Patent Application
20220134593
The present invention relates to portable chain saw equipment. Specifically, the present invention provides for a chain tension adjusting knob that also functions as a chain catcher. The dual function adjusting knob reduces the number of parts and simplifies the assembly process.
This section provides background information related to the present disclosure which is not necessarily prior art.
Typical portable chain saws include a means for adjusting the tension of the chain. This is most commonly accomplished by the front-back movement of a chain bar or guide bar. By increasing or decreasing the distance between the chain bar and a drive sprocket, the tension of the chain is effectively increased or decreased. In most cases, a knob or other user actuated device is attached to the chain bar through a lead screw, which the user rotates directly or via a gear set, thus moving the chain bar.
A chain catcher is used to curtail the rearward motion of the chain in the event of derailment or breakage. When one of these events occurs, the exposed chain is no longer retained by the chain bar and the loose chain falls and its rotational inertia swings it back towards the operator. The chain catcher provides a mechanical stop that reduces the rearward motion of the derailed chain.
Existing regulatory standards govern the use and placement of a chain catcher, requiring them to be placed under the saw chain as far to the front as practicable, and to extend laterally from the centerline of the chain bar at least 5 mm. Obviously, the chain catcher must also have sufficient mechanical strength to withstand the impact of the chain.
To provide sufficient mechanical strength, the chain catcher is often embodied as a metal plate bolted to the housing or via a larger plastic lug extending between the main body of the chain saw and the sprocket cover. The larger plastic lug is preferable when ease of assembly is prioritized, as it can be molded with the housing and so eliminates the need for an additional component. The downside to the plastic lug is that the increased size often impacts the ability of the saw to clear chips while cutting, resulting in decreased performance and user frustration.
This section provides a general summary of the invention and is not a comprehensive disclosure of its full scope or all of its features.
The present invention aims to provide a tension adjusting knob that serves the dual purpose of tensioning a chain and acting as a chain catcher, reducing the rearward motion of the chain in case of breakage or derailment.
Many chain saws have a tension adjusting knob that is capable of moving the chain bar to adjust the chain's tension. The present invention positions the knob at a front portion of the housing and below the chain bar so that it performs the additional function of a chain catcher.
Having the tension adjusting knob perform both functions eliminates the need for a separate chain catcher, allowing for more efficient chip ejection and simplifying the assembly of the chain saw. These benefits and others are achieved through reducing the number of parts.
In another aspect of the invention, the knob has a knurled outer surface to provide a better grip for the user. The knob may also include a slot, hex or other configuration to allow for the use of a corresponding tool to help turn the knob.
Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this application are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
Further features and advantages of the present invention will be better understood by reference to the following description, which is given by way of example and in association with the accompanying drawings, in which:
Referring to
At the rear of the housing 14 is an integrally formed main handle 16. Towards the front is an auxiliary handle 18 and a front guard 20. Protruding from the front of the housing is a chain bar 22 that holds a cutting chain 24. In normal use, an operator would simultaneously have one hand on the main handle 16 and the other hand on the auxiliary handle 18
Referring now to
Below the chain bar 22 at a front portion of the housing 14 is a chain tensioning adjustment knob 32. The knob 32 is capable of moving the chain bar 22 forward or backward to tighten or loosen the chain 24, respectively, as explained below.
Referring to
In operation, when the tensioning knob 32 is rotated, the bevel gears 38 rotate the screw 36. As the screw 36 is rotated, the trolley 40 then moves along its length depending on the direction of the screw's rotation. Because the trolley 40 is secured to the chain bar 22, the chain bar moves further or closer to the sprocket 28, thereby increasing or decreasing the tension on the chain 24. The use of bevel gears 38 allows for the axis of rotation of the screw 36 to be at a different angle from the axis of rotation of the tension adjusting knob 32. This allows for optimizing the knob's 32 orientation to allow for easier user operation.
The tension adjusting knob 32 projects from a side surface of the housing 14, outside of the closed loop of chain 24. The tension adjusting knob 32 is disposed below the chain 24, and as far forward as is practicable.
In the preferred embodiment, the tension adjusting knob 32 extends through an opening in the housing plate 34. The cover 15 is placed over the knob 32, with the cover 15 having a shroud 33 that surrounds the knob 32 to provide additional mechanical strength (see
The knob's 32 outer surface can be knurled or ribbed to provide a better gripping surface for rotation. Additionally, a slot 46 is included on an end face of the knob 32 which allows for a screwdriver or other tool to be used to turn the knob 32. Although a slot is shown, it should be understood that a hex, star, or any other shape to allow for the use of a corresponding tool can be used.
One of the benefits of using the knob 32 is that it serves the additional function as a chain catcher if the chain 24 were to break or derail from the chain bar 22.
The forward placement of the knob 32, and its location outside the perimeter of the chain bar 22 are critical to its operation, allowing it to impede any broken or derailed chain 24. If the knob 32 were placed insufficiently forward, the chain 24 might be blocked too late and the risk of injury to the user would increase. Furthermore, the knob 32 must lie outside the perimeter of the chain bar and should extend away from the housing a sufficient length to ensure that it blocks the chain 24 upon its separation from the chain bar 22. In a preferred embodiment, the knob extends at least 5 mm away from the housing.
The present invention also provides a groove 19 (see
Similarly,
Normally, the chain bar 22 is not positioned along the center of the housing, but rather offset to one side of the centerline. In the present drawings, the chain bar is shown on a right side of the housing, but it could be on the left side and still fall within the scope of the invention. Because the chain bar 22 is offset, any breakage or derailment in the chain would come from the same side of the housing, and so the chain tension knob 32 must be on the same side of the housing as the chain bar 22.
The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure
