Transmission mainshaft gear retainer

A twin countershaft transmission (100) is provided having axially adjacent floating mainshaft gears such as referenced by numerals (30) and (32) whose axial thrust when engaged is transmitted to the mainshaft (48) rather than to the adjacent gear by means of gears (30) and (32) having respective flanges (42) and (44) that extend radially inwardly between their axially spaced-apart thrust washers (46, 50, 52) splined to mainshaft (48).

INTRODUCTION 
This invention relates generally to an improved gear retainer thrust means 
for transferring axial thrust of a floating mainshaft gear being clutched 
to a transmission mainshaft rather than to an adjacent mainshaft gear and 
more particularly to such thrust means comprising a combination of 
components that are simple in design and economical to manufacture and 
assemble in addition to enabling axial thrust to be transmitted to the 
mainshaft without relative rotation between the mainshaft gear and the 
particular component transmitting axial thrust therefrom to the mainshaft. 
BACKGROUND OF THE INVENTION 
Transmissions featuring floating transmission mainshaft gears such as 
associated with twin countershaft transmissions are well know and examples 
of which can be found in U.S. Pat. Nos. 3,237,472; 3,238,613; 3,425,290; 
and 3,885,446, the disclosures of which are incorporated herein by 
reference. 
Such transmissions generally feature a plurality of floating mainshaft 
gears that encircle the mainshaft and are supported and driven by 
countershaft gears, typically two countershaft gears, that are mounted on 
a pair of countershafts disposed on opposite sides of the mainshaft. 
The mainshaft gears are characteristically clutched to the mainshaft by 
means of a clutch mechanism that slides along external splines extending 
axially along the mainshaft and has radially inwardly extending teeth or 
splines that engage internal teeth or splines on the mainshaft gear so as 
to cause rotation of the mainshaft when the mainshaft gear is clutched 
thereto. 
A problem long ago recognized has been the potential transfer of axial 
thrust to a mainshaft gear being clutched due to their characteristic 
close proximity to each other. In view of such, a variety of solutions 
have been devised over past years for the transmitting axial thrust 
imparted by an axially moving clutch to the mainshaft rather than to the 
gear adjacent the gear being clutched to the mainshaft. 
Such solutions have generally been in the form of gear retainer(s) of one 
type or another that characteristically limit axial movement of the 
mainshaft gears to prevent them from engaging each other whether or not 
one of them is being clutched to the mainshaft. 
One example of a retainer assembly for limiting axial movement of a 
transmission gear is disclosed in U.S. Pat. No. 2,397,905, the disclosure 
of which is incorporated herein by reference. Here however, a costly and 
expensive pivotal woodruff key is required to lock a thrust collar onto 
external splines of the mainshaft to prevent a gear from moving axially. 
An example of a splined thrust washer for transmitting axial thrust from a 
gear set to a propeller drive shaft is disclosed in U.S. Pat. No. 
3,894,621, the disclosure of which is incorporated herein by reference. 
Here, a splined thrust washer (52) is slid axially along the shaft splines 
to a transverse groove adjacent a stepped shoulder on the shaft and is 
held in place against the shoulder by a splined collar (30). Thrust washer 
(52) is operative to transmit axial thrust of only one gear to the 
propeller shaft and in addition to requiring the use of Collar (30), also 
requires costly and complex machining of a stepped configuration to the 
Propeller shaft exterior. 
A more recent example of a transmission mainshaft gear retainer for 
preventing axial movement of two closely spaced gears to prevent transfer 
of axial thrust force therebetween is disclosed in U.S. Pat. No. 
4,034,620, the disclosure of which is incorporated herein by reference. 
Here a thrust ring (104) is splined to the mainshaft between two adjacent 
gears and is held in place by means of snap rings (108, 110) on opposite 
sides thereof. The gears are further required to have costly and complex 
mating tongue and groove configurations that operate in conjunction with 
an additional snap ring (102) to limit movement of the gears away from 
each other. 
