Note: Descriptions are shown in the official language in which they were submitted.
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This invention rela~es to a shift control mechanism
for a transmission to prevent the -transmissioM from being
shifted direc-tly from forward to reverse to vice versa.
Small vehicles, such as lawn tractors or riding lawn
mo~ers, frequently are provided with a small transmission having
a reverse, neutral, and one or a few forward speeds. If the
transmission is shifted by an operator directly from reverse to
a forward speed or from a forward speed to reverse, damage can
result to the components o:E the transmission or to other compo-
1~ nents of the drive train of the vehicle and the operator mayalso be injured by the sudden change `n direction.
The present invention provides a shift con-trol mecha~
nism or lockout mechanism which prevents the shift lever of the
transmission from being moved in a manner to shift the trans-
mission directly between a forward speed and reverse. The shift
control mechanism includes a lockout plate having an opening
through ~.~hich the shi~t lever of the transmission extends. The
opening is contoured with three ad~acent notches connected by a
common slot at common ends of the notches. The three notches
correspond to a reverse position, a neutral position, and a for-
ward speed posi-tion of the transmission when the shift lever is
ln a particular notch. A slider has two projections aligned with
the common slot, extending a dlstance sufflcient that the shift
lever cannot pass by elther of them when moved along the slo-t
without being moved down into one of the notches. The two pro-
jections are spaced apart a distance substantially equal to the
width of the notches and are located on either side of the neutral
notch when in a central position to which it is urged by springs
on each side thereof. The slider is mounted in a guide and is
limited ln movement in elther direct:ion from -the central position
by a distance approximately equal to one of the notches. Hence,
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it is not possible -to move the shit lever more than a diskance
to the next adjacent notch directly in one motion. Consequently,
the transmission cannot be shifted directly from forward to re-
verse or vice versa.
It is, therefore, a principal object of the invention
to provide a transmission ~hich cannot be shifted directly be-
tween forward and reverse conditions.
Another object of the invention is to provide a shift
control mechanism by means of ~hich;.a shift lever of a transmission
must be sh~-fted into neutral ~efore shifting into.reverse from
forward or into forward from reverse.
Many other objects and advantages of the invention will
be apparent from the following detailed description of a pre-
ferred embodiment thereof, reference being made to the accompany-
ing drawings, in which:
Fig. 1 is a somewhat schematic view in perspective of
a transmission embodying shift control mechanism adcording to the
invention;
E'~g. 2 i5 a front view in elevation~ with parts broken
away, of the transmission and .shift control mechanism of ~'ig~ 1;
Fig. 3 is a fragmentary v:iew taken along the line 3-3
o:E Fig. 2;
Fig. 4 is a fragmentary view in perspective, with parts
broken away and with parts in section ! of the shift control mech-
anism; and
Figs. 5 and 6 are schematic views in elevation of the
shift control mechanism shown in two different positions.
Referring to the drawings and particularly to Figs. 1-3,
a transmlssion embodying the invention is indicated at 10 and in-
3~ cludes a lower housing 12 to be mounted on a framework of a ve-
hicle and an upper housing 14. An input shaft~ extends downwardly
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below the hous:ing 12 and can be equipped With a suitable pulley or
sproc]~et by means of which it is driven from an engine of the ve~
hicle. The input shaft 16 has a bevel gear 18 within the trans-
mission which meshes with two driven ~evel gears 20 and 22 which
are rotatably mounted on an ou-tput shaft 24~ The shaft 24 has a
sprocket or pulley 26 by means of which an axle of the vehicle is
driven.
The output shaft 24 is driven in one direction when the
bevel gear 20 is connected to it and is driven in the opposite
direction when the bevel gear 22 is connected to it. The direc-
tion depends upon the direction of rotation of the input shaEt 16.
It wil.l be assumed in this disclosure that the bevel gear 2Q drives
the vehicle at a single forward speed and that the bevel gear 22
drives the vehicle at a single reverse speedr
A clutch dog or shift dog 28 is loca-ted between the gears
20 and 22 on the shaft 24 and is keyed thereto b~ a ke~ 3Q which
enables slidable hut non-rotatable movement of the clutch dog 28
on the shaft 24. The clutch dog 28 connects the bevel gear 20 to
the shaft for rotation therewith when moved to the left with lugs
32 extending into recesses 34 i.n the gear 20. Similarly, the
bevel gear 22 is connected to the shaft for rotation therewith
when the clutch dog 28 is moved to the right with lugs 36 extend-
ing into recesses 38 in the gear 22.
The clutch dog 28 has a central annular groove 40 which
receives pins 42 and 44 extending from arms 46 and 48 of a shifter
fork 50. The shifter fork 50 has a vertical shaft 52 having a
lower end rokatably supported in a recess in the bottom of the
lower housing 12 and an upper end extending through an opening 54
in the upper housing 14. When the shaf-t 52 is turned a~out a
vertical a~is, it moves the clutch dog 28 between its three posi-
tions, one engaged with the bevel gear 20, a neutral posi-t.i.on as
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shown in Figs. 2, and a third position engaged with the bevel
gear 22. The shi~ter fork 50 is turned by a shift lever 56
hav.i~g a flattened end 58 received in a recess 60 in the upper
end of the shifter ~ork 50 and pivotally connected -thereto by a
pin 62 having an end extending well beyond th.e shaft 52. The
sh.ift lever 56 is urged down~ardly by a spring 64 having an in-
termediate coil 66 received on the pin 62, having a bent upper
end h8 received in a groove 70 of the shaft 52, and having a
curved end 70 received over the shift lever 56. The outer end
of the shift lever 56 has a suita~le kno~ or handle 72.
