Tool driving or impacting – Means to drive tool about an axis – Fluid motor
Utility Patent
1999-01-15
2001-01-02
Rada, Rinaldi I. (Department: 3724)
Tool driving or impacting
Means to drive tool about an axis
Fluid motor
C030S277400, C030SDIG005, C056S011300
Utility Patent
active
06167973
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a trimming machine in which power from an internal combustion engine is transmitted via a centrifugal clutch, such as a portable grass trimmer, a hedge trimmer and a lawn mower, and more particularly, to a trimming machine provided with a braking device for preventing unexpected rotation of the cutting blade.
DESCRIPTION OF THE PRIOR ART
A trimming machine such as a shoulder-type portable grass trimmer, a backpack type portable grass trimmer, a hedge trimmer or the like, generally employs a driving mechanism which transmits power from an internal combustion engine via a centrifugal clutch to a cutting blade. In such a trimming machine, as disclosed in Japanese Patent Publication No. Sho 52-12089, a braking device is proposed which is provided with a friction member such as a brake shoe, a brake band or the like so as to make slidable contact with a clutch drum of the centrifugal clutch to prevent free rotation of a cutting blade for improved safety when starting the trimming machine. This braking device prevents the clutch drum from rotating and thereby prevents moving blade from unexpectedly rotating when an operator is not holding the brake lever. After having held the brake lever and released the braking device, the operator holds a throttle lever to adjust a throttle opening of a throttle valve to adjust the power from an internal combustion engine and drives the cutting blade via the clutch drum to carry out the trimming operation.
In this type of trimming machine, however, if the operator holds the throttle lever to cause the clutch drum to rotate before holding the brake lever to release the braking device, the clutch drum may be rotated by a rotating power which exceeds the braking force and as a result, the cutting blade may unexpectedly rotate. Further, if the clutch drum is rotated while a friction member pushes against the clutch drum, the braking device may be damaged or its useful life shortened due to a load exerted on the friction member by the rotated clutch drum.
Therefore, the object of the present invention is to provide a trimming machine in which driving power to the clutch drum will shut off when a braking device is operating.
SUMMARY OF THE INVENTION
The purpose of the present invention described above is accomplished by a trimming machine comprising: a cutting blade; an internal combustion engine for driving the cutting blade; a centrifugal clutch for transmitting power from the internal combustion engine to the cutting blade; a throttle valve; a throttle wire operatively connected to the throttle valve; a manually operated throttle lever for controlling an output from the internal combustion engine by adjusting an opening of the throttle valve via the throttle wire; a clutch drum provided in the centrifugal clutch; a friction member arranged to oppose the clutch drum; a first swinging member connected to the friction member and being allowed to swing between a braking position where the friction member is pressed against the clutch drum and a releasing position where the friction member is spaced from the clutch drum; a second swinging member connected to a connecting point at an intermediate portion of the throttle wire and being allowed to pivot about a pivoting pin with respect to the first swinging member when the throttle wire is moved by operating the throttle lever; and the throttle wire extending along a bent path which is bent at the connecting point so that the pivoting pin of the second swinging member is moved toward the bent path by a swinging movement of the first swinging member so that the throttle wire has no play when the first swinging member is at the releasing position and the pivoting pin of the second swinging member is moved away from the bent path by a swinging movement of the first swinging member so that the throttle wire has play when the first swinging member is at the braking position.
In the present invention, the throttle wire extends along the bent path which bends at a connecting point that is coupled with the second swinging member. When the first swinging member is at the releasing position, the pivoting shaft of the second swinging member is moved toward the bent path by a swing movement of the first swinging member. As a result, the throttle wire has no play. When the first swinging member is at the braking position, the pivoting shaft of the second swinging member is moved away from the bent path by the swing movement of the first swinging member to cause the throttle wire to have play. When the braking device is at the braking position, operational transmission from the throttle lever to the throttle valve via the wire and the throttle valve can not be opened even if an operator holds the throttle lever. Therefore, the clutch drum is not rotated. Accordingly, holding the braking device in braking condition enables the operator to avoid the case where the operator holds the throttle lever causes the clutch drum to overcome the braking force of the braking device whereby the cutting blade is unexpectedly driven. Thus greater safety is assured. Further, since the friction member and the clutch drum are not subjected to any overload to cause damage thereto, the life of the braking device can be extended.
REFERENCES:
patent: 3793727 (1974-02-01), Moore
patent: 4006528 (1977-02-01), Katsuya
patent: 4226312 (1980-10-01), Zindler
patent: 4309862 (1982-01-01), Carlson
patent: 4753012 (1988-06-01), Schurr
patent: 5146735 (1992-09-01), McDonner
patent: 5791057 (1998-08-01), Nakamura et al.
patent: 52-12089 (1997-05-01), None
Goodman Charles
Jacobson Price Holman & Stern PLLC
Kioritz & Corporation
Rada Rinaldi I.
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