In view of the above, a need exists to provide a simple and low cost means 
for transmitting axial thrust imparted by a clutch to a floating mainshaft 
gear being clutched to the mainshaft rather than to an adjoining gear by 
retaining means that can be easily assembled into the mainshaft and rotate 
in unison with the mainshaft gear being clutched. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of this invention to provide means to transmit 
axial thrust from a transmission mainshaft gear being clutched to the 
mainshaft. 
It is another object of this invention to provide axial thrust means for 
directing axial thrust imparted to a transmission floating mainshaft gear 
by a clutch mechanism to the mainshaft rather than to an adjacent 
mainshaft gear in close proximity thereto. 
It is still another object of this invention to provide a transmission 
having floating mainshaft gears with an improved means for transmitting to 
the mainshaft axial thrust imparted to a mainshaft gear being clutched to 
the mainshaft by a clutch mechanism rather than to an adjacent mainshaft 
gear. 
It is yet another object of this invention to provide means for 
transmitting axial thrust of a transmission mainshaft gear to the 
mainshaft that is simple in design and economical to manufacture and 
assemble and rotates in unison with the mainshaft gear being clutched to 
the mainshaft.

DESCRIPTION OF SOME PREFERRED EMBODIMENTS 
Transmission 100 is a twin countershaft type transmission similar to 
transmission 10 described in detail in U.S. Pat. Nos. 3,105,395 and 
4,034,620, assigned to the assignee of the present invention, and whose 
operation and many of whose parts will not therefore be described herein 
in detail other than to the extent of the improvement imparted thereto by 
the axial thrust means of the invention hereinafter described in detail. 
In FIG. 1, transmission 100 has an input shaft 14 that is rotated by an 
engine, commonly a vehicular internal combustion engine. Input shaft 14 in 
operative in turn carry countershaft gears such as 20 and 20a having 
external teeth that engage, support, and rotate floating mainshaft gears 
such as 30 and 32 that encircle mainshaft 48 and cause shaft 48 to rotate 
and rotate output shaft 24 when clutched to mainshaft 48 by axial slidable 
clutches such as 78 and 80. 
As can be seen in FIG. 1, input shaft 14, twin countershafts 21 and 21a, 
mainshaft 48, and output shaft 24 are all journaled for rotation on 
housing 12. 
It is readily apparent in FIG. 1 that floating mainshaft gears 30 and 32 
are closely adjacent and might touch each other in response to axial 
movement of either one towards the other such as when axial thrust is 
imparted therefrom when being clutched to mainshaft 48 by clutches 78 and 
80 as hereinafter described in more detail with respect to FIGS. 2A and 
2B. 
As shown in FIG. 2B, mainshaft 48 is provided with a plurality of 
substantially uniformly spaced splines that extend axially along the outer 
surface thereof and whose alternate grooves are referenced by numeral 66 
and whose alternate teeth are referenced by numeral 67. 
Floating mainshaft gear 30 has internal teeth 40 that are engaged by 
external teeth 38 of clutch 78 when clutch 78 is moved axially towards the 
viewer's right in FIG. 2A when clutch 78 is moved axially in response to a 
shift command to clutch gear 32 to mainshaft 48 so as to rotate shaft 48 
and output shaft 24 at some predetermined speed. 
Similarly, floating mainshaft gear 30 becomes coupled or clutched to 
mainshaft 48 when clutch 80 is moved axially towards the viewer's left in 
FIG. 2A to cause engagement between external teeth 34 of clutch 80 and 
internal teeth 36 of gear 30. 
It can readily be seen that without some type of means for maintaining an 
axial-spaced relationship between gears 30 and 32 that they could touch 
each other and transmit undesirable axial thrust from one to the other 
imparted to the one being clutched to the mainshaft by the clutch 
mechanism. 
