Walk outdoor power equipment unit having handle mounted operational controls using compliant mechanisms

An outdoor power equipment unit, such as a lawn mower, includes a frame movable over the ground. A handle assembly is provided on the frame to allow an operator to walk on the ground behind the handle assembly while operating the unit. A traction drive and a ground grooming or working implement are carried on the frame. A traction control hand grip and an implement control bail are carried on the handle assembly. Both the hand grip and the bail are movable relative to the handle assembly by flexure provided by first and send compliant mechanisms.

TECHNICAL FIELD

This invention relates to a walk outdoor power equipment unit, such as a walk power lawn mower, having various powered components which are controlled by an operator using operational controls mounted on a handle of the unit.

BACKGROUND OF THE INVENTION

Walk power mowers of the type commonly used by homeowners to cut the grass in their yards are well known. Such mowers have a frame that carries various wheels for allowing movement of the frame over the ground. The frame is shaped to provide a cutting deck having a downwardly facing cutting chamber that houses one or more rotary blades for cutting grass. The frame may have a traction drive to self-propel the frame over the ground.

A power source, such as an internal combustion engine or an electric motor powered by an onboard battery pack, is mounted on the frame atop the cutting deck. The power source is suitably coupled to whatever cutting blades are enclosed in the cutting chamber to rotate such cutting blades in horizontal cutting planes. The power source is also suitably coupled to the traction drive to rotate or power at least some of the wheels carried on the frame. The traction drive relieves the operator of having to manually propel the frame over the ground.

The frame of the mower includes an upwardly and rearwardly extending handle to allow the operator to guide the frame during a grass cutting operation and to manually propel the frame in a mower which lacks a traction drive. Various hand operated operational controls are typically located on the upper end of the handle. Such controls allow the operator to engage and disengage the rotation of the blades and/or to engage and disengage the operation of the traction drive. When the traction drive is capable of propelling the mower at a variable ground speed, such controls will also allow the operator to set or maintain the ground speed desired by the operator.

The operational controls are often mounted on the handle for pivoting about lateral, substantially horizontal pivot axes. This requires the use of various pivots, bushings and fasteners for securing the controls to the handle while providing smooth and reliable pivoting of the controls on the handle. In addition, various springs are often required as well to normally dispose the controls in a disengaged condition or in a neutral position when the controls are bi-directionally movable. While the use of such mechanical components is effective for the purpose of mounting the controls on the handle and for providing the motion required of the controls, such components add complexity and cost to the mower.

SUMMARY OF THE INVENTION

One aspect of this invention relates to a walk outdoor power equipment unit for performing a ground grooming or working operation. The unit comprises a frame which is movable over the ground. A prime mover is carried by the frame. A traction drive is carried by the frame and is operatively powered by the prime mover for self-propelling the frame over the ground at a variable speed. An implement is carried by the frame and is operatively powered by the prime mover for performing the ground grooming or working operation. A handle assembly is carried by on the frame and is configured for use by an operator who walks on the ground. At least one control is carried by the handle assembly for controlling at least one of the traction drive or the implement. The at least one control acts through a compliant mechanism to effect control of the at least one of the traction drive or implement.

One aspect of this invention relates to a walk outdoor power equipment unit for performing a ground grooming or working operation. The unit comprises a frame which is movable over the ground. A prime mover is carried by the frame. A traction drive is carried by the frame and is operatively powered by the prime mover for self-propelling the frame over the ground at a variable speed. An implement is carried by the frame and is operatively powered by the prime mover for performing the ground grooming or working operation. A handle assembly is carried by on the frame and is configured for use by an operator who walks on the ground. At least one control is carried by the handle assembly for controlling at least one of the traction drive or the implement. The at least one control is movably mounted on the handle assembly by a compliant mechanism.

Another aspect of this invention relates to an outdoor power equipment unit. The unit comprises a frame movable over the ground. A handle assembly is provided on the frame to allow an operator to walk on the ground behind the handle assembly while operating the unit. A traction drive and a ground grooming or working implement are carried on the frame. A traction control hand grip and an implement control bail are carried on the handle assembly. The hand grip and the bail are movable relative to the handle assembly by flexure provided by a pair of compliant mechanisms, respectively.

DETAILED DESCRIPTION

One example of a walk outdoor power equipment unit2having the operational controls of this invention is illustrated inFIG.1. In this example, walk outdoor power equipment unit2comprises a walk power mower4of the type homeowners commonly use to cut the grass in their lawns. However, the operational controls of this invention are not limited for use on a mower4, but could be used on other walk outdoor power equipment units2having a powered implement for performing a ground grooming or working operation and/or a traction drive for self-propelling unit2. These units2could comprise a snowblower, an aerator, a trencher, a stump grinder, a blower, and the like.

