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Патент USA US3048377

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Aug. 7, 1962
3,048,367
L. A. MOCARTY
LOAD HANDLING APPARATUS HAVING OPTIMUM EFFICIENCY
Filed Aug. 26, 1959
3 Sheets-Sheet 1
—850
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L E A.
BY
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A 7' TOPNE I/S
Aug. 7, 1962
|_. A. MOCARTY
3,048,367
LOAD HANDLING APPARATUS HAVING OPTIMUM EFFICIENCY
Filed Aug. 26, 1959
3 Sheets-Sheet 2
mmmm.
LEE A. M5CAR7Y
:
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A 7' TOPNEVS
Aug- 7, 1962
L. A. MCCARTY
3,048,367
LOAD HANDLING APPARATUS HAVING OPTIMUM EFFICIENCY
Filed Aug. 26, 1959
3 Sheets-Sheet 3
52
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INVENTOR.
LEE A. M-‘CARTV
BY
r242
United States Patent O?ice
3,®48,357
Patented Aug. 7, 1932
1
2
3,048,367
apparatus employing an additional feature of the inven
tion by which substantially constant force on the ex
tendible arm is obtained;
FIGURE 5 is a geometrical representation of the ap
LOAD HANDLING APPARATUS HAVING
OPTllVIUM EFFICIENCY
Lee A. McCarty, Pleasant Hill, Calif., assignor to H. S.
paratus of FIGURE 4;
Watson Company, Emeryville, Cali?, a corporation of
_
FIGURE 6 is a side elevational view of another form
California
of load handling apparatus employing the principles of
Filed Aug. 26, 1959, Ser. No. 836,237
10 Claims. (Cl. 254-124)
this invention and in which the rigid arm is one sup
This invention relates to load handling apparatus in 10
port for a horizontal load carrying platform; and
FIGURE 7 is a cross-sectional view partially broken
away of the apparatus of FIGURE 6 taken along the
plane and in the direction indicated by the lines and the
which a constant unidirectional load is moved by a rigid
pivotally mounted arm which is in turn moved by a pivot
arrows at 7—7 in FIGURE 6.
ally mounted extendible arm. In most applications, the
In accordance with this invention, the load handling
load is a mass in the earth’s gravitation ?eld, and the
extendible ‘arm is a piston cylinder combination to the 15 apparatus comprises a rigid arm and an extendible arm
each pivotally connected to a frame about ?rst and sec
interior of which a pressurized ?uid is delivered. More
ond parallel axes respectively, and the arms are pivot
particularly, the invention relates to such apparatus in
ally connected together about a third axis; the ?uctuation
‘which the respective arms are so assembled that maxi
of ‘force on the extendible arm is maintained at the theo
mum e?‘iciency of the apparatus is obtained.
Load handling apparatus of the above identi?ed type
retical minimum ‘for this simple system by locating the
?rst axis in a plane normal to the direction of action of
?nds extensive application in various equipment such as
the unidirectional load to be moved, said plane also being
cranes, lift mechanisms for truck tail gates, etc. because
equidistant between the two positions between which the
this type of load handling apparatus is very compact and
load is to be moved, and by locating the ?rst and second
can be mounted in con?ned spaces without substantially
limiting the path through which it can move a load. 25 axes on a cylinder, the axis of which lies along the line
of intersection of said normal plane and the plane per
From the standpoint of the manufacture of the load
pendicular to and bisecting the plane surface bounded
handling apparatus, the e?iciency of the apparatus is a
by the ?rst axis and the third axis in its position furthest
direct function of the extent to which the force exerted
removed from the normal plane. Thus, minimum force
by the extendible arm ?uctuates during a lifting cycle in
?uctuation on the extendible arm is achieved by locating
the operation of the apparatus. Thus where the appa
the pivot axes for 'both arms in such positions that both
ratus is to employ a hydraulic cylinder as the extendible
arm to lift a weight, the manufacturer desires to use a
?uid pressure pump for operation of the cylinder which
arms will swing through equal angles during a given load
lifting cycle, and by locating the point of pivotal mount
ing of the rigid arm in such a position that during the
the system to lift the given weight through a given dis 35 lifting cycle the rigid arm will describe equal arcs on
either side of the normal plane ‘from said axis of pivotal
tance with the given cylinder. From this point of view
connection to the direction of action of the unidirectional
a load handling system has 100% efficiency when the
load to be lifted.
pressure in the cylinder, and hence the force exerted by
Referring now in detail to the drawings, and particu
the cylinder piston combination, is constant throughout
larly to FIGURE‘ 1, a rigid arm 10 is pivotally connected
the lifting cycle, since only then can a pressure pump lift
to a frame 11 about an axis 12. The free end of arm
ing a maximum rated load be Working at full pressure
10 is pivotally connected to a load 13 at a pivot pin 14.
capacity throughout the cycle.
