Note: Descriptions are shown in the official language in which they were submitted.
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1 BACKGROU~D OF THE I~V~NTION
This invention relates to forks for fork lift trucks
and particularly to the desirability of reducing the weight
therefore by certain changes in configuration.
The usual fork for a fork lift truck consists of an
L-shaped body as viewed in side elevation, in which the off-
standing arm which is designated herein as the load arm is an
integrally connected element with an upstanding arm which for
the purposes hereof will be denominated as a lift arm. The lift
arm is provided with certain attaching elements for connecting
the same to a lift truck structure and thus providing the neces-
sary connection, such forks usually being used in pairs.
It is often the case that such lift forks are differ-
ently described, with the offstanding arm or longitudinal arm
being designated as the blade and the upstanding arm as the
shank, Irrespective of the descriptive designations, the func-
tions are of course identical and as would be expected, very
20little has been changed in the construction of such forks from
the time of th~Ir initial use and construction.
It is of course also well known that forks are made in
a number of different ways as by forging and bending during the
orging process to comprise the L-shaped body which is commonly
provided.
The extremity of the longitudinal or load arm, is ta-
pered from a point about mid-way of such arm to the extremity,
the main body of the fork ~eing of rectilinear cross-s~ction
and of substantial size.
The possibilities of making many changes in a fork
1 structure are obviously limited by the necessity to maintain
the strength for lifting purposes which a heavy cross-section
fork would normally have and obviously this cross-section is
carried through the heel which comprises the connection of the
load arm and lift arms and is of particular importance in the
same as will be apparent, for load bearing purposes.
It might be noted that under some circumstances the
load arm itself is a separate element and may be connected to
`10 a lift truck structure for certain uses and without other as-
pects being consid~red.
With the foregoing in mind, the efforts which have re-
sulted in this invention, to in some way reduce the cost of the
fork, have been directed toward various formations which the
same may assume, it being recalled that where lifting ability
is present, the thickness and width of the fork are important
but primarily the thickness so to speak is the controlling fac-
tor in the usual contemplation and according to calculations
which can be made by those skilled in the art.
The contemplation of this in~ention is therefore di-
rected to various aspects of the fork configuration which as
far as is known have not heretofore been contemplated at least
for forks of substantial capacity and as far as may be available
on the market at the present time is known.
~ aving outlined the general field of the invention and
the background thereof, it is contemplated by the disclosure here-
in to provide a different approach to fork manufacture, inasmuchas the cost of the fork is determined in large measure by the
weight thereof and thus any weight reduction which can be
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effected will obvious:Ly reduce such cost and in the final
analysis reduce the selling price thereof likewise.
Generally speaking, the present invention therefore
provides a fork for a fork lift truck having a forged body
comprising a longitudinal load arm adapted to support a load
and for connection at one end to a lift means, the body
including an integral vertical lift arm extending from the
load arm providing the connection aforesaid, the lift arm
having a surface of parabola-like conformation in side
elevation, the load arm being of unobstructed open-ended
channel-like cross-section throughout a substantial portion
of its length, open at least at one end and having flanges
extending throughout only at the substantial portion of its
length, the flanges having the parabola-like edge
conformation aforesaid.
With that in mind, the disclosure is set forth in
detail hereinafter and disclosed in the drawing wherein:
Figure 1 is a fragmentary view of a lift truck of
any conventional form having supported forwardly thereof a
fork made in accordance with the concept herein in the L-
shaped configuration as shown in elevation, as pointed out
heretofore two of such forks usually being provided.
Figure 2 is a side elevational view of a different
form of fork as availing of some of the aspects of the
invention.
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Figure 3 is a longitudinal cross-sectional view of
the fork shown in Figure 2 to illustrate certain weight
reducing aspects.
Figure 4 is a transverse sectional view of the load
arm oE the fork taken about on the line 4-4 of Figure 2
looking in the direction of the arrows.
Figure 5 is a transverse sectional view of the lift
arm of the fork of Figure 2 taken about on the line 5-5 of
that figure.
Figure 6 is a side elevational view of a fork formed
similarly to that of Figure 1.
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h DETAILED DESCRIPTION O~' TME IN~ENTION
Referring now to Fig. 1, there is disclosed a fork
lift truck at least as to the forward end thereof indicated at
1 supported on the tr~vel wheels such as 2 with a m~t 3 extend-
ing upwardly therefrom and connected to the truck in any pre-
ferred manner, and a pivotal frame 4 in turn connected to such
mast for control thereby and ~or raising and lowering movement
of a fork of L-shaped configuration supported by a carriage
element 5 having suitable transversely extending rail portions
6 at the upper end and 7 on the lower portion thereof.
The fork shown in side elevation in this figure, is of
generally conventional L-shape and designated 8, with the load
arm portion 9 thereof extending longitudinally and -the lift
arm portion 10 thereof extending vertically being connected
by a heel section 11.
At the upper end of the lift arm 10, is a suitable
hook or a head 12 and a further hook 13 is provided to engage
with the transversely extending rail 7.
The fork hereof, as to the load arm 9, is provided at
its upper surface with a flat planar portion 14 which is usual-
ly provided, and however is formed under that planar portion
with what may be termed a parabola-like surface 15, which ex-
tends from a very relatively sharp extremity at 16 to the heel
portion 11 being the thickest part of said load arm.
Thus the surface 15 follows the parabola-like config-
uration as viewed in side elevation.
The lift arm is similarly formed but reversely so
since the planar section thereof is at i~s rear and denoted 16
with the parabola-like surface 17 extending forwardly and is
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1 viewed in side elevation consisting of that parabola-like form.
