Note: Descriptions are shown in the official language in which they were submitted.
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he present invention relates to a transmission of the type
described in the preamble to patent claim 1.
In a known transmission of this kind (Cyclo Transmission) the
eccentric is provided with a number of drivers, that work in
conjunction with two rings that have peripheral teeth and which
work in conjunction with a ring that has internal teeth in such
way that the disks are constantly in engagement with the ring on
one part of its circumference so that, because of the different
number of teeth on the disks, on the onè hand, and on the ring,
on the other, there will be a power or~path multiplication,
respectively. ~lthough these known transmissions permit the
transmission of great forces because their teeth resemble'
undulations, they only permit a change of step-down or step-up
ratios within relatively narrow limits, and for this reason are
suitable mainly as reduction g~ars *or slowly-moving drive
systems. In addition, they involve construction th~t is
extramely costly, both from the point o~ view of design and with
respect to material-technical c~sts, this being caused by the
fact that in order to transmit force, the teeth have to be slid
into en~agèment with each other. On tha one hand, this requires~
the use of extremely costly materials, and, on the other,
requiras costly surface preparation for the worklng surfaces, in
which connection it is impossible to avoid increased frictional
losses because o~ this slidin~ function.
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apanese patent application 58-248324 describes a ball-bearing
transmission in which the driving member, which is configured as
a disk or a plate, is provided with an eccentric groove and the
driven element, which is also configured as a disk or plate,
incorporates an endless undulating groove in which the balls that
transmit the force are guided Eas hemispheres--kalot~enartig--
Tr.], a flange that is fixed to the housing being provided
between the driving disk and the driven disk, said flange being
provided with a number of radial slot guides~ In this type of
transmission, regardless of its much simpler design
configuration, essentially the same things apply as for the
transmissions described heretofore, namely, because of the three-
fold forced guidance of the balls in the two grooves and the slot
guide, the balls are subjected to a high level of wear and the
ball tracks wear very rapidly.
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: Finally, EP-OS 207 206 describes a ball-bearing transmission with ::
a driving disk that is supported on an eccentric of the driving
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shaft by means oE a ball bearing, said driving disk being
provided on both surfaces with guide grooves ~or balls which, in :
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addition, roll in corresponding cou~ter guide grooves in the ~ ;
housing, on the one~:hand, and, on the other hand, in a driven
: : disk.~ The functiona1 construction of this transmission
corresponds to the Cyclo-transmission described in the
:~ introduction hereto, the ball tracks of which, which work in~
~ conjunction with èach other, being:the epicycloids and the
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~ypocycloids of two (mathematical) ~inusoidal curves with
different wave lengths (n:n-2~, the precise maintenance of which
is d~cisive for the operation of the transmission. As in the
case of the cyclo-transmission described in the introduction
hereto, because of this close connection to the ~mathematical)
cycloid shape of the ball tracks, the transmission is subjected
to the same limitations as a gear~type transmission, in
particular with regard to the dependence of the selectable
reduction ratio condi~ions on one module--determined by the
circumference of the cycloid pitch circle--with the result that
selection of the reduction ratio is only possible in large, and
in part broken, increments. ~ further disadvantage of the known
transmission ~s caused by the cycloid form of the ball guide
tracks which each cause the circulating balls to ~low down as
they approach the tip of a cycloid and, having reached the tip of
the cycloid, to accelerate once more into new curved parts that
lie at an acute angle to the former dir~ction of movement. The
irregularity of the path followed by the individual balls that is
caused in this manner is smoothed out because of the effective of
the other balls that are located in a constant curve area and for
this reason is not perceptible at the output, but it exists
regardless of this and aauses uneven running that confines the
use of this transmission to slow-running drive systems.
It is thè task of the ~resent invention ~o create tra~smission
~hi~h, although of a simple design and which is subject to a very
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~ow level of wear, permiks the free selection of the step-down or
step-up ratios within wide limits.
According to the present invention, this task has been solved by
the ball baaring transmission described in claim 1.
