Lightweight chainsaw guide bar

A chainsaw (100) includes a power unit and a working assembly powered responsive to operation of the power unit. The working assembly includes a guide bar (120) around which a chain is rotatable. The guide bar (120) includes a first side plate (200) and a second side plate (210) facing each other and extending away from the housing (110) to a nose of the guide bar (120), the first and second side plates (200 and 210) each including an inner sidewall (224 and 222) facing inwardly toward each other. Each of the inner sidewalls (224 and 222) includes a recessed portion (230) at which material of the inner sidewalls (224 and 222) has been removed.

TECHNICAL FIELD

Example embodiments generally relate to hand held power equipment and, more particularly, relate to a guide bar improvements for a chainsaw.

BACKGROUND

Chainsaws are commonly used in both commercial and private settings to cut timber or perform other rigorous cutting operations. Because chainsaws are typically employed in outdoor environments, and the work they are employed to perform often inherently generates debris, chainsaws are typically relatively robust hand held machines. They can be powered by gasoline engines or electric motors (e.g., via batteries or wired connections) to turn a chain around a guide bar at relatively high speeds. The chain includes cutting teeth that engage lumber or another medium in order to cut the medium as the teeth are passed over a surface of the medium at high speed.

Given that the chainsaw may be employed to cut media of various sizes, the length of the guide bar can be different for different applications. However, in most situations, the guide bar is relatively long, and may actually be substantially longer than the main body of the chainsaw. The guide bar is typically made of steel, and thus, the guide bar can be a substantial contributor to the overall weight of the chainsaw.

Reducing the weight of the chainsaw can allow it to be more easily controlled and carried for long periods of time. However, weight is not the only concern or point of possible improvement in relation to guide bar design. As such, it may be desirable to explore a number of different guide bar design improvements that could be employed alone or together to improve overall chainsaw performance.

BRIEF SUMMARY OF SOME EXAMPLES

Some example embodiments may provide for a guide bar constructed with laminated sheets of the same or different types of materials. The laminate sheets include at least two metallic side plates that have material removed from their inwardly facing interior portions. This material removal lightens the weight of the guide bar. However, areas around those at which the material that is removed are strategically selected to retain good strength, and to allow the laminated sheets to be joined together by any of a number of different methods. Other improvements may also be possible, and the improvements can be made completely independent of each other, or in combination with each other in any desirable configuration. Accordingly, the operability and utility of the chainsaw may be enhanced or otherwise facilitated while lightening the guide bar without sacrificing strength.

A chainsaw of an example embodiment may include a power unit and a working assembly powered responsive to operation of the power unit. The working assembly includes a guide bar around which a chain is rotatable. The guide bar includes a first side plate and a second side plate facing each other and extending away from the housing to a nose of the guide bar, the first and second side plates each including an inner sidewall facing inwardly toward each other. Each of the inner sidewalls includes a recessed portion at which material of the inner sidewalls has been removed.

DETAILED DESCRIPTION

FIG. 1illustrates side view of a chainsaw100according to an example embodiment. As shown inFIG. 1, the chainsaw100may include a housing110inside which a power unit or motor (not shown) is housed. In some embodiments, the power unit may be either an electric motor or an internal combustion engine. Furthermore, in some embodiments, the power unit may include more than one electric motor where one such electric motor powers the working assembly of the chainsaw100and the other electric motor of the power unit powers a pump that lubricates the working assembly or provides momentum for moving other working fluids within the chainsaw100. The chainsaw100may further include a guide bar120that is attached to the housing110along one side thereof. A chain (not shown) may be driven around the guide bar120responsive to operation of the power unit in order to enable the chainsaw100to cut lumber or other materials. The guide bar120and the chain may form the working assembly of the chainsaw100. As such, the power unit may be operably coupled to the working assembly to turn the chain around the guide bar120.

The chainsaw100may include a front handle130and a rear handle132. A chain brake and front hand guard134may be positioned forward of the front handle130to stop the movement of the chain122in the event of a kickback. In an example embodiment, the hand guard134may be tripped by rotating forward in response to contact with a portion of the arm (e.g., the hand/wrist) of the operator of the chainsaw100. In some cases, the hand guard134may also be tripped in response to detection of inertial measurements indicative of a kickback.

The rear handle132may include a trigger136to facilitate operation of the power unit when the trigger136is actuated. In this regard, for example, when the trigger136is actuated (e.g., depressed), the rotating forces generated by the power unit may be coupled to the chain either directly (e.g., for electric motors) or indirectly (e.g., for gasoline engines). The term “trigger,” as used herein, should be understood to represent any actuator that is capable of being operated by a hand or finger of the user. Thus, the trigger136may represent a button, switch, or other such component that can be actuated by a hand or portion thereof.