The load is a weight hanging from arm 10 under the
Furthermore, from the standpoint of the user of the
in?uence of the earth’s gravitational field. A piston cylin—
load handling apparatus, the apparatus is most e?icient
and safest when force variation on the extendible arm is 45 der combination 15 is pivotally connected to frame 11
about an axis 16 and pivotally connected at its free end
reduced to a minimum because failure of the equipment
to arm 10 about an axis 17 which divides arm 10 into
due to excessive loading occurs when the load is ?rst
portions 18 and 19. A ?uid conduit 20 leads into cylin
applied rather than at some intermediate position in the
der 15 and supplies ?uid under pressure thereto from
path of movement of the load.
Accordingly, it is an object of this invention to pro 50 any suitable source ‘thereby contracting the piston cylin
der combination and moving the various parts to the ele
vide a rigid arm-extendible arm load handling apparatus
will have a minimum pressure requirement in order for
in which the ?uctuation of the force on the extendible
arm during a lifting cycle is reduced to a minim-um.
It is a further object of this invention to provide such
vated position indicated by the broken lines and primed
reference characters in FIGURE 1; The location of axis
16 and the difference between the extended and contracted
an apparatus in which the force on the extendible arm is 55 lengths of the cylinder piston combination 15 are selected
so that during the desired maximum lifting arc the rigid
arm 10 moves through equal sectors above and ‘below
the horizontal plane through axis 12 and so- that the
come apparent from the following description read in con
axes 12 and 16 and the axis 17 in its positions most re
junction with the attached drawings in which:
FIGURE 1 is a side elevational view of one form of 60 mote from said horizontal plane all lie on a cylinder 21.
In FIGURE 2, similar reference characters are used
the load handling apparatus employing the principles of
substantially constant throughout a lifting cycle.
Other objects and advantages of the invention will be
this invention;
to denote lines and points as Where used to denote arms
force on the extendible arm, expressed in units of per
when arm 18 makes a given angle 0 with a horizontal
and axes respectively in FIGURE 1. In addition to the
FIGURE 2 is a geometric representation of the appa
structure
of FIGURE 1, FIGURE 2 illustrates the radius
ratus of FIGURE 1;
22 of piston cylinder combination 15 from axis 12 and
FIGURE 3 is a plot of the approximate variation of 65 the horizontal distance 23 of axis 17 from the axis 12
cent variation from ideal force, versus the angle the
rigid arm makes with a horizontal plane as such angle
varies between 85° below the horizontal to 85° above the
horizontal;
FIGURE 4 is a side elevational view of load handling
plane through axis 12. Angle 0 is measured as positive
above the horizontal plane. It should ?rst be noted in
FIGURES l and 2 that the relative magnitude of the
70 ?uctuation of pressure in cylinder 15 as axis 17 moves
from 17 to 17’ is independent of the length of segment
3,048,367
3
4
19 of rigid arm 10 since segment 19 merely determines
the effective weight at axis 17 which weight 13 will cause.
Accordingly the structure of load handling apparatus of
FIGURE 1 is represented geometrically in ‘FIGURE 2
where it is considered that an adjusted weight “W” is
tion of axis 17 on a cylinder 21 thus giving the nearest
practical approximation to the ideal construction for this
suspended at 17, which adjusted weight is the weight 13
multiplied by the ratio of the length of arm 10 to the
length of portion 18.
It will be noted in FIGURE 2 that the force “F” act
simple system. This cylinder 21 is slightly larger than
the most e?icient cylinder 21 which could be used to
swing the arm 18 through the same angle, but the most
e?icient cylinder can not be used because of other prac
tical considerations.
Referring now to FIGURE 4, in which is illustrated
geometrically an improved form of the load handling ap~
ing along piston cylinder combination 15 may be cal 10 paratus of this invention, FIGURES 4 and 5 illustrate
culated by equating the clockwise and counter-clockwise
apparatus similar to that illustrated in FIGURE 1, with
torques tending to move arm 18 around axis 12 so that the
force “F” when arm 18 makes an angle 0 with the hori
the exception that axis 16 of the apparatus of FIGURE 1
has been replaced by a moving axis generally indicated
zontal equals the weight “W” times the horizontal dis
tance 23 divided by the radius 22, which in turn equals
the weight “W” times the length of arm 18 times the
cosine of angle 0 divided by the length of radius 22.
