Title: Gear assembly
Abstract: A planetary gear assembly comprising a primary array (2) of co-axial planetary gear sets and a secondary array (3) of co-axial planetary gear sets, planetary gear set being provided with an associated gear engagement means (21), the arrangement being such that in use each planetary gear set and the associated gear engagement means are arranged for relative translational movement which is substantially parallel to the axis of the respective array of planetary gears and a rotational input drives a selected primary gear set which is engaged with the associated gear engagement means, the rotational output of the engaged primary gear set (2) being transmitted through the associated gear engagement means (21) to gear engagement means which is engaged with the associated selected secondary gear set (3), the output from the selected secondary gear set being transmitted to rotational output means (18, 49).
Patent Number: 6,852,060 Issued on 02/08/2005 to Ash
| Inventors:
|
Ash; Adrian (7 Somerville Road Poulner, Ringwood Hampshire, GB BH24-1XJ)
|
| Appl. No.:
|
129050 |
| Filed:
|
August 8, 2002 |
| PCT Filed:
|
October 30, 2000
|
| PCT NO:
|
PCT/GB00/04170
|
| 371 Date:
|
August 8, 2002
|
| 102(e) Date:
|
August 8, 2002
|
| PCT PUB.NO.:
|
WO01/33104 |
| PCT PUB. Date:
|
May 10, 2001 |
Foreign Application Priority Data
| Current U.S. Class: |
475/296; 74/332; 74/333; 74/337.5; 280/259; 280/260; 280/261; 475/269; 475/271; 475/275; 475/276; 475/277; 475/278; 475/323 |
| Intern'l Class: |
F16H 003/44 |
| Field of Search: |
74/332,333,337.5
475/269,296,271,275,323,276,277,278,279
280/259,260,261
|
References Cited [Referenced By]
U.S. Patent Documents
| 1256371 | Feb., 1918 | Rowledge | 475/277.
|
| 3290962 | Dec., 1966 | McCann et al. | 475/132.
|
| 3728912 | Apr., 1973 | Darnell | 475/290.
|
| 3842691 | Oct., 1974 | Shea.
| |
| 4559848 | Dec., 1985 | Kerr | 475/276.
|
| 4721015 | Jan., 1988 | Hartmann | 475/277.
|
| 4858494 | Aug., 1989 | Healy.
| |
| 5322487 | Jun., 1994 | Nagano | 475/297.
|
| 6048287 | Apr., 2000 | Rohloff | 475/297.
|
| 6387008 | May., 2002 | Chen et al. | 475/296.
|
| 6390487 | May., 2002 | Yoo | 280/237.
|
| Foreign Patent Documents |
| 4124306 | Jan., 1993 | DE | .
|
| 916 462 | Dec., 1946 | FR.
| |
| 2 684 064 | May., 1993 | FR.
| |
Primary Examiner: Pang; Roger
Assistant Examiner: Lee; David D.
Attorney, Agent or Firm: Hogan & Hartson L.L.P.
Claims
What is claimed is:
1. A planetary gear assembly comprising:
primary planetary gear means and secondary planetary gear means, one of
said primary planetary gear means and said secondary planetary gear means
comprising a planetary gear set and the other of said primary planetary
gear means and said secondary planetary gear means comprising a plurality
of co-axial planetary gear sets;
selection means for selecting one of the plurality of co-axial planetary
gear sets; and
a rotatable housing which is mounted for rotation around the planetary gear
sets,
wherein a rotational input drives the primary planetary gear means, an
output from the primary planetary gear means being transmitted to the
rotatable housing, an output from the rotatable housing driving the
selected secondary planetary gear means and an output from the selected
secondary planetary gear means being transmitted to a rotational output
means.
2. A planetary gear assembly as claimed in claim 1 in which the primary
planetary gear means comprises an array of planetary gear sets and the
secondary planetary gear means comprises a secondary array of planetary
gear sets, primary selection means for selecting a primary planetary gear
set and secondary selection means for selecting a secondary planetary gear
set,
wherein the rotational input drives a selected primary planetary gear set,
the output from the selected primary planetary gear set being used to
drive the selected secondary planetary gear set and the output from the
selected secondary planetary gear set being transmitted to the rotational
output means.
