the load hoist means LH previously referred to.
At a suitable elevated and laterally displaced position relative to
the support structure 13 is mounted a control cab C in which an
operator has good vision of the hoisting operations. Located
between the boom arms 14 and 15 and extending from the support
structure 13 horizontally to a location below the outer extremity
of the boom B is a walkway W, having a laterally enlarged loading
deck 26 at its outer extremity. The walkway W, the power unit
platform 20, as well as the barge or platform P are all provided
with suitable guard rails thereabout, and a stairway 27 leads
between the deck of the platform or barge P and the power unit
platform 20.
The load hoist line or cable 10 extends from the load hoist means
LH over an inner sheave 28 which is appropriately rotatably
supported over the load hoist means LH, and extends outwardly of
the boom B and over the outer sheave 29 which is rotatably
supported at the outer extremity of the boom B. A hook or other
load supporting means 30 is connected to the elevator E or other
load so as to raise and lower the latter: The tensioning line 11
leads from the tensioning hoist means TH over a sheave 31, then
along the boom B and over an outer sheave 34 which is rotatably
supported at the outer extremity of the boom B. The tensioning line
11 extends downwardly from the sheave 34 and is provided with a
hook 35 or other suitable means adapted to effect the connection of
the tensioning line 11 to the vessel V at the location 12
previously referred to.
The elevator E comprises a floor 36 having a cage structure 37
extending upwardly therefrom and connected to the top 38 of the
elevator, the top having reinforced support members 39 connected to
the hook 30 centrally of the elevator E. At one side, the elevator
E has a tubular guide 40 extending vertically and through which the
tensioning line 11 extends. Thus, the elevator is prevented from
swinging or spinning on the hoist line or cable 10, and the
location on the deck of the vessel V at which elevator E will land
is established, notwithstanding any tendency of the vessel V to
move in any direction away from a location directly beneath the
outer end of the boom B.
Referring to FIGS. 3A and 3B, it will be seen that the support
structure for the hoist means includes three laterally spaced
uprights or posts 41, 42 and 43. The uprights 41 and 42 have
mounted thereon a pair of laterally spaced bearing blocks 41a and
42a in which is rotatably journalled a horizontally extended
tensioning hoist shaft 44. The tensioning hoist means TH includes a
drum 45 on which the tensioning line or cable 11 is wound, the hub
46 of the drum 45 being keyed as at 47 to the shaft 44 for rotation
therewith. The shaft 44 extends through the bearing block 41a to
provide a driven shaft end 48 adapted to be driven by the drive
means 23 under the control of slip clutch means SC.
More particularly, the drive means 23 includes a drive chain 49
adapted to be driven by the output sprocket (not shown) of the
reduction gear box 22 of the power source 21. This chain 49 is
engaged with a sprocket 50, the hub 51 of which is rotatably
mounted on the shaft end 48 by bearings 52. Affixed to the sprocket
50, is a disc 54 which is in turn affixed by fasteners 55 to the
outer periphery of the back-up plate 56 of the slip clutch means
SC.
This slip clutch means SC includes an outer annular body 57 to
which an annular flange 58 is connected by fasteners 59 in opposed
relation to the plate 56. Internally thereof, the body 57 has a
splined connection 60 with the outer periphery of an axially
shiftable clutch pressure plate 61. Between the clutch plates 56
and 61 is a clutch friction disc 62 having friction facing 63 on
opposite sides thereof and having, as at 64, a splined connection
with a hub 65 which is disposed upon the shaft end 48 and is keyed
thereto by a key 66. Thus, rotation from the sprocket 50 will be
transmitted to the tensioning hoist shaft 44 when the slip clutch
means SC is engaged to transmit rotation from the clutch body 57
and its plates 56 and 61 to the friction disc 62.
Engagement of the slip clutch means SC is accomplished by an
annular expansible actuator tube 67 having an air inlet 68. The
actuator tube 67 engages an annular body of insulating material 69
interposed between the tube 67 and the clutch pressure plate 61.
Each of the clutch plates 56 and 61 has a number of annular
radially spaced and concentric coolant passages 56a and 61a to
which a coolant is supplied to dissipate the heat of friction
caused by slippage of the clutch SC. These passages 56a and 61a are
defined respectively between the clutch plates and a wear disc 56b
carried by the plate 56 and a wear disc 61b carried by the plate
61, the friction material on the friction disc 62 being engaged
with the wear discs 56b, 61b.
