Note: Descriptions are shown in the official language in which they were submitted.
~Q39977
' Thls invention relates to improvements in the
apparatu~ described in ~y Canadian Patent Application Serial No.
202,052 filed June 10, 1974.
Background of the Invention
Large ring gears such as those used in final drives
or in transmissions are usually supplied with peripheral
external splines which are intended to engage similar splines .
provided on an internal peripheral surface of the housing
within which the ring gear is mounted. Conventionally, retain-
ing rings or tab means are provided on the housing to prevent
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axial movement of the ring gear. The torque reaction produced
by planetating pinions orbiting within the ring gear is carried
by the splines provided in the housing.
Ring gears are usually formed from high-strength
alloy steel which has ~een hardened for wear resistance and
strength. On the contrary, the housing or gear case is normally ~~ ~
manufactured from a softer material such as cast steel. -
Consequently, the torque load application to the housing splines
results in time in wear or deformation of the splines in the
~0 housing but not on the splines provided on the ring gear. Such
wear or deformation can result in backlash, not only in the
immediate connection but in the gear train transmitting power
to the ring gear and in some cases in a complete failure of $.
the housing splines.
Inasmuch as final drives and transmission housings `
are extremely expensive, especially in large earth moving
machinery and the like, methods of repair and salvage have
been devised for rejuvenating a worn ring gear-housing assembly.
One method which has been used involves the building up of ,
worn housing spline teeth by means of welding followed by
remachining of such spline teeth on the ring gear and the ~ ;
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housing to provide proper mating. This procedure involves ~ .
considerable time and expense and requires large and ` -.
specialized machine tools.
It is an object of this invention to provide a
new ring gear-housing combination wherein the ring gear is ~ -
retained within the housing by inexpensive, easily replaceable .
means.
To this end the invention consists of a ring gear .
assembly comprising: a ring gear having peripherally :
disposed te~ h means for engaging means of a drive mechanism,
housing means for supporting said ring gear, said ring year . .
of relatively harder material than said housing means and ~- ~
having a first peripheral surface contiguous with a corres- :
ponding second peripheral surface of said housing means, :
said first and second peripheral surfaces forming an annular
interface between said ring gear and said housing means, said
first peripheral surface having a first recess means therein,
said second peripheral surface having second recess means ;:
therein, corresponding to and aligned with said first recess .
2Q means, said first and second recess means forming aperture ~ `
means, connecting element means disposed in said aperture ~: ~
means f~r limiting movement of said ring gear relative . .
said housing, keeper means mounted upon a portion of said
housing means for limiting axial movement of said connecting .
elements means and said ring gear in at least one direction, ~-
said first recess means including a plurality of segmental
recesses in said first peripheral surface, said second
recess means including a plurality of segmental recesses .
in said second peripheral surface, and wherein said
3Q connecting element means include a hardened circular pin
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member having a semi-circular portion for co-acting with :
each of said segmental recesses and wherein each of said
segmental recesses has a diametric dimension greater than
that of said circular pin member, and a depth substantially -
equal to the radius of said circular pin member. ~
Other features of an embodiment of the invention ~ .
will become apparent from the following description. -
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B~ie~'Descrip'tlon of the D~awings ~ '
'Fig, 1 is a partial elevation view of a ring gear _
equipped final drive housing'according to the prior application
mentioned above;
Fig. 2 is an enlarged partial view of a portion of
the ring gear-housing shown in Fig. 1
Fig. 3 is a sectional view taken along the line
III-III in Fig. 2;
Fig. 4 is an enlarged elevation similar to Fig. 2
but showing an alternate context, also as shown in the prior ` '
application;
Fig. 5 is a sectional view taken along the line
V-V in Fig. 4;
~ Fig. 6 is a view similar to Fig. 4 but showing the
enlarged recess configuration of the preferred embodiment
of the present invention; and ;'
Fig. 7 is an enlarged partial view of Fig. 6 showing
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a set of aligned recesses and an installed drive pin.
Detailed Description
With reference to Fig. l in the drawings, a ring
gear-housing assembly or combination is shown generally at 10.
Internally of the rin8 gear, is disposed a planetary drive
mechanism 12. The ring gear element of the combination is
shown at 14. It consists of an annular ring having gear teeth
15 formed on an internal peripheral portion thereof. With ~,;
reference to Fig. 2, it will be seen that the ring gear is
also provided with a plurality of spline teeth 16 formed on
the external peripheral surface thereof. The housing element
of the combination, for instance a final drive housing, is
shown at 18. The housing portion includes an internally '''
splined portion having spline teeth 20 adapted for torque load -~
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Supporting engagement with the splines 16 of the ring gear. ~ ~
The planetary drive mechanism 12 includes a ;~ ;
plurality of pinion gears 24 which are carried upon equally
angularly spaced shaft means 26 and which are adapted for ;
engagement wlth the teeth 15 of the ring gear. The shafts 26
are fixed for rotation with a common carrier 31. A sun gear
28 is rotatably supported upon a tubular input drive shaft 30
in which is concentrically journalled an axle 32. The teeth `-~
of the sun gear 28 mesh with the teeth of each of the
planetating gears 24.
Upon rotation of the sun gear 28, the planetary gears
24 orbit around the interior of the ring gear in meshing ~`
relation to the teeth 15 to drive the planet carrier.31 to
cause rotation of an output shaft (not shown) connected
thereto.
After a given period of use, the hardened spline
teeth of the ring gear gradually wear down the relatively soft -
spline teeth 20 of the housing 18 and eventually cause back- `
lash or failure such that either replacëment of the housing
or repair thereof is required. Repair of the assemblage may
be readily accomplished.
In the case of a conventional splined ring gear- -
housing assembly which is not equipped with the present drive
pin and aperture means, the first repair step is to remove
the ring gear 14 from the housing 18. Next, a plurality of
semi-circular recesses 34 (see Figs. 2 and 3) are ground into
the outer peripheral splined surface of the ring gear. Sub-
sequently, the ring gear is reinstalled within the housing. `
Next, complementary semi-circular recesses 35 are drilled into
the housing 18 to form with the ring gear semi-circular re¢esses ~;
a plurality of circular apertures which span the peripheral
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i~terace between the ring gear and the housing. Hardened
drive pins 36 are then placed within the circular ape~tures
for drivlng, load supporting connection between the ring gear
and the housing. Finally, in order to prevent axial movement
of the pins or the ring gear, keeper plates 37 are installed
in covering relation to the end portions of the pins. The
keeper plates are secured to the housing by means of a pair
of cap screws 38 and locking means 39, or the like.
Figs. 4 and 5 of the drawings illustrate the
apparatus as it relates to an original article of manufacture.
That is, instead of adapting the device to the repair of a
splined ring gear-housing assembly, it can be used as an
original connection means in lieu of the previously utilized ;
splined connections. As shown, a ring gear 40 is provided with
a plurality of teeth 42 on the inner peripheral surface thereof
and is provided with a substantially smooth external peripheral
surface 44. Final drive casing or housing 46 is also provided
with a smooth inner peripheral surface 48 which mates with the
surface 44 and with a plurality of threaded holes 50. The
hardened ring gear 40 is provided with a plurality of semi- ~ -
circular recesses 52 which are machined therein and which are
used as guides, after installation of the ring gear, for
drilling complementary semi-circular recesses 54 in the housing
46. A drive pin 56 is installed in each of the holes formed
by the complementary recesses 52 and 54 to drivingly connect
the ring gear to the housing 46 as described with reference
to Figs. 2 and 3. A keeper plate 58 is then secured to the
housing 46 by means of a pair of bolts 60 to retain the pins 56
axially within the respective holes and to constrain axial move-
ment of the ring gear relative to the housing.
Initial installation of the ring gear 40 within
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the housing 46 first involves the formation of the semi
circular recesses 52 within the outer peripheral surface of
the ring gear 40. Next, the ring gear is installed within the
inner surface 48 of the housing. The semi-circular recesses
54 in the housing are drilled using the recesses 52 as guides -
so as to provide circular apertures spanning the peripheral
interface between the ring gear and the housing. The drive -~
pins 56 are then installed within the circular apertures and
the keeper plates 54 are affixed.