3. A planetary gear assembly as claimed in claim 1 which is a bicycle
planetary gear assembly in which foot pedals drive the primary planetary
gear means and the output from the secondary planetary gear means is used
to drive a drive cog.
4. A planetary gear assembly as claimed in claim 1 wherein the primary
planetary gear means is co-axial with the secondary planetary gear means.
5. A planetary gear assembly as claimed in claim 4 wherein the rotatable
housing is substantially cylindrical.
6. A planetary gear assembly as claimed in claim 5 wherein the housing
substantially encloses the primary and secondary planetary gear means.
7. A planetary gear assembly comprising:
primary planetary gear means and secondary planetary gear means, one of
said primary planetary gear means and said secondary planetary gear means
comprising a planetary gear set and the other of said primary planetary
gear means and said secondary planetary gear means comprising a plurality
of co-axial planetary gear sets;
selection means for selecting one of the plurality of co-axial planetary
gear sets;
a rotatable housing which is mounted for rotation around the planetary gear
sets, wherein a rotational input drives the primary planetary gear means,
an output from the primary planetary gear means being transmitted to the
rotatable housing, an output from the rotatable housing driving the
secondary planetary gear means and an output from the secondary planetary
gear means being transmitted to a rotational output means; and
gear engagement means associated with each of said plurality of co-axial
gear sets, the gear engagement means and the plurality of planetary gear
sets being arranged for relative translation movement in a direction which
is substantially parallel to the axis of the plurality of the planetary
gear sets, and the arrangement of the planetary gear assembly being such
that, in use, the relative translation movement brings a selected one of
the plurality of planetary gear sets into engagement with a respective one
of the gear engagement means, and said respective one of the gear
engagement means acts at least in part as a rotational transmission means
between said primary gear set and said secondary gear set.
8. A planetary gear assembly as claimed in claim 7 in which the assembly
comprises caming means which is operative to cause the relative
translational movement of said planetary gear set and said respective gear
engagement means.
9. A planetary gear assembly as claimed in claim 8 in which the caming
means is adapted to effect the relative translational movement of said
planetary gear set and said respective gear engagement means by a
rotational movement of said caming means.
10. A planetary gear assembly as claimed in claim 8 in which the assembly
comprises a rack and pinion arrangement, and in use, suitable movement of
the rack effects rotation of the pinion which causes the relative
translational movement of said planetary gear set and said respective gear
engagement means.
11. A planetary gear assembly as claimed in claim 10, in which the rack is
arcuate.
12. A planetary gear assembly as claimed in claim 10, in which the pinion
is connected to said earning means by shaft means which extends inwardly
of the planetary gear assembly.
13. A planetary gear assembly as claimed in claim 10, in which the pinion
is connected to the caming means and in use sultable movement of the rack
effects rotation of the pinion which causes rotation of the caming means.
14. A planetary gear assembly as claimed in claim 13, in which the assembly
comprises a plurality of rack and pinion arrangements each corresponding
to a respective one of the planetary gear sets.
15. A planetary gear assembly comprising:
primary planetary gear means and secondary planetary gear means, one of
said primary planetary gear means and said secondary planetary gear means
comprising a planetary gear set and the other of said primary planetary
gear means and said secondary planetary gear means comprising a plurality
of co-axial planetary gear sets;
selection means for selecting one of the plurality of co-axial planetary
gear sets;
a rotatable housing which is mounted for rotation around the planetary gear
sets, wherein a rotational input drives the primary planetary gear means,
an output from the primary planetary gear means being transmitted to the
rotatable housing, an output from the rotatable housing driving the
secondary planetary gear means and an output from the secondary planetary
gear means being transmitted to a rotational output means;
gear engagement means associated with each of said plurality of co-axial
gear sets, the gear engagement means and the plurality of planetary gear
sets being arranged for relative translation movement in a direction which
is substantially parallel to the axis of the plurality of the planetary
gear sets, and the arrangement of the planetary gear assembly being such
that, in use, the relative translation movement brings a selected one of
the plurality of planetary gear sets into engagement with a respective one
of the gear engagement means, and said respective one of the gear
engagement means acts at least in part as a rotational transmission means
between said primary gear set and said secondary gear set; and
caming means which is operative to cause the relative translational
movement of said planetary gear set and said respective gear engagement
means;
wherein the assembly comprises a rack and pinion arrangement, and in use,
suitable movement of the rack effects rotation of the pinion which causes
the relative translational movement of said planetary gear set and said
respective gear engagement means.