Such cooled, slip clutches are well known, and generally are
provided with a coolant circulating system including a stationary
coolant connector member 71 through which coolant flows to and from
a rotary connector member 72 which is connected, as by fasteners
72a, to the clutch flange 58 and which has conduit means 73 and
supplying coolant to the passages 56a and 61a, as well as conduit
means for the return flow of coolant to the stationary coolant
connector 71 and thence to a heat exchanger. In addition, the
rotary connector member 72 provides a connection for air conduit
means 74 which leads to the air inlet 68 for the clutch actuator
tube 67 from a stationary air inlet fitting 75. As is well known,
the torque transmitting capacity of such slip clutches varies with
the pressure of air in the actuator tube 67.
Preferably, the slip clutch means SC is made in accordance with the
disclosure of U. S. patent application Ser. No. 19,601, filed Mar.
16, 1970, in the name of C. D. Barron, so that the clutch plates
and discs are more effectively cooled.
Referring to FIG. 3B, it will be seen that motion compensating
drive means MC are adapted to selectively drivingly connect the
shaft 44 of the tensioning hoist means TH to a shaft 80 of the load
hoist means LH. This shaft 80 is mounted for rotation in bearing
blocks 42b and 43b which are mounted on the supports 42 and 43 so
that the shaft 80 extends in parallel relation to the shaft 44 in
laterally spaced relation. It will be understood that the
relationship between the tensioning hoist means and the load hoist
means is only illustrative of a preferred arrangement under given
conditions, but that the shafts 44 and 80 may be co-axially or
otherwise arranged.
More particularly, the motion compensating drive means MC comprises
a clutch assembly 81 including an adaptor sleeve 82 which is keyed,
as at 83, to the shaft 44 for rotation therewith. Typically, the
clutch assembly 81 also includes a plurality of clutch discs 84.
Alternate discs 84 are splined to the adaptor sleeve 82, and the
other discs 84 are splined to an annular clutch body 85, whereby
rotation is transmitted to the body 85 from the shaft 44 when the
discs 84 are engaged between the usual back-up plate 86 and the
shiftable pressure plate 87. In order to engage the clutch discs 84
between the plates 86 and 87, actuator means responsive to fluid
pressure are provided including a thrust bearing 88 which is
engaged with the pressure plate 87 to shift the latter towards the
back-up plate 86 in response to corresponding movement of an outer
actuator sleeve 89 which also is engageable with the thrust bearing
88. This actuator sleeve is slidable on a fixed actuator sleeve 90
within which the adaptor sleeve is rotatable, the sleeve 90 being
secured by fasteners 90a to a suitable housing 90b which is
connected to the support 42 and shrouds the motion compensating
drive means MC. These actuator sleeves 89 and 90 are suitably
formed and sealed to provide a pressure chamber 91 to which fluid,
such as air, may be admitted through a connection 92 to effect
engagement of the clutch 81.
Suitably mounted on the driven clutch body 85, as by fasteners 93,
is a sprocket 94. A drive chain 95 is engaged with the sprocket 94
and with a similar sprocket 96 which is suitably affixed to the end
97 of the lift hoist shaft 80, as by a key 97a, whereby the shaft
80 will be driven by the tensioning hoist means TH when the
releasable connection provided by the clutch 81 is engaged. Such
rotation of the shaft 80 is adapted to cause operation of the load
hoist means LH synchronously with the tensioning hoist means TH,
during the initial stage of movement of the elevator E from the
deck of the vessel V and during the final stage of movement of the
elevator E towards the deck of the vessel.
In the preferred construction, the load hoist means is so arranged
that the motor means for raising and lowering the load when the
motion compensating drive means MC is disconnected is also operable
when the motion compensating drive means is connected, whereby to
superimpose on the synchronous movement of the load with the vessel
V, further movement to move the load relative to the vessel. The
load hoist means LH, therefore, includes a drum 100, corresponding
to the drum 45 of the tensioning hoist means TH, and the load hoist
line 10 is wound on this drum 100. Support flanges 101 are provided
within the drum 100, these flanges being connected to or having
formed at their inner periphery bearing rings 102 engageable with
bearing assemblies 103, whereby the drum 100 is rotatably supported
on the shaft 80 so as to be rotatable relative to the shaft. At one
end of the drum 100 is the usual brake drum or flange 104 with
which winch drums are provided. In the present case however, the
flange 104 is modified internally to provide internal gear teeth
105. These teeth 105 provide for connecting both reversible
hydraulic motor means 106 and normally engaged brake means 107 to
the drum 100. Such motor means 106 and brake means 107 are both
carried by a plate 108 which is mounted at its inner periphery on
the shaft 80, a key 109 being provided to cause rotation of the
plate 108 with the motor means 106 and brake means 107 in the
direction and at the rate of the shaft 80, the direction and rate
of rotation of which is a function of the direction and rate of
rotation of the tension hoist means shaft 44.
