Cutlery – Cutting tools – Saw
Patent
1980-10-30
1982-06-15
Peters, Jimmy C.
Cutlery
Cutting tools
Saw
B27B 1700
Patent
active
043343570
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to apparatus for improving the safety of a portable chain saw; and in particular, to an improved apparatus for braking the chain saw in the event of an unexpected or uncontrollable hazardous movement, to which chain saws can be subject.
It is well known that portable chain saws are subject to a potentially hazardous kick-back motion during operation, and that a chain brake can be provided to reduce the risk of operator injury in the event of a kick-back resulting in an untoward saw movement. The present state of the art has tended toward a less complicated and complex safety brake construction in which a safety brake handle is provided forward of a gripping handle, so that during kick-back, the operator's hand or arm will force the safety brake handle forward thereby applying a braking force to the chain saw motor. Such systems are applicable to both electrically powered and gasoline powered chain saws. While these newer systems often reduce the complexity of the mechanism, they can also tend to provide additional wear and less mechanical flexibility since a single spring is employed to perform the two tasks of resiliently restraining the safety brake handle and biasing the handle to the forward position. This dual requirement provides off-center forces which cause uneven wear on the latch and release mechanism components. Notwithstanding therefore the significant advancements in the art of safety brakes for chain saws, there still is room for further improvement.
Accordingly, therefore, it is an object of this invention to provide an improved chain braking structure for a portable chain saw. Other objects of the invention are to provide a safety brake mechanism for a chain saw having improved reliability, low manufacturing costs, greater flexibility, and applicability to both electric and gasoline powered chain saws.
SUMMARY OF THE INVENTION
The invention thus relates to a manually portable chain saw having a housing with a gripping handle, a cutting chain, a support bar projecting forwardly from the housing for supporting the cutting chain for endless movement, and a motive force mechanism carried by the housing for driving the cutting chain. The motive force mechanism can derive its power from either a gasoline or an electric motor.
The invention further has a safety brake assembly for stopping movement of the cutting chain. The safety brake assembly features the sensing arm mounted on the housing for swinging movement, a portion of the sensing arm being located forward of the gripping handle during operation of the chain saw and arranged to be swung in a forward direction in response to being struck by an operator of the chain saw. The brake assembly further features a flexible brake band including an anchoring assembly for securing a first band end, preferably to the housing, and a releasable bistate assembly for capturing a second end of the brake band for longitudinal movement in the direction of the brake band and transverse movement with respect to the sensing arm. With respect to the longitudinal movement, the captured second end has a first state, when the sensing arm is swung in the forward direction, wherein the flexible brake band moves into frictional braking engagement with the motive mechanism to stop the cutting chain, and a second state, when the sensing arm is swung to the rearward position, wherein the flexible brake band is loosely and non-interferingly spaced with respect to the motive mechanism movement. In the transverse movement direction, the brake band second end has a rest position wherein the second end is constrained, yieldingly, in the second state and a brake position wherein the second end can unimpededly move to the first state. The first state corresponds to a brake condition and the second state corresponds to a normal operating condition.
The invention further features a first spring arranged to urge the sensing arm to move in the forward direction for effecting movement of the second end of the brake band to the f
REFERENCES:
patent: 3776331 (1973-12-01), Gustafsson
patent: 3964333 (1976-06-01), Hirschkoff
patent: 3991469 (1976-11-01), Frederickson
patent: 4057900 (1977-11-01), Nagy et al.
patent: 4059895 (1977-11-01), Hirschkoff
patent: 4121339 (1978-10-01), Nikolich
patent: 4197640 (1980-04-01), Murray
patent: 4246701 (1981-01-01), Johansson
Black & Decker Inc.
Murphy Edward D.
Ottesen Walter
Peters Jimmy C.
Weinstein Harold
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