The ?uctuation of force “F" as angle 0 changes is mini
mized when the load handling apparatus is constructed
as described above, i.e., the ?uctuation is less than it 20
by the arrow 16' in FIGURES 4 and 5. The moving
axis 16’ conveniently comprises a circular disc 25 pivot
ally connected at its center to frame 11 and having piston
cylinder combination 15 pivotally connected to its pe
riphery at axis 24. Disc 25 is connected to arm 18 by
any suitable means so that disc 25 rotates through 360°
would be if arm 18 were employed to lift weight “W”
as arm 18 swings from position 18 to 18’. Conven~
iently, a spring biased rack 26 is pivotally connected to
from point 17 to point 17’ with axis 16 either inside or
outside of cylinder 21. However, as illustrated herein
after, even when axis 16 lies on cylinder 21 the force
movement of disc 25 is in the rotary direction opposite
the direction of rotation of arm 18, as illustrated by the
“F” on cylinder 15 ?uctuates a small amount as axis 17
arrows 28 and 29 in FIGURE 4.
arm 18 and engages with a pinion 27 on disc 25 so that
moves ‘from 17 to 17’ and the magnitude of such ?uctua
tion increases as the system is altered to lift the same
weight “W” with the same arm 18 between points 17 and
17’ which are increasingly separated. As the distance
When the load handling apparatus is constructed in
accordance with FIGURES 4 and 5, the disc 16 is pivot
ally connected to frame 11 at‘ axis 30 inside cylinder 21
in such a position that diametrically opposed positions of
between points 17 and 17' increases, the angle subtended 30 axis 24 (24 and 24b) on the disc 25 lie, respectively,
by the remote positions of arm 18 increases and accord
one on cylinder 21 and one on cylinder 31, the circum
ingly cylinder 21 increases in diameter. However, even
when the distance 17-17' is very large when compared
ference of which passes through axis 12 and is internally
to the length of arm 18‘ so that angle between the remote
positions of arm 18 approaches 180°, the magnitude of
the ?uctuation of the force on cylinder 15 is still smaller
tangent to the are described ‘by arm 18. The positions
24 and 24b of axis 24 are equidistant from axis 12. It
will be noted from a comparison of FIGURES 2 and 5
that the moving pivot point 16 ‘changes the radius of
than such ?uctuation would be if the arms were not as
assembled with axis 16 on cylinder 21.
As illustrative of the fact that even when the maximum
?atten the pressure variation curve of FIGURE 3. More
swings through unequal angles above and below the hori
been moved to a line below the horizontal but a line still
cylinder piston combination 15 from axis 12 in order to
particularly, when arm 18 is in position 18a in FIGURE
positions of arm 18 are widely separated, the force fluc 40 5, disc 25 has moved axis 24 to a position 24a whereby
tuation on cylinder 15 is small, reference is had to FIG
the radius of piston cylinder combination 15 from axis
URE 3 which illustrates the character of this force ?uctua
12 is increased, and hence the pressure increase indicated
tion where arm 18 moves from 85° below the horizon
in FIGURE 3 is reduced; when the arm 18 has moved to
tal to 85 ° above the horizotnal, a total angular move
position 1811, disc 25 has moved axis 24 to position 24b,
ment of 170°. The force ?uctuation is plotted in FIG
at which position the force along cylinder 15 is equal to
URE 3 as the percent variation of actual force from ideal
the force along cylinder 15 when arm 18 lies at positions
force where ideal force is the constant ‘force which would
18 and 18'; when arm 18 has moved to position 180,
be necessary to lift the adjusted weight “W” from 17 to
disc 25 has moved axis 24 to position 240 whereby the
17’ while force “-F" acts through a distance equal to the
radius of piston cylinder combination 15 from axis 12 is
distance between the expanded and, contracted lengths
reduced and accordingly causes the pressure reduction
of the cylinder piston combination 15. It will be noted
indicated in FIGURE 3 to be eliminated. While the
from FIGURE 3 that as 0 varies between minus 85 ° and
improvement of my invention, as illustrated in FIGURE
plus 85 °, the maximum relative ?uctuation of force on
4, may not completely eliminate the pressure variation
cylinder 15 is ‘limited to 13% above ideal force and 17%
indicated in FIGURE 3, the apparatus of FIGURE 4
below ideal force. Variation in force is of course a linear
reduces such pressure variation to a point where it is
function of the variation of pressure in cylinder 15 since
substantially undetectable.
