WO2015133940A1

WO2015133940A1 - Coast brake control system

Info

Publication number: WO2015133940A1
Application number: PCT/SE2014/050255
Authority: WO
Inventors: Markus Maag; Michael Kistler; Wolfgang Kast; Daniel UNKEL
Original assignee: Husqvarna Ab
Priority date: 2014-03-04
Filing date: 2014-03-04
Publication date: 2015-09-11

Abstract

A hand-held power tool (100) may include a housing (110), a power unit disposed within the housing (100), the power unit being configured to operate at least in part in response to actuation of a trigger (136), a working assembly (122) powered responsive to operation of the power unit based on actuation of the trigger (136), a brake assembly comprising a coast brake configured to slow the working assembly (122), and a throttle trigger lockout assembly (138) configured to alternately enable actuation of the trigger (136) responsive to the throttle trigger lockout assembly (138) being in an actuated position and prevent actuation of the trigger (136) responsive to the throttle trigger lockout assembly (138) being in an extended position. The throttle trigger lockout assembly (138) may include a coast brake release assembly (220) configured to release the coast brake while actuation of the trigger (136) is prevented.

Description

COAST BRAKE CONTROL SYSTEM

TECHNICAL FIELD

[0001 ] Example embodiments generally relate to hand held power equipment and, more particularly, relate to a coast brake mechanism for a chainsaw.

BACKGROUND

[0002] 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 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.

[0003] Given that the chain is expected to turn at relatively high speeds, and that the teeth are designed to cut, it can be appreciated that the chain should not be allowed to come into contact with any material that is not specifically intended for cutting while the chain is rotating around the bar. Certain phenomena such as kickback can create conditions in which the chances of inadvertent contact with a rotating chain could occur. Accordingly, many chainsaws are designed to include a chainbrake activated by a hand guard that is placed proximate to a forward hand of the operator (i.e., the hand closest to the chain during operation) in order to stop operation of the chainsaw (and rotation of the chain) if a kickback occurs. In this regard, for example, if the chainbrake is activated when hand guard is actuated responsive to contact with a hand or inertia generated by a kickback, the rotation of the chain may be quickly stopped.

[0004] One way to stop chain rotation is to remove the motive force applied to the chain. Thus, a switch may be used to stop a power source from turning the chain. It can be appreciated that it is desirable to stop the chain from rotating relatively quickly, however, simply stopping the application of power to the engine or motor may not be sufficient to achieve a corresponding rapid stopping of chain movement. Inertia of the chain and engine or motor components may cause there to be a delay between the securing of power application and the stopping of chain rotation. Accordingly, a chainbrake may be provided to rapidly stop the chain in addition a switch that removes power to the chain.

[0005] In some cases, it may also be desirable to have the chain stop rotating within a reasonable time period after normal release of the trigger that controls operation of the power unit. Again, inertia can keep the chain rotating after the trigger, which may be used to activate chain rotation, is released. Thus, some chainsaws may further include a coast brake mechanism to slow the chain when the trigger is released.

[0006] Given the value of including such safety features as the chainbrake and coast brake, it can be appreciated that design improvements in relation to these features would be desirable.

BRIEF SUMMARY OF SOME EXAMPLES

[0007] Some example embodiments may provide for a coast brake assembly that can be released while a trigger lockout is activated. Thus, for example, the trigger may remain locked out so that it cannot be operated, but the coast brake may be released so that the chain of a chainsaw may be advanced (e.g., for sharpening). To accomplish this, some embodiments may provide for the definition of one or more intermediate positions for a throttle trigger lockout assembly and when the throttle trigger lockout assembly is in the intermediate position(s) the trigger may remain locked out while the coast brake is released. Accordingly, the maintenance and/or repair of the chainsaw may be facilitated.

[0008] In one example embodiment, a hand-held power tool is provided. The hand-held power tool may include a housing, a power unit disposed within the housing, the power unit being configured to operate at least in part in response to actuation of a trigger, a working assembly powered responsive to operation of the power unit based on actuation of the trigger, a brake assembly comprising a coast brake configured to slow the working assembly, and a throttle trigger lockout assembly configured to alternately enable actuation of the trigger responsive to the throttle trigger lockout assembly being in an actuated position and prevent actuation of the trigger responsive to the throttle trigger lockout assembly being in an extended position. The throttle trigger lockout assembly may include a coast brake release assembly configured to release the coast brake while actuation of the trigger is prevented. [0009] In another example embodiment, a coast brake release assembly is provided. The coast brake release assembly may include a ratchet pawl, a rack element, and a pivotable drum. The pivotable drum may include a gear portion configured to engage the ratchet pawl, a cable drum upon which a force transmitting member is wound, the cable drum being configured to engage a coast brake of a hand-held power tool via the force transmitting member to slow a working assembly of the hand-held power tool, and a toothed rack configured to engage the rack element. The coast brake release assembly may interface with a lockout member forming a portion of a throttle trigger lockout assembly to alternately enable actuation of the trigger responsive to the throttle trigger lockout assembly being in an actuated position and prevent actuation of the trigger responsive to the throttle trigger lockout assembly being in an extended position. The coast brake release assembly may be configured to release the coast brake while the lockout member is in an intermediate position between the actuated position and the extended position of the throttle trigger lockout assembly while actuation of the trigger remains prevented with the lockout member in the intermediate position.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

[0010] Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:

[0011 ] FIG. 1 A illustrates a perspective view of a chainsaw according to an example embodiment;

[0012] FIG. IB illustrates a side view of the chainsaw from the opposite side of that which is shown in FIG. 1A according to an example embodiment;

[0013] FIG. 2, which includes FIGS. 2A and 2B, illustrates a side view of the inner side of a clutch cover and of components mounted on, in or otherwise associated with the clutch cover for defining a typical brake arrangement for implementing the coast brake function along with a kickback brake function in accordance with an example embodiment;

[0014] FIG. 3A illustrates a lockout member in an extended (non-actuated) state in accordance with an example embodiment;

[0015] FIG. 3B illustrates the lockout member in an intermediate position or state in accordance with an example embodiment; [0016] FIG. 3C illustrates the lockout member in an actuated or depressed state in which the trigger 136 is enabled to be actuated in accordance with an example embodiment;

[0017] FIG. 4 illustrates a partially cutaway side view of a coast brake release assembly in accordance with an example embodiment;

[0018] FIG. 5 illustrates a perspective view of a pivotable drum of the coast brake release assembly in accordance with an example embodiment;

[0019] FIG. 6 illustrates a partially cutaway perspective view of portions of the coast brake release assembly positioned when the ratchet pawl engages a gear portion of the pivotable drum in accordance with an example embodiment;

[0020] FIG. 7 illustrates a partially cutaway perspective view of portions of the coast brake release assembly positioned when the ratchet pawl is released from thea gear portion of the pivotable drum in accordance with an example embodiment;

[0021 ] FIG. 8, which includes FIGS. 8A and 8B, is a block diagram showing a series of operations associated with operation of the lockout member in connection with utilizing a coast brake release assembly of an example embodiment;

[0022] FIG. 9, which includes FIGS. 9A, 9B, 9C, 9D, 9E, 9F and 9G, shows a sequence of partially cutaway images of the components of the coast brake release assembly in their respective states during the operations illustrated in FIG. 8 in accordance with an example embodiment; and

[0023] FIG. 10 is a side view of a chainsaw with a throttle trigger lockout assembly having a pivot point disposed rearward instead of forward on the rear handle in accordance with an example embodiment.

DETAILED DESCRIPTION

[0024] Some example embodiments now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all example embodiments are shown. Indeed, the examples described and pictured herein should not be construed as being limiting as to the scope, applicability or configuration of the present disclosure. Rather, these example embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like reference numerals refer to like elements throughout. Furthermore, as used herein, the term "or" is to be interpreted as a logical operator that results in true whenever one or more of its operands are true. As used herein, operable coupling should be understood to relate to direct or indirect connection that, in either case, enables functional interconnection of components that are operably coupled to each other.

[0025] For a typical chainsaw that employs a coast brake mechanism, the coast brake would be applied any time the trigger is not actuated, depressed or otherwise moved from its rest position (i.e., not activated). In many cases, the coast brake is designed to be applied in response to release of the trigger. Thus, for example, if a throttle trigger lockout is employed to prevent depressing the trigger until the throttle trigger lockout is fully depressed or actuated (to indicate presence and control by the operator), the throttle trigger would be locked in a not activated position any time the throttle trigger lockout is not fully depressed or actuated and therefore the coast brake would be applied. As such, if the operator had any reason to turn the chain (e.g., for sharpening of the chain links) while the throttle trigger is not activated, the operator would have to do so against the tension provided by the coast brake mechanism.

[0026] Example embodiments may be provided to enable a hand-held power tool (e.g., a chainsaw) to be placed in a condition in which the throttle trigger is locked, but the coast brake is not applied. This condition may be accessible by defining an intermediate position of the throttle trigger lockout in which the throttle trigger remains locked, but the coast brake is left unapplied. By defining such a condition, the tool can, among other things, be more easily maintained and/or repaired by enabling the operator to more easily sharpen blades or take other actions that might require the chain to be advanced while the throttle trigger is not activated. It should be appreciated that although an example embodiment will be shown and described illustrating a hand-held chainsaw, example embodiments could be practiced in connection with other similar devices such as pole saws or other cutting devices that employ a chain that rotates to affect cutting, where it is advantageous to enable chain advancement for better performance or safety.

[0027] FIG. 1, which includes FIGS. 1A and IB, illustrates a chainsaw 100 according to the prior art. FIG. 1A illustrates a perspective view of the chainsaw 100 and FIG. IB illustrates a side view of the chainsaw 100 from the opposite side of that which is shown in FIG. 1A according to an example embodiment. It should be appreciated that the chainsaw 100 is merely one example of power equipment that includes a working assembly (i.e., the cutting components of the chainsaw 100) that may require or otherwise benefit from rapid slowing of the components thereof. Thus, example embodiments could also be practiced in connection with some other power equipment that may include working assemblies of different types.