More particularly, the motor means 106 includes a housing 110
connected by fasteners 110a to the plate 108 and an output shaft
111 which extends through the plate 108. On the output shaft 111 is
a pinion 112 which is drivingly in mesh with the internal gear
teeth 105 of the drum flange 104. Fluid is supplied to the motor
106 in a selected direction through conduits 113 and 114 to effect
reverse operation of the motor, such fluid being supplied through
passages 113a and 114a which extend longitudinally in the shaft 80
and are supplied from stationary source conduits 113b and 114b,
respectively, which are connected to a rotary fluid connector 115
suitably mounted in the housing 90b, as by fasteners 116. Such a
rotary connector 115 is common and requires no further specific
discussion. The motor 106 also has a fluid outlet 117 which, as
will be more fully described hereinafter, supplies fluid to the
inlet conduit 118 of the brake means 107 to release the latter when
the motor 106 is operating, whereby the drum 100 is revolvable
about the drum shaft 80 in addition to being revolvable with the
shaft 80. When the motor means 106 is operating, the net rotary
motion of the drum 100, is a function of the direction and extent
of rotation of the shaft modified by the direction and extent of
rotation of the drum 100 about the shaft in either direction.
Therefore, the load hoist line 10 and the elevator may be raised or
lowered by the motor 106, while the hoist line is also moving the
elevator E in unison with movement of the boat or vessel V.
The brake means 107 comprises a housing 120 secured to the plate
108 so as to revolve with the shaft 80. Carried by and rotatably
disposed in the housing 120 is a shaft 121. This shaft 121 extends
through the plate 108 and has a pinion gear 122 keyed thereon as at
122a, the shaft being journalled in bearings 123 within the housing
120. A rotary brake member 124 is secured on the shaft 121 for
rotation therewith by a key 125. Friction discs 126 are interposed
between the brake rotor 124 and an actuator member 127, alternate
discs being splined to the rotor 124 and to the housing 127, so
that when the discs are engaged, the rotor 124 will be held
stationary, thereby holding the pinion 122 against rotation, to
brake the hoist drum 100. The brake 107 is normally engaged by a
number of coiled compression springs 128 spaced circumferentially
of the actuator member 127 and acting on the same and on an
internal flange 129 in the housing 120 to bias the member 127 in a
brake-engaging direction. To disengage the brake means 107, fluid
under pressure is supplied from the conduit 118 to a sealed piston
chamber 130 in which is a piston 131 connected to the actuator
member 127, as by screws 132, to move the actuator member 127 to a
brake-release position. When the brake means 107 is engaged, the
hoist drum 100 is effectively connected to the shaft 80 for
rotation therewith, but when the brake means 107 is released, the
motor means 106 is effective to not only connect the drum 100 to
the shaft 80, but also to effect relative rotation thereof, as
previously described.
The load hoist means LH also includes brake means 135 for holding
the shaft 80 stationary when the motion compensating drive clutch
means 81 is disengaged, during the periods that the elevator E is
high enough above the boat or vessel V as to be safely raised or
lowered by the motor means 106, without compensating for relative
movement of the boat beneath the boom.
Such brake means 135 includes a rotor 136 keyed, as at 137, to the
outer extremity of the hoist shaft 80, and a stationary brake
housing 137 connected to the support 43 by fasteners 139. Friction
discs 140 are interposed between the rotor 136 and an actuator 141,
alternate discs being splined to the rotor 136 and to the housing
138. A number of circumferentially spaced springs 142 are
interposed between the actuator member 141 and an internal flange
143 in the housing 138 to normally bias the member 141 towards the
rotor 136 to engage the brake and hold the drum shaft 80 against
rotation. Fluid under pressure supplied through a conduit 144 to a
sealed piston chamber 145 acts on a piston 146, which is connected
to the member 141 by fasteners 147, to move the member to a
brake-released position, when, as will be later described, fluid
under pressure is supplied to the piston chamber 91 of the motion
compensating drive clutch means 81 to engage the latter to rotate
the drum shaft 80 synchronously with the tensioning hoist drum
shaft 44. While the brake means 135 is shown as being spring set
and pressure released, the brake means may be of the type adapted
to be engaged by fluid pressure. The significant point is that the
brake means 135 is released when the clutch means 81 is engaged,
and vice-versa, as will be later described.