.
the pressure always equals the force divided by constant
Referring now in detail to FIGURE 6, a load handling
piston area.
apparatus similar to that illustrated in FIGURE 1 is illus
Though the principles of this invention may be em
trated with the exceptions that in FIGURE 6 the axis
ployed in load handling apparatus where the arm 18 60 of pivotal connection 16 of cylinder 15 to frame 11 has
zontal, the efficiency of the system so constructed is less
on cylinder 21. Accordingly, cylinder 15 in FIGURE 6
than the e?iciency of the system where both remote posi
is employed to push up on arm 10 instead of pull arm
tions of axis 17 lie on cylinder 21; thus if in a given
10 as did cylinder 15 in FIGURE 1. Furthermore, the
system the arm 18 swings through a smaller angle than 65 load 13 in FIGURE 1 has been replaced by a horizontal
the angle subtended by points 17 and 17’ in 'FIGURE 2,
load handling platform 32 in FIGURE 6. The platform
the system could be redesigned, relocating axes 12 and
32 is pivotally connected to arm 10 at axis 14. A rigid
16 so that the diameter of cylinder 21, and accordingly
arm 33 of the same length as arm 10 is provided parallel
the ?uctuation of pressure over the lifting cycle, is re
to arm 10 and pivotally connected at its opposite ends to
duced. However, in many cases the characteristics of 70 axes 34 and 35 on platform 32 and frame 11, respectively.
the equipment on which the load handling apparatus is
As hydraulic ?uid is supplied to piston cylinder combi
mounted preclude pivotally mounting the‘ arm 18 in a
nation 15 to lift arm 10 to position 10’, the parallelo
position where it will swing through equal angles above
gram formed between axes 12, 14, 34 and 35 maintains
and below the horizontal. In these cases, the system is
platform 32 in a horizontal position.
constructed with axes 12 and 16 and the most remote posi 75
As illustrated in FIGURE 7, lateral stability of the
8,048,367
6
5
apparatus of FIGURE 6 is obtained’ by providin'gtW0
laterally spaced sets of arms 10 and 33, each‘ one pivot
ally connected to platform 32 and frame 11. ‘Piston
cylinder combination 15 is pivotally connected‘to ex
tended axle 16 connected to frame 11 and is pivotally
connected to axle 1'7 extending between the two ri'gid
arms 10.
p
,
,
While preferred embodiments of the‘invention have
mounted about a second axis on said frame and having an
extendible portion pivotally connected about a linking
axis on said rigid arm whereby said linking axis describes
a cylindrical are when said load is moved from said
?rst position to said second position, and means for ap
plying a force to said extendible portion of said ex
tendible arm to change the length of said extendible arm,
the improvement comprising said load handling appara
tus, as herein structually and operationally de?ned, in
been shown and described, it is to be understood that all
substantial equivalents thereof ‘are considered to be with 10 which said ?rst axis lies in a plane perpendicular to the
direction of movement of said load, and in which said
in the spirit of the invention and the scope of the ap
pended claims.
What is claimed is:
'
'1. In a load handling apparatus for lifting a load from
a ?rst position to a second position which is in vertical 15
alignment with said ?rst position, said apparatus com
?rst and second axes and a point on said cylindrical arc
of maximum remoteness from said plane all lie on a cylin
der, the center of which lies in said plane.
7. The improved load handling apparatus of claim 6
characterized further iby the inclusion of a second rigid
arm pivotally connected about a third axis connected
prising a frame, a rigid arm adapted to be connected to
to said frame and pivotally connected at a remote point
said load and pivoted about a ?rst axis connected to said
thereon to a fourth axis on said load, said ?rst rigid
frame, an extendible arm pivoted about a second axis
connected to said frame and having an extendible portion 20 arm being pivotally mounted about a ?fth axis on said
load, said ?rst, third, fourth and ?-fth axis ‘forming a
pivotally connected about a linking axis on said rigid
parallelepiped.