[0028] As shown in FIG. 1, the chainsaw 100 may include a housing 110 inside 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 chainsaw 100 and the other electric motor of the power unit powers a pump that lubricates the working assembly. The chainsaw 100 may further include a guide bar 120 that is attached to the housing 110 along one side thereof. A chain 122 may be driven around the guide bar 120 responsive to operation of the power unit in order to enable the chainsaw 100 to cut lumber or other materials. The guide bar 120 and the chain 122 may form the working assembly of the chainsaw 100.

[0029] The chainsaw 100 may include a front handle 130 and a rear handle 132. A chain brake and front hand guard 134 may be positioned forward of the front handle 130 to stop the movement of the chain 122 in the event of a kickback. In an example embodiment, the hand guard 134 may 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 chainsaw 100. In some cases, the hand guard 134 may also be tripped in response to detection of inertial measurements indicative of a kickback.

[0030] The rear handle 132 may include a trigger 136 (e.g., a throttle trigger) to facilitate operation of the power unit when the trigger 136 is actuated. In this regard, for example, when the trigger 136 is actuated (e.g., depressed), the rotating forces generated by the power unit may be coupled to the chain 122 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 trigger 136 may represent a button, switch, or other such component that can be actuated by a hand or portion thereof.

[0031 ] In an example embodiment, the chainsaw 100 may further include a throttle trigger lockout assembly 138. The throttle trigger lockout assembly 138 may include a pivotally mounted lever or actuator that is normally in an extended position, but is depressed (or actuated) when the operator places his/her hand over the rear handle 132 to facilitate actuation of the trigger 136. The throttle trigger lockout assembly 138 may be interlocked or otherwise operably connected to the trigger 136 to prevent actuation of the trigger 136 unless the throttle trigger lockout assembly 138 is actuated. Actuation of the throttle trigger lockout assembly 138 may involve pressing the throttle trigger lockout assembly 138 inward to a predetermined threshold (e.g., nearly fully depressed) at which time the trigger 136 is unlocked and enabled to be actuated. Prior to actuation of the throttle trigger lockout assembly 138, the throttle trigger lockout assembly 138 may be positioned to block otherwise prevent operation of the trigger 136.

[0032] Some power units may employ a clutch to provide operable coupling of the power unit to a sprocket that turns the chain 122. In some cases (e.g., for a gasoline engine), if the trigger 136 is released, the engine may idle and application of power from the power unit to turn the chain 122 may be stopped. In other cases (e.g., for electric motors), releasing the trigger 136 may secure operation of the power unit. The housing 110 may include a fuel tank for providing fuel to the power unit via removal of fuel cap 140. The housing 110 may also include or at least partially define an oil reservoir 150, access to which may be provided to allow the operator to pour oil into the oil reservoir 150. The oil in the oil reservoir 150 may be used to lubricate the chain 122 as the chain 122 is turned.

[0033] As can be appreciated from the description above, actuation of the trigger 136 may initiate movement of the chain 122 around the guide bar 120. Meanwhile, at least two different events may cause the movement of the chain 122 around the guide bar 120 to be interrupted or stopped. In this regard, for example, release of the trigger 136 and tripping of the hand guard 134 may cause movement of the chain 122 around the guide bar 120 to be stopped.

[0034] Tripping of the hand guard 134 occurs in response to detection of conditions indicative of a kickback. Since a kickback is an undesirable and potentially dangerous condition, movement of the chain 122 may be stopped quickly in response to tripping the hand guard 134. The chainsaw 100 may therefore be provided with a chainbrake mechanism that is configured to stop movement of the chain 122 within a first predetermined period of time after the hand guard 134 is tripped. In some cases, operation of the chainbrake mechanism may tighten a brake band around a drum (e.g., a brake drum or clutch drum).

[0035] Meanwhile, releasing of the trigger 136 is a routine event that does not necessarily present the same urgency for stopping movement of the chain 122. Thus, it may not be necessary to stop movement of the chain 122 as quickly after release of the trigger 136 as would otherwise be accomplished in response to activating the chainbrake. However, it may also be undesirable to simply allow the chain 122 to rotate responsive to inertial forces after the trigger 136 is released until the inertial forces decay away naturally. Moreover, some chainsaws may see the time it takes for the chain 122 to stop rotating after release of the trigger 136 change over time as components age. Thus, it may be desirable to facilitate coast brake of the chain 122 so that the chain 122 stops moving within a second predetermined period of time that may be different than the first predetermined period of time (e.g., longer). A coast brake function may therefore be provided by the application of friction to the rotation of a drum that is operably coupled to the chain 122 (e.g., a brake drum or clutch drum).