OPERATION
The operation of the load compensating hoist system will be further
understood with reference to FIG. 4, wherein the apparatus is
schematically illustrated together with operating and control means
therefor.
In this view, it will be noted that air under pressure is supplied
to the inlet connector 75 of the slip clutch means SC through
controller or pressure regulator R1, so that the slip clutch means
may be adjusted to transmit sufficient torque to the drum shaft 44
as to maintain a predetermined tension on the tension line 11 of
the tension hoist means TH which is connected to the vessel V. The
controller R1 needs no specific illustration but is preferably of
the type that will cause an outlet pressure which is a function of
a "SET POINT" signal and a signal derived from tension on the
tension line 10. The line tension on the tension hoist TH is
selected so as to be proportionate to the total load represented by
the elevator E, namely, the weight of the elevator E together with
the weight of the load to be carried in the elevator, and inertia
forces to be overcome in accelerating the load when the system is
compensating for movement of the vessel V.
In order to cause motion compensating motion of the load line 10,
whether or not it is connected to a load or to the elevator, the
clutch means 81 of the motion compensating drive MC is engaged and
the brake means 135 for the load hoist shaft is released. This is
accomplished in the case of a spring loaded brake means 135 by a
control valve CV1 which is interposed between a suitable source of
air under pressure and the pressure conduits 92 and 141, the valve
CV1 being operable in one position to connect the air supply to
both the clutch means 81 to engage the same and the brake means 135
to release the same, and conversely, in the other position, to
exhaust the clutch and brake to allow release and engagement
thereof, respectively. Thus, with the clutch means 81 engaged, the
drum shaft 80 will rotate in the same direction and at the same
rate as the tension hoist drum 45, as the latter is caused,
alternately, to turn in one direction by the pull on the line 11 by
the vessel V, as the vessel moves downward, and in the other
direction, as the vessel rises on a wave, the tension on line 11
remaining substantially constant at the value established for the
slip clutch means SC.
With the load hoist line 10 thus moving with the vessel V, the line
10 may be raised or lowered, whether or not connected to the
elevator E, by the operation of the reversible hydraulic motor 106,
when the brake means 107 is released, whereby the load hoist drum
100 is caused to rotate about the shaft 80, a motion which is
superimposed on the shaft motion caused by the rise and fall of the
vessel V.
To accomplish this, a control valve CV2 is adapted to control the
flow of hydraulic motor fluid to the motor means 106 and to the
brake means 107, and from the motor means to a reservoir. The valve
means CV2 has a position for directing fluid from a suitable
pressure source through conduits 113b and 113 and to an exhaust to
cause motor rotation in one direction, and another position for
directing fluid through the conduits 114b and 114 to cause motor
rotation in the other direction. In either event, motor fluid is
also supplied to the brake inlet conduit 108 from a shuttle valve
SV interposed between the conduits 113 and 114.
For moving the load hoist line 10 independently of the tension line
11, the control valve CV1 is operated to relieve operating air
pressure from the clutch means 81 and the brake means 135, so that
the drum 100 may be driven independently of the tension hoist
means, to raise or lower the load line 10 when it is safely above
the vessel V, whether the line 10 be loaded or unloaded.
With the foregoing in mind, it will now be understood that the
tension on the tension line 11 caused by the application of a
controlled air pressure to the slip clutch means SC is preferably
maintained at a constant value whether or not the load hoist line
10 is supporting a load. Accordingly, load sensing means LS are
provided to cause the application of a variable air pressure to the
slip clutch means SC to adjust the torque capacity of the slip
clutch means SC so that the pressure supply to the slip clutch
means is decreased, if the tension on line 11 tends to increase, or
the pressure supply to the slip clutch means is increased, if the
tension on the line tends to decrease.