arm whereby said linking axis describes a circular are
8. The improved load handling apparatus of claim 6
When said load is moved from said ?rst position to said
characterized further by the inclusion of means for mov
second position, and means for applying force to said ex
tendible portion of said extendible arm to change the 25 ing said second axis relative to said vframe along a closed
path responsive to pivotal rotation of said rigid arm as
length of said extendible arm, the improvement compris
said rigid arm moves said load from said ?rst to said
ing said load handling apparatus, as herein structurally
second position.
and operationally de?ned, in which said ?rst axis lies on
the horizontal plane lbisecting said circular arc, and said
?rst and second axes lie on a cylinder whose axis lies at
9. The improved load handling apparatus of claim 8
in which said means ‘for moving said second axis com
prises a disc pivotally connected at its center to said [frame
the intersection of said horizontal plane and the perpen
dicular bisector ‘of the plane surface connecting said ?rst
axis and 1a position of said linking axis of maximum re
extendible arm at said second axis, said disc being so
characterized further in that said extendible arm com
cylinder and the other on a second cylinder the circum
arm pivotally connected about a third axis connected to
said frame and pivotally connected at a remote point
thereon to a fourth axis on said load, said ?rst rigid arm
essentially vertically in opposition to the ‘force of gravity
and pivotally connected adjacent its periphery to said
positioned that ?rst and second diametrically opposed
moteness from said horizontal plane.
2. The improved load handling apparatus of claim 1 35 positions thereon of said second axis lie one on said
ference of which passes through said ?rst axis and is in
prises a piston cylinder combination, and said means for
ternally tangent to said arc, said ?rst and second posi
applying a force to said extendible portion of said ex
tions of said second axis Ibeing equidistant from said
tendible arm comprises means adapted to deliver fluid
under pressure to the interior of the cylinder of said 40 ?rst axis whereby the force applied to said extendible
arm is substantially constant as said load is lifted from
combination.
said ?rst position to said second position.
3. The improved load handling apparatus of claim 1
10. In a ‘load handling ‘apparatus for moving a load
characterized further by the inclusion of a second rigid
being pivotally mounted about a ?fth axis on said load,
said ?rst, third, fourth and ?fth axis forming a paral
lelepiped.
from a ?rst position to a second position with respect to
a frame, said apparatus having a rigid arm adapted to
be connected to said load and pivotally mounted about
a ?rst axis on said frame, an extendible arm pivotally
mounted about a second axis on said frame and having
an extendible portion pivotally connected about a link
4. The improved load handling apparatus in claim 1 50
ing axis on said rigid arm whereby said linking axis
characterized ‘further by the inclusion of means for mov~
ing said second axis relative to said frame along a closed
moves along a cylindrical are from a ?rst position closer
to said second axis to a second position more remote
from said second axis as said extendible arm is lengthened
said rigid arrn moves said load from said ?rst to said
to move said load ‘from said ?rst position to said second
second position.
55 position, and means [for applying a force to said extendible
5. The improved load handling apparatus of claim 4
portion of said extendible arm to change the length of
in which said means for moving said second axis com
said extendible arm, the improvement comprising said
prises a disc pivotally connected at its center to said
path responsive to pivotal rotation of said rig-id arm as
load handling apparatus as herein structurally and op
frame and pivotally connected adjacent its periphery to
said extendible arm at said second axis, said disc being 60 erationally de?ned in which said ?rst axis lies in a hori
zontally disposed plane which is perpendicular to the
so positioned that ?rst and second ‘diametrically opposed
vertical direction of movement of said load, and in which
positions thereon of said second axis lie one on said cylin
said ?rst and second axes and said ?rst position of said
der and the other on a second cylinder the circum
linking axis all lie on a cylinder, the center of which
ference of which passes through said ?rst axis and is
internally tangent to said are, said ?rst and second posi 65 cylinder lies in said horizontally disposed plane.
tions of said second axis being equidistant ‘from said ?rst
References Cited in the ?le of this patent
axis whereby the force applied to said extendible arm is
UNITED STATES PATENTS
substantially constant as said load is lifted from said ?rst
position to said second position.
6. In a load handling apparatus for moving a load
essentially vertically in opposition to the force of gravity
from a ?rst position to a second position with respect to
a frame, said apparatus having a rigid arm adapted to
be connected to said load and pivotally mounted about
a ?rst axis on said ‘frame, an extendible arm pivotally
2,464,224
2,675,209
2,841,299
Gratbert _____________ __ Mar. 15, 1949
Freed _______________ __ Apr. 13, 1954
Gildner ______________ __ July 1, 1958
1,133.110
France ______________ __ Nov. 12 1956
FOREIGN PATENTS
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