16. A planetary gear assembly as claimed in claim 15, in which the rack is
arcuate.
17. A planetary gear assembly as claimed in claim 15, in which the pinion
is connected to said earning means by shaft means which extends inwardly
of the planetary gear assembly.
18. The planetary gear assembly of claim 15, in which the pinion is
connected to the caming means and in use suitable movement of the rack
effects rotation of the pinion which causes rotation of the caming means.
19. A planetary gear assembly as claimed in claim 18, in which the assembly
comprises a plurality of rack and pinion arrangements each corresponding
to a respective one of the planetary gear sets.
20. A planetary gear assembly comprising:
a primary planetary gear assembly and a secondary planetary gear assembly,
the gear assemblies each comprising a plurality of co-axial planetary gear
sets;
a selection device for selecting a co-axial planetary gear set in the
primary planetary gear assembly and a co-axial planetary gear set in the
secondary planetary gear assembly; and
a rotatable housing for housing the gear assemblies and mounted for
rotation around the gear assemblies, wherein the housing is rigidly
attached to first and second portions of the selection device such that
when the selected co-axial planetary gear set in the primary planetary
gear assembly is driven by a rotational input, the first portion of the
selection device engaging the primary planetary gear assembly drives the
selected co-axial planetary gear set in the secondary planetary gear
assembly via the housing and the second portion of the selection device
engaging the secondary gear assembly and an output of the selected
secondary planetary gear assembly is transmitted to a rotational output
means.
Description
The present invention relates to gear assemblies and in particular, but not
exclusively, to planetary gear assemblies for bicycles.
A known planetary gear assembly is disclosed in FR 2684064 (BOURDILLON)
which comprises a plurality of primary planetary gear sets which is
coaxial with a plurality of secondary planetary gear sets. Each of the
planet cogs are mounted on a `cage` (5) having a stepped profile, and the
planet cogs and the cage are adapted to rotate about the axis of the crank
shaft. In use it is the cage which rotates and transfers the torque from a
selected primary planetary gear set to a selected secondary planetary gear
set.
The present invention seeks to provide an alternative planetary gear
assembly.
According to a first aspect of the invention there is provided a planetary
gear assembly comprising primary planetary gear means and secondary
planetary gear means, one of said primary planetary gear means and said
secondary planetary gear means comprising a planetary gear set and the
other of said primary planetary gear means and said secondary planetary
gear means comprising a plurality of co-axial planetary gear sets,
selection means for selecting one of the plurality of co-axial planetary
gear sets, the assembly being characterised in that the assembly further
comprises a rotatable housing which is mounted for rotation around the
planetary gear sets, the arrangement of the assembly being such that, in
use, a rotational input drives the primary planetary gear means, the
output from the primary planetary gear means being transmitted to the
rotatable housing, and the output from rotatable housing driving the
secondary planetary gear means, and the output from the secondary
planetary gear means being transmitted to a rotational output means.
Preferably the primary planetary gear means comprises a primary array of
planetary gear sets and the secondary planetary gear means comprises a
secondary array of planetary gear sets, selection means for selecting a
primary planetary gear set and selection means for selecting a secondary
planetary gear set, and in use the arrangement is such that a rotational
input drives a selected primary planetary gear set, the output from the
selected primary planetary gear set being used to drive the selected
secondary planetary gear set and the output from the selected secondary
planetary gear set being transmitted to a rotational output means.
Preferably the primary planetary gear means is co-axial with the secondary
planetary gear means.
Preferably the rotatable housing is substantially cylindrical.
The housing preferably substantially encloses the primary and secondary
planetary gear means.
The planetary gear assembly may be a bicycle planetary gear assembly in
which foot pedals drive the primary gear means and the output from the
secondary gear means is used to drive a drive cog.
