Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to cranes and more
particularly but not excluslvely to grab cranes.
Grab cranes as presently used in the logging and
dredging industries, as well as the general application of
grab cranes to pick up bulk materials such as coal, ore, etc.,
employ a grab consisting usually of two jaws or two shells
which open and close to pick up the load and subsequently
discharge it. These movements are produced by the actuation
of a holding rope and a closing rope. For example, in these
conventional cranes the holding rope opens the jaws and the
closing rope closes and lifts the jaws. This arrangement has
the disadvantage that the function of each rope being separate
in that they were not simultaneously employed to lift the load
with the result that the cranes are limited in lifting capac-
ity since only one of the ropes carries out the lifting
function.
It is the object of the present invention to over-
come or substantially ameliorate the above disadvantages.
There is disclosed herein a winch arrangement for a
crane having a grab, a holding rope and a closing rope, said
arrangement comprislng a closing drum to receive a portion of
the closing rope and apply force thereto, a holding drum to
receive a portion of the closing rope and apply a force there-
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to, first means to apply a first torque to the closing drum,
second means to apply a second torque to the holding drum,
control means for controlling said first and second means so
that a lifting force is applied to both the ropes to lift the
grab with the effective lifting force applied to said closing
rope being greater than the effective lifting force applied
*~0 to said holding rope, and wherein said first means includes
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a closing hydraulic motor means and a first closing pump
means to drive said closing motor means, and said second means
includes a holding hydraulic motor means and a second holding
pump means to drive said holding motor means, and a first
hydraulic circuit coupling the closing pump and closing motor
means and a second hydraulic circuit coupling the holding
pump and holding motor means, and said control means includes
a displacement control hydraulic circuit to adjustably control
the output of the said first and second pump means.
A preferred form of the present invention will now
be described by way of example with reference to the accom-
panying draw.ings wherein:
Fig. 1 is a plan view illustrating a winch arrange-
ment;
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Fig. 2 is a side elevation of the winch arrangement
of Fig. l;
Fig. 3 is a sectioned elevation of the winch arrange-
ment of Fig. l;
Fig. 4 is a hydraulic circuit including motors and
pumps for the winch arrangement of Figs. 1 and 2; and
Fig. 5 is a hydraulic control circult to be used with
the circuit of Fig. 3.
With reference to Figs. 1 to 3, the winch arrangement
10 comprises a frame 11 rotatably supporting a holding drum 12,
a closing drum 13 and a luff drum 14. The holding and closing
drums 12 and 13 are coaxially mounted on individual shafts 15
and 16 respectively by means of bearings 17. The holding drum
12 is provided with a gear 18 which meshingly engages three
gears 19 (A, B, C) so as to be driven thereby. The gears 19
are each driven by one of shafts 20 ~A, B, C) extending from a
respective one of the hydraulic motors 21 ~A, B, C). Similarly
the closing drum 13 is provided with a gear 22 driven by
hydraulic motors 23 (A, B, C) via shafts 24 (A, B, C) and gears
25 (A, B, C).
The holding drum 12 and closing drum 13 are adapted
to receive a holding rope and closing rope respectively, which
ropes extend, in the case of a logging crane, to a grab com-
prising two pivotally attached jaws which are adapted to engage
a bundle. The closing rope engages the jaws so that when a
force is applied thereto the jaws move relatively to each other
so as to grip the bundle. A lifting force is then applied to
both~ropes so as to raise the gripped bundle. To retain the
bundle in the jaws a greater proportion of the lifting force
required to raise the bundle is applied through the closing
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rope. ~ suitable proportiorl is 60~ of the total load.
~ cJreater force can be applied to the closing rope, ...
as compared to the holding rope, by applyincJ a higher torclue
to the closin~ drum 13 by means oE gear ratios. ~ccordingly
if a hi~her torque is to be applied to the closin~ drum 13 then
the ratio of the pitch circle diameter of gear 22 to gears 25
i5 lar~er tllan the ratio of the pitcll circle diameter oE
gear 18 -to ~ears 19.