Some power units may employ a clutch to provide operable coupling of the power unit to a sprocket that turns the chain. In some cases (e.g., for a gasoline engine), if the trigger136is released, the engine may idle and application of power from the power unit to turn the chain may be stopped. In other cases (e.g., for electric motors), releasing the trigger136may secure operation of the power unit. The housing110may include a fuel tank for providing fuel to the power unit. The housing110may also include or at least partially define an oil reservoir, access to which may be provided to allow the operator to pour oil into the oil reservoir. The oil in the oil reservoir may be used to lubricate the chain as the chain is turned.

As can be appreciated from the description above, actuation of the trigger136may initiate movement of the chain around the guide bar120. A clutch cover150may be provided to secure the guide bar120to the housing110and cover over the clutch and corresponding components that couple the power unit to the chain (e.g., the sprocket and clutch drum). As shown inFIG. 1, the clutch cover150may be attached to the body of the chainsaw100(e.g., the housing110) via nuts152that may be attached to studs that pass through a portion of the guide bar120. The guide bar120may also be secured with the tightening of the nuts152, and a tightness of the chain can be adjusted based on movement of the guide bar120and subsequent tightening of the nuts152when the desired chain tightness is achieved. However, other mechanisms for attachment of the clutch cover150and/or the guide bar120may be provided in other embodiments including, for example, some tightening mechanisms that may combine to tighten the chain in connection with clamping the guide bar120.

As mentioned above, the guide bar120can be an important contributor to the weight of the chainsaw100. Thus, it may be desirable to provide various improvements to the guide bar120to improve the functionality and/or decrease the weight of the guide bar120. Various example embodiments will now be described in reference toFIGS. 2-6, which illustrate some of these example embodiments.

In this regard,FIG. 2illustrates an exploded perspective view the guide bar120in accordance with an example embodiment.FIG. 3, which includesFIGS. 3A, 3B and 3C, illustrates a side view (or top view) of various components of the guide bar120in accordance with an example embodiment. Referring toFIGS. 2 and 3, it can be appreciated that the guide bar120may be formed from multiple laminate sheets that lie in parallel planes along side each other. These laminate sheets may be made from stainless steel and other sufficiently rigid and durable materials. As mentioned above, because steel and other metallic materials tend to have increased weight, some example embodiments may remove some of the metallic material where it is possible to do so, and leave reinforced steel portions in certain strategically important locations. Other materials of a lower weight (e.g., graphene, glass fiber, carbon fiber, or the like) may be employed in some portions of the guide bar120, as will be discussed below.

In the example ofFIGS. 2 and 3, the guide bar120includes a first side plate200and a second side plate210, which may form outer portions or surfaces of the guide bar120. The first and second side plates200and210may generally be spaced apart from each other be at least a certain distance, which may be substantially consistent over the lengths of the first and second side plates200and210. The consistent spacing between the first and second side plates200and210may be maintained by the existence of one or more other plates. However, in some cases, the distance may be maintained by extension portions formed or otherwise provided on interior surfaces of the first and second side plates200and210to extend toward each other. These extension portions will be discussed in greater detail in reference to an alternative example embodiment below.

In the example ofFIGS. 2 and 3, the spacing between the first and second side plates200and210may be maintained by a base plate240. The base plate240and each of the first and second side plates200and210may be made of sheet metal (e.g., steel) that is relatively thin. However, in some cases, the base plate240may be made of a different material than the first and second side plates200and210. For example, the base plate240could be made of a non-metallic material, while the first and second side plates200and210are made of metallic materials. As can be appreciated fromFIGS. 2 and 3, the base plate240and each of the first and second side plates200and210may lie in parallel planes when assembled together. In an example embodiment, the first and second side plates200and210may be formed from relatively thin, plate-like sheets of metallic material that initially has a generally common thickness over the entirety of such sheets. However, in accordance with an example embodiment, portions of the first and second side plates200and210may be removed (e.g., by milling, etching, and/or the like) to reduce the weight of the guide bar120. In particular, for example, inwardly facing sidewalls of the first and second side plates200and210may have some material removed while the outwardly facing sidewalls are left intact.

Referring toFIGS. 2 and 3, an outer sidewall220of the first side plate200is visible, and an inner sidewall222of the second side plate210is visible. The inner sidewall222of the second side plate210faces an inner sidewall224of the first side plate200, and the second side plate210should also be understood to have an outer sidewall that faces opposite the outer sidewall220of the first side plate200. Thus, both the inner sidewall222of the second side plate210and the inner sidewall224of the first side plate200may have material removed to form recessed portions230therein.

