HOIST LOCK

VERROUILLAGE POUR TREUIL DE LEVAGE

English Abstract

There is provided a gripping device with lifting arms mounted for relative
rotational movement on a slider and having free ends spaced from each other
and adapted to receive a load there-between. An arm link assembly coupled
to the arms is movable between a gripping position and a release position to
respectively close the arms to grip a load and to separate the arms to receive
a load. An over-center clamp is incorporated into the device to move the arm
link assembly between said gripping position and release position and to hold
the arm link assembly in the release position for the arms to receive a load.

French Abstract

Cette invention concerne un dispositif de préhension à bras de levage pivotant l'un par rapport l'autre sur une coulisse et dont les extrémités libres sont espacées et adaptées pour recevoir une charge entre elles. Une tringlerie couplée aux bras peut se déplacer entre une position de serrage et une position de desserrage pour respectivement refermer les bras sur la charge et les ouvrir pour accueillir la charge. Le dispositif comprend un excentrique qui sert à déplacer la tringlerie entre les positions susmentionnées.

Claims

CLAIMS
The embodiments of the invention in which an exclusive property or
privileges is claimed are defined as follows:
1. A gripping device having a pair of lifting arms pivotally mounted to a
first
body for relative rotational movement to each other and having free ends
spaced from each other for receiving a load therebetween;
an arm link assembly coupled to the arms and to a second body, the arm
link assembly being movable between a first position to close the arms to grip
a load and a second position to separate the arms to receive a load; and
an over-center locking clamp coupled to said first and second bodies and
operable to move the arm link assembly into the first position and to
releasably retain the arm link assembly in the second position.
2. A gripping device having a pair of lifting arms pivotally mounted to a
first
body for relative rotational movement to each other and having free ends
spaced from each other and adapted to receive a load therebetween;
an arm link assembly coupled to the arms and to a second body, the arm
link assembly being movable between a first position to close the arms to grip
a load and a second position to separate the arms to receive a load; and
an over-center locking clamp coupled to said first and second bodies and
operable to move the arm link assembly into the first position and to
releasably retain the arm link assembly in the second position;
wherein the second body is a suspension structure and the arm link
assembly moves into said first position upon lifting the device using the
suspension structure.
3. A gripping device having a pair of lifting arms pivotally mounted to a
first
body for relative rotational movement to each other and having free ends
spaced from each other and adapted to receive a load therebetween;
an arm link assembly coupled to the arms and to a second body, the arm
link assembly being movable between a first position to close the arms to grip
6

a load and a second position to separate the arms to receive a load; and
an over-center locking clamp coupled to said first and second bodies
and operable to move the arm link assembly into the first position and to
releasably retain the arm link assembly in the second position;
wherein the over-center locking clamp comprises a first link pivotally
connected at one end to the second body on a first pivot, an actuating
lever being pivotally connected to the other end of said first link, and a
second link pivotally connected at one end to the first body on a second
pivot, the other end of said second link being pivotally connected to an
intermediate portion of said actuating lever.
4. In a gripping device having a body associated with coupling means
adapted to support a load;
a slider relatively movable to said body;
a pair of lifting arms transversely disposed on opposite sides of said
body, each arm having an end pivotally secured to the slider and a free
end adapted to engage a load to be gripped between said arms in a
gripping configuration when said slider moves in a first direction;
the improvement in which an over-center locking assembly is provided
to lock said arms in a release configuration to receive a load, the center
of equilibrium for the over-center locking assembly being defined by a
first pivot secured to said body and by a second pivot secured to said
slider,
an actuating lever forming part of said over-center locking assembly
being pivotally connected to said first pivot by at least one first link, the
actuating lever being pivotally connected to said second pivot by at least
one second link, the actuating lever being adapted to pull said slider in a
second direction opposite to said first direction, and to thereby release
said arms from a load being gripped; and
the actuating lever, said first link and said second link being located
relative to each other such that, upon said second link crossing said center
of equilibrium as said arms move from the gripping configuration to the
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release configuration, the actuating lever comes into engagement with
said first link, said first link thereby stopping the actuating lever from
pivoting further, whereby said over-center locking assembly maintains
said arms in the release configuration.
5. Gripping device according to Claim 4 in which said at least one first
link is pivotally connected at one end thereof to said body on said first
pivot, the actuating lever being pivotally connected to the other end of
said at least one first link, and said at least one second link is pivotally
connected at one end thereof to said slider on said second pivot, the other
end of said second link being pivotally connected to an intermediate
portion of said actuating lever.
6. In a gripping device having an elongate shaft with coupling means at
one end adapted to support a load;
a slider axially movable on said shaft;
a pair of lifting arms transversely disposed on opposite sides of said
shaft, each arm having an end pivotally secured to the slider and a free
end adapted to engage a load to be gripped between said arms;
a pair of arm links each pivotally secured at one end to said shaft and
pivotally secured at the other end to an intermediate portion of said arms
and adapted to move with the arms between a gripping configuration to
grip a load and a release configuration to receive a load;
the improvement in which an over-center locking assembly is provided
to lock said arms in a release configuration, the center of equilibrium for
the over-center locking assembly being defined by a first pivot forming
part of the over-center locking assembly and secured to said shaft between
said coupling means and said slider and by a second pivot secured to said
slider;
an actuating lever forming part of said over-center locking assembly
being pivotally connected to said first pivot by at least one first link, the
actuating lever being pivotally connected to said second pivot by at least
one second link, the actuating lever being adapted to pull said slider
8