According to a second aspect of the invention there is provided a planetary
gear assembly comprising primary planetary gear means and secondary
planetary gear means, one of said primary planetary gear means and said
secondary gear means comprising a planetary gear set and the other of said
primary planetary gear means and said secondary planetary gear means
comprising a plurality of co-axial planetary gear sets, and the assembly
further comprising gear engagement means associated with each of said
plurality of co-axial gear sets, the assembly being characterised in that
the gear engagement means and the plurality of planetary gear sets being
arranged for relative translational movement in a direction which is
substantially parallel to the axis of the plurality of the planetary gear
sets, and the arrangement of the planetary gear assembly being such that,
in use, the relative translation movement brings a planetary gear set into
engagement with a respective gear engagement means, and said gear
engagement means acts at least in part as a rotational transmission means
between a primary gear set and a secondary gear set.
Preferably the assembly comprises caming means which is operative to cause
the relative translational movement of a planetary gear set and an
associated gear engagement means.
The caming means is preferably adapted to effect the relative translational
movement of a planetary gear set and an associated gear engagement means
by a rotational movement of the caming means.
The assembly desirably comprises a rack and pinion arrangement and in use
suitable movement of the rack effects rotation of the pinion which causes
the relative translational movement of a planetary gear set and a
respective gear engagement means.
The assembly most preferably comprises a rack and pinion arrangement, the
pinion being connected to the caming means, and in use, movement of the
rack effects rotation of the pinion which causes rotation of the caming
means.
The rack is preferably arcuate. In this case rotation of the rack causes
rotation of the pinion. The pinion is preferably connected to the caming
means by shaft means which extends into the planetary gear assembly.
The assembly preferably comprises a rack and pinion arrangement
corresponding to each planetary gear set.
In a preferred embodiment of the invention there is provided a planetary
gear assembly comprising a primary array of coaxial planetary gear sets
and a secondary array of coaxial planetary gear sets, each planetary gear
set being provided with an associated gear engagement means, the
arrangement being such that in use each planetary gear set and the
associated gear engagement means are arranged for relative translational
movement in a direction which is substantially parallel to the axis of the
respective array of planetary gears and a rotational input drives a
selected primary gear set which is engaged with the associated gear
engagement means, the rotational output of the engaged primary gear set
being transmitted through the associated gear engagement means to gear
engagement means which is engaged with the associated selected respective
secondary gear set, the output from the selected secondary gear set being
transmitted to rotational output means.
The invention will now be further described, by way of example only, with
reference to the accompanying drawings in which:
FIG. 1 is a schematic perspective view of a planetary gear assembly in
accordance with the invention,
FIG. 2 is a schematic part exploded view of the assembly shown in FIG. 1,
FIG. 3 is a schematic exploded view of a gear selection arrangement of the
assembly shown in FIGS. 1 and 2,
FIG. 4 is a more detailed schematic view of the gear selection arrangement
shown in FIG. 3,
FIG. 5 is a partial schematic view of the gear selection arrangement of the
inventive assembly,
FIG. 6 is a schematic end-on view of the planetary gear assembly in situ
attached to a bicycle frame,
FIG. 7 is an end view of a pressure plate used to engage a planetary gear
set in the inventive assembly,
FIG. 8 is a schematic cross-section of the arrangement of the secondary sun
cogs,
FIG. 9 is a schematic side view of two caming portions arranged to engage a
planetary gear set,
FIG. 10 is a schematic end view of the gear assembly,
FIG. 11 is a schematic side view of the innermost caming portions in an
engaged condition, and
FIG. 12 is a cross-sectional view of a caming portion shown in
FIG. 11 on line A--A.
With reference to FIG. 1 (showing only part of the gear selection
arrangement for clarity) there is shown a bicycle planetary gear box
assembly 1 comprising a plurality of co-axial planetary gear sets. More
particularly there are provided four primary gear sets and four secondary
gear sets (FIG. 1, for reasons of clarity showing only one primary set 2
and one secondary gear set 3). A gear selection arrangement (hereinafter
described) allows the rider to select a primary gear set and a secondary
gear set, the torque produced by rotation of the foot pedals driving the
selected primary gear set 2, the output from which is transmitted to drive
the selected secondary gear set 3 through a rotatably mounted housing 4,
and the output from the second gear set 3 being transmitted to rotate the
drive cog 18. The drive cog 18 engages with a toothed belt 17 which drives
the rear wheel of the bicycle.
