U.S. patent number 3,901,478 [Application Number 05/168,310] was granted by the patent office on 1975-08-26 for crane incorporating vertical motion apparatus.
Invention is credited to Earl A. Peterson.
United States Patent |
3,901,478 |
Peterson |
August 26, 1975 |
Crane incorporating vertical motion apparatus
Abstract
A crane incorporating vertical movement compensation apparatus.
A crane having a boom with suspended hoisting cable is adapted to
support a load substantially independent of the vertical movement
of the crane and associated apparatus. The hoisting cable is
supported by a winch incorporating a continuously slipping clutch
which maintains the load in a controlled tension mode. The winch
shaft about which is secured the crane drum drives through an
overrunning clutch to a braking device to permit the load to be
moved in the in-haul direction without interference of the brake
while precluding inadvertent downward movement of the load as a
result of vertical displacement of the crane.
Inventors: |
Peterson; Earl A. (Long Beach,
CA) |
Family
ID: |
26863988 |
Appl.
No.: |
05/168,310 |
Filed: |
August 2, 1971 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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823894 |
May 12, 1969 |
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Current U.S.
Class: |
254/270;
188/71.2; 192/12B; 254/366; 254/367; 254/378; 254/903 |
Current CPC
Class: |
B66C
13/02 (20130101); B66D 1/52 (20130101); Y10S
254/903 (20130101) |
Current International
Class: |
B66D
1/52 (20060101); B66D 1/28 (20060101); B66C
13/02 (20060101); B66C 13/00 (20060101); B66C
023/60 () |
Field of
Search: |
;254/139,139.1,145,172,173,185,187 ;212/39 ;188/71.2
;192/12B,12BA |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Blunk; Evon C.
Assistant Examiner: Nase; Jeffrey V.
Parent Case Text
This application is a continuation-in-part of my application Ser.
No. 823,894 filed May 12, 1969.
Claims
I claim:
1. A crane apparatus for use with a supported platform
comprising:
a. a boom pivotally secured to the platform;
b. a first shaft;
c. a drum concentrically disposed about and secured to said first
shaft;
d. a hoisting cable secured to said drum and moveably disposed over
said boom;
e. a continuously slipping clutch having an outer housing and inner
hub coupled to frictionally rotate with respect to each other and
fluid means for dissipating the frictionally generated heat
therein, said inner hub being securely coupled to said first shaft
whereby said hoisting cable is maintained in a controlled tension
mode;
f. a second shaft;
g. an overrunning clutch interposed between said first and second
shafts having means for engaging said first and second shafts when
said drum is paying out hoisting cable whereby said overrunning
clutch is in a free-wheeling mode when said drum is rotating to
reel in hoisting cable; and
h. a brake interposed between said second shaft and the platform
whereby braking force is imposed on the hoisting cable when said
drum is rotating to pay out hoisting cable.
2. A crane apparatus as defined in claim 1 wherein said
continuously slipping clutch includes a friction disc secured to
said inner hub, friction elements adapted to slidably engage and
rotate with said outer housing, said fluid means for dissipating
heat adjacent said friction elements, and air actuated expandable
elements secured to said housing and adjacent said friction
elements, whereby said friction elements frictionally engage said
friction disc upon actuating said expandable elements.
3. A crane apparatus as defined in claim 2 including tension
measuring means for measuring the tension in said hoisting cable
and outputting indicia of same, said tension measuring means
including tension transducing means for detecting the tension in
said hoisting cable and outputting indicia of same, and pressure
means for outputting a pressurized source responsive to the output
of said tension transducing means, said tension transducing means
being coupled to said hoisting cable, said pressure means being
coupled intermediate said tension transudcing means and said
expandable elements.
4. A crane apparatus as defined in claim 1 including a constant
speed power source coupled to the housing of said continuously
slipping clutch whereby said housing is rotated at a constant
speed.
