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Патент USA US2410654

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Nov. 5, 1946.
Filed March 25, 1944
5 Sheets-Sheet 1
Ha/rar 0. v Hem
Nov. 5, 1946.
H. o. HEM
Filed March 25, 1944
5 Sheets-Shed”I 2
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NOV. 5, 1946.
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Filed March 25, 3,944
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Nov. 5, 1946.
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Filed March 25, 1944
5 sheets-sheet 4
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_ Nov. 5, 1946.
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Filed Màrch 25, 1944
5 Sheets-Sheet 5A
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Patented Nov. 5, 1946
Halver 0. Hem, Toledo, Ohio, assignor to Toledo
Scale CompanyyToledo, Ohio, a corporation of
New Jersey
Application March 25, 1944, Serial No. 528,083
2 Claims. (Cl. ’I3-65)
This invention relates to weighing scales and
'in particular to a combination of weighing scales
adapted -to determine the center of gravity of
loads supported by the scales _in combination. It
is customary as a íinal test in the assembly of an
other that an aircraft may be located thereon
with one of its ground engaging wheels supported
on each scale. In the arrangement shown in Fig
ure I conventional aircraft may be located with
the fixed landing wheels on the scales III and II
and the tail wheel on the scale I2. If the air
craft is of the so-called Itricycle landing gear type
airplane to determine its center of gravity with
and without load. This is necessary to insure that
its nose wheel may be located on the scale I2.
the plane will be stable in flight and that it will
In Figure I parts are broken away from the
respond correctly to its controls.
II and I2 to reveal the lever system of Áthe
It has been common practice to provide three
scale II and the elevating mechanism of the
scales, one for each >of the three ground engaging
scale I2.
wheels of an airplane, and to calculate, using
The lever systems of the three scales are simi
the weight indication of each scale, the position
lar. Each comprises a set of main levers I3
of .the center of gravity. Such a procedure gives
supported on fulcrum stands I4 located near ythe
the horizontal location of the center of gravity
corners of the enclosing pit. . The main levers I3
but does not provide any information from which
are pivotally connected to end levers I5 which
its vertical height may be determined.
are fulcrumed on stands I6 located at the ends ,
The primary object of this invention is to pro
of each of the pits. The end levers I5 are piv
vide a combination of Weighing scales which by
otally connected to an extension lever I1. An
means of an elevating platform on each scale may
other extension lever I8, pivotally connected to
be used to determine the height of the center of
the extension lever I'I, transmits force to a coun
gravity as well as its horizontal position.
terbalancing and indicating mechanism I9.
Another object _is to provide a compact elevat
The counterbalancing and indicating mecha
ing mechanism suitable for use under the deck
nism I9, shown in detail in Figure II, is housed
of a weighing scale.
25 in a cabinet 20. The extension lever I8 which
These and other objects and advantages are
enters the cabinet 20 through an opening 2l in
apparent from the description, in which refer
the rear Wall thereof is pivotally connected to a
ence is had to the accompanying drawings illus
steelyard rod 22 suspended from a load pivot 23
trating a preferred form of the invention.
of a tare beam lever 24. The fulcrum pivot 25
30 of the tare beam lever 24 rests on bearings in a
In the drawings:
Figure I is a plan view, partly in section, show
fulcrum stand 26 erected from a shelf 2l of the
ing an arrangement of three substantially iden
cabinet 20. The tare beam lever 24 is provided
tical .scales adapted to be operated according to
with beams 28 and 29 fitted with poises 30 and
the invention.
3l respectively which may be used to counterbal
Figure II is afront elevation of one of the 35 ance part of the load supported by the lever
force counterbalancing and indicating mecha
system. A unit weight hanger 32 extending into
nisms as seen from the line II-II of Figure I.
the cabinet below .the shelf 21 is suspended from
Figure III is aside elevation of one of the three
a pivot 33 of the tare beam lever 24. Unit weights
scales shown in Figure I, .the elevation being
for increasing the capacity of the scale may be
taken substantially along the line III-III of 40 engaged by operating a handle 34 which is opera
Figure I.
tively connected to a unit weight supporting
Figure IV is an end elevation taken substan
mechanism enclosed in the cabinet 20 below the
tially along the line IV-IV of Figure I.
shelf 21.
Figure V is an end elevation, partly in section,
A power pivot 35 in the tare beam lever 24 is
of the platform elevating mechanism.
operatively connected through a stirrup 3B, steel
Figure VI is a plan view, partly in section, of
yard rod 31, and «a pendulum lever 38 to an auto
the elevating mechanism as seen with the plat
matic counterbalancing mechanism 39 enclosed
form removed.
in a substantially watchcase-shaped housing 40
Figure VII is a fragmentaryr section taken
surmounting the cabinet 20. The automatic
along the line VII-VII of Figure VI.
counterbalancing mechanism 39 comprises a pair
Figures VIII and IX 'are schematic diagrams
of pendulum bodies 4I each of which is ñtted with
illustrating the computations involved in solving
arcuate surfaces 42 and 43 and a pendulum mass
for the location of the center of gravity of a
44. ' The pendulum bodies 4I are suspended from
structure placed on the scales.
a vertical rectangular frame 45 by means of me
Three weighing scales I0, II and I2 of similar
tallic ribbons 46 which overlie the arcuate sur
design each consisting of a lever system, an ele
faces 42. Load is applied to the pendulum bodies
vating mechanism and a platform are located in
4I through a pair of ribbons 4l overlying the
pits in the floor so that the platforms, when in
arcuate surfaces 43, .the lower ends of the ribbons
their lowered position, are flush with the floor.