With reference to the primary gear set 2 shown in FIG. 1, each planetary
gear set comprises a sun cog 13, three planet cogs 14 and an outer cog 15.
The relative diameters of the sun cogs and the planet cogs for each gear
set will of course be different so that various gear ratios between
primary and secondary gear sets may be obtained. Both the primary and
secondary gear sets are co-axial with a pedal shaft 11 which is rigidly
secured at each distal end to a pedal crank 25 and a pedal 24.
With regard in particular to the primary gear sets, the sun cogs thereof
are rigidly secured to the pedal shaft 11. Each primary and secondary
outer cog is provided with axially engageable teeth 19 and circumferential
groove 44 provided on the radially outermost surface of the outer cog.
Each groove 44 accommodates an annular guide 65 which is fast with the
inner surface of the cylindrical housing 4 and on which each outer cog may
rotate freely.
The cylindrical housing 4 is free to rotate on bearings which are provided
between said housing 4 and a housing 6, the housing 6 being fixed to
bicycle frame members 46, 47 and 48 (best shown in FIG. 6). A central
plate 7 divides the primary side from the secondary side, the plate 7
being rotatably mounted within the cylindrical housing 4 by bearings 71
which are accommodated in a groove 72. The primary and secondary gear sets
are enclosed by two end portions 70 which are located towards the distal
end of the housing 6.
With reference to the schematic representation of FIG. 8, in which the gear
selection arrangement has been omitted, the arrangement of the secondary
sun cogs will be explained. The four secondary sun cogs 13a, 13b, 13c and
13d and the drive cog 18 are fixedly attached to a sleeve 49. The sleeve
49 encloses the pedal shaft 11 is radially separated therefrom by
phosphorous bushing 50. The pedal shaft 11 is thus free to rotate within
the sleeve 49. The sleeve 49 is rotatably mounted by bushing 50 and roller
bearings 51. As is evident from FIG. 8 the secondary sun cogs are of
different diameters so as to produce, different gear ratios for each
secondary gear set.
The gear selection arrangement of the assembly will now be described. Each
planetary gear set (both primary and secondary) is provided with an
associated engagement ring 21 which is located adjacent to and inwardly of
the respective planetary gear set. Each engagement ring 21 comprises a set
of axially engageable teeth 28, an annular shoulder 26 and three equally
angularly spaced recesses 20. The recesses 20 accommodate three guides 16
which are fast with the rotatably mounted cylindrical housing 4. Each
engagement ring 21 is thus capable of axial movement along the respective
guides 16 within the housing 4.
Each engagement ring 21 has an associated pressure plate 5. With reference
in particular to FIG. 7, each pressure plate 5 comprises an arcuate
abutment surface 29, three upstanding equally angularly spaced pins 27 and
three equally angularly spaced apertures 30, a central aperture 31 and
three caming portions 37, the caming portions being provided on the
opposite surface of the pressure plate that on which the pins 27 are
provided.
The caming portions of the innermost pressure plates 5a are referred to by
reference numeral 37a and the caming portions of the outer pressure
plates, 5b, 5c and 5d are referred to by reference numerals 37b, 37c and
37d respectively.
The caming portions 37b, 37c and 37d are of part cylindrical shape and
extend generally orthogonal to each respective pressure plate. The outer
rims of caming portions 37b, 37c and 37d are of inclined profile when
viewed side on (as best shown in FIG. 5).
With reference to FIG. 11, the caming portions 37a comprise a relatively
narrow raised portion 75 of part cylindrical shape.
The arcuate abutment surfaces are formed so as to abut with the annular
shoulder 26 of the respective engagement ring 21 and such abutment is such
as to allow for rotational movement of the engagement ring 21 with respect
to the pressure plate 5.
The pins 27 are formed so as to rotatably mount the planet cogs of the
respective planetary gear set.