The recessed portions230of the inner sidewall222of the second side plate210each have corresponding recessed portions230formed on the inner sidewall224of the first side plate200. Thus, the recessed portions230mirror each other. Referring now to both of the inner sidewalls222and224, it should be appreciated that the recessed portions230may be distributed over interior portions of the respective inner sidewalls222and224. As such, after removal of the material that is removed to form the recessed portions230, the remaining portions of the inner sidewalls222and224are raised relative to the recessed portions230(in the inward facing direction) around peripheral edges of the recessed portions230. Thus, the peripheral areas of the inner sidewalls222and224are raised, and the portions of the inner sidewalls222and224between each of the recessed portions230are also raised.

In this example, the base plate240may have cutout portions242that are punched, etched, laser cut, water cut, or otherwise formed in the base plate240to substantially match the size and shape of the opening of the recessed portions230. Thus, for example, when the first and second side plates200and210are joined with the base plate240therebetween, recessed portions230of the second side plate210, the cutout portions242of the base plate240and recessed portions230of the first side plate200may each be substantially aligned. After the cutout portions242are formed, the base plate240may be defined by a peripheral portion244and ribs246that separate the cutout portions242. Raised portions between the recessed portions230of the second side plate210, the ribs246between the cutout portions242of the base plate240, and raised portions between the recessed portions of the first side plate200may each also be substantially aligned to allow joining of the base plate240to each of the first and second side plates200and210by any of various different methods.

FIG. 3Aillustrates a side view of the first side plate200with the recessed portions230distributed on the inner sidewall224.FIG. 3Billustrates a side view of the base plate240having the cutout portions242formed therein between the ribs246and the peripheral portion244.FIG. 3Cillustrates the first side plate200joined to the base plate240so that the recessed portions230are substantially aligned with the cutout portions242. It can be appreciated that the second side plate210could then be joined to the base plate240such that the inner sidewall222faces the inner sidewall224of the first side plate200and the recessed portions230of the second side plate210align with both the recessed portions230on the first side plate200and the cutout portions242.

As can be seen inFIG. 3C, the length and height of the base plate240is less than the length and height of the first side plate200. Thus, when the first and second side plates200and210are joined about the base plate240, a channel250may be formed between peripheral edges of the first and second side plates200and210. The channel250may extend around cutting portions of the guide bar120, but a nose portion of the guide bar120may include a nose sprocket280to guide the chain around the nose portion. In some cases, the nose sprocket280may be a replaceable nose sprocket280. Thus, some bars may be provided with or without a replaceable nose sprocket. Portions of drive links of the chain will otherwise ride within the channel250while cutter links of the chain interface with peripheral edges of the first and second side plates200and210.

Peripheral edges of the base plate240, and edges of the cutout portions242may provide interface regions that can be joined using various adhesion mechanisms. For example, the base plate240may be joined to the first side plate200(and the second side plate210) at or near any or all portions of the peripheral edges of the base plate240and edges of the cutout portions242via welding (e.g., laser welding or spot welding), soldering, or the provision of adhesive materials. In some cases, adhesive materials could be applied to opposing faces of the base plate240to adhere the base plate240to corresponding contact portions with each of the first and second side plates200and210. If spot welding is employed, the edges may be welded at selected locations. If laser welding or soldering is performed, continuous weld or solder joints may be employed along all or substantial portions of the edges.

As can be appreciated from the descriptions above in reference toFIGS. 2 and 3, the guide bar120may be made from at least three laminate sheets where internal gaps are formed at the interior of the guide bar120so that the reduction in material results in a corresponding reduction in weight of the guide bar120without sacrificing strength. The guide bar120(and each respective one of the laminate sheets or layers) may have one or more rivets or other connectors that can pass through each sheet or layer via orifices260formed in each respective sheet or layer to further assist in holding the sheets or layers together and preventing delaminating.

Although some embodiments can be practiced with three laminate sheets, as described above, it is also possible that more or fewer laminate sheets could be employed in various alternative embodiments. For example, the base plate240could be eliminated in some designs, and the creation of a channel for the drive links of the chain could be accomplished either by adding additional spacer material on to each of the side plates, or by milling or otherwise removing material from the side plates to leave enough material in certain locations to allow for separation to be defined between the side plates to define the channel.FIG. 4illustrates an example of such an embodiment.

