Machine element or mechanism – Control lever and linkage systems – Hand operated
Reexamination Certificate
1999-06-25
2001-04-03
Marmor, Charles A (Department: 3681)
Machine element or mechanism
Control lever and linkage systems
Hand operated
C074S531000, C123S398000
Reexamination Certificate
active
06209412
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an operation-control lever unit for regulating power of an engine of an engine-powered working machine to control operation of a working tool of the engine-powered working machine. The engine-powered working machine may include a carrying bush cutter, a chemical sprayer, a vacuum dust collector and so on.
2. Description of the Related Art
A carrying bush cutter having a circular cutter driven for rotation by an engine carried on the back of an operator is known from Japanese Utility Model Publication No. (SHO) 63-14035. The circular cutter is attached to one end of a hand-operating rod. The rod is provided with an operation handle near the other end thereof. In use of the known bush cutter, the operator swings the rod up and down and right and left while gripping the operation handle. With this swinging operation, bushes are cut or removed by the rotating circular cutter.
In order to control the rotational speed of the cutter, output power of the engine is regulated by a throttle lever provided on a grip portion of the operation handle. However, because the operator is forced to continue gripping of the throttle lever and the operation handle throughout the bush-removing work, a heavy work load is put on the operator.
According to somewhat successful prior improvements, a lock mechanism is associated with a throttle lever to temporarily lock the throttle lever in a desired position, so that the work load on the operator can be reduced. Typical examples of the prior improvements are disclosed in Japanese Utility Model Publication Nos. (SHO) 53-42661 and (SHO) 55-21536, Japanese Utility Model Laid-open Publication No. (SHO) 60-41539, and Japanese Patent Laid-open Publication No. (HEI) 8-303263.
According to the disclosed operation lever units, the throttle lever is displaced to a predetermined operating position, then locked in this operating position by activating the lock mechanism. The lock mechanism is released at need.
More specifically, the operation lever unit disclosed in Japanese Utility Model Publication Nos. (SHO) 55-21536 includes a throttle adjustment lever and a throttle release lever provided side by side on the operating handle. However, because these levers have different axes of pivotal movement, the operation lever unit is complicated in construction, requires an increased number of structural components, and is uneasy to manipulate. Additionally, due to wear and deformation occurring during a long period of use of the engine-powered working machine, a frictional force acting on the throttle lever to lock the same lever in position against pivotal movement tends to decrease and eventually allows the throttle lever to move from the locked position. The throttle lever may sometimes return to its original position when the operation lever unit is subjected to vibration. The operation lever unit has no means to adjust the frictional force acting on the throttle lever.
In the operation lever unit shown in Japanese Utility Model Laid-open Publication No. (SHO) 60-41539, a throttle lever and a lock lever are mounted on the same pivot pin. However, due to a strong spring force acting directly on respective pivoted portions of the levers, a great muscular effort or force is required to turn each lever. Thus, the manipulability of the operating lever unit is relatively low. If the spring force is weakened, the lock lever will fail to lock the throttle lever at a desired position with sufficient reliability.
The operation lever unit disclosed in Japanese Utility Model Publication No. (SHO) 53-42661 includes a locking pawl pivotally mounted between the pivot axis of a throttle lever and the pivot axis of a lock lever for operatively interlocking the two levers. Because of the presence of the locking pawl, the operating lever unit is complicated in construction and requires an increased number of structural components.
In the operation lever unit shown in Japanese Patent Laid-open Publication No. (HEI) 8-303263, a throttle lever and a lock lever are pivotally mounted on the same pivot pin. However, because the lock lever is normally held stationary against pivotal movement using the force of a spring only, this operation lever unit has the same problem as the operation lever unit disclosed in Japanese Utility Model Laid-open Publication No. (SHO) 60-41539 previously described.
SUMMARY OF THE INVENTION
The present invention is conceived to solve the foregoing problems associated with the prior art.
A more specific object of the present invention is to provide a operation-control lever unit for an engine-powered working machine, which includes a throttle lever, a lock lever and a throttle-lever holding mechanism of simple construction having a relatively small number of components.
Another object of the present invention is to provide an operation-control lever unit for an engine-powered working machine, which is simple in construction and is capable of reliably locking a throttle lever in a desired position to regulate output power of an engine of the engine-powered working machine while keeping good manipulability of a lock lever disposed close to the throttle lever.
To achieve the foregoing objects, an operation-control lever unit of the present invention for regulating power of an engine of an engine-powered working machine to control operation of a working tool of the engine-powered working machine includes an operation-control handle having a grip portion and an enlarged head portion at an end of the grip portion, a throttle lever pivotably mounted to the head portion of the handle and pivotally movable about its pivot axis within a predetermined angular range, a lock lever pivotably mounted by a support shaft to the head portion and pivotally movable about an axis of the support shaft, the lock lever being slidably movable along the axis of the support shaft, and a throttle-lever holding mechanism operative in response to pivotal movement of the lock lever in a locking direction to frictionally hold the throttle lever at a desired position within the predetermined angular range. The throttle-lever holding mechanism includes a first cam coaxial with the support shaft and formed integrally with the head portion of the handle, a second cam coaxial with the support shaft and provided on the lock lever, the second cam being co-active with the first cam to displace the lock lever along the support shaft in a first direction away from the first cam, and a resilient means disposed behind the second cam when viewed from the first cam and resiliently urging the second cam toward the first cam.
Because the first cam is integral with the head portion of handle, the throttle-lever holding mechanism is relatively simple in construction and has a small number of structural components.
Preferably, one of the first and second cams has an integral tubular portion coaxial with the support shaft and projecting toward the other cam. The other cam has an outer peripheral surface slidably received in the tubular portion. With this arrangement, the cams are protected against contamination with dirt and dust and can smoothly operate in response to pivotal movement of lock lever.
The first and second cams each have an annular cam surface having at least one radial ridge. At least one of the ridge of the first cam and the ridge of the second cam has a flat top surface. With this flat top surface, the throttle lever can be stably held in a locked position even when the lock lever is pivoted to some extent. The flat top surface is preferably perpendicular to the axis of the support shaft. The ridge may have a generally trapezoidal cross-sectional shape.
Preferably, the throttle-lever holding mechanism further includes a friction member disposed between the throttle lever and the lock lever and forced against the throttle lever when coaction between the first and second cams displaces the lock lever in the first direction against the resiliency of the resilient means The throttle-lever holding mechanism may als
Hiratsuna Kenjiro
Ikeda Takashi
Kojima Atsushi
Nakaya Tomomi
Adams & Wilks
Honda Giken Kogyo Kabushiki Kaisha
Marmor Charles A
Parekh Ankur
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