41 being connected to a yoke 48 which by means
The scales are so positioned relative to each
of a connection 49 is pivotally attached to the
pendulum lever 38. Because the radius of the
arcuate surfaces 43 is greater than the radius
of the arcuate surface 42 any downward force
applied to the ribbons 41 results in .the pendulum
bodies rolling upward along the sides of the
frame 45. This upward motion with load is trans
mitted through compensating bars 50 and a rack
subplatform 58 and actuated by cams 89 and 90
when the platform 66 approaches its safe limits
of travel. A strip 9i carrying the cams 89 and
98 extends downward from the under structure
of the platform 66 and is guided by a bracket 92
secured to the subplatform 58 adjacent the limit
switches 81 and 88.
5I `attached thereto to drive a pinion 52 mounted
on an indicator shaft 53 and thus rotate the
The airplane or other structure whose center
of gravity is to be determined is placed upon the
shaft and an attached indicator 54. The end of
the indicator 54 sweeps over an annular chart 55
on which weight graduations are inscribed.
three scales in such a manner that a portion of
its weight is carried by each scale. It is also de
sirable that the surfaces in contact with the
scales be kept as small as practical in order that
Osclllatíons of the indicator and counterbal
ancing mechanism with changes in load are con
trolled by a dashpot 55 whose stem 51 is pivotally
attached to the tare beam lever 24.
Each of the lever systems supports a skeletonized
subplatform or frame 58. Parallel link suspen
the center of pressure on that scale may be ac
curately determined. When the airplane or
other structure is so located, the three platforms
are elevated to their midposition and the weight
sions 59 interposed between the subplatform 5S 20 readings are taken. The reading of scale I9 will
and the lever systems allow a limited horizontal
be referred to as w1, that of scale l l as wz and
scale l2 as w3. 'I'he horizontal projection of the
center of gravity may be located from these three
motion of the supported structure without impos
ing lateral forces to the knife edges in the main
levers I3. Each of the parallel link suspensions
59 comprises a T shaped member 89 whose stem is
cross-arms 62 of the T shaped member 6D are also
readings by considering that the airplane or
other structure is comprised of three masses,
equivalent to W1, W2, and W3 each located at the
point of contact of the load on that particular
scale. The center of gravity of the combination
bifurcated and fitted with pins from which links
of W1 and W2 lies on a line connecting these and
bifurcated to straddle the cooperating main lever
I3‘ and engage the load pivots 6| therein. The
63 are suspended. The links 83 engage and sup
port crossbars 64 of a U shaped bracket 65 at
30 divides the line into two segments whose lengths
tached to the undersurface of the subplatform 58.
are inversely proportional to the adjacent mass
es. Then the center of gravity of the three
Each of the scales is further provided with a
platform 88 supported on girders
61. The girders 61 at the corners of the plat
form 66 rest on large shoulder nuts 68 threaded
upon vertical elevating screws 69 which are jour
gravity of Wi-l-Wz and W3 and divides this line
into two segments inversely proportional to the
. load receiving
naled in bearings 10 mounted on the subplat
form 58. Rotation of the elevating screws 69
thus raises or lowers the platform 86 without
affecting the indication of a load which might
be carried thereon.
A motor 1| supported on the subplatform` 58
provides power for rotatingr the elevating screws
89. The motor ‘Il is belt connected to a shaft 12
which extends longitudinally along the subplat
form 58 and which at each end is provided with
a worm 13. Each of the worms 13 drivingly
engages two worm wheels 14 and 15 mounted on
vertical shafts 16 and 11. The lower ends of .
these shafts are journaled in crossmembers 18
of the subplatform 58 and the upper ends are
journaled in plates 19 disposed parallel to and
above the crossmembers 18. The plates 19 are
supported on bearing stands 88 (which journal
the ends of the shafts 12 carrying the worm 13)
and are stiffened by braces 8l attached to ad
jacent sides of the subplatform 518. The shafts
16 and 11 also carry pinions 82 and 83 meshing
with gear wheels 84 and 85 mounted on the ele
vating screws 69.
The^downward thrust of the platform through
the elevating' screws 69 is carried by thrust bear
ings 86 forming a portion of the bearings 10.
It should be noted that some of the elevating
screws have right hand threads and the re
mainder left hand threads.
This difference in
threads is necessary because the gear trains on
opposite sides of the worms rotate in opposite
The motor 1I must be of a -readily reversible
type and may be controlled by push button stations located in positions convenient for the op
erator. These control systems should incor
porate limit switches 81 and 88 mounted on the
masses lies on a line connecting the center of
eifective masses at its ends.
The point so lo
cated is the horizontal projection of the center
of gravity of the airplane or other structure and
thus defines the location of the center of gravity
except for its height above the horizontal plane
through the scale platforms.
To determine the vertical height of the center
of gravity above the plane of the platforms, the
aircraft is tilted lirst one way and thon the other
by selectively raising and lowering the platforms
of the scales i9 and Il leaving the platform of
scale I 2 in its midposition. After lowering the
platform of the scale il) and raising the platform
oi' the scale H the readings of these scales are
again taken and are designated as w1’ and wz’.
Another set of readings are taken with the plat
form of' scale ii] raised to its full height and the
platform of scale Il dropped. These readings
are designated as 1v1” and wz”. The reading of
scale l2, i. e. w3, will not be affected by the tilting
as long as the platforms are raised and lowered
equal amounts. In Figure VIII the diiierence in
the height between the platforms when the struc
ture thereon is tilted is indicated by the symbol
“d” and the distance between the points of con
tact of the load on the scales iD and il by the
length “L” Then the angle of tilt “qb” is sub
stantially equal to d/L, (since for small angles
tan «fl is equal to the angle (t in radians). The
distance d, Figure VIII, is the distance from the
mass W2 to the center of gravity of the combina
tion of the masses W1 and W2. Therefore,
a* im#
The projection of the actual center of gravity lies
on a line connecting A (the cen'ter of gravity of
Wl-l-Ws) and W3 at a distance from W3 equal to
“E” where “E” is deñned by the >equation
wherein C is equal to the distance from A to W3.
the change in weight as indicated on one of the
After tipping the airplane by lowering the plat
form l0 and raising the platform I l equal
amounts of the center of gravity will be shifted
along a line parallel to the line connecting W1
scales by twice the change in platform elevation
times the total weight.
and W2 such as the line x-:c in Figure IX.
tilting also shifts the apparent center of gravity
of the load carried on the scales I0 and Il to a
point B whose distance from W2 is a’ where
w1' being the weight indication of scale l0 when
its platform is lowered. This shift in the hori
zontal projection of the center of gravity is equal
to the height of the center of gravity multiplied
by the angle of tilt q2, thus:
The center of gravity of an airplane may thus
be completely determined by a series of weight
measurements combined with the linear measure
ments between the points of contact of the air
plane and the respective scales and the elevation
of the platforms.
While the scales have been described in con
nection with center of gravity determinations of
a structure supported at three points, it is also
apparent that the same principle may be utilized
for similar measurements on objects supported
on four points. In this case two Scales would be
arranged side by side. The object would first be
placed on the scales such that the two points on
one side would be on one scale and the other
points on another, and the readings taken at both
Similarly when the airplane is tilted the other
level and tilted conditions. From these weight
way the apparent center of gravity is shifted the
readings the transverse plane and the height of
other way so that its distance from W2 is a’ ’ where
.the center of gravity in such plane may be deter
mined. The object is then shifted ninety degrees
„z wi'
and a similar set of weighings taken. From these
Thus the total shift a'-a” expressed in terms 25 another vertical plane containing the center of
gravity may be determined. The actual center
of weight readings and the distance L is:
of gravity is located in the intersection of these
l ___ l/ = wí- wi’
two planes at a height determined by the weigh
Also, assuming the angle of tilt is the same each 30
ings taken when the object is tilted.
Thus a system of scales is shown which with a
minimum of expense and manipulation will per
mit a complete measurement of the distribution
of Weight of a structure placed upon them.
Having described the invention, I claim:
Solving these for h. gives:
l. In a device for determining the distribution
of weight of an object supported jointly on a plu
h =L2(w'1-w'1')
rality of scales, in combination, a platform, a
frame supported on a scale lever system, a plu
This equation for h gives the apparent height of
rality of screws supporting said platform from
the center of gravity in the vertical plane through 40 said frame, and means for rotating said screws
A and B. The actual height is less in the propor
tion of “E” to “C‘,” i. e. in proportion of mass
2. In a device for determining the center of
W1 -l-Wz to the total. Therefore, the actual height
gravity of an object by supporting it on a plu
“H” in the plane through m-œ is:
rality of scales acting jointly, means for tilting
the object to produce an apparent shift in the
(w1 “l” wz)
H= L2 (wi ““ wi')
horizontal position of its center of gravity, said
2d(w1 -l- w2) w1 -1- q«U2-t wa
means comprising a platform supporting part, of
L2 cv; - wf)
2¿(101 't' ’wz 'l- w3)
the object, a frame on a lever system, a plurality
of screws supporting said platform from said
Thus the actual height of the center of gravity 50 frame and a motor and gears adapted to rotate
is equal to the result of dividing the square of
said screws.
the distance between the supporting points times
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