Referring now toFIG. 4, which includesFIGS. 4A, 4B and 4C, an example is provided in which slightly modified first and second side plates200′ and210′ are employed without a base plate.FIG. 4Ais a side view of the first side plate200′ in accordance with an example embodiment.FIG. 4Bis a cross section view of the first side plate200′ taken along line A-A′ ofFIG. 4A.FIG. 4Cis cross section view of the first side plate200′ after combination with the second side plate210′ taken along the line A-A ofFIG. 4A. As can be seen inFIGS. 4B and 4C, the first and second side plates200′ and210′ each have portions thereof that have three different thicknesses. The thinnest part of the first and second side plates200′ and210′ corresponds to the portions thereof where material is removed to form the recessed portions230′. The portions of the first and second side plates200′ and210′ with intermediate thickness correspond to peripheral edges, the nose portion, and the portion that interfaces with the chainsaw100and housing110. Finally, the portions of the first and second side plates200′ and210′ that are thickest correspond to areas added onto the laminate sheet (or left after material removal) to approximate the function and shape/size of the base plate of the prior example structures. Moreover, as can be appreciated fromFIG. 4C, the base plate has effectively been split in half, with each half being affixed to its respective side plate.

The thickest portions of the first and second side plates200′ and210′ may be referred to as raised portions290. These raised portions290may meet each other to maintain sufficient space between peripheral regions of the first and second side plates200′ and210′ to form the channel250similar to the example above. Opposing faces of the raised portions290of respective ones of the first and second side plates200′ and210′ may meet at an interface295. AlthoughFIG. 4Cillustrates an example where the first and second side plates200′ and210′ mirror each other to meet at the interface295, it should be appreciated that the design ofFIG. 4Ccould be substantially duplicated with one flat side plate and the other side plate having raised portions extended to be as long as both the raised portions290ofFIG. 4C. This would represent a simpler design option since only one of the side plates would be milled and the other would be substantially flat.

In another alternative, it should be appreciated that either or both of the first and second side plates200′ and210′ could be composite plates. The same could also be true of the first and second side plates200and210described above. In either case, a flat outer plate may be welded or otherwise joined to an inner plate that is laser cut or punched to include boundaries to define the recessed portions230and230′. This may allow the recessed portions230and230′ to effectively be formed without any milling.

Any of a number of different joining methods may be employed at one or more of the interfaces295. For example, welding (e.g., laser welding or spot welding), soldering, or the provision of adhesive materials may be used to join one or more of the interfaces295. In some cases, adhesive materials could be applied to the opposing faces at the interfaces295to adhere the corresponding contact portions of each of the first and second side plates200′ and210′. If spot welding is employed, the inner or outer edges of the interfaces295may be welded at selected locations. If laser welding or soldering is performed, continuous weld or solder joints may be employed along all or substantial portions of the inner or outer edges of the interfaces295. In some cases, welding or soldering could be employed at the interfaces295proximate to the channel250via the channel250opening. However, in some cases, laser welding or other welding techniques may be employed to weld the side plates together, and/or to weld the side plates together with any base plate in use. In such an example, the welding may be accomplished through one of the side plates to weld all components together.

FIG. 5Aillustrates a side view of an example first side plate200″ andFIG. 5Billustrates a side view of an example second side plate210″ according to an example embodiment. The outline region300may represent an area of the first and second side plates200″ and210″ on which adhesive may be applied to allow the raised portions (similar to raised portions290ofFIG. 4Cto be adhered to each other. In this example, and the above examples in which adhesives are employed, surfaces to which adhesives are to be applied may first be pretreated with plasma to ensure cleanliness of such surfaces.

As also shown inFIGS. 5A and 5B, cross sections along lines B-B and C-C, respectively, may be drawn at an area of the nose section so that the views ofFIGS. 5D and 5Eto help illustrate how pinching of the nose section may be prevented. In this regard, for example, a nose sprocket hub310may be defined on the first and second side plates200″ and210″. The nose sprocket hub310may provide an area at which the nose sprocket280can be supported (seeFIG. 2), and a wear ring320(seeFIG. 5C) may be employed in connection with provision of the nose sprocket280to improve wear resistance by providing a wear surface between the hub310and nose sprocket280, or between the hub310and bearing discs of the nose sprocket280. The wear ring320, nose sprocket280and bearing discs can be manufactured for low friction and low wear by choosing materials or combinations of materials that are suitable or have surface treatments or coatings.

FIG. 5Cillustrates a perspective view of the wear ring320, andFIGS. 5D and 5Eillustrate the cross section views along lines C-C and B-B, respectively. As shown inFIGS. 5D and 5E, the first and second side plates200″ and210″ may meet to form the hub310based on a hollow structure and protrusion that can fit therein. Where the first and second side plates200″ and210″ meet, an adhesive area330may be formed at which surfaces facing each other can be joined with adhesive.

The examples above each relate to the provision of side plates with hollowed out portions (e.g., the recessed portions230and230′) that facilitate lightening the overall weight of the guide bar120. One such example employed a base plate, but the other did not. However, in both cases, the recessed portions230and230′ are provided to substantially mirror each other about a plane passing through a center of the guide bar120parallel to the planes in which the laminate sheets lie. The recessed portions230and230′ are formed to face each other, and are formed by removing material from inwardly facing sidewalls of the side plates of the guide bar120. However, it may be possible in some cases to remove the material all the way through the side plates instead of just in the inwardly facing sidewalls. Such an example is shown inFIG. 6, which includesFIGS. 6A, 6B, 6C, 6D and 6E.

