Note: Descriptions are shown in the official language in which they were submitted.
14g
The invention relates to an apparatus for lifting a load,
comprising a load hook or eye to be coupled to a lifting means, such as
a crane, at least two oppositely disposed gripping arms movable relative-
ly to each other having gripping jaws for gripping the load, whereby the
lifting eye is so connected via pulling members to the gripping arms
that during the hoisting, the clamping arms are urged towards each
other.
Such an apparatus is used e.g. for loading and unloading
bags, tubes, paper coils and the like, during which the weight of the
load is utilized for exerting the required clamping force. For instance
it has already been proposed to design two clamping arms movable in
telescopic relationship to each other, each clamping arm and lifting
eye being provided with a rope sheave whereon runs a cable, which ends
are connected to the two gripping arms. By exerting a hoisting force
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the two gripping arms are drawn towards each other. It is also known
to use a linkage construction wherein the opposite ends of the arms of
the link are provided at the one end of the pivot point with gripping
jaws, while the arms disposed at the other side of the pivot point
are provided with eyes through which extends a hoisting chain. ~uring
the hoisting operation said eyes will therefore be drawn together at
the arms, so that the grip~)ine jaws are clamped accordingly against
the product to be hoisted.
A drawback of such an embodiment is that during the reduction
of the hoisting force the clamping force is reduced accordingly.
It is the object of the invention to provide an improved
apparatus o~ the above described type.
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~ o this effect according to the invention at least one pulling
member is coupled to the one end of a first hydraulic piston-cylinder
assembly, provided with a resilient member adapted to urge the hydraulic
piston-cylinder assembly to a starting position, while there is further-
more provided a second hydraulic piston-cylinder assembly which is so
connected mechanically to one of the gripping arms, as well as via a
hydraulic line to the first hydraulic cylinder that during the hoisting
of the apparatus the oil pressurized in the first cylinder tends to
flow towards the second cylinder, urging the gripping jaws towards
each other, there being provided at least one non-return valve in the
hydraulic line from the first to the second cylinder, as well as an
operable valve means adapted for communication between the second
cylinder and an oil collection space. In this manner the pressure
generated in the first cylinder during the hoisting operation is
transferred via the non-return valve in the second cylinder so that t`ne
two gripping jaws are urged towards each other. l~he non-return valve
prevents the elimination of the gripping force after the hoisting force
has dropped out. In order to selectively eliminate the gripping force
yet, there is provided the operable valve member for the out~low of
oil from the second cylinder. Although use may be made of an oil
reservoir for compensating the volume variation in the cylinders,
preferably the first and the second cylinder are so interconnected that
during the elimination of the hoisting force and the resulting engage-
ment of the release spring of the first piston-cylinder assembly, there
is generated in the first cylinder a partial vacuum which during the
operation of the valve member is active for returning the second
cylinder to the starting position. ~aturally it is also possible to
provide the second piston-cylinder assembly with a release spring in
order to return same to the starting position.
In accordance with another embodiment of the invention there is
provided a third hydraulic piston-cylinder assembly which likewise is
urged by a resilient member to a starting position, whereby there is
provided a non-return valve in a hydraulic line from the first tothe
second cylinder, while furthermore the third cylinder is connected
throu6h a non-return valve to the second cylinder. During the hoisting
of a load, oil will flow from the first cylinder to the second and the
third cylinder. When the hoisting force drops out, under influènce of
the release spring of the third piston-cylinder assembly, oil will
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continue to flow from the third cylinder to the second cylinder, while
maintaining sufficient pressure the~in.
Preferably use is made thereby of a three-way cock in the
connections between the three cylinders in such a way that in a position
of the three-way cock the connection between the second cylinder and the
first and third cylinder is completely cut off, whereby in a second or
clamping position exclusively oil from the first or the third cylinder
can flow to the second cylinder, while in a third or unloading position,
there exists a free connection between the first and the second cylinder.
Preferably each gripping jaw is mounted on the gripping arm i
with interposition of a pivot arm in such a way that during the hoisting
of a load the pivot point of the pivot arm with the gripping jaw is
disposed above the corresponding pivot point of the pivot arm at the
clamping arm, whereby there is mounted a stop on the pivot arm so that
an excessive upward displacement of the pivot arm with gripping jaw
relative to the gripping arm is avoided. Durine the hoisting the weight
of the load will tend to pull the gripping jaws downwardly. Due to the
double-pivoting arm there will thus be exerted an additional gripping
effect.
Further particulars will also appear from the following
description of an embodiment according to the invention.