[0036] As mentioned above, in many conventional chainsaws, a Bowden cable is used to connect the trigger 136 to the coast brake so that activation of the trigger 136 can be sensed to release the coast brake and deactivation of the trigger 136 can be sensed to activate the coast brake. FIG. 2, which includes FIGS. 2A and 2B, illustrates a side view of the inner side of a clutch cover 6 and of components mounted on, in or otherwise associated with the clutch cover for defining a typical brake arrangement for implementing the coast brake function along with a kickback brake function. As shown in FIG. 2, the brake arrangement may include a kickback brake mainly housed in the clutch cover 6 and including a brake band 11 extending around a brake drum of the chains aw and having a fixed first end 12 attached to the clutch cover 6 and a moveable end 13b, and a kickback spring 14 for rapidly exerting a pulling action on the movable end 13b to rapidly tighten the brake band 11 around the drum in case of a kickback action of the handheld power tool. The brake arrangement may also include a hand guard coupling 15 connected to the front hand guard 134 for activating the kickback brake. In some cases, the brake band 11 may be longitudinally split into two band portions including a first band portion providing a first moveable end for operation in connection with the kickback brake, and a second band portion 1 lb providing a second moveable end 13b for operation in connection with the coast brake.

[0037] Via coupling 15, the front hand guard 134 may be pivotally attached to the engine housing and operatively connected to a pivotal front link 17 of a toggle-link mechanism 17-19 housed in the clutch cover 6. The front link 17 and the front hand guard 134 may have a common pivot 16. The toggle-link mechanism 17-19 may further include a non-pivotal rear link 19 attached to the movable ends 13b of the brake band 11, and an intermediate link 18 pivotally attached to the front link 17, via a second pivot pin 50, and the rear link 19, via a first pivot pin 32. The kickback spring 14 biases the rear link 19 towards the pivot 16. During normal operating conditions, the toggle-link mechanism 17-19 has an interlocked normal position, i.e. a position, with the links forming a substantially straight line, but where the second pivot pin 50 is arranged to be slightly beneath a straight line drawn through the common pivot 16 and the first pivot 32. Thus, in normal interlocked position, as the kickback spring 14 biases the rear link towards the pivot 16, the front link 17 will be biased in clockwise direction. The mechanism can be snapped into a second position, i.e. a kick back position, forming a zigzag line, where the second pivot pin 50 comes above the straight line between the common pivot 16 and the first pivot 32, i.e. biasing the front link 17 in anticlockwise direction. In the shown embodiment, the links are provided with cooperating stops 51, 52 that prevent the links from appreciably deviating from the substantially straight line in a direction opposed to the direction of the snapping movement. The rear link 19 has a front member 20 and a rear member 21. The front member 20 is attached to the second movable end 13b of the brake band, the rear member 21 is attached to the first movable end of the brake band and is pivotally attached to the intermediary link 18, and the two members 20, 21 are telescopically movable in relation to each other.

[0038] Further, the brake arrangement may include a coasting brake having a coasting spring 22 for biasing the second portion 1 lb of the brake band 11. The coasting spring may be less strong than the kickback spring, and a force transmitting member (e.g., Bowden cable 23) may operatively connect tool operating mechanisms to the front member 20. The coasting spring 22 may urge the front member 20 towards the pivot 16, and the kickback spring 14 during normal running conditions of the power tool urges the rear member 21 against said intermediate link 18, but upon actuation of the kick back brake, the kickback spring 14 urges the rear member 21 against the front member 20 to rapidly tighten both portions of the brake band 11 around the drum.

[0039] As indicated above, it may be desirable to improve upon the brake arrangement of FIG. 2 by enabling the coast brake to be released when the trigger 136 is not activated. An example embodiment will now be described in reference to FIGS. 3-7, which illustrate one example embodiment of a brake arrangement or assembly that is capable of providing an intermediate position for the throttle trigger lockout that permits the coast brake to be released while the trigger 136 remains not activated (and in fact, locked out from activation). In this regard, FIG. 3, which includes FIGS. 3A, 3B and 3C, illustrates a partially cutaway perspective view of a handle portion of a chainsaw that employs a brake assembly in accordance with an example embodiment. In this regard, FIG. 3A illustrates a lockout member in an extended (non- actuated) state. FIG. 3B illustrates the lockout member in an intermediate position or state. FIG. 3C illustrates the lockout member in an actuated or depressed state in which the trigger 136 is enabled to be actuated. FIG. 4 illustrates a partially cutaway side view of a coast brake release assembly in accordance with an example embodiment. FIG. 5 illustrates a perspective view of a pivotable drum of the coast brake release assembly in accordance with an example embodiment. FIG. 6 illustrates a partially cutaway perspective view of portions of the coast brake release assembly positioned when the ratchet pawl engages a gear portion of the pivotable drum in accordance with an example embodiment. FIG. 7 illustrates a partially cutaway perspective view of portions of the coast brake release assembly positioned when the ratchet pawl is released from thea gear portion of the pivotable drum in accordance with an example embodiment.