The axial thrust means of the present invention shown in FIGS. 1A and 2B 
provides the means for transferring the axial thrust to the mainshaft 
rather than to the adjacent floating mainshaft gear which itself is being 
rotated by a countershaft gear. 
In FIG. 2A, the axial thrust means is provided by gear 30 having a flange 
42 that extends towards but does not touch external spline teeth 67 on 
shaft 48. Likewise, gear 32 is provided with a flange 44 that extends 
towards but does not touch external spline teeth 67 on shaft 48. 
A first thrust washer 46 is disposed in an annular groove 58 in shaft 48 
that cuts through and is substantially transverse to spline teeth 67. 
Flanges 42 and 42 each have respective thrust surfaces 51, 53 and 57, 59 on 
opposite sides thereof that face away from each other in substantial 
parallel relationship with mainshaft 48. 
Thrust surface 53 of flange 42 is operative to engage washer 46 when gear 
30 is clutched to mainshaft 48 and reacts with the edge of groove 58 to 
transmit axial thrust to shaft 48. 
Similarly , thrust surface 57 of flange 44 is operative to engage washer 46 
and enable washer 46 to react and transmit axial thrust to shaft 48 by 
engaging an opposite edge of groove 58. 
A second thrust washer 52 is disposed in an annular groove 56 in the outer 
surface of mainshaft 48 that is substantially parallel with groove 46 and 
axially spaced therefrom to position thrust washer 52 adjacent thrust 
surface 51 of flange 42 of gear 30. 
A third thrust washer 50 is disposed in an annular groove 60 in the outer 
surface of mainshaft 48 that is substantially parallel to groove 46 and is 
axially spaced therefrom to position washer 50 adjacent thrust surface 59 
on flange 44 of gear 32. 
Thrust washers 46, 50 and 52 respectively encircle mainshaft 48 and are 
axially spaced-apart from each other a distance predetermined to enable 
gears 30 and 32 to rotate relative shaft 48 when neither is clutched 
thereto and to enable the one being clutched to shaft 48 to engage and 
transfer axial thrust to thrust washer 46 which in turn will react with an 
edge of groove 58 to enable the axial thrust to be transferred to shaft 48 
rather than to the mainshaft gear in close axial proximity thereto. 
It is highly preferable that thrust washers 46, 50 and 52 rotate in unison 
with mainshaft 48 so that they do not rotate relative the mainshaft gear 
clutched to the mainshaft. 
Although other means may be used to secure thrust washers 46, 50 and 52 to 
shaft 48, they are preferably secured thereto by their respectively 
including internal teeth or splines that are substantially uniformly 
spaced circumferentially about their respective central openings such as 
alternate grooves 64 and alternate teeth 69 shown in FIG. 2B. 
Grooves 64 and teeth 69 of washer 46, 50 and 52 are adapted to mate with 
teeth 67 and grooves 66 of the external splines about shaft 48 so that 
internal grooves 64 of washers 46, 50 and 52 can slide axially along 
exterior splined teeth 67 of shaft 48 to enable the washer to be moved 
axially therealong until positioned in their respective retaining grooves 
58, 60 and 56 and then respectively rotated about the grooves until 
internal grooves 64 of washers 46, 50 and 52 are in substantial alignment 
with external spline grooves 66 in shaft 48, at which point, a key 62 is 
inserted axially therethrough to secure the thrust washers to shaft 48. 
Thrust washers 46, 50 and 52 are made from any material having the 
compatibility, corrosion resistance, strength, durability, and wear 
resistance characteristics desired and provide a simple and economical 
means of transferring to a mainshaft axial thrust of mainshaft gear being 
clutched thereto in response to a shift command. 
Although they may differ from each other in structural features provided 
they operate in the manner herein described, thrust washers 46, 50 and 52 
are preferably substantially identical to each other as well as being 
characteristically disposed in a substantially symmetrical spatial 
arrangement along the central rotational axis of the mainshaft.