Throttle lever mechanism

A throttle lever mechanism in which both ends of a wire cable arranged in a curved manner are connected to a throttle valve opening/closing member of a carburetor and a first throttle lever, respectively, one end portion of an outer tube covering the wire cable is held in a stationary manner, the other end portion of the outer tube is coupled to a link member supported rotatably, and the link member is connected to a second throttle lever through a connecting rod movable within an elongated slot formed in the link member.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a throttle lever mechanism and more 
particularly to a so-called failure proof mechanism such that a throttle 
lever adjustment is possible only by combining operational actions of two 
throttle levers. 
2. The Prior Art 
A throttle lever mechanism provided with a safety locking means is adapted 
in view of the safety aspect in order to avoid a possible danger for 
engine drive control, in particular, for controlling a handy type working 
machine such as engine-driven type hedge trimmer or the like. The throttle 
lever mechanism is such that the throttle lever is operable only in the 
case where the safety locking means is intentionally unlocked. In such a 
mechanism, even if the operator's hand must separate away from the 
throttle lever due to some reason and there would be a danger that the 
working machine body could not be held well, the throttle would not be 
returned immediately back to the initial position. Thus, there is a fear 
that it would be impossible to stop the working section such as a cutter 
blade by returning the engine to the idle speed condition. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a safety throttle lever 
mechanism which causes a working section to be operable only in the case 
where the working machine is held by both operator's hands, and which is 
simple in construction, small in number of mechanical parts, high in 
reliability and low in cost to overcome the disadvantages inherent in the 
prior art mechanism. 
The throttle lever mechanism according to the invention is characterized in 
that both ends of a wire cable arranged in a curved manner are connected 
to a throttle valve opening/closing member of a carburetor and a first 
throttle lever, respectively, one end portion of an outer tube covering 
the wire cable is held in a stationary manner, the other end portion of 
the outer tube is coupled to a link member supported rotatably, and the 
link member is connected to a second throttle lever through a connecting 
rod movable within an elongated slot formed in the link member. 
Accordingly, in the throttle lever mechanism according to the invention, 
the number of necessary mechanical parts is reduced by utilizing the 
relative movement between the wire cable and the outer tube covering ths 
wire cable. At the same time, the safety aspect and the reliability of the 
throttle lever mechanism are enhanced, and the manufacture cost is reduced 
while facilitating the maintenance. 
In other words, in the throttle lever mechanism according to the present 
invention, since rigidity of the wire cable and the outer tube covering 
the wire cable is reasonably utilized to reduce the number of the 
mechanical parts and portions where mechanical wear would be likely to be 
generated, it is possible to considerably simplify the safety mechanism 
for the throttle levers and to enhance the working safety aspect and the 
reliability while reducing the manufacture cost.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention will now be described with reference to the 
accompanying drawings. 
FIGS. 1 and 2 are a front elevational view and a plan view, respectively, 
showing an engine-driven type hedge trimmer provided with a throttle 
safety mechanism according to the present invention. 
The throttle lever mechanism shown comprises a drive means composed of a 
few of parts and a throttle cable is arranged in a curved manner. The 
throttle cable 15 is composed of a wire cable 3 and an outer tube or 
sheath 4 covering the wire cable 3. As shown in FIG. 3, the wire cable 3 
is connected at one end 5a to a throttle valve opening/closing member 11 
of a carburetor 5 of the engine 14 and at the other end 1a to a first 
throttle lever 1 pivotally coupled to a front handle 12. The outer tube 4 
covering the wire cable 3 is fixedly secured at one end 4a to the machine 
body by a fastening means 6. The other end 4b of the outer tube 4 is 
freely slidable on the wire cable 3 in conformity with a curvature 
deformation of the wire cable 3. 
