Gear shift device for vehicles

A gear shift device for vehicles of the type including a reverse speed stage is disclosed. The device is provided with a rotation inhibiting member for inhibiting rotation of a gear shift drum when the latter is caused to turn to the reverse position. The rotation inhibiting member is displaced to the inhibition releasing position by operation of the remote control member only when a vehicle is kept in a braked state, thereby permitting the gear shift drum to turn to the reverse position. With this arrangement, shifting to the reverse speed stage during forward travelling of the vehicle is prevented reliably.

BACKGROUND OF THE INVENTION 
The present invention relates to a gear shift device for vehicles and more 
particularly to a gear shift device for vehicles movable in the rearward 
direction such as motor tricycles and four-wheeled automobiles like sand 
buggy car and its object resides in providing a gear shift device for 
vehicles which enables a reverse speed stage to be established only when 
braking operation is performed. 
SUMMARY OF THE INVENTION 
To accomplish the above object, according to the present invention, there 
is provided a gear shift device for vehicles wherein a gear shift drum is 
provided thereon with a guide groove for a reverse speed stage into which 
groove a reverse shift fork is engaged, a rotation inhibiting member for 
inhibiting rotation of the gear shift drum to the reverse position is 
disposed displaceably between the rotation inhibiting position and the 
inhibition releasing position, the rotation inhibiting member being 
normally urged toward the rotation inhibiting position, and a remote 
control member is incorporated in a brake actuating system in such a 
manner that it is allowed to operate, only when the vehicle is kept in a 
braked state, so as to displace the rotation inhibiting member from the 
rotation inhibiting position to the inhibition releasing position. 
With this arrangement, a brake actuating member is forced to be operated 
necessarily when a driver wants to move the vehicle rearwardly whereby 
shifting to the reverse speed stage during forward running of the vehicle 
can be prevented reliably. 
The above and other objects, features and advantages of the invention will 
become more clearly apparent from reading of the following description of 
embodiments in conjunction with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Now, the present invention will be described in a greater detail hereunder 
with reference to the accompanying drawings which illustrate some 
preferred embodiments thereof as mounted on a sand buggy car. 
Referring first to FIG. 1, a pair of left and right front wheels 8 are 
rotatably mounted on the front part of a car body 1 so that they are 
steered by a steering handle 2. Further, a pair of left and right rear 
wheels 4 are rotatably mounted on the rear part of the car body 1. The 
steering handle 2 is provided with grips 5 and 6 at both the outermost end 
parts thereof and a front wheel brake lever 7 adapted to be actuated by a 
right hand of a driver placed on the righthand grip 6 and a rear wheel 
brake lever 8 adapted to be actuated by a left hand of the same placed on 
the lefthand grip 5 are turnably supported on the steering handle 2, 
respectively. The car body 1 has a seat 9 mounted on that upper part 
thereof located in the proximity of the rear end thereof on which the 
driver is to sit in a straddling manner. Further, steps 10 are projected 
outwardly from both the side walls of the body at the lower, 
longitudinally central part thereof. An engine 11 is mounted at the 
central part of the car body 1 and the driving force generated by the 
engine 11 is transmitted to both the front and rear wheels 3 and 4 via a 
power transmission mechanism which includes a gear shift device according 
to the invention and is equipped with an automatic centrifugal clutch or a 
fluid torque converter. 
FIG. 2 is a cross-sectional view of an essential part of the gear shift 
device of the invention. A gear shift drum 13 is rotatably supported on a 
crankcase 12 of the engine and guide grooves 14 and 15 for gear shifting 
of two forward speed stages and a guide groove 16 for a reverse speed 
stage are arranged in a curved manner on the outer periphery of the gear 
shift drum 13 in an axially-spaced relation from each other. Further, a 
guide shaft 17 is mounted on the crankcase 12 in parallel with the gear 
shift drum 13 and shift forks 18, 19 and 20 engaged into the guide grooves 
14, 15 and 16 are fitted onto the guide shaft 17 in an axially slidable 
manner. The gear shift drum 13 is caused to rotate in response to 
actuation of a speed changing pedal which is not shown in the drawings 
whereby the shift forks 18, 19 and 20 are selectively displaced on the 
guide shaft 17 in dependence on the amount of angular displacement of the 
gear shift drum 13. Selective displacement of the shift forks 18, 19 and 
20 causes a gear train to be established for a corresponding speed stage 
which are not shown in the drawings. Particularly, displacement of the 
reverse shift fork 20 causes a reverse speed stage gear train to be 
established. 