In the ball bearing transmission according to the present
invention, force is transmitted by means of balls, whereby,
because of kh~ guidance of the balls in a freely rotatable
~earing ring (inertial ring), forced guidance in a direction
which is transverse to the input and output side ball guide
tracks, and which causes high frictional losses, is avoided. The
transmission of force is thus effected ~nder frictlon which, for
all practical purposes, is rolling friction, with only sli~ht
oscillations about a centre plane and thus with only negligible
friational losses. The ball bearing transmlssion according to
the present invention can be manufactured so as to provide for
any step-up or step-down ratios, and these can be selPcted freely
and not as a function of a given modulus. Reductions smaller
than 9:1 are possible, which cannot be achieved with the help of
conventional gear-type transmissions. Commercially available
balls can be used for transmission of the force and the guide
tracks in the housing and in the output side can be produced ~y
the most simple machining procedures. For this reason,
pr~duc~ion cost.s are low~. ~Furthermor~, the.tran~mission makes it
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possible to tra~smit greater forces~becau e of the fact that all
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~ne balls that are used are simultaneously and constantly in
power-transmitting engagement.
Additional embodiments and advantages are set out in the
following description in which the present invention is explained
in greater deta.il on the basis of the drawings appended hereto.
These drawings show the following:
Figure 1: a longitudinal ~ection through a ball bearing
transmission according to the present invention;
Figure 2: a view of the transmission shown in figure 1, from the
left;
Figure 3: a view of the interior of the input side housing wall
o~ the transmission shown in figure 1;
Figure 4: a longitudinal section through the driving element of
an embodiment of a multi-stage or multi-train
transmission;
Figure 5: a view of the transmission ~hown in figure 4, from the
right;
Figure 6: a longitudinal cross section through the driven element
of the transmission shown in figures 4 and 5;
Figure 7: a longitudinal section through another embodiment of a
~ulti-stage or multi-train transmission;
Figure 8: a view from the `left into the transmission, which has
been open by removal of the h~using top and the input
drive sha ~t;
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--Figure 9: a ball track groove combinati~Q ~ explanation of
the associated calculations;
Fiqure 10 to figure 12: three additional examples of ball track
groove combinations
Figure 13: a cross section through a ball bearing transmi~sion
with ball~supported force transmission balls;
Figure 14: a view of a section of the ball race in figure 8;
Figure 15: a cross section through a ball bearing transmission
with an input and output force transmission balls that
are separated and supported in a slide;
Figure 16: a partial croqs ~ection through a slide than can be
. used in conjunction with the ball bearing ~ransmission as in
figure 10~ this having individual ball-supported force
transmission balls;
Figure 17: a cross section through a slide that can be used in
~onjunction with the ball bearing transmission as in figure 10,
with the force transmi~sion balls being fiupported in pairs by
ball bearings;
Figure 18: a view of a slide;
Figure 19: the ball race shown in figure 1~ as viewed from the
side;
Figure 20: a view of another embodiment of a slide;
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igure 21: a view of the slide shown in figure 16, from the
side;
Figure 22: a view of figure 16 from above;
Fi~ure 23: a view of a radial slot disk;
Figure ~4: a view of another embodiment of a ra~ial slot disk;
Figure 25: a cross section through a reduction gearing with
ball bearings supported force transmission balls.
The single stage ball bearing transmission that is shown in
figures 1 to 3 consists of a driven element 3 that is arranged in
a housing 2a, 2b and a driving member 1 with an eccentric that is
arranged on this and surrounded by a bearing 5 for the force-
transmission elements. ~alls 6 that surround the bearing 5 in a
ring are provided so as ~o transmit force, and these are held
against the bearing 5 by a bearing ring 7 that is supported so as
to be freely rotatable. In addition, the balls 6 are guided. on
one side in ~ixed radial ball guide groove~ 10 that are formed in
the housing 2 and, on the other side, in an undulating track lla,
llb that is formed in the driven member 3. The number of balls,
and correspondingly of radial guide grooves 10, being in the
ratio between n:(n-2) and n:(n+2) to the number of undulations in
the undulating track 11. The simplicity of the design of this
transmission can be seen from the drawing, for commercially
available parts can be used for the balls and ball bearings and
the transmissio~ a a whol-e consi-sts- of simply shaped elements
that do not require any 005tly machining. Thus, as is ~hown in
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_igure 3, the radial guide grooves can be produced in a suitably
stepped cover element by simple milling or grinding, whereas the
ball bearings 5 and the bearing ring 7, which are not involved in
the transmission of force but are used to guide the balls 6, can
be configured as simple flat rings, i.e., they do not re~uire a
guide ~rack that con*orms to the curvature of the balls.