Even the`improved ring gear-housing combination is
sub~ect to wear after prolonged use. The drive pins 56, -
continually bearing against the recesses 54 can wallow out
such recesses such that a repair or salvage operation is
required. With concurrent reference to Figs. 4 and 5, it is `
apparent that such repair of the assemb:Lage could be readily
accomplished by removing the pins 56 from between the ring
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gear and the housing, removing the ring gear from the housing, `
rotating the ring gear so that the semi-circular recesses 52
would be disposed in angularly spaced relation to the recesses
54 within the housing, drilling new semi-circular recesses 64
(shown in phantom), to complement the repositioned recesses
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in the ring gear so as to again form circular apertures, and
reinstalling the drive plns and keeper plates 58, as previously -
described. `
Figs. 6 and 7 illustrate a modified form of the
apparatus according to the present invention, particularly
adaptable for field installation where precise tolerances are `~
difficult to meet. As shown, a ring gear 40' is provided with
a plurality of teeth 42' on the inner peripheral surface
thereof and is provided with a substantially smooth external ~-
peripheral surface 44'. A final drive housing 46' is also
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provided with a smooth inner peripheral surface 48' which mates
with the surface 44'. The hardened ring gear 40' is provided
with a plurality of semi-circular recesses 52' somewhat -
similar to the recesses 52 shown in Fig. 4 except that the
diameters of the recesses 52' are larger than that of the
drive pins 56. Complementary enlarged diameter recesses 54' -
are also provided along the peripheral portion 48' of the
housing 46'. As in the case of the Fig. 4 embodiment, a keeper
plate 58 may be secured to the housing 46' by means of a pair
of bolts 60 to retain the pins 56 axially within the holes
formed by the respective enlarged semi-circular recesses in
the housing and ring gear. ,,
It will be apparent from Figs. 6 and 7 that the
centers of radii of both the enlarged recesses 52' and 54'
are not coincident wlth the center of the drive pin 56' when
installed. It may also be seen from Fig. 6 of the drawings
that the leftward most set of complementary recesses 52', 54'
are angularly displaced with respect to one another by an
amount "a" where the complementary set of semi-circular '-
recesses shown on the rightward most portion of Fig. 6 are
not angularly displaced with respect to one another.
The structure of Figs. 6 and 7 has certain
advantages over that shown in Figs~ 4 and 5. In the Fig. 4 '
arrangement, wherein the semi-circular recesses 52 and 54 have
radii centers coincid-ent with those of the drive pins 56,
precise machining is paramount. Because of the precise
< machine tolerances required, each ring gear and housing
assembly must in fact be a matched set since any slight angular
displacement of the recesses 52 with respect to the recesses ~-
54 would result in a difficult or impossible installation of
the drive pins 56. As may readily be appreciated in Fig. 6,
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the pins 56 may readily be installed within the complementary
recesses 5~', 54' even though there may be some slight
misalignment thereof. The pins 56, when inserted, merely roll
into a stable position contiguous with points of tangency on
both of the enlarged recesses 52',54'. `
It is highly desirable from a parts replacement
standpoint to have a free interchange of parts so that any --
suitably dimensioned ring gear may be installed within a given
housing. It is also highly desirable to provide for the `;;
replacement of a ring gear quickly and efficiently in the field
with a minimum of expense and machining. In a field situation, -i
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where it is difficult to machine semi-circular recesses, such
as 52, 54, having diameters precisely equal to one half the
diameter of the drive pins 56, it is relatively easier to ~ -
machine enlarged diameter semi-circular recesses, such as 52',
54', where the ~olerances are not as critical.
In a typical installation of the Fig. 6 embodiment,
the ratio of radii of the semi-circular recesses with respect
to those of the drive pins will be of the order of .375 to ~
.246. The centers of the radii for the recesses would be `~-
offset with respect to the centers of ~he radii for the pins
such that the roots of the recesses would be substantially
tangent to the outer diameters of the pins. With such an
arrangement it would be possible to install the pins even i~ i~
there were a slight angular displacement between adjacent i ~i
recesses in the ring gear and housing. This would permit a
free interchange of parts in the field and would assure the
maintenance of little or no relative movement between the
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ring gear and housing since the pins would roll to center ;
themselves in the elongate holes formed by the complementary :~
recesses.
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' Another advantage realized by the Fig. 6 construction
is its shock absorbing capacity. An operational ring gear has
a propensity to ro~ate intermittently with respect to the
housing which contains it. In a conventional system, wherein
spline teeth are utilized to prevent such relative motion, the
flat surfaces of such spline teeth tend to "hammer" against
one another as the parts tend to rotate relatively and this
hammering accelerates wear. However, in the elongate hole
system of the instant Fig. 6 embodiment, the frictional
engagement between the hardened pin 56 and the enlarged --
recesses cause such pin to roll within the elongate hole when
the ring gear and the housing tend to relatively rotate. As
this occurs, the pin gradually absorbs the shock of the counter
rotation of the ring and housing.
'rhe method of repair of the embodiment of Fig. 6
would be essentially the same as that described with respect
to the round hole arrangement of Fig. 4.
While the invention has been described with particular
reference to a preferred embodiment, it is apparent that
variations and modifications are possible within the spirit
of the inventive concept. No limitation with respect to such
variations and modifications is intended, except by the purview
of the appended claims.
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