5. A crane apparatus for use with a supported platform
comprising:
a. a boom pivotally secured to the platform;
b. a drum shaft;
c. a drum concentrically disposed upon and secured to drum
shaft;
d. a hoisting cable disposed about said drum, a portion thereof
suspended over said boom whereby a load is supported;
e. a constant speed power source;
f. a continuously slipping clutch having an inner hub and outer
housing, a friction disc secured to said inner hub, friction
elements adapted to slidably engage and rotate with said outer
housing, fluid means for dissipating heat adjacent said friction
elements, and air actuating, expandable elements secured to said
housing and adjacent said friction elements whereby said friction
elements frictionally engage said friction disc upon actuating said
expandable elements maintaining a speed differential therebetween,
said inner hub being concentrically disposed upon and secured to
said drum shaft, said continuously slipping clutch keeping said
hoisting cable in a controlled tension mode;
g. a brake shaft spaced from and in axial alignment with said drum
shaft;
h. an overrunning clutch interposed between and secured to said
drum shaft and said brake shaft, said overrunning clutch adapted to
free-wheel said drum shaft with respect to said brake shaft and
couple said shafts upon alternate rotational movement of said drum
shaft whereby said shafts rotate together when said drum is
rotating to pay out said hoisting cable;
i. tension measuring means for measuring the tension in said
hoisting cable and producing a hydraulic pressure signal
porportional to the tension in said hoisting cable, said tension
means including a tension transducer and pressure output means for
producing said hydraulic pressure signal, said tension transducer
being in cooperative relationship with said hoisting cable and
producing an output signal responsive to the tension in said
hoisting cable, said pressure output means being coupled
intermediate to said tension transducer and said expandable
elements; and
j. a brake interposed between said brake shaft and the platform
whereby braking force is imposed on said hoisting cable when said
drum is rotating to pay out the hoisting cable.
6. In combination with a platform mounted crane including a pivotal
boom and a power source for the poistioning of the boom, a vertical
motion compensating apparatus comprising:
a. a drum shaft;
b. a drum concentrically disposed about and secured to said drum
shaft;
c. a hoisting cable disposed about said drum, a portion thereof
suspended over the boom whereby a load is supported;
d. a continuously slipping clutch having an inner hub and outer
housing, and having a friction disc secured to said inner hub,
friction elements adapted to slidably engage and rotate with said
outer housing, fluid means for dissipating heat adjacent said
friction elements, and air actuated, expandable elements secured to
said housing and adjacent said friction elements, said inner hub
being disposed about and secured to said drum shaft whereby a speed
differential is maintained between said friction elements and said
friction disc keeping said hoisting cable in a controlled tension
mode;
e. a brake shaft, in spaced relation with and in axially alignment
with said drum shaft;
f. an overrunning clutch interposed between and coupled to said
drum shaft and said brake shaft, said overrunning clutch adapted to
free-wheel said drum shaft with respect to said brake shaft and
couple said shafts upon alternate rotational movement of said drum
shaft whereby said shafts rotate together when said drum is
rotating to pay out the hoisting cable; and
g. a brake interposed between said brake shaft and the platform
whereby braking force is imposed on said hoisting cable when said
drum is rotating to pay out the hoisting cable.
7. A vertical motion compensating apparatus as defined in claim 6
including tension measuring means for measuring the tension in said
hoisting cable and outputting indicia of same, said tension
measuring means including tension transducing means for detecting
the tension in said hoisting cable and outputting indicia of same,
and pressure means for outputting a pressurized source responsive
to the output of said tension transducing means, said tension
transducing means being coupled to said hoisting cable, said
pressure means being coupled intermediate said tension transducing
means and the expandable elements of said continuously slippint
clutch.
8. A vertical motion compensating apparatus as defined in claim 7
wherein said pressurized source is hydraulic pressure proportional
to the tension in said hoisting cable.
9. A vertical motion compensating apparatus as defined in claim 6
including a constant speed power source coupled to the housing of
said continuously slipping clutch whereby said housing rotates at a
constant speed.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention crane apparatus is generally related to the
field of hoisting devices and, in particular, to those devices
incorporating apparatus for vertical movement compensation.
2. Prior Art
The need to equip marine vessels and other like structures with
winches or cranes which are capable of compensating for the
vertical motion of the vessel or supporting structure has long been
recognized. The ability to vertically lift a load independent of
the vertical movement of the crane or winch structure has been a
problem which has heretofore not been totally resolved by the
devices disclosed in the prior art. The requirements for a crane or
winch intended for vertically lifting loads are considerably more
complicated than systems designed for the horizontal movement of
loads. These complications arise out of the need to institute
safeguards to prevent inadvertent release of the loads in the event
of power failure, vertical movement of the lifting mechanism or
other similar occurrances.