Such load sensing means may be any typical devices adapted to sense
load on a line to produce a related signal, such as a load cell of
the hydraulic type, as indicated at 150 in FIG. 4. This load cell
150 has a piston 151 which projects from the cylinder 152 and is
engaged by a portion 31a of a lever 31b which supports the above
described tension line sheave 31 on the axle 31c, the lever being
pivotally mounted on a pin 31d carried by the support structure, as
is obvious. Leading from the load cell cylinder 152 is a conduit
153 which is connected to a pressure regulator or transmitter R2 of
any suitable type which, as is well known, is operative to regulate
the drop in air pressure supplied from a source 154 and establish
an outlet air signal pressure in a conduit 155 which is a function
of the applied hydraulic pressure from the load sensor means LS.
The air pressure from the regulator R2 provides a signal which is
conducted by the conduit 155 to the controller R1 to modify the net
output pressure from the controller R1 to the slip clutch means
SC.
Assuming that the vessel V, with a load thereon, such as certain
equipment or personnel to be elevated to the platform P is situated
at a location below the boom B, the tension line 11 is lowered,
either first or with the load line 10, and the tension line 11 is
connected to the vessel V. Air is supplied at a controlled value to
the slip clutch means SC causing a tension on the line 11
proportionate to the weight of the elevator E and any load which it
is to lift, or proportionate to the load to be lifted if the load
is to be engaged by a lift device such as a hook. At this time, the
rise and fall of the vessel V will cause the tension drum 45 to
oscillate. The motion compensating clutch means 81 is engaged, and
the drum shaft brake means 135 correspondingly released, so that
the load hoist drum 100 will oscillate in unison with the tension
hoist drum 45, causing synchronous movement of the load line with
the tension line, corresponding to movement of the vessel. While
such synchronous motion occurs, the load hoist drum motor 106 may
be supplied with fluid, and the brake means 107 is released, to
enable controlled downward movement of the elevator E, or other
load support, to the deck of the vessel for loading.
Thereafter, the motor 106 is reversed, causing upward movement of
the load relative to the vessel, while the load continues to rise
and fall synchronously with the rise and fall of the vessel. As the
load is lifted from the deck of the vessel, the load will require
an increase in the torque output of the slip clutch means SC. There
is, at the same time, a resultant tendency to reduce the tension on
the tension line 11, which tendency is sensed by the load sensor
means 152. The reduced hydraulic signal from the load cell 150
causes a decrease in the air pressure supplied from the transmitter
R2 to controller R1 and a resultant increase in the air pressure
supplied from the controller R1 to the slip clutch means until the
torque capacity of the slip clutch SC is sufficient to not only
maintain the initial tension on the line 11, but also to elevate
the load, while the motion compensation continues. When the load is
at a safe distance above the vessel, and motion compensation is no
longer necessary, the brake means 135 for the load hoist shaft are
engaged and the motion compensating clutch means 81 are released.
At this time, since the slip clutch means SC no longer is subjected
to the load, the entire torque from the slip clutch is applied to
the tension drum 45 tending to increase the tension on line 11, but
the load cell 150 will sense the increase in tension, resulting in
an increased hydraulic signal to the transmitter R2 and a reduction
in the net air pressure supplied to the slip clutch means from the
controller R1 to the original value, whereby the tension on line 11
will be held substantially at the constant value through all modes
of operation, since the clutch and the hoist means driven thereby
are effectively in a closed loop, feed back system which constantly
seeks to maintain a constant tension on the tension line 10, the
system adjusting for load and increased and decreased tension
caused by the rise and fall of a vessel relative to a fixed
platform, or differences in the rise and fall of two vessels, i.e.,
relative vertical movement between the two locations.
The lowering of a load onto the vessel will simply involve reversal
of the operations described above in elevating a load.
During all of the travel of the elevator E between a location
adjacent to the loading platform 26 of the boom B and a location on
the deck of the vessel V, the sliding connection between the
elevator and the tension line 11 provided by the tube 40, will
prevent the elevator or other load from spinning on the load line
10. In addition, the load is guided to a precise location on the
deck of the vessel, notwithstanding movement of the vessel beneath
the end of the boom.
For the sake of safety, it will be understood that fail safe means
(not shown) may be provided. In this connection, it is customary
that hoist winches have normally engaged or spring-set band brakes
associated with the drum, and more particularly with the flange 104
of the hoist drum 100 and with the corresponding flange 45a of
tensioning hoist drum 45. Such brakes may be also employed in the
present apparatus and released responsive to the fluid pressure in
the operating system, so that the band brakes would automatically
set in the event of loss of pressure in the system or any portion
thereof. The brake on the load hoist drum should be able to support
the maximum load, but the brake on the tensioning hoist drum should
be capable of slipping to allow downward movement of the
vessel.
* * * * *