In a further development of the ball bearing transmission
according to the present invention (see figures 4 to 6), several
force transmission lines, each of which consists of a row of
balls 6a, 6b and bearing ring 7a, 7b as well as corresponding
radial ball guide grooves 10 and annular~ball guide tracks 11
that run annularly and are concentric to each other can be
provided for special applications. For the case in which the
concentric undulating ball guide tracks are arranged in a common
driven element (not shown herein~, this involves a ~ingle-stage
transmission that is suitable for transmitting correspondingly
greaker forces, in which the individual force transmission lines
are configured so as to be congruent, i.e., which must have the
same number of undulations in the undulating ball guide tracks
and an equal number of radial ball guide grooves in the two force
transmission lines. Such a transmission can be used to transmit
very great forces or can be used if structural requirements
demand a particularly flat structure.
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owever, in another embodiment of a transmission of this type,
which incorporates ~everal force transmission lines, the
concentric undulating ball guide tracks lla, llb (see figure 6)
can be arranged in separate driven elements 3~, ~b, in which case
the force transmission lines can also be configured differently,
i.e., can have a different nu~ber o* undulations in the
undulating ball guide tracks and a different number of radial
ball guide grooves in the two force transmission lines for a
correspondingly different number of balls. Such a transmission
is a multi-stage transmission that can be configured as a
transmission with fixed outputs or a~ a change-speed
transmission, in which one output shaft ~an be connected by means
of a clutch to one or the other driven member as desired, and the
output drives that are not connected can idle.
A ~urther configuration o a ohange-speed transmission according
to the present invention is shown in figure 7. In this
transmission, the driven element 22 of the next~stage of the
transmission is 6upported concentrically on the driven element 21
of the preceding stage of the transmission concentrically, such
that its annular shoulder 24 that supports th~ undulating track
23 is opposite an annular shoulder 28 that i5 formed in ~he
housing 25, 26, this annular shoulder 28 forming an annular gap
29 with the following driven element 22. The preceding driven~
12ment 21 is confi~ured as an e~centric 30 in the-~rea of the
i annular ~ap 29 on which the bearing 3i for the balls 32 and the
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nertial ring 33 which holds the ball 32 of thP followinglstage
of the transmission which holds the ball 32 i~ arran~ed. Because
of the resulting multiplication effect, this embodiment i5
particularly suited for manufacturing transmissions with very
large step-up or ~tep-down ratios when, as a particular
advantage, a power take-off is possible in each of the stages, as
desired, so that the transmission can also be used as a change-
speed transmission, in which connection, in order to produce a
multi-stage or multi-train transmission in the manner described
above additional driven elements can follow the last driven
element in each instance.
Figure 7 also shows an additional, particularly advantageous
embodiment of a transmission according to the present invention,
such that in place of the radial ball guide grooves 27 that are
used in the following force transmission line, an additional
undulating track 37 is provided in the preceding force
transmission line. For the first time, this creates a ball
bearing transmission in which the balls are guided in two
constant undulating tracks (i.e., which cause no sudden change in
the direction of the balls and which are freely selectable, which
is to say, independent o~ the ~mathematical) sinusoidal cycloid
shape, In this way, the reduction xatio is freely selectable in
whole and half steps, in which connection one can select a wave
form that is flat~ i~P , is close to a ~ircular track, so that
the balls run quieter or, which is advantageous for high-speed
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rive ~ystems) the transmission of greater forces in slow-running
transmissions, one can select a wave form with a greater
amplitude. A further important advantage o~ the transmission
according to the present invention, as compared to known ball
bearing transmissions, in particular cyclo-transmissions, is the
elimination of the guide flange, or the separate driving disk
that i~s fixed in the housing, and thus a pair of curves, so that
the transmission is also of a much simpler design.
