Note: Descriptions are shown in the official language in which they were submitted.
-- 1 --
CHAIN GRAB ~OOK PROVIDING FQR
A F~AT LAY CROSS-OVER LINK
TECHNICAL EIELD OF THE INVENTION
The present invention relates to chain grab hooks.
More Specifically; the invention relates to a specific chain
grab hook which holds the engaged chain cross-over link in
~. a generally flat or horizontal position.
: ~ 5
BACKGROUND OF THE INVENTION
Chain grab hooks grab a chain in such a way that the
chain is preve~ted from running through the hook. To accom-
plish this end, the throat of the hook, defined by the shank
portion at one side, the free-end portion at khe other side,
` and an inte~mediate connecting bigh~ portion, is made large
; enough to recaive one link in an upright cross-over orienta-
: tion but small enough to prevent passage there~hrouqh of an
adjacent link. ~he upright cross-over link rests edgewise on
the bridging bight por~ion at the lower end o the ~hroat.
With presently constructed grab hooks, the chain,
when placed under loaded conditions, is subjected ~o combined
stresses which, when large ~nough, ultima~ely cause the chain
~0 to ~ail. One of the stresses to which the chain is subjected
i~ a tensile stress acting long.i~udinally of the chain. Chains
are constructed to withstand such tensile stresses so that no
problem is presented. When a chain link is seated in an up-
right or edgewise position in the throat of the grab hook to
rest on the lower bight portion however~ the cross over link
- 2 -
. is also subjected to a shearing or cut-tlng ~rce~ A chain
link is not ordinarily designed to withstand such a shearing
force acting transversely of the link. ~ccordingly, when a
chain is used in conjunction with a gra~ hook, the breaking
S strength of the upright link within the throat of the hook
is reduced so that, when overloaded, the chain invariably
breaks at this point. I~ is therefare often necessary to use
larger chai.ns than are required to lift a desired load in
order to assure an acceptable margin o safety. This, in
turn, cause~ increased expense and inconvenience to the users
of the chain.
In addition ~o possible chain failure, the hook isalso subject to failure under either overload conditions or
conditions of cyclic fatigue. Both the overload failure value
and the fatigue life of a part are detrimentally effected by
high stress concentration~ as opposed to a more uniform over-
all stress distribution. A chain grab hook having ~ verti-
cally oriented slot for receiving the cro~s-over link produces
very high localized stress concentrations in the hook since
the cross-over link is vPr~ically supported by the hook in a
very limited area of the saddle or bight portion of the hook.
In many hook designs, ~he cross-over link, under the influ-
ence of the load, pivots at one side of the hook to lift off
of téh support saddle along most o its length with the result
o being supported by an even smaller area of ~he hook. In
order to prevent early hook failure, conventional hooks have
o nece~sity been fabrica~ed with excessive quanti~ies of
material and/or have ~een given a relatively low maximum load
limit.
Accidental disengagement of the chain from conven-
kional chain gra~ hook also presents a hazzard. In an un-
loaded or slack condition, it is possible for the cross-over
link of the engaqed chain to ~lide out o the engaging hook
in a manner which either completely disengages the chain from
35 the hook or removes the cro~s-over link to a position which
~5~
-- 3 ~
would cause either chain or hook damage if the loaded colldi-
tion were to be resumed.
THE INVENTION
The present invention relates to an improved chain
grab hook wherein improved stress di.stribution characteristics
in both the hook itself and the engaged chain are achieved;
wherein improved safety by -the prevention of accidental chain
fallout is achieved; and wherein a reduction in hook reach is
achieved thereby minimizing the quantity of material needed
: for fabrication of the hook.
The chain grah hook of the present invention is
basically characterized by the fact that the shank~ free-end,
and bight portion of the hook are configured to grab the chain
in a manner which supports the cross--over link of the engaged
chain in a flat attitude forming an angle with the horizontal
no greater than 45. This "flat lay" is particularly advan-
tageous in that both legs or barrels of the chain link are
~ 20 supported by and rest on an upwardly facing supporting sur-
: - face of the free-end of the generally C-shaped hook. Such
: support avoias stress concentrations and the bending forces
experienced by both the hook and the cross-over chain link.
The extended.support surface provided for this "flat lay"
~ 25 link has a dimension substantiall.y equal to the length of the
: cross-over link. Recesses in the side of the free-end por-
tion of the hook are provided to receive therein a portion o
each of the side downstanding links joined to the cross-over
link of the engaged chain.
The tip of the free-end portion is upwardly turned
to~ard the shank portlon of the hook in order to provide an
: obstruction to accidental removal of the cross-over llnk.
This upwardly turned tip cooperates ~ith the erlgagement of
the downstandiny side links in the side recesses to virtually
el.iminate accidental d.isengagement of the chain from the hook.
-`,`i~
~.