One of the devices disclosed by the prior art is set forth in
Applicant's U.S. Pat. No. 3,373,972. The device disclosed is a
winch incorporating a continuously slipping clutch to permit
movement of loads utilizing the controlled tension in the hoisting
line of the winch. One of the problems left unresolved by this
device concerns the inability to compensate for failures in the
energy source for the winch or to provide improved methods for
initiating movement of loads without encountering the complications
inherent in the transition from a static to a dynamic
condition.
Another device disclosed by the prior art constitutes an apparatus
for horizontally transferring loads between displaced stations.
This mechanism in no way encounters the problems of vertically
displaced loads since the supporting stations fully provide
stability for the hoisting line and the attached loads. The
problems sought to be solved by the present invention are created
where loads must be vertically lifted in a manner which will
minimize disturbances of the load while concurrently eliminating
the possibility of dropping the load as a result of power failures
or other adverse conditions.
Another device disclosed by the prior art is used for the drilling
of well bores, typically in an off-shore environment. The device
utilizes a fluid coupling in the attempt to compensate for vertical
motion of the floating support structure. A fluid coupling presents
inherent problems with respect to response time, load capacity and
control over a supporting load. In addition, the device disclosed
by the prior are includes no means for insuring that the load will
not be inadvertently dropped. In the particular application, a
drill string is supported by a winch powered through the fluid
coupling. A flaw in this system could easily result in damage to
the drill string and attached drill bit, problems which are
substantially resolved by the present invention.
The present invention crane substantially resolves the problems
left unsolved by the devices disclosed in the prior art. The power
source for the present invention crane is supplied through a
continuously slipping clutch coupled to the drum shaft. In order to
prevent unintended damage to the load as a result of inadvertent
vertical displacement thereof, the drum shaft is coupled to a
supplemental braking system through an overrunning or one-way
clutch. In this manner, the load will be supported in an in-haul
direction by free-wheeling against the brake, the out-haul movement
of the hoisting line being subject to a supplemental braking
system.
SUMMARY OF THE INVENTION
The present invention comprises a crane having means for
compensating for vertical displacement of the crane supporting
structure as well as incorporated apparatus for preventing
inadvertent out-haul movement of the hoisting line. The present
invention crane incorporates a boom supported by an adjustable
block and tackle assembly or other like structure. The hoisting
line is supported by a sheave at the top of the boom, the hoisting
line being wound about and secured to the hoisting drum. The drum
is securely mounted upon the drum shaft, the shaft being powered
through a continuously slipping clutch. The housing of the clutch
is driven in an over-speeded condition to insure that there is a
predetermined speed differential between the driving and driven
elements of the clutch. A tension measuring device is responsive to
the tension in the hoisting line, the tension measuring device
providing an output indicative of any adjustment to be made to the
respect to the output torque of the continuously slipping clutch.
The tension measuring device is coupled to the continuously
slipping clutch to enable incremental changes in the output torque
of the continuously slipping clutch to maintain a controlled
tension in the hoisting line.
The driving element of the continuously slipping clutch rotates in
the in-haul direction, the speed differential between the driving
and driven elements of the clutch insuring adequate recovery rates
for vertical displacement of the crane assembly. To prevent
inadvertent vertical displacement of the load supported on the
hoisting line, the drum shaft is run through a one-way clutch to a
supplemental braking system. When the braking system is actuated,
the drum clutch will rotate in the in-haul direction in a
free-wheeling mode independent of the braking system, any out-haul
movement of the clutch being subject to the action of the braking
system. The present invention crane permits upward or downward
movement of the load by the operation of the clutch in a
continuously slipping mode, the movement being controlled by
control over the output torque of the clutch. By driving the drum
shaft through a one-way or overrunning clutch and allowing same to
rotate in the in-haul direction in a free-wheeling manner, a load
can be supported by the braking system yet in-haul movement
initiated totally free of any inadvertent and adverse vertical
displacement of the load.
It is therefore an object of the present invnetion to provide a
crane incorporating vertical movement compensating apparatus.
It is another object of the present invention to provide an
improved crane apparatus to prevent inadvertent vertical
displacement of a supported load.
It is still another object of the present invention to provide a
crane capable of compensating for vertical displacement of the
crane as well as apparatus for eliminating the adverse affect
resulting from the transition from static to dynamic movement of
the load.
It is still yet another object of the present invention to provide
a crane for initiating upward vertical displacement of a load from
a static condition substantially eliminating perturbations of the
load.