The central aperture 31 is so dimensioned so as to accommodate the pedal
spindle 11 and in the case of the pressure plates on the secondary side,
to accommodate both the sleeve 49 and the pedal spindle 11 which passes
therethrough.
With reference to FIGS. 3, 4 and 5 the gear selection arrangement further
comprises an outer plate 8 and an inner plate 9 at each end of the
assembly 1, corresponding to the primary and secondary gear sets, three
clusters of pinions 10 and a plurality of elongate members 52, 53, 54 and
55 which are connected to respective pinions.
Each plate 8 and 9 is provided with three substantially arcuate apertures
32. As best seen in FIG. 4, the radially inner region of each of the
apertures of the plates 8 and 9 comprises an arcuate rack of teeth 33 and
35 respectively. Axially spaced from the rack 33, the radially outer
region of each of the apertures of the plates 8 and 9 comprises racks 34
and 36 respectively which are axially spaced from racks 33 and 35
respectively. Thus each plate 8 and 9 each comprises three pairs of
axially spaced arcuate racks.
Each cluster of pinions 10 comprises four coaxial pinions 40, 41, 42 and 43
(from the outermost to the innermost pinion) which are accommodated by the
apertures 32 and which engage with the racks 33, 34, 35 and 36
respectively.
Each pinion is rigidly attached to an elongate member which extends
inwardly of the assembly 1. More specifically the pinion 40 is attached to
rod 52 and the pinions 41, 42 and 43 are attached to sleeves 53, 54 and 55
respectively. As is evident from FIG. 5 the rod 52 and the sleeves 53, 54
and 55 are of progressively larger diameter respectively. Thus sleeve 55
enclosed part of sleeves 54, 53 and rod 52, sleeve 54 encloses part of
sleeve 53 and rod 52 and sleeve 53 encloses part of rod 52. Around each of
the rod 52 and the sleeves 53, 54 and 55 there is provided a caming
portion, shown generally as 38, which complements and co-operates with the
facing rim of the caming portion 37 of each respective pressure plate 5.
Thus, in FIG. 11 the caming portion 38a is attached to the rod 52 and
co-operates with the outer facing rim of the caming portion 37a.
End portions 80 of each of the rods 52 are accommodated in recesses 81
provided in the central plate 7.
Returning to the plates 8 and 9, the outer plate 8 has affixed thereto a
disc 56 which comprises teeth 57. The teeth 57 mesh with the teeth of
lever 59, the lever 59 being pivotally mounted on pin 58 which is attached
to the inner plate 9. The lever comprises a lug 60 which may move in
curved aperture 62 which is provided in the outer plate 8.
The operation of the planetary gear assembly 1 will now be described. The
rotation of the pedals causes rotation of the pedal shaft 11. This in turn
causes the sun cog of the selected primary gear set to rotate which
rotates the three planet cogs about the pins 27 of the respective pressure
plate. The outer cog is caused to rotate and hence the respective
engagement ring rotates, which causes the housing 4 to rotate. The housing
4 is rotatably fixed to the engagement rings on the secondary side so that
the outer cog of the selected secondary planetary gear set is caused to
rotate. This rotation is transmitted through the planet wheels of the
selected secondary planetary gear set and to the respective sun wheel
which through sleeve 49 drives the drive cog 18. It will be appreciated
that those planetary gear sets in the primary and secondary sides which
have not been selected at any one time rotate on the respective annular
guides 65.
Should the rider wish to alter the gear ratio then this is achieved as
follows. A particular planetary gear set on either the primary or
secondary side is engaged by means of rotating the caming portions 38 to a
position where the respective pressure plate 5 is urged outwardly of the
assembly and in so doing the associated engagement ring 5 is urged along
the respective guides 16 towards the respective planetary gear set. The
teeth 28 of the engagement ring subsequently engage with the teeth 19 of
the planetary gear set so that that planetary gear is selected. The
engaged condition of the caming portions 37b, 37c and 37d and 38b, 38c and
38d for selection of a planetary gear set is shown in FIG. 9 and the
engagement condition for caming portions 37a and 38a is shown in FIG. 11.
Both the primary and secondary gear sets are engaged in this manner.
The rider is provided with two pairs of levers (not shown) on the
handlebars of the bicycle. One pair corresponds to the primary planetary
gear sets and the other corresponds to the secondary planetary gear sets.