Referring also to FIG. 3, the gear shift drum 13 is coaxially and 
integrally mounted with a disc-shaped rotation limiting member 21 at one 
end thereof and the rotation limiting member 21 has a limiting projection 
22 projected outwardly in the radial direction. 
On the other hand, a rotational shaft 23 which has an axis extending in 
parallel with the gear shift drum 13 is rotatably mounted on the crankcase 
12 and a rotation inhibiting member 25 which is provided with a rotation 
inhibiting arm 24 extending toward the rotation limiting member 21 is 
fixedly secured to the rotational shaft 23. The rotation inhibiting arm 24 
is so arranged as to come in abutment against the limiting projection 22 
of the rotation limiting member 21 on the lower side of a rotational 
direction 26 toward the reverse speed stage (see FIG. 3) just before the 
gear shift drum 13 rotates to fall into the reverse position, whereas the 
rotation inhibiting arm 24 is turnable between a rotation inhibiting 
position 27 where rotation of the rotation limiting member 21 in the 
direction 26 is inhibited due to abutment of the rotational inhibiting arm 
24 against the limiting projection 22 and an inhibition releasing position 
28 where rotation of the rotation limiting member 21 in the direction 26 
is permitted without causing abutment of the rotation inhibiting arm 24 
against the limiting projection 22 (as identified by phantom lines in FIG. 
3). It should be noted that the rotational shaft 23 is normally urged to 
rotate toward the rotation inhibiting position 27 under the effect of 
resilient force of a coil spring 29 which is mounted around the rotational 
shaft 23. 
An actuating arm 30 extends in a substantially opposite direction to the 
extending direction of the rotation inhibiting arm 24 with respect to the 
axis of the rotational shaft 23 and is fixedly secured at one end thereof 
to the one end of the rotational shaft 23 and a wire 31 is connected to 
the other end of the actuating arm 30. Specifically, the wire 31 extends 
from the other end of the actuating arm 30 in the same direction as that 
of rotation of the rotational shaft 23 toward the inhibition releasing 
position 28 from the rotation inhibiting position 27, and this wire is 
connected to a remote control member 32 (see FIG. 1) pivoted on the rear 
wheel brake lever 8. Accordingly, when a driver grips by his left hand the 
remote control member 32 and draws the wire 31, the rotational shaft 23 is 
caused to rotate in the clockwise direction as seen in FIG. 3 against 
resilient force of the coil spring 29 on the rotational shaft 23, and then 
the rotation inhibiting member 25 is correspondingly displaced from the 
rotation inhibiting position 27 to the inhibition releasing position 28. 
As illustrated in FIG. 4, a supporting member 33 is immovably mounted on 
the steering handle 2 at the position located in the proximity of the grip 
5 and the rear wheel brake lever 8 is carried on this supporting member 33 
to be turnable about a support shaft 34. As the rear wheel brake lever 8 
is turned toward the grip 5 by the left hand of the driver, a braking wire 
35 is pulled thereby to actuate the rear wheel braking mechanism (not 
shown). Turning movement of the brake lever 8 away from the grip 5 is 
restricted by abutment of an end face 37 of the braking lever 8 against a 
stopper face 36 of the supporting member 33. 