axially on said shaft toward said coupling means, and to thereby release
said arms from a load; and
the actuating lever, said first link and said second link being located
relative to each other such that, upon said second link crossing said center
of equilibrium as said arms move from the gripping configuration to the
release configuration, the actuating lever comes into engagement with
said first link, said first link thereby stopping the actuating lever from
pivoting further,
whereby said over-center locking assembly maintains said arms in the
release configuration.
7. Gripping device according to Claim 6 in which said first link is
pivotally connected at one end to said shaft on said first pivot, the
actuating lever being pivotally connected to the other end of said first
link, and said second link is pivotally connected at one end to said slider
on said second pivot, the other end of said second link being pivotally
connected to an intermediate portion of said actuating lever.
8. Gripping device according to Claim 7 in which the actuating lever
includes a pivot connection positioned such that, upon said second link
crossing said center of equilibrium as said arms move from the gripping
configuration to the release configuration, the pivot connection on the
actuating lever comes into engagement with said first link, said first link
thereby stopping the actuating lever from pivoting further.
9. Gripping device according to Claim 8 in which the first link is curved
to accommodate the actuating lever when the second link is moved over
the center of equilibrium.
10. A gripping device having a pair of lifting arms pivotally mounted to
a first body for relative rotational movement to each other and having free
ends spaced from each other and adapted to receive a load therebetween;
an arm link assembly coupled to the arms and to a second body
comprising a suspension structure, the arm link assembly being movable
between a first position to close the arms to grip a load upon lifting the
9

device using the suspension structure and a second position to separate
the arms to receive a load; and
an over-center locking clamp coupled to said first and second bodies
and operable to move the arm link assembly into the first position and to
releasably retain the arm link assembly in the second position.
11. A gripping device having a pair of lifting arms pivotally mounted to
a first body for relative rotational movement to each other and having free
ends spaced from each other and adapted to receive a load therebetween;
an arm link assembly coupled to the arms and to a second body, the arm
link assembly being movable between a first position to close the arms to
grip a load and a second position to separate the arms to receive a load;
and
an over-center locking clamp coupled to said first and second bodies,
the over-center locking clamp comprising a first link pivotally connected
at one end to the second body on a first pivot, an actuating lever being
pivotally connected to the other end of said first link, and a second link
pivotally connected at one end to the first body on a second pivot, the
other end of said second link being pivotally connected to an intermediate
portion of said actuating lever, the over-center locking clamp being
operable to move the arm link assembly into the first position and to
releasably retain the arm link assembly in the second position.
10