- ~ -
The support surface of ~he free-end L~ortion ma~ be
inclined to the horizontal by an angle of up to 45. Accord-
ingly, the cross-over link of the engaged chain is also tilted
from the horizontal so that its joined side links have a ten-
dency to rotate back toward the body of the hook. This ten-
dency to rotate or slide toward the body of the hook minimizes
the distance between the load axis of the loaded chain and the
neutral fibre axis of the hook to thereby minimize the t,ending
moment placed on the hook.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention rnay be better Inderstood and
its numerous objects and advantages will become apparent to
lS those skilled in the art by reerence to the accompanying
drawings wherein like reference nurnerals refer to like ele-
ments in the several figures and in which:
Figure 1 i.s an elevational side view of the pre--
erred embodiment of the present invention showing the hook
in its loaded condition;
Fig~re 2 is a vertical cross-section of the loaded
hook of figure 1 taken along the view lines 2-2; and
Figure 3 is a cross-section of the hook of figure
: 1 taken along view lines 3-3.
DESCRIPTION OF THE BEST MODE OF THE INVENTION
While the invention is susceptible of various mod-
i~ications and alternative constructions, there is shown in
the drawlngs and there ~ill hereinafter be described, in de-
kail, a description of the preferred embodirnent o~ the inven-
t.ion. It is to be understood, however, that the specific
description and drawings are not intended to limit the inven-
tion to the specific form disclosed. On the contrary, it is
intended that the scope of this paten-t include all modifications
, ~;
.,,~ .
- s
and alternative cons~ructions ~hereof ~alli~ it~in ~he
spirit and scope of the invention as express2d in tlle al~L~en-
ded claims to the full range of their equivalents.
The preferred embodiment of the chain grab hook 10
of the present invention, as illustrated in -the figures, con-
sists of a shank 1~, a free-end 14 and a connecting bight 16,
all of which lie in the same plane and which toqether generally
'form a C-shape. Shank 12, free-end 14 and bight 16 define
therebetween a slot or throat 18 adapted to receive therein
a traversing or cross-over link 30 of an engaged load c~rrying
chain 20 of the bent wire link type. Shank portion 12 is pro-
vided with a hook eye 38 ~or connecting the hook to a chain 28.
Free-end portion 14 includes a generally upwardly
facing surface 40 which is the primary bearing surface for
supporting ~he cross-over link 30 in a generally flat atti~ude.
The figures show that support surface 40 lies gen-
erally in a plane which is tilted from the horizontal by a
given angle in the plane of the hook when the hook is loaded.
Inclining support surface 40 and therefore link 30 to the
horizontal, as shown in figure 1, causes the downstanding
lateral links 3Z and 36 joined to the cross-over link 30 of
the engaged load chain 20 to swing in the downhill direction.
This tendency to swing or rotate toward the bight 16 and
away rom the central longitudinal axis 34 of link 30 ~see
figure 3) as well as away from the hook axis 24 causes the
load line 22 of tlle chain 20 to be moved closer to the neu-
tral "~iber" 26 of the hook whereby the bending moment placed
on the hook by the tensioned chain 20 is reduced.
When the hook 10 of the invention ;s loaded with a
load bearing chain 20 as shown in figure 1, the slot or throat
18 lies with a generally horizontal attitude so that free-end
portion 14 of the hook and i-ts upwardly facing surface 40 de-
fine the bottom of the throat 18. With this attitude, link
30 is supported, a~ shown, in a genérally horizontal attitude
so that surface 40 provides vertical support to both of the
-- 6 --
opposite legs or barrel sections 44, 46 of lin~ 30 Isee
figure 3). In order to provide the greatest de~l^ee of sup-
port so that stress concentrat;ons are minimized, surface
40 i5 formed to have a width across the plane of the hook
substantially equal to the length of one of the barrel S~?C-
tions of the link cross-over link 30, which is virtuall~ the
entire length of the lin~ itself. While it is ~)referred to
support both barrels 44, 46 along substantially their entire
lengths, it should be understood that the scope of the in-
vention is broad enough to include supporting link 30 sub-
stantially along the entire length of only one barrel ~hile
supporting the other barrel over a significantly reduced
surface. It is also conceivable, although less desira~le,
to provide a flat lay without supporting either barrel along
its entire length.