[0040] As shown in FIGS. 4-7, a brake assembly or arrangement of an example embodiment may interact with the throttle trigger lockout assembly 138 to selectively release the coast brake based on throttle trigger lockout assembly 138 operation, while maintaining the trigger 136 in a locked state. Thus, according to an example embodiment, the throttle trigger lockout assembly 138 may include a lockout member 200 mounted to a pivot 202 that is provided in a portion of the rear handle 132 to selectively interact with the coast brake and a trigger lock mechanism. Of note, the lockout member 200 may form a button, lever or other such physical member that forms the primary visible portion of the throttle trigger lockout assembly 138. The throttle trigger lockout assembly 138 may further include a coast brake release assembly 220.

[0041 ] The lockout member 200 may rotate about the pivot 202 responsive to pressure being exerted in the direction of arrow 204 by the operator's hand. A biasing member (e.g., lockout spring 206) may be provided to bias the lockout member 200 toward an extended position as shown in FIG. 3A. However, when the operator puts pressure on the lockout member 200 to cause rotation about the pivot 202, the lockout spring 206 may be compressed as the lockout member 200 rotates to an intermediate position as shown in FIG. 3B. The lockout member 200 further includes a trigger lock assembly 210 that is configured to block movement of the trigger 136 until the lockout member 200 is substantially fully depressed (or actuated) as shown in FIG. 3C. Thus, when the lockout member 200 is moved to the fully depressed position, the trigger lock assembly 210 allows the trigger 136 to be actuated by a finger of the operator. At this position, the lockout spring 206 is fully contracted and poised to return the lockout member 200 to the extended position (of FIG. 3A) when the operator's hand is removed so that pressure is no longer placed on the lockout member 200.

[0042] In terms of the operation of the lockout member 200 to serve as a trigger locking mechanism, the operation of the lockout member 200 as described above and shown in FIGS. 3A, 3B and 3C may be substantially similar to that which would be expected for a typical chainsaw. However, example embodiments may be further provided with the coast brake release assembly 220, which may be configured to release the coast brake (e.g., release the brake band from the brake drum) while the trigger 136 remains in the non-actuated state. As such, the coast brake release assembly 220 may be configured to release the coast brake while the lockout member 200 is in an intermediate position and the trigger 136 remains locked from operation by the lockout member 200. In an example embodiment, the intermediate position may further include one or more discrete and stable intermediate positions. As such, for example, the coast brake release assembly 220 may define a plurality of discrete positions at which the lockout member 200 may be held without maintaining hand pressure on the lockout member 200. Thus, the operator may use hand pressure to position the lockout member 200 in one of the discrete and stable intermediate positions and the lockout member 200 may stay in that position until further action is taken. While in the discrete and stable intermediate position, the trigger 136 may remain locked, but the coast brake may be released. Accordingly, the chain may be advanced (e.g., for sharpening or grinding on the cutters) manually without resistance from the coast brake.

[0043] As shown in FIGS. 4-7, the coast brake release assembly 220 may include some components that are part of or mounted to the lockout member 200, some components that are part of or interface with brake assembly components, and/or other components that are part of or mounted to portions of the rear handle 132. In particular, a Bowden cable 230, which may interact with the brake arrangement as described above in reference to FIG. 2, may be operably coupled to a pivotable drum 240. The pivotable drum 240 may include a cable drum 242 around which the Bowden cable 230 may be wrapped and/or affixed, a gear portion 244 that may interact with a ratchet pawl 250 and a toothed element 246. The pivotable drum 240 may be pivotally mounted to the handle to ride within a slot 252 disposed in the lockout member 200. The slot 252 may be disposed in a portion of the lockout member 200 that is proximate to an opposite end of the lockout member 200 than the pivot 202. As the lockout member 200 is moved from the extended position, through the intermediate position and to the actuated position, the pivot point of the pivotable drum 240 may remain within the slot 252.

[0044] A toothed rack 260 may be provided spaced apart from the slot 252 by a relatively constant distance over the length of both the toothed rack 260 and the slot 252. The toothed rack 260 may include a plurality of teeth 262 that are capable of interacting with teeth of the toothed element 246. In this regard, as the toothed rack 260 moves responsive to hand pressure on the lockout member 200, the teeth 262 sequentially engage the teeth of the toothed element 246 and cause the toothed element 246 to rotate away from a rest position. In an example embodiment, a stopper 264 may be provided to engage a distal end 268 of the toothed element 246 (relative to the end at which the teeth of the toothed element 246 are located) to define the rest position.

[0045] As the toothed rack 260 causes rotation of the pivotable drum 240 based on interaction between the teeth 262 and the teeth of the toothed element 246, the gear portion 244 also turns with the toothed element 246 and the Bowden cable 230 is tightened due to corresponding rotation of the cable drum 242 to release the coast brake (while the trigger 136 is still blocked). A biasing element (e.g., pawl biasing spring 270) may push the ratchet pawl 250 toward engagement with the teeth of the gear portion 244 (see FIG. 6). The ratchet pawl 250 may therefore define a series of discrete and stable intermediate positions where the ratchet pawl 250 engages and is capable of holding contact with each sequential tooth of the gear portion 244.