Turning now to Fig~ 4 wherein -there is illustrated a
hydraulic circuit including the hydraulic motors 23 (A,'B, C)
and 21 (A, B, C) which are driven by variable displacement
hydraulic pumps 26 (A & B) and 27 (A & B). With reference now
to the closing circuit 47, the motors 21, which drive the
closing drum 13, are connected with the pumps 27 in parallel
by hydraulic lines 28 to 31. The lines 28 and 30 are su~plied
with hydraulic fluid under pressure when tihe closing drum 13
is to retract the closing rope, while if lines 29 and 31 are
supplied with hydraulic fluid under pressure then the closi.ng
drum 13 unwinds the closing rope therefrom. The closing circuit
47 is provided with pressure limit switches 32 and suction
limit switch 33 which when activated cause the operation of a
brake mechanism to en~a~e drums 12 and 13 to prevent further
movement thereof. Control devices 34 are provided to select-
ively vary the displacement of the pumps 27. The item 35
indicates a pressure gauge.
Each of the pumps 27 is provided with pressure relief
valves 36 and with a hydraulic fluid boost input valve 37 to
inject hydraulic fluid into the closed loop circuit 47 to
replace fluid leaking therefrom. Similarly the holding
circuit 38 is provided with hydraulic lines 39 to ~2 to
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connect tlle pumps 26 (~ & B) in parallel wi~h mo-tors 23
(~, B, C) to dr.ive tlle holdi~g drum 12. The circuit 38 is
provided with pressure relief valves 43 ancl hydraulic fluid
boost inpu-t valves 44. The pumps 26 (A & B) are provided with
control devices 45 to selectively vary the displacement of -the
pumps 26 (A & B).
Joining the two circuits 47 and 3~ is valve 46 which
is adapted to selectively connect the circuits 47 and 38 in
parallel. Thus in operation the closing circuit 27 is first
activated to close the ~rab, thereafter the two circuits 38
and 47 are placed in parallel by activating valve 46. The
pumps 26 and 27 then supply hydraulic fluid under pressure by
lines 2~, 30, 39 and 41 to drive motors 23 and ~1. The drums
12 and 13 are then caused to rotate and wind in the holding
and closing rope. So that the ropes are progressed at the
same rate the displacement of pumps 26 is adjusted so as to be
less than pumps 27 in order to compensate for the different
gear ratios. Located adjacent -the valve 46 are two pressure
switches 67 which ensure that the main control valves 49 and S0
cannot operate electrically until 500 ps.i is present in both
the closing circuit 47 and holding circuit 38. This prevents
any sudden pressure rise in the event of one rope being slack.
Control of the pumps 26 and 27 to effect up and down
movement of the grab as well as rate thereof is achieved by
operator control valves 49 and 50. Valve 50 controls the
direction and displacement of pumps 26 while valve 49 controls
the direction and displacement of pumps 27. The control circuit
48 is provided with hydraulic fluid under pressure through
line 51, which fluid is selectively directed by valves 49 and
50 to lines 52 to 55. For example one of lines 52 or 53, if
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supplicd Wit]l fluicl under pressure, could cause the increase
in displacement of pumps 2G while if the other line is supplied
with fluid under pressure would cause a reverse displacement
to t}lereby drive the motors 23 in the opposite direction. A
similar condition coulc7. be applied to lines 54 and 55. Lines
52 ~ Z 53 al-e provic~cc~ wi.tH~ prcssurc r~ lci~ valvc-~s 5~ cl 57
to regulate the displacement of pumps 26 so as not to exceed
the displacement of pumps 27 to thereby ensure that the rate
of movement of the holc1ing rope is the same as the closing rope.
The winch assembly 10 is provided with a brake,
mechanism 58 for the holding drum 12 and a brake mechanism 59
for the closing drum 13. Both mechanisms 58 and 59 are biased
on and are only released by the application of fluid under
pxessure to line 60 or 61. However, the control circuit 48 is
provided with two safety valves 62 and 63 which are operated
by switches 32, 33 and 64. If any one of switches 32, 33 or
64 is activated the pressure is relieved from lines 53 and 54
by activation of valves 62 and 63 which in turn activates valves
65 and 66. Valves 65 and 66 then clrain the fluid from the
brake mechanism 58 and 59 to thereby release them to engage
and stop drums 12 and 13.
The shuttle valve 67 i.s provided to prevent the hold
li.ne loacl from being added to the close line.