In the case of such an embodiment with two interacting undulating
tracks, it is advantageous ~see figure a) that the inertial rings
37 and 40 are provided with slot guides 38, 39 that enclose the
balls and which hold the balls at a prescribed (mean~ distance
~rom each other without hindering the 61 ight oscillation of the
~alls about their working position (as is functionally caused),
and which, in this manner, carry them in the desired and uniform
direction of rotation.
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Single-stage transmissions can be provided with a radial groove
guide or with double undulating groove guides, as desired. In
the same way, multi-s~age or multi-train transmissions as shown
in figures 4 or 7 can be provided with radial groove guides or
with undulating groove guides in the housing in the individual
stages, either unlformly or differently from ea~h other. I~f this
em~odiment is used, in order to ensu~e trouble-free operation of
the transmission all that has to ~e done is to maintain a
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2033~61
ifference of at least (~/-) two undulations in the housing side
undulating track compared to the drlven-side undulating track,
whereas if the embodiment with radial groove guides is used it is
preferred that a difference of one radial groove compared to the
number of undulations in the dri~en side undulating track be
provided, although a difference of two radial grooves compared to
the ~umber of undulations in the undulating track can also be
accommodated.
Figure 9 shows the interaction of the undulating tracXs and the
computation of these, in which connection, in this embodiment, a
~ix-wave track interacts with a four-wave undulating track. In
the drawing, the mean rolling circle is numbered 41, the six-wave
undulating track is numbered 42, and the four-wave undulating
track is numbered 43. When the six-wave undulating track ~2 is
arranged in the housing and the four-wave undulating track 43 is
arranged in the driven disk, this will result in a reduction of
1:~, and with the reverse arrangement, it will result in a
reduction ratio of 1:3. The arrangement of the balls is effected
at the points at which the two undulating tracks ~2, 43 and the
rolling circle 41 ha~e a common point of intersection. In the
~quation that represents the basis for calculation of the
fundamentals for computing the curve
rx = the radial distance of a point on the undulating
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track midline from the axis of xotation
e = accentricity
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2033061
Phix = the angle of curvature on the undulating track
mldline
Z1 - the number of waves in one undulating track
Z2 = the ~mber o~ waves of the other undulating track
or the number of radial grooves
rs - the radial distance of the eccentric at the point
set by rx
Figures 10 to 12 show different examples for undulating track
combinations based on using a seven-wave undulating track 44.
When this seven-wave undulating track is arranged on the driven
side, this will result in a reduction of 1:3.5 regardIess of ~he
number of waves on the housing side. In contrast to thisJ in the
event that the seven-wave undulating track ls arranged in the
housing in the ~ase of figure 10 (a five-wave track on the driven
side) this will result in a reduction of 1:2.5; in the case of
figure 11 (a four-wave track on the driven side) there will be a
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reduction ratio of 1:2; in the case of figure 12 (a three-wave
track on the driven side) there will be a reduction of 1:1.5.~ ;
Thus this will result in a functional variability which will
permit extensive standardization of the transmission elements
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numbers of waves it will be possible to produce a number of
transmission types by using driven disks with undulating tracks
having diff2.ent number~ of waves.
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igures 13 to 25 show developments of the embodiment of a ball
bearing transmission that is shown in figures 1 to 12, in which,
unlike the transmissions used f~r transmitting force that have
been described hereto~ore, separate sets of balls are used
between the driving element and the fixed part (housing or radial
slot disks) on the one hand, and between the driving element or
the radial slot disk, respectively, and the driven element on the
other, and which are supported on a ball race so as to be freely
rotatable.