[0046] As indicated above, there could be one or several intermediate positions for which the ratchet mechanism (e.g., the ratchet pawl 250 and the gear portion 244) is engaged. Thus, for example, upon further pushing in of the lockout member 200 such that the toothed rack 260 makes the toothed element 246 turn, the ratchet pawl 250 may slip to a next notch

(corresponding to another stable and discrete intermediate position of the lockout member) until the toothed rack 260 of the lockout member 200 is disengaged from the toothed element 246 in a disengagement position. At the disengagement position of the lockout member 200, a surface of the toothed element 246 will be approximately vertically disposed in the region of the rightmost tip of the uppermost tooth (i.e., the largest one of the teeth 262) of the toothed rack 260. Thus, upon further pushing in of the lockout member 200 the tip will slide against the approximately vertical surface so that the cable drum 242 will not be turned any more in the winding up direction and the spring force of the coasting spring is not sensed upon further pushing in of the lockout member 200. [0047] Upon release of the lockout member 200, a chamfer 280 may engage a rear portion of the ratchet pawl 250 and pull the ratchet pawl 250 out of engagement of with the gear portion 244 (i.e., against the pressure of the pawl biasing spring 270). The pivotable drum 240 may then return to the rest position in preparation for a potential repeat of the cycle. However, if the lockout member 200 is simply pushed in fully (e.g., as shown in FIG. 3C), then the trigger 136 is no longer blocked and the coast brake remains released to permit actuation of the trigger 136 for operation of the chainsaw 100.

[0048] FIG. 8, which includes FIGS. 8A and 8B, is a block diagram showing a series of operations associated with operation of the lockout member 200 in connection with utilizing the coast brake release assembly 220 of an example embodiment. FIG. 9, which includes FIGS. 9A, 9B, 9C, 9D, 9E, 9F and 9G, shows a sequence of partially cutaway images of the components of the coast brake release assembly 220 in their respective states during the operations illustrated in FIG. 8.

[0049] Referring now to FIGS. 8 and 9, the operator may use his or her hand to push the lockout member to disengage the coast brake and (to the extent the lockout member is pushed all the way) perhaps also release the throttle trigger at operation 300 as shown in FIG. 9A. Teeth from the lockout member may mesh with teeth of the toothed element of the pivotable drum at operation 310 as shown in FIG. 9B. At operation 320, the largest tooth of the toothed rack of the lockout member may reach a substantially flat or vertical portion on the toothed element of the pivotable drum and the toothed rack may obviate rotation back as shown in FIG. 9C. The lockout member may continue to lock the trigger from operating, but the coast brake may be released in this intermediate position so that, for example, grinding of cutters can be

accomplished. Torque from the pivotable drum may be absorbed by the toothed rack as indicated at operation 330. As shown in FIG. 9D, the largest (or raised) tooth may rotate the pivotable drum forward and the mechanism is locked at operation 340. The throttle trigger 136 may be released if the lockout member is moved far enough, as indicated at operation 350.

While the mechanism is locked, some partial movement of the lockout member may be permitted at operation 360 as shown in FIG. 9E, and shown in greater detail in the zoomed-in view of FIG. 9F. Then at operation 370, when the lockout member is opened back to the extended position (e.g., by operation of the lockout spring 206), the chamfer may release the ratchet pawl from the gear portion of the pivotable drum and the pivotable drum may return to its rest position where tension on the Bowden cable is released, and the coast brake can be applied. As can be appreciated from the description above, the force of the lockout spring 206 may exceed the force of the pawl biasing spring 270.

[0050] Although the pivot 202 for the lockout member 200 may be positioned at a front end of the throttle trigger lockout assembly 138 as shown in the examples of FIGS. 1, 3 and 4, it should be appreciated that the lockout member 200 could alternatively pivot from a rear end of the assembly as well. To illustrate such an embodiment, FIG. 10 is provided to show an alternative structure for a throttle trigger lockout assembly 138' having its pivot point provided proximate to a rear end of the rear handle 132. In the context of the description above, it should further be appreciated that the "front" end of the tool (e.g., chainsaw 100) is considered to be the end at which the working assembly (e.g., the guide bar 120 and the chain 122) is located.

[0051 ] Example embodiments may therefore provide a relatively easy way to release the coast brake to enable movement of the working assembly (e.g., chain) while still maintaining the trigger in a locked state. This may facilitate maintenance or repair of the power tool (e.g., the chainsaw). Some embodiments may enable the throttle trigger lockout to be pushed to an intermediate position to disengage the coast brake, but require full actuation of the throttle trigger lockout (i.e., the lockout member 200) to achieve release of the trigger 136. Example embodiments may provide a structure that removes any force from the coast brake from being felt at the trigger. Additionally, the lockout member 200 can open the coast brake by moving into its intermediate position and be isolated from the force of the coast brake. The ratcheting nature of the pivotable drum 240 works at least in part to provide such isolation. Example embodiments may therefore enable the coast brake to be locked in a nearly open position for sharpening of the saw chain and/or for removal of the clutch cover.