The novel features which are believed to be characteristic of the
invention, both as to its organization and method of operation,
together with further objectives and advantages thereof, will be
better understood from the following description considered in
connection with the accompanying drawing in which a presently
preferred embodiment of the invention is illustrated by way of
example. It is to be expressly understood, however, that the
drawing is for the purpose of illustration and description only and
is not intended as a definition of the limits of the invention.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a perspective view of a crane fabricated in accordance
with the present invention.
FIG. 2 is a side, elevation, cross-sectional view of the
continuously slipping clutch of FIG. 1 adapted to operate in
accordance with the present invention.
FIG. 3 is a schematic view of the control system for the
continuously slipping clutch of FIG. 1.
FIG. 4 is a schematic view of the drum, drum shaft, one-way clutch
and braking system of the crane of FIG. 1 in accordance with the
present invention.
FIG. 5 is a side elevation, partial cross-sectional view of the
one-way clutch of FIG. 4 taken through line 5--5 of FIG. 4.
FIGS. 6a, 6b and 6c are schematic, partial cross-sectional views of
a one-way clutch illustrating the mode of operation thereof.
DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENT
An understanding of the structure of the present invention
apparatus can be best gained by reference to FIG. 1 wherein a
perspective view of a crane incorporating the elements of the
invention is shown therein, the crane being generally designated by
the reference numeral 1. Crane 1 is constructed upon platform 2,
platform 2 being a portion of a floating or fixed structure. As
stated, an object of the present invention is to provide a crane
capable of vertical motion compensation as is typically encountered
in off-shore applications. Although a preferred embodiment of the
present invention is utilized upon a marine vessel or other
floating support structure, the scope of the present invention
encompasses the same with fixed structures. A hoisting assembly 3
is coupled to boom 4 for the purpose of orienting boom 4 in any
desired position. Load 5 is supported by hoisting cable 6. To raise
and lower boom 4, cable 7 is secured to the upper portion thereof,
cable 7 being coupled to hoisting assembly 3 by block and tackle
assembly 8. Although the scope of the present invention embodies
the use of same with a gantry, A-frame derrick or similar
structure, the preferred embodiment of the present invention
utilizes the boom assembly as shown in FIG. 1.
Hoisting cable 6 is disposed over sheave 10, portion 9 of hoisting
cable 6 being disposed for measurement of the tension therein as
will be explained in detail below. Hoisting cable 6 is supported
and disposed around drum 11, the winch assembly coupled thereto
being powered by motor 12. Motor 12 is coupled to clutch 14, clutch
14 being coupled to shaft 15 which supports drum 11 and is coupled
to brake assembly 13 as will be explained in detail below. The
operation of motor 12, clutch 14, drum 11 and associated hoisting
cable 6 are similar to that described in Applicant's U.S. Pat. No.
3,373,972.
The ability of the present invention to maintain constant tension
in hoisting cable 6 irrespective of vertical displacement of
platform 2 can be best understood by reference to FIG. 2 wherein a
side elevation, cross-sectional view of clutch 14 is shown. Clutch
14 is one capable of one operating in a continuously slipping mode
whereby a predetermined speed differential can be maintained
between the driving and driven elements of clutch 14. Motor 12 is
coupled to drive ring 16 which is concentrically disposed about and
journeled upon shaft 15 by suitable bearings 17. Drive ring 16 is
securely coupled to clutch housing 18. The preferred embodiment of
the present invention utilizes a motor 12 having a substantially
constant output torque which is imposed upon clutch housing 18
through drive ring 16. The driving elements of clutch 14 which are
concentrically disposed within and adapted to rotate with housing
18 are friction elements 19 and 20. Friction elements 19 and 20 are
disposed at axially opposed interior surfaces of housing 18,
friction element 20 being axially moveable upon the introduction of
actuating energy at expandable element 21. Driven friction disc 22
is concentrically disposed about and secured to clutch hub 23 by
spline teeth or other suitable coupling means. Clutch 14 is
suitable to allow a predetermined differential speed to be
maintained between driving friction elements 19 and 20 and driven
friction disc 22. In order to dissipate the heat horsepower
generated at friction discs 19 and 20, annular channels 24 are
disposed in clutch housing 18 adjacent friction elements 19 and 20
to appropriately dissipate the generated heat. Annular channels 24
and 25 are adapted to receive appropriate cooling liquid such as
water. In order to provide for cooling of clutch 14 through the use
of liquid coolant, roto-coupling 26 provides for coolant input and
output lines 27 and 28, the connections between the coolant lines
and annular channels 24 and 25 not shown.