An ~ntermed.~ate portion of the shift lever 56 extends
through a generally E-shaped openîng 74 in a lockout plate or
member 76 which is mounted on the front of the upper housing 14
by machine screws 78 or the like. The opening 74 has a generally
horizontal upper slot 80 communicating with upper ends of three
notches 82, 84, and 86. ~hen the shift lever 56 is in the first,
outer notch 82, the shifter fork 50 is turned so th.at the clutch
dog 28 engages the gear 2Q to move the vehicle at the sinyle for
ward speed, ~hen the shift lever 56 i8 in the second! central
notch 84, the shifter :fork 50 holds the clutch dog 28 in the
neutral position. When the shift lever 56 is in the third! outer
notch 86, the shifter fork 50 is turned so that the dog 28 en-
gages the bevel gear 22 to moye the vehicle at th.e single reverse
speed. With this arrangement, it would be possible for the opera~
tor to move the dog 28 directly from engagement with one of the
gears 20 and 22 into engage~ient with the other of the gears 20
and 22. This could damage components of the transmission or other
components of the drive train of the vehicle. It could also injure
the operator by the sudden reverse change in direction of the ve-..;~ .
hicle.
To prevent such direct shifting! a slider 88 and a guide
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bar 90 are provided. I'he slider 88 has two projection5 92 and
94 projecting into alignment with the slot ~0 of the opening 74.
The projections 92 and 94 ~re of sufficient size so that the
shift lever 56 cannot be moved from one of the notches 82-86 to
any other one of the notches through, the slot 80 wi-thout engaging
one of the pro~ections. Also, the projections 92 and 94 are
spaced apart about the width of one of the notches 82-86., with
the width of the notche~ and the spacing of the projections be-
ing sufficient to receive the shift lever 56. The slider 88 has
an arcuate notch 95 bet~een the projections 92 and 94 which can
receive the shift lever 56. Above the projections 92 and 94,the
slider has a groove 96 and a ridge 98, with a shorter groove 100
and a shorter ridge 102 thereabove.
The guide 90 has fastening tabs 104 and 106 at the
ends by means of which the yuide is attached to the lockout plate
76 ~y rivets or other suitable fas-teners 108. The tabs 106 also
act as end stops for the slider 88 when corltacted by the pro-
jections 92 and 94 (see Fig~ 5). The guide 90 has a ridge 110
which extends between the tabs 104 and 106 and is received in the
groove 96 of the slider 88. ~bove the ridge 110 is a groove 112
which also extends between the -tabs and receives -the ridge 98 of
the slider 88. This cooperation of the ridges and grooves guides
the slider ~8 and prevents cocking of -~he projections 92 and 94.
The guide 90 has a second ridye 114 above ,the groove 112 which
extends into the short groove 10 a of -~he slider and also has a
longer and larger groove 116 above the ridge 114 which extends the
full length of -the guide 90 to positions beyond the inner edges
of the tabs 104 and 106. The slider ridge 102 is in this groove.
~oil springs 118 and 120 are also located in the longer
and larger groove 116 with outer ends abutt:ing the ends of the
groove 116 and inner ends abutting the short ridge 102 of the
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of the slider 88. The springs 118 and 120 urge -the slider 88
toward the cen-tral, neutral position of Fig. 2 except when forced
out of position by enga~ement of the shift lever 56 with one of
the projections 92 and 94.
The operation of the lockout mechanism will be discussed
particularly with reference to F.igs. 5 and 6. Assume that the
shift lever 56 is in the reverse notch 86, as sh.own in dotted lines
of Fig. 6. To shift the transmission, the operator then raises
the shift lever 56, overcoming the force of the spring 64, and
moves the lever into the elon~ate slot 80. He then moves the
lever horizontally toward the next notch and in doing so contacts
the projection 94, forcing the slider 88 toward the left and over-
coming the force of th.e spring 118. This movement continues un-
til the leve~ 56 reaches the solid line position in Fig. 5, over
the neutral notch 84. ~t this Point, the slider 88 an~ specifi-
cally the projection 92 contacts. the ta~ 10~ of th.e guide 90 and
can move no farther. The operator then must move the lever 56 down
into the notch 84~ at ~hich time the springs 118 and 120 move the
slider 88 hack into the ne.utr~l position, as shown in Fi~. 2.
~o sh:L:Et the trans.mission to the Eorward speed, the op-
erator must then raise the lever 56 a second time~ moving it into
the arcuate notch 95 of the slider. The opera-tor then moves the
lever 56 horizontally to~ards the .first speed notch 82. At this
time the lever engages the projecti~on 92 and moves the slider 88
again to the left. The lever is over the notch 82 by the time the
slider 88 rea~hes its end position and the operator can then move
the lever 56 down into the for~ard speed no-tch 82~ as shown in
dotted lines in Fig. 6.
If the operator wishes to shift the transmission Erom
forward to reverse ! the slider acts in -the s.ame manner in the op-
posite direction. Hence, it will be seen that in an~ case, the
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lever 56 must be moved lnto -the neutral position.when shiftlng
from reverse to forward or from.forward to reverse.
A neutral start switch 122 can also be mounted on the
lockout plate 76 by rivets 124. The swi-tch 122 has l~wer -terminals
126 to which conductors of an electric starting system of -the ve-
hicle can be connected. The switch also has a -tab 128 ex-tending
into the neutral notch 84 of the plate 76 ! as shown in Figs. 5
and 6. When the sh.ift lever 56 is in the neutral notch 84, lt
depresses the tab 128 and operates the switch in a ~anner to en~
able the starting system to function so that the engine can be
started. In any other position of the lever 56, the tab 128 is
up and the engine cannot ~e started.