[0052] A hand-held power tool of an example embodiment may include a housing, a power unit disposed within the housing, the power unit being configured to operate at least in part in response to actuation of a trigger, a working assembly powered responsive to operation of the power unit based on actuation of the trigger, a brake assembly comprising a coast brake configured to slow the working assembly (e.g., responsive to release of the trigger and/or a throttle trigger lockout assembly), and the throttle trigger lockout assembly configured to alternately enable actuation of the trigger responsive to the throttle trigger lockout assembly being in an actuated position and prevent actuation of the trigger responsive to the throttle trigger lockout assembly being in an extended position. The throttle trigger lockout assembly may include a coast brake release assembly configured to release the coast brake while actuation of the trigger is prevented.

[0053] The power tool of some embodiments may include additional features that may be optionally added either alone or in combination with each other. For example, in some embodiments, (1) the throttle trigger lockout assembly may further include a lockout member operably coupled to the coast brake release assembly to release the coast brake while the lockout member is in an intermediate position between the actuated position and the extended position of the throttle trigger lockout assembly, and actuation of the trigger (136) may remain prevented while the lockout member (200) is in the intermediate position. In some cases, (2) the intermediate position may include a plurality of discrete and stable intermediate positions. In an example embodiment, (3) the plurality of discrete and stable intermediate positions may correlate to different respective engagement positions of a ratchet pawl with a pivotable drum of the coast brake release assembly. In some embodiments, (4) the coast brake release assembly may include a ratchet pawl configured to engage a gear portion of a pivotable drum upon which a force transmitting member coupled to the coast brake is wound. The gear portion may be configured to turn with a toothed element that engages a toothed rack of the lockout member responsive to movement of the lockout member. In some cases, (5) the ratchet pawl may be biased toward engagement with the gear portion via a pawl biasing spring. In an example embodiment, (6) the lockout member is biased toward the extended position of the throttle trigger lockout assembly by a lockout spring. In some embodiments, (7) a force of the lockout spring may be greater than a force of the pawl biasing spring. In some cases, (8) the lockout member may further include a chamfer defined at a portion thereof, and the chamfer (280) may be configured to engage the ratchet pawl to overcome the pawl biasing spring as the lockout member moves toward the extended position. In an example embodiment, (9) the lockout member may further include a slot defined in a portion thereof, and the pivotable drum may be mounted to ride in the slot as the toothed rack engages portions of the toothed element to turn the pivotable drum.

[0054] In some embodiments, any or all of the items (1) to (9) above may be provided individually or in combination with each other and the coast brake release assembly may be configured to isolate the trigger from any force from the coast brake. Additionally or alternatively, any or all of the items (1) to (9) above may be provided individually or in combination with each other and the coast brake release assembly may be configured to isolate the lockout member from any force from the coast brake. In any of the situations described above, the power tool may be a chainsaw or another cutting device such as, for example, a trimmer, hedgetrimmer, lawnmower or the like.

[0055] Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Moreover, although the foregoing descriptions and the associated drawings describe exemplary embodiments in the context of certain exemplary combinations of elements and/or functions, it should be appreciated that different combinations of elements and/or functions may be provided by alternative embodiments without departing from the scope of the appended claims. In this regard, for example, different combinations of elements and/or functions than those explicitly described above are also contemplated as may be set forth in some of the appended claims. In cases where advantages, benefits or solutions to problems are described herein, it should be appreciated that such advantages, benefits and/or solutions may be applicable to some example embodiments, but not necessarily all example embodiments. Thus, any advantages, benefits or solutions described herein should not be thought of as being critical, required or essential to all embodiments or to that which is claimed herein. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

1. A hand-held power tool (100) comprising:

a housing (110);

a power unit disposed within the housing (100), the power unit being configured to operate at least in part in response to actuation of a trigger (136);

a working assembly (122) powered responsive to operation of the power unit based on actuation of the trigger (136);

a brake assembly comprising a coast brake configured to slow the working assembly (122); and

a throttle trigger lockout assembly (138) configured to alternately enable actuation of the trigger (136) responsive to the throttle trigger lockout assembly (138) being in an actuated position and prevent actuation of the trigger (136) responsive to the throttle trigger lockout assembly (138) being in an extended position,

wherein the throttle trigger lockout assembly (138) comprises a coast brake release assembly (220) configured to release the coast brake while actuation of the trigger (136) is prevented.

2. The hand-held power tool (100) of claim 1, wherein the throttle trigger lockout assembly (138) further comprises a lockout member (200) operably coupled to the coast brake release assembly (220) to release the coast brake while the lockout member (200) is in an intermediate position between the actuated position and the extended position of the throttle trigger lockout assembly (138), and wherein actuation of the trigger (136) remains prevented while the lockout member (200) is in the intermediate position.

3. The hand-held power tool (100) of claim 2, wherein the intermediate position comprises a plurality of discrete and stable intermediate positions.