As stated, friction elements 19 and 20 will frictionally engage
friction disc 22 upon actuation of expandable element 21.
Expandable element 21 is typically an air actuated element. Air is
introduced at roto-coupling 29, the air line being designated by
the reference numeral 30. Air is distributed at ring 31, the output
line 32 being coupled to input line 33 of expandable elements 21.
The coupling between output line 32 and input coupling 33 not being
shown.
As stated, the output of motor 12 provides the driving torque on
clutch housing 18 which is transmitted to friction disc 22 through
friction elements 19 and 20. The output torque of clutch 14 appears
at shaft 15 and is determined by the level of actuation at
expandable element 21. Drive ring 16 and therefore clutch housing
18 constantly rotates in the in-haul direction, the output torque
on shaft 15 being controlled to maintain a predetermined tension in
hoisting cable 6 (FIG. 1). By maintaining a speed differential
between clutch housing 18 and shaft 15, the tension in hoisting
cable 6 will maintain load 5 in a dynamic condition whereby load 5
can be raised or lowered by adjusting the air pressure at
expandable element 21. In addition, maintaining cable 6 in a
controlled tension mode will permit accurate control over the
in-haul/out-haul or stationary mode of hoisting cable 6 and load 5.
Although it is within the scope of the present invention to
implement clutch 14 by a number of conventional clutches, clutch 14
is preferably an air actuated, water cooled disc clutch capable of
operating in a continuously slipping mode wherein there is a
controlled differential speed between clutch hub 23 and housing 18
and therefore between friction disc 22 and friction elements 19 and
20.
An understanding of the apparatus used to control the tension in
hoisting cable 6 can be best seen by reference to FIG. 3 wherein a
schematic diagram of the regulating system, clutch 14, braking
system 13 and a tension measuring device can be best seen, the
regulating system being generally designated by the reference
numeral 60. Load cell or tensiometer 61 is coupled to portion 9 of
hoisting cable 6, load cell 61 being a conventional device adapted
for sensing and measuring the tension line. Load cell 61 is
responsive to the tension in hoisting cable 6, changing the
hydraulic pressure in pressure line 34 in proportion to the tension
in hoisting cable 6. Gauge 35 is coupled to pressure line 34 to
visually illustrate the tension in hoisting cable 6.
As stated, the output of load cell 61 is coupled to regulator 60 by
pressure line 34. One of the advantages of the present invention is
to provide simplified control over operation of the present
invention crane structure. As shown in FIG. 3, a single manual
control 62 will permit full control over the operation of the
tension regulating system as well as braking assembly 13. Air under
pressure is input at pressure line 36 from a conventional pressure
source not shown. Pressure line 36 conducts the pressurized air to
the variable air pressure load control valve 37 and variable brake
release valve 38. The variable air pressure valve 37 is actuated by
manual control 62 as shown, the output of valve 37 being connected
to the conventional selector valve 39. Pressure line 40 couples the
output of variable brake release valve 38 to the spring set air
release of braking assembly 13.
Regulator 60 includes bellows chamber 41 which is coupled to
hydraulic pneumatic transducer 42 by pressure line 43. Although it
was stated that load cell 61 produces a hydraulic or pneumatic
pressure output, it is obvious that load cell 61 could be
fabricated from any sensing device which is compatible with the
selected transducer 42. The output of transducer 42 is coupled to
regulator valve 44 through pressure line 45. Air is introduced to
regulator valve 44 from pressure line 36 via pressure line 46. A
conventional booster relay 47 is serially coupled in pressure line
36 and therefore to air line 30 of roto-coupling 29 via pressure
line 48. Bellows chamber 49 receives pressurized air from reset
rate adjustment valve 50, valve 50 receiving pressurized air from
proportional valve 51 via pressure line 52. Proportional valve 51
is coupled to relay valve 53 by pressure line 54. Pressurized air
is supplied to relay valve 53 and proportional valve 51 through
pressure line 55 which extends from selector valve 39. As a result
of the above-defined coupling, the elements of regulator 60 are
pressurized and controllable from manual control 62.