Description

21 86642
HOIST LO('.
Field of the Invention
This invention relates to a hoist or gripping device commonly associated
with a crane or any other lifting apparatus for moving heavy loads. The
device generally comprises a pair of clamping arms c~nnPctPd by a system of
links. In particular, the invention relates to locking means for m:lint:lining
the clamping arms in a spaced apart uJIIriguld~ion adapted to release a load
and to allow the crane to be repositioned to grip another load.
Background to the Tnvpnrion
Various gripping devices are known in which clamping arms are pivotally
mounted so that the free ends of the arms that grip a load are brought closer
together for a still firmer grip when the load is suspended, for example, by a
crane. Conveniently, premature, accidental releases of the load are avoided.
Locking devices provided to maintain the arms in a release configuration
ready to be positioned on a load may comprise a notched bar engaged by a
pin at a pre-~prprminpfi separation of the arms as in US 3,451,711 and US
2,853,336 or an interference device for limiting axial movement between a
collar carrying the arms and a lifting rod such as in US 1,129,664 and US
2,951,725. These locking devices work well in situations where there is easy
access to the apparatus and an operator has the opportunity to assure himself
that pins, hooks and collars are positioned in the required location, usually
with the assistance of a second operator who must first bring the arms to a
release collL~,uld~ion.
The object of this invention is to provide a locking mP~h ~ n i ~m for gripping
devices of the afore-m~mi-)nP-I kind which is easy to position into a release
collL~,uld~ion of the arms by one operator only.
Summar,v of the Invention
In accordance with this invention, there is provided a gripping device with
lifting arms mounted for relative rotational movement and having free ends
spaced from each other and adapted to receive a load there-between. An arm

2~ 86642
link assembly coupled to the arms is movable between a gripping position and
a release position to ~ e~LiY~ly close the arms to grip a load and to separate
the arms to receive a load. An over-center clamp coupled to first and second
bodies associated with the lifting arms and arm link assembly, l~e~Liv~ly,
is operable to move the arm link assembly between said gripping position and
release position and is adapted to releasably retain the arm link assembly in
the release position where the arms are separated to receive a load.
Brief Descrip~ion of the Drawings
In order that the invention may be more clearly understood, a preferred
embodiment thereof is described with reference to the a~o-lll,dllyillg
drawings, in which:
Fig. 1 is a side elevational view of a gripping device made in accordance with
the invention with an arm link assembly drawn in a release position;
Fig. 2 is a similar view to Fig. 1 with the arm link assembly drawn in a
gripping position in ~cco~i~tion with a load; and
Fig. 3 is an end elevation of area 3 shown in Fig. 1.
Description of PrPf~rred Emho(~imf-nt
A gripping device made in accordance with the invention is generally
indicated in the drawings by reference numeral 20. The device 20 is intended
to be used in ~cco~i~tion with a crane or some other lifting apparatus (not
shown) and is coupled, in use, to the crane by an "eye" 22 formed at a free
end of a shaft 24.
A slider assembly 26 disposed axially on the shaft 24 comprises a
cylindrical collar 28 and a pair of lugs 30, 32 extending transversely to the
shaft 24 and on opposite sides of the collar 28. Only one lug 30 is shown in
Figs. 1 and 2, the other lug 32 being hidden from view behind the lug 30. It
will be understood that the lugs 30,32 and the cylindrical collar 28 together
define one body (the slider assembly 26) which slides axially on the shaft 24.
Lifting arms 34,36 are pivotally mounted at respective ends on pivots 38,40
. ,, . , . , ... .. , ... ,,, .. .... . , .. . , , . , _ , _ . ... _ _ ... .... ....... . . .

6 ~ 2
to the lugs 30, 32 of the slider assembly 26 and are disposed on opposite sides
of the shaft 24. It will be understood that the pivots 38, 40 each traverse the
lugs 30, 32 and a respective arm 34, 36.
The uy~.d~ ly-lower ends of the arms 34, 36 have a generally arcuate
shape and the arms are disposed so that the ends curve toward each other.
The arms 34, 36 terminate in respective grips 42, 44 which retain respective
grip pads 46, 48. The grip pads 46, 48 are made of smooth polished resin
material selected to minimize abrasion on smooth planar surfaces such as a
mom1m.qnt 50 of polished granite. The grip pads 46, 48 are pivotally received
inside the grips 42, 44 using a centrally located fastener (not shown) so that
their relative angular disposition will self-adjust when applied to a load. The
pads 46 and 48 may also be replaced when worn or damaged, as necessary.
It will be understood that other terminations may be formed on the ends of
the arms in accordance with the nature of the load to be gripped.
An arm link assembly generally indicated by numeral 52 is provided to
close the arms 34, 36 to grip a load as shown in Fig. 2 or to separate the arms
to receive a load as shown in Fig. 1. The arm link assembly 52 comprises
first and second link pairs 54, 56 of which each pair is pivotally mounted on
respective pivots 58, 60 to the arms 34, 36 and to a common pivot 62 on the
end of the shaft 24 opposite from the eye 22. k will be understood that only
one link of each link pair 54, 56 is shown in the drawings of Figs. 1 and 2,
the other link of each link pair being hidden from view and on the opposite
side of the associated arms 34, 36.
The gripping device described thus far is of a kind which is generally well-
known and of which many equivalent structures are known. In essence, the
operation of the device consists in positioning the grip pads in the spaced-
apart ~:unrl~;uld~ion of Fig. 1 on opposite sides of a load. The pads will be
spaced from the load until the shaft 24 is hoisted by a crane or some other
lifting apparatus. As the shaft 24 is raised, the link pairs 54, 56 pivot on their
common pivot 62 thereby bringing the lifting arms 34, 36 closer together as
they pivot on respective pivots 38, 40. Eventually, the grip pads 46, 48 are
., .. . .. ... . ... , .. .. _ . . ..... .... .. ..... ... . ..