FIG. 6Aillustrates a side view of a base plate400in accordance with an example embodiment. The base plate400may be made of steel, or another rigid material similar to the base plate240described above. However, the base plate400may have a plurality of eyelets410formed around various cutout portions420formed in the base plate400by punching, etching, cutting or other suitable means. The eyelets410may be positioned around a periphery of each of the cutout portions420to face each other. Thus, an array of eyelets410equal in number and size may be provided on each opposing side of the cutout portions420. In this example, eyelets410disposed to run parallel to a longitudinal axis of the base plate400may be longer and greater in number than eyelets410disposed to run perpendicular to the longitudinal axis of the base plate400.

FIG. 6Billustrates a first side plate430having a recessed portion440formed therein. The recessed portion430may actually pass entirely through the thickness of the first side plate430in interior regions (spaced apart from the periphery of the first side plate430).FIG. 6Cshows the base plate400operably coupled to the first side plate430. In this example, the base plate400is on the opposite side of the first side plate430relative to the viewer, and the dashed lines illustrate an interface450at the edges of the base plate400where the joining (e.g., by laser welding or other joining methods) of the base plate400and the first side plate430may be provided. As can be seen fromFIG. 6C, the eyelets410are all exposed in the recessed portion440of the first side plate430. A second side plate may be attached to an opposite side of the base plate400and affixed thereto by any of the mechanisms described above.

Thereafter, as shown inFIG. 6D, woven material or unidirectional fiber may be used to define cross members that extend between opposing eyelets410. The cross members may include first cross members460that extend between opposing eyelets410disposed to run parallel to a longitudinal axis of the base plate400. The cross members may also include second cross members462that extend between opposing eyelets410disposed to run perpendicular to the longitudinal axis of the base plate400. The first cross members460may therefore extend substantially perpendicular to the longitudinal axis of the base plate400while the second cross members462extend substantially parallel to the longitudinal axis of the base plate400. The first cross members460are wider and shorter than the second cross members462.

As shown inFIG. 6D, the first and second cross members460and462may be interleaved with each other so that each first cross member460passes adjacent to (and contacts) opposite sides of adjacent second cross members462encountered while extending between eyelets410. Similarly, each second cross member462passes adjacent to (and contacts) opposite sides of adjacent first cross members462encountered while extending between eyelets410. The resultant structure ofFIG. 6Dmay be a well supported, but lighter structure than a fully metalized side plate.

In some cases, the recessed portions440of the side plates may then be filled in with resin480that can be injected therein to fill the gaps in the recessed portions440to provide smooth outer surfaces for both the first side plate430and the second side plate.FIG. 6Eillustrates the resin480provided in all cavities of the recessed portions440. The first and second cross members460and462may be made of a relatively low weight, non-metallic material such as graphene, glass fiber, carbon fiber, or the like. The resultant guide bar490may be relatively light, and yet very strong and durable. It should also be appreciated that some embodiments may omit the weaving ofFIG. 6Dand effectively move directly from the structure of6C (or something similar thereto) to the structure ofFIG. 6E, where the hollow interior of the guide bar490is completely filled with resin480instead of filling the resin480over the woven materials ofFIG. 6D. Alternatively, one or more inserts or insert portions could be provided into the same gap. The inserts or insert portions could be non-metallic material (e.g., carbon fiber) sheets glued therein. It should also be appreciated that in these alternative embodiments, the gap in question could be one or more of the recessed portions440and aligned cutout portions420. In other words, there could be only one large recessed portion/cutout portion instead of multiple smaller ones.

In other example embodiments, the side plates may be milled or molded to have cavities formed to receive a middle plate that is made of a low weight and/or high stiffness material in such a way that the middle plate defines a width for the channel inside which the chain rides.FIG. 7illustrates an exploded perspective view of a lightweight guide bar500in accordance with an example embodiment. The guide bar500is formed from a first side plate510and a second side plate512, each of which may be made of steel, or another rigid, metallic material. Each of the first side plate510and second side plate512may be formed to have a substantially smooth and/or flat outer surface (facing away from each other), while having inner surfaces (facing each other) that include recessed portions (e.g., recessed portions520(seeFIG. 8E) and522) that also face each other. The recessed portion520may be milled out of the second side plate512or may be formed in the second side plate512when the second side plate512is formed.

