Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to a variable-speed power
transmission device.
Various types of device6 adapted to continuously vary
the speed in a transmission of motion are known, among which
mention may be made of mechanical, hydrostatic and electric
variators.
Among mechanical variators, those in most widespread
use are based on the concept of employing the friction
torque transmitted by a belt stretched between two pulleys
having a fixed center distance and a variable diameter.
The speed change occurs by axially moving the plates of
which the pulleys are compo~ed so as to vary the winding
diameters of said pulleys.
Hydro~tatic variators transform mechanical energy into
hydraulic energy with the ald of a pump-motor assembly.
Direct-current motors in which the applied voltage can
be varied can be considered electric variators; as is known,
the applied voltage is linked to the number of revolutions.
Other kinds of electric variators employ the principles
of varying electrostatic and electromagnetic fields.
All these kinds of variators are however characte~ized
by more or less modest results as to the factors of speed,
power, torque, weight, dimensions and effici'ency.
The aim of the present invention is to provide a device
capable of varying continuously the output speed with a
simpler de~ign and structure than known devices.
~- A further aim is to provide a speed varying device
which is simple in concept and easy to manufacture.
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Not least object is to provide a speed
varying device which can be obtained at low cost
with conventional systems.
This aim, these objects and others which
s will become apparent hereinafter are achieved by a
variable-speed power transmission device, character-
i~ed in that it comprises an input gearing for
dividing the powex into two fractions having
different and variable speeds, the first of said two
10 fractions being transmitted directly to an output
gearing, the second of said two fractions being
transmitted to a hydrostatic pump-motor assembly
which varies its speed and then to said output
gearing adapted to recombine it with said first
15 fraction.
In accordance with a particular embodiment
of the invention there is provided a variable-speed
power-transmission device, comprising:
an input planetary gearing for splitting
input power into two, first and second variable
power fractions having different and variable
speeds,
first and second power transmission paths
connected mutuaIly in parallel and to said input
2s plànetary gearing for receiving from said input
planetary gearing said first and second power
fractions and generating respectively a first and a
second speeds,
an output planetary gearing connected to
said first and second power transmission paths for
combining said first and second power fractions and
generating an output rotation rate as the sum of
said first and second speeds,
said first power transmission path
3s including a first intermediate shaft extending from
said input to said output planetary gearings,
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said second power transmission path
including a hydrostatic pump-motor assembly, a
second intermediate shaft interposed between said
input planetary gearing and said hydrostatic pump-
5 motor assembly, and a third intermediate shaftinterposed between said hydrostatic pump-motor
assembly and said output planetary ~earing,
said hydrostatic pump-motor assembly
including a hydraulic pump, a hydraulic motor and a
con~rollable flow regulator interposed between said
hydraulic pump and said hydraulic motor, said
controllable flow regulator controlling flow of
fluid in said hydrostatic pump-motor assembly and
thus controlling splitting of power between first
15 and second power transmission paths and varying said
first and second speeds.
In accordance with a further particular
embodiment of the invention there is provided a
variable-speed power transmission device comprising:
an input planetary gearing for splitting
input power into a first and a second variable power
fractions,
a first and a second power transmission
paths connected mutually in parallel and to said
25 input planetary gearing for receiving from said
input planetary gearing said first and second power
fractions and generatin~ respectively a first and
second speeds,
an output planetary gearing connected to
30 said first and second power transmission paths for
combining said first and second power fractions and
generating an output rotation rate as.the sum of
said first and second speeds,
said first power transmission path
35 including a first intermediate shaft extending from
said input to said output planetary gearings,
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said second power transmission path
including a hydrostatic pump-motor assembly, a
second intermediate shaft interposed between said
input planetary gearing, and
said hydrostatic pump-motor assembly, and
a third intermediate shaft interposed between said
hydrostatic pump-motor assembly and said output
planetary gearing,
said hydrostatic pump-motor assembly
10 including a hydraulic pump, a hydraulic motor and a
controllable flow regulator interposed between said
hydraulic pump and said hydraulic motor for
controlling flow of fluid in said hydrostatic pump-
motor assembly and thus controlling splitt1ng of
15 power between said first and second power
transmission paths and said first and second speeds,
wherein an input is connected to said
input planetary gearing and an output shaft is
connected to said output planetary gearing, said
input shaft, said output shaft and said ~irst
intermediate shaft being arranged coaxially to each
other
In accordance with a still further parti-
cular embodiment of the invention there is provided
25 a variable-speed power transmission device,
comprising:
an input shaft,
an output shaft,
an input planetary gearinq including an
input sun gear rigid with said input shaft, input
planetary gears and an input crown gear,
an output planetary gearing including an
output sun year rigid with said output shaft, output
planetary gears and an output crown gear,
3s a first intermediate shaft connected
between said input and said output planetary gears,
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a hydrostatic pump~motor assembly,
a second intermediate shaft interposed
between said input crown gear of said input
planetary gearing and said hydrostatic pump-motor
s assembly,
a third intermediate shaft interposed
between said hydrostatic pump-motor assembly and
said output crown gear of said output planetary
gearing,
said hydrostatic pump-motor assembly
including a hydrostatic pump, a hydraulic motor and
a controllable flow regulator interposed between
said hydraulic pump and motor for controlling flow
of fluid in said hydraulic pump-motor assembly.