In thii~ sense, figures 13 and 14 show a transmisision that
corresponds essentially to figure 1, in which the force is
transmitted from the driving element 41 that is provided with the
eccentric disk 61 through the fixed housing 44, to the driven
element 51 by means of two sets of balls ~4, 65, which are
supported so as to rotate freely on two rows of balls 66, 67 such
that each of the balls 66, 67 that serve to transmit the force
are supported on four balls of the two rows of balls 64, 65. In
their turn, these supporting balls are each contained in an
inertial ring 62, 63, of which, in parti.cular, the inner ring ~3
can be formed by a rolling bearing, in particular a needle roller
bearing, instead of by a simple profile ring that has bearing
tracks on both sides. This effQcti.vely eliminates any sliding
fxiction between the force-transmitting elements of the
transml~;siorl .
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_n contrast to the embodiments shown in figures 1 to 14, in the
embodiment shown in figures 15 to 25, in which corresponding
parts bear the same reference numbers as in figures 13 and 14,
the force is transmitted by means of an inertial ring 68 that
acts axially through a ball bearing on the eccentric 61 in place
of the radially acting inertial ring as in figure 14. For the
remainder, the force is transmitted through~two sets of balls to
the driven element 51, in which connection in ~his case of a
transmission with an axially acting in~rtial ring the balls can
each be arranged either i~dividually or by pairs in slides that
are supported so as to be able to slide within radial slots of a
guide disk that is ~ixed within the housing.
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In the case of ~igure 15, Which shows a simplified embodimen~ of
the present invention, ~he balls 55,~56 which~tr~nsmits the force
are supported directly and without ball supports in the slides s7
and the~lides within the radial slots 5~ of a disk 59 that is
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~fixed within the housing;~ variations of slides:with ball support
systems are shown in:figures 16 to 22, and figures 23 and 24 show
two :further embodiments of guide disks that are fixed withln the ~:
housing.
Thus:1 figure~l6 shows an embodiment of a slide 70, in:~which the ~
balls 71! 72 that transmit the force are~each supporjted by~a ~all
race 73,:~4 that is ~pported in the baIl guidP~ ~rack:75i,~:w~e~eas~
in the~embodiment~6hown in;~figure~l7, the balls 76,~ 77 that~
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.ransmits the force are supp~rted in pairs on a common ball race
78. In this, the ~upporting balls 78 are guided in a ball guide
groove 79 tsee figures 18 and 19) of the slide 70 that is also
provided with an external i~liding track 80 with which it overlaps
the edges of the slot 58 of the disk 59 that is fixed in the
housing (figure 15) in which it slides radially inwards or
outwards, respectively, under the action of the force of the
driving element 41, as a function of the eccentricity of the
eccentric 61.
The slide 81 that is shown in figures 20 to 22 differs from that
shown in figures 16 to 19 only in that here both the variants
shown in ~igures 1~ and 17 have been combined into one slide.
Slides o~ this kind can be used to increase ~he transmission of
force or to build multi-step transmissions as shown in figure 25.
Depending on the type of transmission, the slides can be used in
conjunction with any guide disk, for example the guide disk 59
shown in figure lS, or also (see figure 23) the guide disk 85
that is provided with a total of eight radial slots 86 that
extend from the outer edge in order to allow the slides to move
and drillings 87 with which it is screwed to the housing. Figure
24 shows a corresponding view of an additional embodiment of a
guide disk 88 with, in this case, ~our raidial slots 89 that
ex~nd ~rom a cen~ral drillin~ and which are milled ~ simpli~y
installation of the slides on the corners. However, i61ides can
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lso be formed in two parts and the parts can then be screwed
together after insertion into the radial slot.
Finally, figure 25 shows a ~ulti-step transmission that uses a
dou~le isilide as shown in figures 20 to 22, in which connection
the balls 91, 92, 93 that transmit the force are guided in the
inertial ring 68, in the housing 44, and in the driven element 51
are each guided in grooves, whereas the balls 94 that circulate
only on the surface of the inertial ring 68, i.e., not in the
ball guide tracks, only have a supporting functio~. In this:
case, the guide disk 83 is supported ~y means of a ball bearing
84 so as to be rotatable, so that the guide disk 83 can follow
th~ rotational motion that is governed by the balls 91, 9!2 that
are guided in the undulating track.
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