As wil7 be recognized, as the angle of incline to
the horizontal is increased, more or the load o~ chain 20 is
shifted to the "inside" barrel 46 of link 30. One of the
major advantages of distributing the load over increased
areas of both link 30 and hook surface 40 of the invention
will be los~, therefore, if the angle of incl;ne to the llor-
izontal is too large. An angle of incline no more than 45
from the horizontal provides a generally "flat" attltude for
cross-over link 30 while still deriving the support benefits
inheren~ in the "flat" lay. On the other hand, angles of
incline greater than 45 place the cross-over link in a gen~
erally "upstanding" attitude rather than in the desirable
"flat" attitude of the invention and such a hook-chain syst:em
would thus lack the added suppor~ advan~ages o~ the present
invention~
I,ooking specifically a-t figure 1, a preferred hook
design in which surface 40 is slightly angled to the horizon-
tal before loading the hook is shown. After the hook has
been engaged by a chain 20 and loaded, a~ shown, the hook
has rotated under the influence of ~le load in the clockwise
5f~
7 _ ,
.direction to shift load line 2~ of the cl~ail~ to~.ird ~ 16
as a result of ~he previously described swingin~.l of sidc~ li.nk
32. The hook l0 is shown in its loaded, static con~lition in
which the angle between surface 40 and the horizontal is
approximately 15~. While the angle has been selected as ~hat
which is preferred, it should be recognized that ot}ler angles
may be selected and may result de~ending on engineering design
and on the balance of the hook. Nevertheless, the ~resellt in-
vention is intended to include hook designs which result in
~s much as a 45 incline of suppor-t surface 40 to the hori-
zontal when the hook has been loaded. It is felt that al~gles
greater than 45 diminish the ability of support surface 40
to support both opposite barrel sections of cross-over l.ink
30 to a degree tha-t renders such greater angles undesiraLle.
As has been described, it is desirable to forln free-
end 14 and support surface 40 so that the support surface has
: a dirnension perpendicular to the plane of the hook which, in
at least one location, is at least as long as one of the
barrel sections 44 or 46 of the cross-over link 30. One way
of accomplishing this desirable end without interfering with
the attitude of the side downstanding links 32 and 36, is to
form hook 10 with a relatively hefty free-end ~ortiot~ 14 and
to provide longitudinally extending depressions 42 in the
sides of the free-end 14 for receiving therein one barre:l
section of the side links 32, 36. Longitudinally e~tending
~epression 42 may be formed generally parallel to the vertical
so as not to interfere with the tendency of links 32 and 36
to freely assume an orientation in line with the ~orce of
gravity or the depression may be formed to extend generally
parallel to the unloaded ax.is 24 or or:iented to ex-tend at an
;ntermediate angle.
Grooves 42 therefore permi~ each barr~l section o~
link 30 to be supported in a vertical direction substantially
over their entire lengths without undue interference between
the side link 32 or 36 and the body of the hook. Since link
~5~
30 is vertically su~ ol le(l alor~g vir-tuall~ iL:s e~l~ ire Ic~ tll,
and si.de link 32 is permitted to penetrate int~ ~ OV~ 4~,
there is very little if any tendency for link 30 t~ roc~ up
away from the support surface 40 as is the tendenc~ in m~ny
prior known chain hooks, Accordingly, chain link 30 is
supported by upwardly facing sur~ace 40 substantially alollg
the entire length of both barrel.sections 44, ~6 of the
cross-over link 30, thereby distributinq the .I~ d ~:itroiJlh
out the length of the link and over a signific3nt cont.lc~
area of the hook lO. Both chain 20 and hook lO are therei'ore
less likely to fail under heavy loads and under accumul.3ted
cyclic stresses.
As best seen in figure 1, free-end portion 14 n;ay
include an upwardly turned tip 48 which cooperates with the
configuration of shank 12 in order to form a two~part t~lroat
18 having a mouth part and a cross-over link engaging part.
The mouth part as shown is angled relative to the cross-over
link engaging part so that removal. o~ the cross-over link
30 from -throat 18 requires that cross-over link 30 be twisted
as it is removed from the throat~ Tip 48 then ~cts as an
obstr~ction to the removal of the cross-o~7er link-from tlle
chain grab hook lO and lessens the ~robability oE unint.~n-
tional disengagement of the chain 2n from the hook lO.
Grooves 42 formed in free-end portion 14 also act
to lessen the chance of acciden~al removal of the chain from
the hook. Side links 32 and 36 seat themselves within grooves
42 so that grooves 42 limit their o~ltward movement with khe
result that they may not be accidentally slid in the chain
disengaging directi,on. Disengagemellt of chain 20 from the
chain grab hook lO is easily manually accomplished, however,
by concurrently lifting lateral links 36 and 32 to align
their axes generally w.ith -the axis of cross-over link 30,
sliding cross--over link 30 outwardly along the slo-t 18 while
simultaneously :rotating link 30 to avoid the projecting tip
48. This complicated disengagement rnotion is one which can
- 9
e~sily b~ aLcomplisl)ed l~y a ~or~.man who;~ intet-lt~o~ l5 t.o
remove the chain from the l100~. However, the ~ ge~r~ t.
motion is so complicated that the probability of its acci-
dcntal occurence is very slight even if the chain hook ln
were to be tumbled end-over-end or held upside down. Chai.n
hook 10 of the presen-t invention therefore is sigllificant.ly
s~fer than prior known chain grab hoo~s.