In the assembly 1 the lowest gear of each side, either primary or
secondary, is the innermost planetary gear set. Thus if either of the
lowest gears is selected the innermost caming portions 37a and 38a will be
in an engaged condition so that the caming portions 38a co-operate with
the caming portions 37a to urge the respective engagement ring 21a into
engagement with the, associated planetary gear set. As shown in FIG. 11
the angular orientation of the raised portion 76 of the caming portion 38a
corresponds to that of the raised portion 75 of the portion 37a so that
the pressure plate 5a is urged axially outwards of the assembly 1.
Operation of one of the levers mounted on the handlebars will pull cable
66 which causes the lever 59 to rotate by a predetermined amount and thus
rotation of outer plate 8 in a clockwise direction will occur thanks to
the meshing of the teeth on lever 59 with teeth on disc 56. The three
pairs of the outermost pinions 40 and 41 are thus caused to rotate in
opposite senses, whilst the three pairs of pinions 42 and 43 meshing with
the racks of the inner plate 9 remain stationary. Such rotation of the
pinions 40 results in the caming portions 38a rotating to a position where
the raised portions 75 and 76 are no longer aligned and thus the pressure
plate 5a moves axially inwards to allow the engagement ring 21a to become
disengaged from the respective planetary gear set. In a disengaged
condition the raised portion 75 abuts against a shoulder 77 and raised
portion 76 abuts against a shoulder 74. At the same time rotation of the
pinions 41 causes the caming portions 38b to rotate to an engaged position
with respect to caming portions 37b (see FIG. 9) and thus the second
planetary gear set is engaged.
A further pull on cable 66 by way of the handlebar mounted lever will
engage the lug 60, which is attached to the lever 59, with a recess
provided in the aperture 78 provided in the inner plate 9. Thus both the
inner plate 9 and the outer plate 8 are caused to rotate anti-clockwise so
that the pinion pairs 40 and 41 are rotated in the opposite senses to
which they were rotated by selection of the second gear and the pinion
pairs 42 and 43 are rotated in opposite senses to each other. This
anti-clockwise rotation of the plates will result in the disengagement of
the second gear and engagement of the third gear, the caming portions
corresponding to third gear adopting an engaged condition. It will be
appreciated that on selection of third gear that first and fourth gears
remain disengaged and in particular the extent of rotation of the outer
plate on selection of the third gear is not sufficient to re-engage first
gear and thus the raised portions 75 and 76 remain unaligned.
A further pull on cable 66 will cause plates 8 and 9 to again rotate
anti-clockwise so that the caming portions corresponding to the third gear
are rotated to adopt a disengaged condition and the caming portions
corresponding to the fourth gear are rotated to adopt an engaged
condition. It will again be appreciated that this further anti-clockwise
rotation of the plate 8 is not sufficient to realign the caming portions
corresponding to the first gear set into an engaged condition.
It is also important to note that the caming portions corresponding to
second, third and fourth gears are phased i.e. set at different stages of
the respective engaged and disengaged cycles of the caring portions to
ensure that only one of those gears is engaged at any one time.
Since the assembly 1 comprises four sets of primary gears and four sets of
secondary gears a total of sixteen gear ratios are possible.
Springs 23 (located on the inner surface of the inner plate 9) are attached
at one end to the plate 9 and at the other to lugs 22 (projecting
outwardly from the end portion 70) and a spring 61 is attached at one end
to the outer plate 8 and at the other to the lever 59 so that a returning
force is provided on controlled release of cable 66 to reselect gear sets
in reverse order by the second lever (not shown) mounted on the
handlebars.
Although not shown in the accompanying drawings it may be desirable to
provide resilient return means for each gear set selection arrangement
which acts to urge each engagement ring 21 axially away from the
respective planetary gear set so as to ensure disengagement when the
caming portions adopt a disengaged condition.
It will be appreciated that although the inventive assembly 1 comprises a
plurality of primary gear sets and a plurality of secondary gear sets a
modified embodiment may comprise a single primary (or secondary) planetary
gear set and a plurality of secondary (or primary) planetary gear sets.
*