4. The hand-held power tool (100) of claim 3, wherein the plurality of discrete and stable intermediate positions correlate to different respective engagement positions of a ratchet pawl (250) with a pivotable drum (240) of the coast brake release assembly (220).

5. The hand-held power tool (100) of claim 2, wherein the coast brake release assembly (220) comprises a ratchet pawl (250) configured to engage a gear portion (244) of a pivotable drum (240) upon which a force transmitting member (230) coupled to the coast brake is wound, the gear portion (244) being configured to turn with a toothed element (246) that engages a toothed rack (260) of the lockout member (200) responsive to movement of the lockout member (200).

6. The hand-held power tool (100) of claim 5, wherein the ratchet pawl (250 is biased toward engagement with the gear portion (244) via a pawl biasing spring (270).

7. The hand-held power tool (100) of claim 6, wherein the lockout member (200) is biased toward the extended position of the throttle trigger lockout assembly (138) by a lockout spring (206).

8. The hand-held power tool (100) of claim 7, wherein a force of the lockout spring (206) is greater than a force of the pawl biasing spring (270).

9. The hand-held power tool (100) of claim 6, wherein the lockout member (200) further comprises a chamfer (280) defined at a portion thereof, and wherein the chamfer (280) is configured to engage the ratchet pawl (250) to overcome the pawl biasing spring (270) as the lockout member (200) moves toward the extended position.

10. The hand-held power tool (100) of claim 5, wherein the lockout member (200) further comprises a slot (252) defined in a portion thereof, and wherein the pivotable drum (240) is mounted to ride in the slot (252) as the toothed rack (260) engages portions of the toothed element (246) to turn the pivotable drum (240).

11. The hand-held power tool (100) of any preceding claim, wherein the coast brake release assembly (220) is configured to isolate the trigger (136) from any force from the coast brake.

12. The hand-held power tool (100) of any of claims 2-11, wherein the coast brake release assembly (220) is configured to isolate the lockout member (200) from any force from the coast brake.

13. The hand-held power tool (100) of any preceding claim, wherein the hand-held power tool comprises a chainsaw, trimmer, lawnmower or hedgetrimmer.

14. A coast brake release assembly (220) comprising:

a ratchet pawl (250);

a rack element (260); and

a pivotable drum (240), the pi vo table drum comprising:

a gear portion (244) configured to engage the ratchet pawl (250), a cable drum (242) upon which a force transmitting member (230) is wound, the cable drum (242) being configured to engage a coast brake of a hand-held power tool

(100) via the force transmitting member (230) to slow a working assembly (122) of the hand-held power tool (100), and

a toothed rack (246) configured to engage the rack element (260), wherein the coast brake release assembly (220) interfaces with a lockout member (200) forming a portion of a throttle trigger lockout assembly (138) with the coast brake release assembly (220) to alternately enable actuation of the trigger (136) responsive to the throttle trigger lockout assembly (138) being in an actuated position and prevent actuation of the trigger (136) responsive to the throttle trigger lockout assembly (138) being in an extended position, and wherein the coast brake release assembly (220) is configured to release the coast brake while the lockout member (200) is in an intermediate position between the actuated position and the extended position of the throttle trigger lockout assembly (138) while actuation of the trigger (136) remains prevented with the lockout member (200) in the intermediate position.

15. The coast brake release assembly (220) of claim 14, wherein the intermediate position comprises a plurality of discrete and stable intermediate positions.

16. The coast brake release assembly (220) of claim 15, wherein the plurality of discrete and stable intermediate positions correlate to different respective engagement positions of the ratchet pawl (250) with the pivotable drum (240).

17. The coast brake release assembly (220) of claim 15, wherein the ratchet pawl (250 is biased toward engagement with the gear portion (244) via a pawl biasing spring (270).

18. The coast brake release assembly (220) of claim 17, wherein the lockout member (200) is biased toward the extended position of the throttle trigger lockout assembly (138) by a lockout spring (206).

19. The coast brake release assembly (220) of claim 18, wherein a force of the lockout spring (206) is greater than a force of the pawl biasing spring (270).

20. The coast brake release assembly (220) of claim 17, wherein the lockout member (200) further comprises a chamfer (280) defined at a portion thereof, and wherein the chamfer (280) is configured to engage the ratchet pawl (250) to overcome the pawl biasing spring (270) as the lockout member (200) moves toward the extended position.

21. The coast brake release assembly (220) of claim 14, wherein the lockout member (200) further comprises a slot (252) defined in a portion thereof, and wherein the pivotable drum (240) is mounted to ride in the slot (252) as the toothed rack (260) engages portions of the toothed element (246) to turn the pivotable drum (240).

22. The coast brake release assembly (220) of any of claims 14-21, wherein the coast brake release assembly (220) is configured to isolate the trigger (136) from any force from the coast brake.

23. The coast brake release assembly (220) of any of claims 14-21, wherein the coast brake release assembly (220) is configured to isolate the lockout member (200) from any force from the coast brake.