An L-shaped bracket 7 is fixed to the freely movable end 4b of the outer 
tube 4. Further, the L-shaped bracket 7 is coupled by pin means 16 to a 
link member 8 which in turn is swingably held to the machine body. Namely, 
the link member 8 and the freely movable end 4b of the outer tube 4 are 
coupled to each other in such a manner that these members may be each 
moved linearly and angularly. 
An elongated slot 9 is formed in the link member 8. An end 10a of a 
connecting rod 10 which is moved in corporation with a second throttle 
lever 2 is slidably moved within the elongated slot 9. In the embodiment 
shown, the end 10a of the connecting rod 10 which is slidably moved within 
the slot 9 is bent so as to be engagable with an end of the elongated slot 
9. 
FIG. 3 is an illustration showing a primary part of the throttle lever 
mechanism in the case where the operator does not hold the machine body 
but the engine is operated at an idle speed. 
With such arrangement, when the operator grips the front handle 12 by his 
hand while pulling the first throttle lever 1, the end 1a of the wire 
cable 3 is moved leftwardly as shown in FIG. 4. At this time, since the 
one end 4a of the outer tube 4 is held by the fastening means 6, a part of 
the curved throttle cable 15 is deformed to the condition as indicated by 
solid lines in FIG. 4. As the throttle cable 15 is deformed, the freely 
movable end 4b of the outer tube 4 is moved leftwardly while sliding on 
the wire cable 3. In compliance with this deformation, the link member ia 
also moved leftwardly. The deformation os displacement of the throttle 
cable 15 and the link member 8 is finally shown in FIG. 4. 
Although the movement of the components by the operation of the first lever 
1 has been described above, it should be noted that the throttle valve 
opening/closing member 11 for the carbretor 5 and the one end 5a of the 
wire cable 3 are kept unchanged in constant positions under the engine 
idle condition. The reason for this is that the deformation of the wire 
cable 15 caused by the operation of the first throttle lever 1 is absorbed 
by the rigidity and the deformation of the outer tube 4. 
Under such a condition, when a rear handle 13 is gripped by the other hand 
to pull the second throttle lever 2 so that the connecting rod 10 is 
pulled in the right in FIG. 5, the bent end 10a of the connecting rod 10 
is brought into contact with a right end of the elongated slot 9 to return 
to the right the link member 8 which has been swung to the left. As a 
result, the outer tube 4 having rigidity is returned to the original 
position indicated by solid lines in FIG. 5. Since the other end 1a of the 
wire cable 3 is kept at the constant position by the first lever 1, the 
end 5a is moved to the right as indicated by the solid line, so that the 
throttle valve opening/closing member 11 is moved, thus adjusting the 
throttle. 
In contrast to the above-described operation, when either one of the first 
and second throttle levers 1 and 2 is released from the operator's hand, 
the one end 5a of the wire cable 3 is returned back to the position shown 
by the solid line in FIG. 4 and the opening/closing member 11 is also 
returned back to the original or home position, so that the engine is 
returned back to the idling condition. 
FIG. 6 shows the case where the throttle operation is commenced by the 
second throttle lever 2 unlike the case shown in FIG. 4. Even if the 
second throttle lever 2 is solely pulled, the end 10a of the connecting 
rod 10 is simply moved rightwardly along the elongated slot 9 of the link 
member 8 but there is no deformation of the throttle cable 15. Under this 
condition, when the first throttle lever 1 is also pulled as shown in FIG. 
7 to move the end 1a of the wire cable 3 leftwardly, since the connecting 
rod 10 serves to prevent the leftward movement of the other end 4b of the 
outer tube 4 through the link member 8, the one end 5a of the wire cable 3 
is moved rightwardly to move the opening/closing member 11 and to perform 
the corresponding throttle adjustment. 
In the same manner as in the operational order explained in conjunction 
with FIGS. 4 and 5, when the operator's hand separates away from either 
one of the first and second throttle levers in the case of FIGS. 6 and 7, 
the one end 5a of the wire cable 3 is returned back to the solid position 
in FIG. 6, so that the engine is returned back t the original idling 
condition.