A base plate530may be formed to substantially match a shape of the recessed portions520and522to substantially fill the space formed by the recessed portions520and522and define a width (W1) of a channel550inside which the chain rides around the guide bar500. The base plate530may be made from non-metallic, lower weight material (e.g., graphene, glass fiber, carbon fiber, or the like). By replacing the higher weight steel or metallic material of a typical guide bar with the base plate530at interior portions of the guide bar500, the overall weight of a chainsaw employing the guide bar500may be reduced. The base plate530may be affixed to the first and second side plates510and512by an adhesive.

FIG. 8, which is defined byFIGS. 8A, 8B, 8C, 8D and 8E, illustrates several aspects of the guide bar500in greater detail. In this regard,FIG. 8Aillustrates a side view of an outside surface of the second side plate512, whileFIG. 8Billustrates a side view of an inside surface of the second side plate512. Of note, the recessed portion522of the second side plate512ofFIG. 8Bis partially filled with an insert540. The insert540is configured to mate with an alternate base plate530′ (seeFIG. 8C) to substantially fill the void space formed when the first and second side plates510and512are joined with the base plate530′ and the insert540. The base plate530′ is shown in greater detail inFIG. 8C, while the insert540is shown in isolation inFIG. 8D. A cross section view of the guide bar500taken along line A-A′ ofFIG. 8Ais shown inFIG. 8E.

It should be noted that although the base plates530and530′ are each shown as substantially unitary structures without any through holes therethrough, it may be possible to remove some material from the base plates as well to reduce weight and material requirements. In such examples, portions of sides of the base plates530and530′ may be removed while leaving a lattice structure for support. The portions removed may extend all the way through the width of the base plates530and530′ or may be formed such that they do not pass all the way through the base plates530and530′. It may also be possible to form the base plates530and530′ from individual pieces that can be joined together or otherwise placed proximate to each other during assembly.

As mentioned above, the base plate530may be configured to fit substantially all of the void space created by the recess portions520and522. Meanwhile, the alternate base plate530′ may be shaped to fit substantially all of the void space except that which is filled by the insert540. The insert540may be employed at the proximal end of the guide bar500relative to the housing110. In this regard, for example, the insert540may be disposed at a portion of the guide bar500that is covered by the clutch cover150. The clutch cover150may inhibit heat dissipation at portions of the guide bar500that are disposed between the clutch cover150and the housing110(seeFIG. 1). As such, since some adhesives may tend to degrade in the presence of excessive heat, the use of the insert540may enable welding or riveting to be used to join the insert540and the first and second side plates510and512so that any adhesive is generally used where sufficient heat dissipation can occur to avoid adhesive degradation. At other portions of the guide bar500, the base plate530′ may be joined to the first and second side plates510and512via adhesive. In some cases, a thermal barrier may be provided between the insert540and the base plate530′.

In some examples, the insert540may include a receiving slot542configured to receive a projection532formed on the proximal end of the base plate530′. The receiving slot542may be formed between respective arms544of the insert540. The arms544may project toward a distal end of the guide bar500and, in some cases, may extend beyond the point at which the clutch cover150would cease to cover the guide bar500. The receiving slot542may extend all the way to a slot560formed in the guide bar500to allow the nuts152to pass therethrough for chain tension to be adjusted by lateral movement of the guide bar500forward or rearward relative to the nuts152(seeFIG. 1). Thus, the projection532may extend rearward (i.e., toward the proximal end of the guide bar500) to the slot560. The slot560may also be formed into both of the first and second side plate510and512. The use of steel for the insert540may allow improved handling of mechanical stress, as well as handling of thermal stress.

In examples with the base plate530, the slot560may be formed to pass through the base plate530as well. Additionally, when other through holes562are employed in the first and second side plates510and512, such through holes562may also be formed in either the base plate530, or if the base plate530′ is employed, the through holes562may be formed in the insert540. However, in some examples (seeFIG. 9A), a base plate530″ may be employed that accommodates smaller inserts540′ that only surround the through holes562. In this example as well, the through holes562may be located at an area that sees relatively high heat production. Moreover, since the slot560has some open space to facilitate heat dissipation, and the area proximate to the through holes562can be separate from the slot560, it may be desirable to provide steel or other metallic material that can be welded or riveted (instead of using adhesives) proximate to the through holes562.FIG. 9Bshows an alternative in which the inserts540″ inside which the through holes562are formed are much larger, andFIG. 9Cillustrates a one piece insert540′ inside which the slot560and the through holes562may be formed.