It is of course understood that this parabola-like
form 17 as disclosed is flat although following the contours
suggested.
Turning now to a consideration of Fig. 2, which shows
a somewhat different form of fork for illustrative purposes,
it will be seen that the load arm in this particular figure,
designated 18, is configured with a planar surface 19 upwardly
for support of the load, and at its lower surface is equipped
with a further planar element 20 extending from the extremity
21 divergently to the lower surface 22, which in turn extends
rewardly in a parallel plane to the surface 19 until it is con-
nected with the heel section 23.
The upright element or lift arm 24 i9 conventionally
formed generally, but as will be explained both of these arms
are modified in the ultimate analysis in accordance with the
concept hereof as will be subsequently explained in detail.
The lift arm 24 is provided at its upper extremity
with the usual head connecting element 25 which is hook-shaped
as is well known and in some manner affixed to said arm such
as by welding if not integrally formed therewith.
The usual hook element 26 is provided at the lower
end of said arm near the heel of the fork.
The difference in this particular fork is by reason
of its conformation, shown in Fig. ~ as to the load arm, which
indicates that the same is generally channel-shaped including
the channel area 27 thereof which is positioned between the
flanges 28 and 29, which terminate in edges 28a and 29a respec-
tively.
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Thus the web of the channel area is of obviously re-
duced section as compared with the thickness of the usual fork
which would be that designated by the arrows which are denomin-
ated 30, the width being designated by the arrows extending and
denominated 31.
As will be understood the lift arm 2~ is similarly
configured as suggested by Fig. 5 so that it comprises flanges
32 and 33 with corresponding edges 32a and 33a the open area
of said channel section being denominated 34.
This is further illustrated in Fig. 3 to sh~w the area
which is cut out so to speak and thus comprises ~hannel-shaped
sections of the respective arms with the heel portion of said
fork 23 being of the best cosidered and shape form consisten~
with the othersshape of this fork but obviously of a solid
transverse heavy section.
It might be e~plained that forks of this general shape
are usually as to the most common size those forks which con-
sist of a load arm for example about forty-eight inches long
and a lift arm in the area of twen~y-four inches high, being
substantially two to one for all intents and purposes.
It is also to be understood that thè channel-shaping
of the respective arms is intended to extend for the greatest
possible distance consistent with the load carrying capacity
of said fork as can be and has been calculated under various
loads Eor whatever purposes they may be necessary and to have
the equivalent lifting capacity to that which is found in forks
of solid configuration and of the conventional form of equal
size as to length of load arm and height of lift arm.
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As suggested in Fig. 2, if the load arm 18 is config-
ured as to its lower surface really, surfaces since this illus-
trates a channel-shaped portion generally, with the parabola-
like form of outline suggested in Fig. l, and by the dotted
line designated A in Fig. 2, with a coniguration suggested by
the dotted line B in Fig. 2, further weight reduction will be
accomplished as compared with the conventional fork of what may
be termed generally rectilinear configuration throughout.
The fact of the matter is that by initially configur-
ing the fork as shown in Fig. 1 with parabola surfaces 15 and
17 used, a weight reduction of approximately lO percent of the
fork as compared with a conventional fork will be provided.
Where the channel-shaped fork of Fig. 2 is provided
without more, a lO percent saving at least can be provided
li~ewise.
By combining the respectiv~ configurations suggested
in Fig. 2 so that the parabola-like surfaces A and B are pro-
vided with the channel section, a weight saving of approximately20 percent is accomplished.
As will be apparent such weight saving is in fact a
very substantial amount and obviously results in an ability to
sell the forks at a less cost after manufacturing costs are re-
duced likewise.
It may be noted that in Fig. 6 the fork disclosed is
provided with a different exterior configuration as to the lift
arm since the parabola-like portion is in rear of the arm as
indicated at C with the same kind of parabola-like configuration
A being used therein, the fork load arm 32 being connected to
the lift arm 33 by the heel 34 in somewhat conventional fashion
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~1 being integral obviouslyl.
This fork configuration may be necessary because of
manufacturing problems but basically the concept of parabola-
like configuration is used here for the same purposes namely
weight saving as is accomplished by the prior forms disclosed.
It is of course obvious that the fork of Fig. 6 may
have a similar channel like configuration as to both of its
arms as is true of Fig. 2, and Fig. 3, and thus further weight
saving accomplished likewise.
In view of the detailed description, it will be appar-
ent that the objects of the invention have been carried out as
to weight saving and it is thei.entire value of the invention
found in this particular arrangement, with the suggestion that
there may be other cross-sectional configurations which could
accomplish similar weight reduction or possibly more bearing in
mind that the thickness so to speak of the load arm and lift
arm are the controlling factors in lifting strength.
Thus where the usual fork is four inches wide and
about 1 3/4 inches thick as to the major dimensions, it is
possible to make a fork of 3 inch width and 2 inch thickness
which will have the same lifting capacity, and yet with the
configurations described in the previous forms herein, addition-
al weight saving accomplished which is desirable andmay be neces-
sary without sacrificing the lifting ability at all.
It should be pointed out however that while lifting
capacity or ability of the forks is not affected adversely by
the configurations disclosed and described in detail, there may
be some additional deflection under maximum loads without at the
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~1 same time destroying the fork or otherwise adversely affecting
its use.
When the term fork is used, it is understood that
plural use of the term is intended where necessary and appli-
cable, usually a pair of forks being supplied for most circum-
stances.
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