Referring also to FIGS. 5 to 7, the remote control member 32 is turnably 
mounted on the rear wheel braking lever 8 around the same axis as that of 
the lever 8. Specifically, the remote control member 32 has an inverted 
U-shaped cross-sectional configuration, which is fitted onto the rear 
wheel braking lever 8 from the side opposite to the grip 5 and is 
supported turnably about the shaft 34. Thus, the remote control member 32 
can be pivoted toward the grip 5 only when the rear wheel braking lever 8 
is actuated for braking operation, and the wire 31 can be pulled as the 
remote control member 32 is displaced toward the grip 5. Further, turning 
movement of the remote control member 32 away from the grip 5 is 
restricted by abutting against the stopper face 36 of the supporting 
member 33 in the same manner as described above with respect to the rear 
wheel braking lever 8. 
The remote control member 32 is formed with a hole 38 at the position 
located corresponding to the position assumed by the end face 37 of the 
rear wheel braking lever 8 when the latter carries out braking operation, 
into which hole one end of a substantially C-shaped locking piece 39 is 
fittable. The other end of the locking piece 39 is operatively held by 
means of a supporting pin 40 which immovably stands upright on the remote 
control member 32. Specifically, the other end of the locking piece 39 is 
wound around the supporting pin 40 so that it can be turnably held about 
the supporting pin 40 by fitting the ring-shaped other end of the locking 
piece 39 onto the supporting pin 40 and inserting a locking pin 43 through 
the hole 42 of the supporting pin 40 with a washer 41 interposed between 
the other end of the piece 39 and the locking pin 40. 
Next, operation of the gear shift device of the invention as constructed in 
the above-described manner will be described below. 
When a driver operates his sand buggy car to move rearwardly, he turns the 
rear wheel braking lever 8 toward the grip 5 with his left hand to perform 
braking operation. At this moment the remote control member 32 is placed 
in a condition turnable toward the grip 5. Thus, the wire 31 is pulled by 
turning the remote control member 32 whereby the rotation inhibiting 
member 25 is caused to turn from the rotation inhibiting position 27 to 
the inhibition releasing position 28. As a result, it becomes possible to 
rotate the gear shift drum 13 to the reverse position and thereby a gear 
train for reverse speed stage is established by performing shifting 
operation to the reverse position, which enables the sand buggy car to 
travel rearwardly. 
When he wishes to stop his sand buggy car in certain position, he actuates 
the rear wheel brake lever 8 toward the grip 5 and inserts the one end of 
the locking piece 39 into the hole 38 of the remote control member 32 
while holding the brake lever 8 in its brake effecting state. This causes 
the one end of the locking piece 39 to come into contact with the end face 
37 of the rear wheel brake lever 8. Since, at this moment, turning 
movement of the remote control member 32 away from the grip 5 is 
restricted by the stopper face 36 of the supporting member 33, the rear 
wheel brake lever 8 is kept in the turned state, that is, in the brake 
effecting state, by means of the locking piece 39. Accordingly, the rear 
braking mechanism is kept in the operative state even when the hand of the 
driver is removed from the rear wheel braking lever 8. 
Next, description will be made as to another embodiment of the present 
invention with reference to FIG. 8. 
In this embodiment a lost motion mechanism 44 is disposed between the 
actuating arm 30 and the wire 31. Specifically, the lost motion mechanism 
44 comprises a slot 45 formed on the actuating arm 30 in the direction of 
pulling of the wire 31 and an engagement piece 46 fixedly secured to the 
lower end of the wire 31 and displaceably engaged in the slot 45. This 
specific arrangement of the lost motion mechanism 44 assures that return 
movement of the rotational shaft 23 from the inhibition releasing position 
28 to the rotation inhibiting position 27 under the effect of resilient 
force of the coil spring 29 is carried out smoothly without any hindrance 
caused by resistance of the wire 31 during turning movement of the gear 
shift drum 21 from the reverse position to the neutral position or to the 
forward running position, that is, in the direction opposite to the 
rotational direction 26 for reverse speed stage. 
As a modification of the foregoing embodiment, the lost motion mechanism 
may be disposed between the actuating arm 30 and the rotational shaft 23. 
While the present invention has been described above with respect to 
preferred embodiments thereof, it should of course be understood that it 
should not be limited only to them but various changes or modifications 
may be made in any acceptable manner without departure from the scope of 
the invention which is determined only by the appended claims.