As can be appreciated fromFIG. 8E, a width (W2) of the base plate530′ may be larger than the width (W1) of the channel550. However, the width (W2) of the base plate530′ effectively defines the width (W1) of the channel550. In this regard, a width (W3) of the guide bar500may be equal to the width (W2) of the base plate530′ plus a width (W4) of each of the side plates510and512proximate to the recess portions520and522. As such, the width (W3) of the guide bar500may also be equal to the width (W1) of the channel530′ plus a width (W5) of each of the side plates510and512at portions thereof that are not proximate to the recess portions520and522.FIG. 8Efurther demonstrates that metal does not contact metal in this example over a majority of the length of the guide bar500. Moreover, the first and second side plates510and512do not contact each other at all. Instead, metal only contacts other metal at portions where the insert540or540′ is employed. And at such locations, the first side plate510would be joined to the insert540or540′ (e.g., using adhesives, riveting or welding), and then the insert540or540′ would be joined to the second side plate512. If welding is employed, in some cases, all three components could be welded in a single operation through one of the side plates.

Alternate structures to that ofFIG. 8Eare also possible. For example,FIG. 8Fillustrates an example that is substantially identical to the example ofFIG. 8Eexcept that the recess portions520and522are not formed by milling, but are instead formed by using first and second side plates510′ and512′ that are formed from separate portions including, for example, base portions511and perimeter portions513. The perimeter portions513may have substantially the same shape as the base portions511, but may be hollowed out at their centers with the hollowed out portion substantially matching a shape of the base plate530′. The perimeter portions513may be attached to their respective base portions511by welding, riveting, adhesives, soldering and/or the like. As yet another alternative (shown inFIG. 8G), the base plate530″ may extend all the way through the first and second side plates510″ and512″.

As shown inFIGS. 7-9, the slot560and through holes562may be the only holes formed through the proximal end of the first and second side plates510and512in some cases. Moreover, the inclusion of material, whether metallic or non-metallic, proximate to the slot560and through holes562may be continuously provided. However, in some examples, it may be desirable to remove some more of the metallic material of the guide bar, particularly in regions that are not visible due to coverage of the clutch cover150(seeFIG. 1).

Accordingly, yet another alternative embodiment may be provided in which portions of the side plates are removed to further lighten the guide bar. In this regard, an alternative guide bar500′ is shown inFIG. 10, which is defined byFIGS. 10A, 10B and 10C.FIG. 10Aillustrates a perspective view of the guide bar500′ in accordance with an example embodiment. The guide bar500′ includes first and second side plates510′ and512′ that are similar to the first and second side plates510and512described above except that they include more material removed at the proximal end of the guide bar500′. The additional material removed from the first and second side plates510′ and512′ results in the formation of more numerous and larger through holes562′, which can have irregular shapes. These through holes562′ may create a reinforcing metallic lattice of material that keeps strength high, but the removal of material lightens the overall weight of the guide bar500′. It should also be appreciated that this strategy may be employed in connection with the examples described above in reference toFIGS. 2-6.

FIG. 10Billustrates a side view of the second side plate512′ in accordance with an example embodiment, andFIG. 10Cillustrates a similar side view except that it provides a more detailed view of the region in which the through holes562′ are formed (i.e., the proximal end of the guide bar500′). As shown inFIGS. 10B and 10C, the through holes562′ formed in the second side plate512′ may not match exactly with through holes564formed in insert540″. The insert540″ may therefore be similar in shape to the insert540described in reference toFIG. 8, except that the insert540″ includes the through holes564formed therethrough. Although the through holes564could be formed to match the shape and position of the through holes562′ formed in the side plates, more material could be removed in the insert540″ to further lighten the guide bar500′. In this example, multiple through holes562′ of the side plates may correspond to a single through hole564of the insert540″ in at least one instance, and one through hole562′ may be provided to correspond to at least one through hole564of the insert540″ in at least another instance. However, it could be the case that more than one through holes562′ of the side plates corresponds to a single through hole564of the insert540″ in all instances in an alternative embodiment. Similarly, it could be the case that only one through hole562′ is provided to correspond to each individual through hole564of the insert540″ in another alternative embodiment. The shapes of such holes may be either the same or different as well in various example embodiments.

In some examples, the base plate (240,400,530,530′) may be made from a single layer of woven material or unidirectional fiber. However, in other examples, the base plate itself may be made from multiple layers of material. As such, an example base plate600is shown inFIG. 11. The base plate600may be an example that may be used as a replacement for a base plate with a single layer of unidirectional fibers that may be used in connection with any of the examples described above.