Further characteristics and advantages of
the invention will become apparent from the detailed
description of an embodiment, illustrated only by
way of non-limitative example in Figure 1 of the
accompanying drawings.
With reference to the above described
figure, the variable-5peed power transmission device
comprises, in a preferred embodiment, an input shaft
1 rotoidally coupled to the axis of a first
epicyclic train 2 adapted to transmit the motion to
2s a first intermediate shaft 3, coaxial with respect
; to said shaft l, and to a second intermediate shaft
4 connected to the outer planetary gear of said
gearing 2.
Said second intermediate shaft 4 is
30 associated with a hydrostatic assembly 5 which
transmits the motion to the planetary gear of a
second epicyclic train 7 through a .third
intermediate shaft 6; said gearing 7 also receives
the motion from the first intermediate shaft 3.
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The motion resulting from the combination of the
motions arriving from the intermediate shafts 3 and 6 is
transmitted by the second epicyclic train to an output shaft
8 coaxial to said shaft 3.
Accordi-ng to the invention, said hydrostatic assembly 5
is preferably constituted by a hydraulic pump 9 with a fixed
and/or variable displacement, by a hydraulic motor 10 with
fixed and/or variable displacement and by a flow regulator
11 interposed therebetween.
In the illustrated example, the second intermediate
shaft 4 is connected to the external toothing of a crown
gear 2a of the epicyclic train 2. The crown gear 2a is
rotatable and, in a known manner, is connected to planetary
gears 2b, in turn connected to a solar gear 2c.
The third intermediate shaft 6 is conneated to the
external toothing of the crown gear 7a of the epicyclic
train 7, which similarly has planetary gears 7b and a solar
: gear 7c.
: The solar gear 2c lS connected to the input shaft 1,
'~ : 20 the solar gear 7c is connected to the output shaft 8 and the
planetary gears 2b and 7b are connected by the first
intermediate shaft 3.
When the flow regulator 11 blocks the flow of fluid in
the hydrostatic assembly 5, the intermedïate shaft 4 is
blocked and so is the crown gear 2a of the epicyclic train
, 2. Similarly the shaft 6 is blocked and ~o is the crown gear
' 7a of the epicyclic train 7.
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In this condition motion is transmitted fro~ input
shaft 1 to output ~haft 8 entirely via the epicyclic trains
~, 30 2 and 7 and shaft 3.
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By regulating the aperture of the flow regulator 11,
motion can progressively be transmitted through the
hydrostatic assembly 5 since the crown gear 2a tends to
rotate because of the planetary gears' 2b action.
The operating concept of the device according to the
present invention is illustrated in figure 2, wherein:
the arrow 12 indicates the power N1 in input, having a
torque Mtl and an rpm rate nl;
the arrows 13 and 14 respectively indicate the powers
N2 and N3 obtained by variably dividing N1, each
respectively having a torque Mt2 and Mt3 and an rpm rate n2
and n3;
; the arrow 15 indicates the power N4 obtained after the
conversion in the hydro~tatic assembly 5, having a torque
Mt4 and an rpm rate n4 which are always and in any ca~e
different from n3;
the arrow 16 indicates the power M5 resulting in output
from the sy~tem, having a torque Mt5 and an rpm rate n5.
Considering ideally an efficiency of 1 for the device,
the relation linking the various powers is:
N5 = N2 + N4 = N1
In a first numeric example related to the rotation
rate, the followiny are assumed:
nl = lO00 rpm
n2 = 400 rpm
n3 = 600 rpm
n4 = 300 rpm
so that n5 = n2 + n4 = 400 ~ 300 = 700 rpm.
~ In a second numeric example, the following are assumed:
nl = 1000 rpm
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n2 = 200 rpm
n3 = 800 rpm
n4 = 400 rpm
so that n5 = n2 + n4 = 200 + 400 = 600 rpm.
From the above two examples it is apparent that the
resulting speed is variable, while the power is constant if
efficiencies are ignored.
The advantage of the device, according to the present
invention, over the known devices, i9 that speed can be
lo variated continuously in a finer manner with a very
simplified design.
The invention thus conceived is su3ceptible to numerous
modifications and variations, all of which are within the
scope of the inventive concept.
For example, ~ the hydrostatic assembly 5 can be
connected to the solar gear or the planetary gear sha~t of
the epicyclic train, instead of the~crown gear as in the
illustrated example, depending on the speed ratio needed
between input and output or on de~ign features o~ the
device.
Furthermore all the details will be appropriately
dimensioned according to the specific design of each
individual application required by the technology and may be
replaced with other technically equivalent elements.
In practice, the materials employed, as well as the
dimensions, may be any according to the requirements.
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