The single figure of the drawing diagrammatically shows a
hoisting apparatus according to the invention, wherein 1 indicates a
load to be hoisted, e.g. a paper bag to be hoisted. ~liS load is
clamped by means of two gripping jaws 2, the shape of which may be
adapted to that of the load, e.g. of circular cross section when a
round bag has to be hoisted. Each gripping jaw 2 is pivotally mounted
on a pivoting ar m 3 which at 4 comes in engagement with the gripping
jaw. The pivoting arms 3 are on the one end connected at 5 pivotally
to the gripping jaw and on the other end at 6 pivotally connected to
respectively a left gripping arm 7 and a right gripping arm 8. Said
gripping arms are integral with horizontal tubular guide pieces 9,
respecitively 10. Said tubular pieces 9 and 10 are incorporated in
a frame generally indicated by 11. ~his comprises in the example two
parallel web plates which are interconnected by a plurality of connect-
ion bolts 12 whereon are mounted rollers 13. Between said rollers 13
the tubular pieces 9 and 10 can be horizontally reciprocated. The right
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gripping arm 8 with tubular piece 10 is secured relative to the ~rame
11 by means of a lock pin 14. In the tubular piece 10 there are applied
a plurality of holes 15 for securing the right-hand or fixed gripping
arm 8 in another position adapted to the diameter or width of the
product to be hoisted. The left-hand or movable gripping arm 7 is
connected at 16 to the piston rod 17 of a hydraulic piston~cylinder
assembly indicated in general by'18. This assembly is indicated in the
above as second hydraulic piston-cylinder assembly. The end of the
hydraulic cylinder 19 is secured with a pin 20 to the frame 11. Said
pin 20, or possibly more attachment portions, extends through an
elongated recess 21 indicated partly by broken lines in the tubular
member 9.
By conducting via a line 22 oil to the hydraulic cylinder 19,
the piston rod 17 with tubular member 9 in the figure is ureed to the
right, thus activatine the gripping apparatus. In the fieure the outer
gripping position i8 indicated.
The hoisting apparatus is provided at the top with a lifting
eye23. This lifting eye i8 provided with a rope sheave on which runs
a rope 24 as pulling member. Said rope 24 is secured at 25 to the
right grippin~ arm ô. The left part of the pulling rope runs via a
rope sheave 26 in the frame 11 and is connected to the eye 27 of a
piston rod 2O of a first, see above, hydraulic piston-cylinder assembly
29. ThiB assembly 29 is provided with a tension spring 30 adapted to
urge the piston rod in the completely retracted position in cylinder
31. Furthermore the embodiment shows a third hydraulic piston-cylinder
,assembly generally indicated by 32 and having a piston rod 33, a
hydraulic cylinder 34 and a tension spring 35 adapted to maintain said
hydraulic piston-cylinder assembly likewise in the retracted position.
The first piston-cylinder assembly 29 is connected via a line
36 to a three-way cock 37 and via a non-return valve 38 to the cylinder
space underneath the piston in the piston-cylinder assembly 32 by
means of a line 39. In said line 39 there is provided a branch 40 which
is connected via a non-return valve 41 to another inlet of the three-
way cock 37. Furthermore there is connected to said three-way cock
the line 22 to the cylinder assembly 17.
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Prior to taking up a load, the left gripping arm 7 is in the
position 45 indicated by broken lines. The apparatus is then lowered
onto the load 1, thereby adapting if necessary by means o pin 14 the
position of the right gripping arm 8 to the width OE the diameter of
the load to be hoisted. At this moment there is no tension in the
rope 24, so that under influence of spring 30 the piston-cylinder
assembly 29 will be urged towards the retracted position. Above the
piston in cylinder 31, i.e. at the left-hand side of the piston, not
shown, in said cylinder there will thereby prevail a partial vacuum.
By bringing the three-way cock 37 in the right-hand position, line
22 will be connected to line 36. The partial vacuum in cylinder 31 will
exert its influence through line 22 into cylinder 19 whereby the
assembly 18 will likewise be drawn to its retracted~ position while
the gripping arm will occupy the position indicated by 45. Prior to
starting the hoisting operation, the three-way cock 37 will be broueht
in the left position, i.e. the line 22 is throughconnected to line 40.
Insofar the third piston-cylinder assembly 32 has not yet attained
the completely retracted position, oil, under influence of the spring
35, will flow from cylinder 34 via lines 39 and 40, non-return valve
20 4, three-way cock 37 and via line 22 to the cilinder 19, as a result
of which the piston rod 17 thereof will be protracteawhile the gripping
arm 7 will be pressed to the right in the figure to against the load 1
to be hoisted.