As shown inFIG. 11, the base plate600may include a first layer610, a second layer620, a third layer630and a fourth layer640. However, it should be appreciated that more layers (e.g., seven) or fewer layers (e.g., 2 or 3) could be used in alternative embodiments. When multiple layers are used, the layers may be laminated together to form the base plate600and may be joined by adhesives or any other suitable joining method. Although in some cases, each of the first layer610, the second layer620, the third layer630and the fourth layer640may be formed to have fibers that have the same orientation, it may be desirable to employ layers with different fiber orientations in alternative embodiments. Thus, for example, as shown inFIG. 11, the first layer610may have fibers612having a first fiber direction, while the second layer620has fibers622having a second fiber direction, the third layer630has fibers632having a fourth fiber direction, and the fourth layer640has fibers642having a fourth fiber direction. Each of the first fiber direction, the second fiber direction, the third fiber direction and the fourth fiber direction may be different from each other. However, in some cases, it may be desirable to repeat layers with similar fiber directions.

As can be appreciated fromFIG. 11, the second fibers622may be arranged to extend along the longitudinal length of the guide bar. Thus, the second fibers622may be as long as (or nearly as long as) the length of the guide bar. Meanwhile, the fourth fibers642may be arranged to extend substantially perpendicular to the direction of extension of the second fibers622. Thus, the fourth fibers642may be substantially shorter than the second fibers622. Moreover, the fourth fibers642may be shorter than the width of the guide bar. The first fibers612and the third fibers632may be provided at some angle in between the directions of extension of the second fibers622and the fourth fibers642, and therefore may have lengths in between the lengths of the second fibers622and the fourth fibers642. In some cases, the first fibers612may extend to form a 0 degree or 45 degree angle (and as much as 90 degrees) relative to the direction of extension of the second fibers622.

A chainsaw of an example embodiment may therefore include a power unit disposed in a housing and a working assembly powered responsive to operation of the power unit. The working assembly may include a guide bar around which a chain is rotatable. The guide bar may include a first side plate and a second side plate facing each other and extending away from the housing to a nose of the guide bar. The first and second side plates may each include an inner sidewall facing inwardly toward each other. Each of the inner sidewalls may include a recessed portion at which material of the inner sidewalls has been removed.

In some embodiments, additional optional features may be included or the features described above may be modified or augmented. Each of the additional features, modification or augmentations may be practiced in combination with the features above and/or in combination with each other. Thus, some, all or none of the additional features, modifications or augmentations may be utilized in some embodiments. For example, in some cases, respective recessed portions of the inner sidewalls may substantially mirror each other about a plane passing through a longitudinal centerline of the guide bar parallel to respective planes in which the first and second side plates extend. In some embodiments, a base plate may be disposed between the first and second side plates. In an example embodiment, the base plate may be spot welded, laser welded, riveted, soldered, or joined with an adhesive to the first and second side plates. In some cases, the base plate and the first and second side plates may be welded to each other through one of the first side plate or the second side plate. In an example embodiment, the base plate may include a plurality of cutout portions disposed in the base plate to substantially align with the respective recessed portions of the inner sidewalls. In some embodiments, the cutout portions may have substantially a same size and shape as openings of the respective recessed portions. In some cases, an insert may be disposed between the first and second side plates at a proximal end of the guide bar. In an example embodiment, the insert may be welded or riveted to each of the first and second side plates. In some embodiments, the base plate may include multiple laminated layers of carbon fiber material. In such an example, fibers in at least one of the layers have a different orientation than fibers of another layer. Alternately or additionally, the fibers of the at least one of the layers are substantially orthogonal to the fibers of the another layer. Alternately or additionally, fibers in at least one of the layers may have an angle of orientation between about 0 degrees and 90 degrees different than fibers of another layer. In an example embodiment, a width of the base plate may be greater than a width of a channel in which the chain moves around the guide bar. In some cases, the first and second side plates do not contact each other. In an example embodiment, the first and second side plates each include extension portions having a larger thickness than other portions of the first and second side plates, and the extension portions may extend toward each other from the inner sidewalls to define boundaries of the respective recessed portions. In some cases, the extension portions of the first and second side plates may be joined to each other by spot welding, riveting, laser welding, soldering, or an adhesive. In an example embodiment, the recessed portions may extend fully through the first and second side plates. A base plate may be disposed between the first and second side plates, such that the base plate includes a plurality of cutout portions that are visible through the recessed portions when the base plate is joined to the first and second side plates. Eyelets may be disposed on opposing sides of the cutout portions, and cross members may be alternatingly woven amongst each other between respective eyelets on the opposing sides of the cutout portions. In an example embodiment, a resin may be provided over the cross members within the recessed portions to define a guide bar with a metallic periphery and substantially non-metallic interior. In some cases, a wear ring having a low friction may be provided at a nose portion of the guide bar. In some embodiments, the recessed portions extend fully through the first and second side plates. In such an example, a base plate may be disposed between the first and second side plates. The base plate may include a plurality of cutout portions that are visible through the recessed portions when the base plate is joined to the first and second side plates along with resin or an insert including one or more sheets of a non-metallic material fills the cutout portions.