In operation, when the output of load cell 61 increases the
pressure in pressure line 34, this in turn will increase the
pressure in bellows chamber 41 via the output transducer 42 and
coupling pressure line 43. The increase in pressure in bellows
chamber 41 will move plate 56 upwardly toward nozzle 57 to
simultaneously increase the pressure at booster relay 47 and
proportional valve 51 and therefore at the input to bellows chamber
49. The increase in pressure at bellows chamber 49 will halt the
increase in pressure to booster relay 47. The pressure in the
pressure line leading to bellows chamber 49 will slowly pass
through reset rate adjustment valve 50 and will increase the
pressure in the lower part of bellows chamber 49. This will cause
plate 56 to move towards nozzle 57, again increasing the pressure
throughout the system to booster relay 47 and the upper part of
bellows 49. This build up in pressure will increase pressure
through the reset rate adjustment valve 50 to the lower part of
bellows chamber 49 and start another increase throughout the system
and to booster relay 47. The increase in pressure in the system
will continue until the pressure from load cell 61 and transducer
42 is decreased and the system is brought back to its predetermined
set point as established at control valve 63.
The adjustment of the output torque of clutch 14 via regulator 60
will increase or decrease the output torque based upon the tension
in hoisting cable 6. Where it is desired to maintain the stability
of load 5 irrespective of the vertical displacement of platform 2,
drum 11 and the coupled hoisting cable 6 will adapt to the changing
vertical displacement of platform 2. As discussed, a predetermined
differential speed is maintained between clutch housing 18 and
coupled friction elements 19 and 20, and the driven friction disc
22 and coupled shaft 15. The differential speed between the pair of
members will change to maintain controlled tension in hoisting
cable 6. Where platform 2 is moving vertically downward, the
tension in hoisting cable 6 will tend to increase and therefore
drum 11 and hoisting cable 6 will move in the out-haul direction to
compensate for the vertical displacement. When platform 2 is moving
vertically upward, the tension in cable 6 would tend to decrease,
drum 11 and hoising cable 6 being moved in the in-haul direction to
compensate for this vertical displacement. The combination of load
cell 61 and coupled regulator 60 maintains the tension in hoisting
cable 6 at the preset level established at valve 63. When hoisting
cable 6 and attached load 5 are to be vertically moved, operation
of manual control 62 enables movement of hoisting cable 6 in the
desired direction while maintaining proper compensation for
vertical displacement of platform 2 and the crane elements.
As stated, an object of the present invention was to provide means
for initiating the movement of load 5 when same was being held by
braking assembly 13. In order to accomplish this, the present
invention crane 6 provides the ability to initiate upward vertical
displacement of load 5 negating the effect of braking assembly 13
while imposing the effects of braking assembly 13 to prevent
inadvertent downward displacement of load 5. Referring now to FIG.
4, an understanding of the structure used to implement the
safeguard apparatus can be best seen. Drum 11 is keyed to shaft 15,
hoisting cable 6 being disposed thereon. Shaft 15 is extended to
and coupled within overrunning or one-Way clutch 70. The outer race
of overrunning clutch 70 is coupled to shaft 71 which is in axial
alignment with shaft 15. Shaft 71 is coupled to and secured within
hub 72 of brake assembly 13. Overrunning clutch 70 will be
explained in detail below. Although the scope of the present
invention is broad enough to permit brake assembly 13 to be
fabricated by any number of conventional braking systems such as
air actuated band brakes, brake assembly 13 is preferably an air
actuated disc brake. Brake assembly 13 comprises outer housing 73
which is rotatably mounted about shaft 71 on suitable bearings 74.
Friction elements 75 and 78 are concentrically disposed within
brake housing 73 and can be caused to frictionally engage friction
disc 76 upon the actuation of expandable elements 77 through
roto-coupling 79. The coupling, roto-coupling 79 and expandable
elements are not shown. Brake housing 73 is referenced to a fixed
frame of reference such as platform 2. Friction disc 76 is
concentrically disposed upon and secured to clutch hub 72 which in
turn is keyed to shaft 71. The actuation of brake assembly 13 will
cause the relative motion between shaft 71 and brake housing 73 to
cease.
An understanding of overrunning clutch 70 can be best gained by
reference to FIG. 5. FIG. 5 is a schematic, partial cross-sectional
view of a cam-clutch utilized to implement overrunning clutch 70.