However it is possible that the piston-cylinder assembly 32
has attained its retracted position, so that no or insufficient
quantity of oil is available for extending the second piston-cylinder
`assembly 18. During the hoisting operation the pulling rope 24 will
be tensioned, so that the piston rod 28 is drawn via connection 27 to
the protracted position. The spring 30 is thereby so dimensioned that
3 the weight of the apparatus proper is sufficiently large to overcome
the force thereof, at least initially. As a result oil will be pressed
to the clamping cylinder 19 via line 36, non-return valve 38, line 40,
non-return valve 41 and via the three-way cock 37 and line 22, so that
a certain degree of clamping is effected. This oil pressure need not
be sufficient yet to prot~act the piston rod 33 against the action of
spring 35. However as soon as the weight of the apparatus proper has
been overcome, a greater force in rope 24 of the hoisting apparatus will
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be active under influence of the weight of the load 1. As a result a
greater force will be transmitted from the piston-cylinder assembly 29
to the clamping cylinder 19, so that the load will be clamped with a
greater ~orce, depending on the weight of the load. Thereby the force
of the spring 35 will likewise be overcome to an increasing extent and
said spring will be extended and tensioned.
Should the force in the rope 22 decrease, possib~ to zero,
e.g. in that the load impinges an obstacle or is put down, then the
piston rod 28 will be retracted under influence of spring 30 until a
partial vacuum at the left side of the piston in cylinder 29 is in
equilibrium with the force of spring 30. Due to the activity of the
non-return valve 38 and the connection between lines 36 and 22 blocked
by the three-way cock 36, this will have no further influence on the
clamping force of the arms of the apparatus. Even when for some reason
no pressure can be supplied any loneer from the third piston-cylinder
assembly 32 e. e . in that the sprine 35 has completely retracted the
piston rod 33, the cla~ping cylinder 19 will still be active due to
the activity of the non-return valve 41. In this manner it is reliably
prevented that for some reason the clamping apparatus becomes unwilling-
ly inactive. After positioning of a load, the three-way cock 37 can be
brought in the righ-hand position, whereby the line 22 is throughconnect-
ed to line 36. Insofar then no pressure or partial vacuum prevails in
the cylinder 31, oil will be drawn away from the clamping cylinder 19,
so that the clamping arm 7 will be moved to the left, as a result of
which the clamping apparatus releases the load.
~ o prevent that during displacement of the apparatus from a
load to another one, the clamping cylinder 19 becomes active, thereby
urging the clamping arm 7 to the right, the three-way cock 37 can be
set in the mid-position, whereby the lines communicating with said
cock are not throughconnected. During the hoisting operation there will
be produced though a pressure in cylinder 31 of the assembly 29 and
possibly in that of assembly 32, in accordance with the weight of the
apparatus proper, but the clamping arm 7 will continue to occupy its
released position, as indicated by 45. After the lowering of the
apparatus on a load 1, it is possible by moving the three-way cock 37
to the left-hand position, to effect the clamping under influence of
the possibly more or less protracted piston-cylinder assembly 32 and/or
through the operation during hoisting of the piston-cylinder assembly 29
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as indicated in the above.
It is observed that instead of using a partial vacuum in the
piston-cylinder assembly 29 for bringine the clamping ar~ 7 in the
released position, also the clamping cylinder 19 may be provided with
a release spring. In such an embodiment it is also possible to connect
the cylinder 31 of the piston-cylinder assembly 29 via a non-return
valve to a storage reservoir so that during the pressing of piston rod
28 in the cylinder 31 oil will be drawn into said cylinder. Naturally
the three-way cock 37 should then be so designed that oil, if desired,
10 can flow back from line 22 to the reservoir.
It is observed yet that, if desired, the three-way cock 37
may be remote-controlled, e.g. mechanically, electrically or
pneumatically. This operation may take place both from the crane and
from a position adjacent the hoisting apparatus.
The pivot point 5 in the clamping position is disposed sliehtly
higher than the pivot point 6. During the hoisting of a load, whereby
a vertical force is acting on the grippin~ jaws, the pivot points of
the two gripping jaws will be subjected both to a vertical and to a
horizontal movement towards each other. The resulting additional
horizontal force increases the gripping force on the load. The position
of the gripping jaw 2 relative to the associated pivoting arm 3 is
determined by the stop 4. Possibly the pivoting arm 3, when no load
is present, may be retained approxi~ately in the position as shown, e.g.
by means of a spring.
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