2 1 86642
~ brought into engagement with the load or monument 50 and continued lifting
of the shaft 24 will raise the load which is held by friction between the grip
pads.
The problem which is addressed by this invention is that of m~int~ining
the lifting arms 34,36 in a spaced-apart configuration so that the grip pads 46,48 may be properly positioned about the load prior to raising it. Positive
locking devices to maintain the arms in a spaced-apart ~-nL~,uldLion are found
in the prior art, as mentioned above, and commonly require at least two
operators. One operator must physically space the arms apart which
otherwise are naturally inclined to come together under their own weight
while the other operator engages the lock.
In accordance with the invention, there is provided an over-center clamp
which is generally indicated in the drawings by numeral 64 and which is
operable to move the arm link assembly 52 into the gripping position of Fig.
2 and also to releasably retain the arm link assembly in the load-receiving or
release position shown in Fig. 1. The over-center clamp is comprised of an
actuating lever 66 and a pair of links 68, 70.
The actuating lever 66 is in the form of a handle (Fig. 3) of U-shape
lL~,uld~;on and is pivoted at its ends on pivot 71 to the first link 68 which,
in turn, is pivotally connected on pivot 72 to the shaft 24 just below the eye
22. The second link 70 is pivotally connected on pivot 74 to the collar 28 on
the slider 26 and the other end of the link 70 is pivotally cf)nn~ ct~d on pivot76 to an i~ te portion of the actuating lever 66.
The pivot 72 on the shaft 24 and the pivot 74 on the slider 26 define the
center of equilibrium for the over-center clamp 64.
In use, the over-center clamp 64 is moved by a single operator between a
release ~JIlL~,ul.lLion (Fig. 1) and a gripping configuration (Fig. 2) by lifting
and pulling the handle or actuating lever 66, as the case may be. It will be
seen that the handle 66 is down in the gripping position of the arm link
assembly 52 shown in Fig. 2 and is up in the release position shown in Fig.
1. Lifting the handle 66 from the Fig. 2 position causes the clamp 64 to

2~ 86642
simultaneously pivot on pivot 76 while raising the slider assembly 26 so that
the slider 26 is pulled upwardly toward the pivot 72 fixed to the shaft 24.
The motion of the handle or actuating lever 66 is limited by the arc described
by the second link 70 as the link rotates on the pivot 74 by which it is
attached to the slider 26. As its highest point, the link 70 is aligned with theshaft 24, the center of equilibrium for the clamp 64 and the arm link
assembly 52 has been brought to the release position of Fig. 1.
It will be seen that the first link 68 is curved to accommodate the actuating
lever 66 when the second link 70 is moved over the center of equilibrium and
the handle or actuating lever 66 has a bend so that it is out of alignment with
the shaft when it has been lifted and it may easily be grasped.
The actuating lever 66 and the first link 68 are also shaped so that, once
the link 70 crosses this equilibrium line, the pivot cnnn~tinn 76 on the
actuating lever 66 comes into engagement with the first link 68 thereby
stopping the clamp from pivoting any further and ~ ini~g the release
position of the arm link assembly 52.
When the gripping device 20 is properly positioned on a load, the handle
or actuating lever 66 needs merely to be tugged away from the shaft 24 and
pulled down. This motion of the actuating lever 66 pulls the second link 70
over the center of equilibrium releasing the slider assembly 26 to slide down
the shaft 24 and to allow the lifting arms 34, 36 to freely pivot on their
respective pivots 38, 40 and come into engagement with the load.
It will be understood that several variations may be made to the above-
described embodiment of the invention within the scope of the appended
claims and that, for example, the configuration of the arm link assembly 52
may vary in well-known manner, the lifting arms 34,36 may have a common
pivot on a slider, and the over-center clamp may likewise have alternative
configurations known in other applications.

Representative Drawing