It shall be understood that the terms cam-clutch, overrunning
clutch or one-way clutch are synonomous with respect to the use
within the present invention. Axially disposed on opposite ends of
overrunning clutch 70 are cylindrical bores 80 and 81 for receiving
shafts 71 and 15 respectively. Keys 82 and 83 are axially aligned
with cylindrical bores 80 and 81 respectively and will prevent
inadvertent rotation of shaft 71 or 15 with respect to overrunning
clutch 70. Shaft 71 is secured to outer race 84 and drum shaft 15
is secured to inner race 85. Inner race 85 is rotatably disposed
within outer race 84, inner race 85 being suitably journeled within
outer race 84 by bearings 86. Cams 87 frictionally engage the inner
cylindrical surface of outer race 84 and the outer cylindrical
surface of inner race 85. The orientation of cams 87 is controlled
by outer cage 88 and inner cage 89.
The operation of overrunning clutch 70 can be best seen by
reference to FIG. 6a, FIG. 6b and FIG. 6c wherein schematic views
of the operation of overrunning clutch 70 are shown. As stated,
overrunning clutch 70 is used to allow drum shaft 15 to free-wheel
with respect to shaft 71 when braking assembly 13 is engaged and it
is desired to initiate movement of load 5 and hoisting cable 6 in
the in-haul direction. Overrunning clutch 70 will effectively lock
drum shaft 15 and shaft 71 when drum 11 is paying out hoisting
cable 6 in the out-haul direction. When braking assembly 13 is
engaged, hoisting cable 6 can be payed out only against the force
of brake assembly 13.
Referring now to FIG. 6a, the free-wheeling mode of overrunning
clutch 70 is illustrated therein. Inner race 85 and outer race 84
will be free-wheeling with respect to each other when the
respective angular rotation is as shown. Inner race 85 is being
rotated in a counterclockwise manner whereby hoisting cable 6 is
being reeled in upon drum 11 through the action of clutch 14. Inner
cage 89 and outer cage 88 are concentric with respect to each
other, each transverse edge of each section of inner cage 89 and
outer cage 88 contacting a point on cam 87. In this mode, inner
cage 89 rotates counterclockwise with respect to outer cage 88
orienting cams 87 to allow inner race 85 to be in an overrunning
condition with respect to outer race 84. Since the top and bottom
surfaces of cams 87 are not forced against the respective radial
surfaces of inner and outer races 85 and 84, the shafts coupled to
inner and outer races 85 and 84 will be effectively disengaged from
each other thereby precluding the transmission of torque from one
shaft to the other. Springs 90 insure that cams 87 maintain contact
with races 84 and 85.
Referring now to FIG. 6b, a mode of operation is illustrated
whereby outer race 84 is rotated counterclockwise with respect to
inner race 85 thereby effectively engaging overrunning clutch 70
and providing for the transmission of torque from shaft 71 to shaft
15. It will be recognized that this mode of operation is not
encountered since brake assembly 13 does not initiate any
rotational force. This mode would be utilized where brake assembly
13 was replaced by a clutch and power source used to counter the
over-haul movement of drum 11 and attached hoisting cable 6. As can
be seen by comparing FIG. 6b with FIG. 6a, outer cage 88 and inner
cage 89 have rotated counterclockwise with respect to each other
forcing cams 87 to rotate counterclockwise thereby loading
overrunning clutch 70 and effectively locking shaft 71 and drum
shaft 15. The loading of overrunning clutch 70 will provide for the
transmission of torque from shaft 71 to drum shaft 15.
Referring now to FIG. 6c, overrunning clutch 70 is illustrated
under the mode whereby inner race 85 is rotated clockwise with
respect to outer race 84, this mode arising where hoisting cable 6
is being payed out and brake assembly 13 engaged. In this
configuration, inner cage 89 will be rotated clockwise with respect
to outer cage 84 thereby fully loading cams 87 and imposing the
force of brake assembly 13 on the outhaul movement of drum 11.
Where there is effective engagement between drum shaft 15 and shaft
71, brake assembly 13 will act as a braking system thereby
providing for the safeguard needed to initiate upward vertical
displacement of load 5 while load 5 is being held by braking
assembly 13 as well as preventing inadvertent downward vertical
displacement of load 5.
The present invention crane provides means for compensating for
vertical displacement of the supporting platform as well as
providing means for dynamically initiating the vertical movement of
a load without the severe problems inherent in systems disclosed by
the prior art. The ability to initiate the upward vertical movement
of a suspended load without encountering deleterious perturbations
yields a system which provides substantial advantages regarding
economy, safety and ease of operation.
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