Referring further to mower4ofFIG.1by way of example, mower4has a frame6supported for movement over the ground by a plurality of wheels8. A central portion of frame6forms a generally circular cutting deck10which provides a downwardly facing cutting chamber12that is open at the bottom. A prime mover14, e.g. an internal combustion engine, an electric motor powered by an onboard battery pack, or the like, is mounted atop cutting deck10. A vertical drive shaft (not shown) of prime mover14extends downwardly into cutting chamber12.

In mower4ofFIG.1, at least one grass cutting blade (not shown) is coupled in any suitable manner to the drive shaft of prime mover14. The blade comprises or the blades collectively comprise the powered implement for performing a ground grooming or working operation. In this case, that operation is cutting grass. The results of that operation, namely the grass clippings generated by the operation of the blade(s), are thrown into a rearwardly disposed bag16in a collecting mode of operation or may be driven downwardly into the cut swath in a mulching mode of operation if bag16is not installed on mower4or mower4was not built to accommodate bag16.

In one embodiment of this invention, mower4has a traction drive (not shown) for self-propelling frame6of mower4over the ground at least in a forward direction at a variable ground speed. In other embodiments, the traction drive could be configured to self-propel frame6in both forward and reverse directions at variable ground speeds in each direction. The variable ground speeds could be infinitely variable, e.g. by infinitely changing the speed of an electric motor driving an axle that mounts rear wheels8or by shifting a continuously variable transmission driving the axle. Alternatively, the variable ground speeds could be changed in discreet steps, e.g. by shifting a multi-speed transmission driving the axle.

As further shown inFIG.1, mower4includes an upwardly and rearwardly extending handle assembly18. Handle assembly18includes a pair of parallel, laterally spaced, side tubes20connected at their lower ends to frame6of mower4. Side tubes20are joined together at their upper ends by a substantially horizontal cross tube22. When the traction drive is not powered, the operator would be able to manually maneuver frame6of mower4by gripping cross tube22and by using cross tube22to push forwardly or pull rearwardly on frame6of mower4.

Handle assembly18includes a traction speed control that in one embodiment thereof comprises a laterally extending, pivotal hand grip24carried on the upper rear end of handle assembly18forward of and above cross tube22of handle assembly18. During an actual grass cutting operation, the operator's hands will usually be gripping hand grip24rather than cross tube22. Handle assembly18further includes an implement control that in one embodiment thereof disengages and engages the operation of the blade(s) of mower4. As shown inFIG.1, the implement control may comprise a laterally extending, pivotal bail26having a general size and shape that mimics that of hand grip24. Bail26may be positioned forward of and slightly below hand grip24. Other positions of bail26relative to hand grip24are possible.

The blade(s) of mower4are disengaged when bail26is spaced away from hand grip24as shown inFIG.1. The blade(s) of mower4are engaged when the operator reaches out with the fingers of at least one hand and pivots bail26into a closed position closer to or against hand grip24. This blade engagement continues for so long as the operator holds bail26in the closed position. Bail26will automatically return to its spaced position relative to hand grip24to disengage the blade(s) when the operator releases bail26. If so desired, some type of bail latch (not shown) that must be released could be required in order for the operator to close bail26against hand grip24to mitigate the chance of the operator inadvertently starting the operation of the blade(s).

In some embodiments, this invention relates to the use of one or more compliant mechanisms to mount either or both of traction control hand grip24and implement control bail26on the top of handle assembly18. In mechanical engineering, a compliant mechanism is commonly defined as a flexible mechanism that achieves force and motion transmission through elastic body deformation. It gains some or all of its motion from the relative flexibility of its members rather than from rigid-body joints alone. The term compliant mechanism shall be used herein in accordance with this definition.

Referring now toFIGS.2-6, a first compliant mechanism28is duplicated on each side of handle assembly18to affix the opposite ends of hand grip24to the upper ends of side tubes20of handle assembly18. As best shown inFIGS.2and3, first compliant mechanism28has a fixed body portion30substantially rigidly secured to the top of the upper end of side tube20by a plurality of threaded fasteners32. Fasteners32extend upwardly through apertures in the bottom of side tube20and thread into internally threaded bores contained in posts34, best seen inFIG.5, provided on fixed body portion30of first compliant mechanism28. When each first compliant mechanism28is being installed on its respective side tube20, posts34are pushed into the interior of side tube20through apertures in the top of side tube20with the threaded bores of posts34aligning with the apertures in the bottom of side tube20. When fasteners32are then pushed up through the apertures in the bottom of side tube20and are then tightened in the downwardly facing bores of posts34, fixed body portion30of each first compliant mechanism28will be substantially rigidly mounted to its respective side tube20.

First compliant mechanism28further includes a movable body portion36that is an integral part of first compliant mechanism28but is able to flex in a generally pivotal manner with respect to fixed body portion30. Referring toFIG.3, movable body portion36has an upwardly facing, generally cylindrical socket38that receives the downwardly facing, generally cylindrical end40of one side of hand grip24. Once hand grip end40is inserted into socket38, a laterally extending, horizontal bolt42passes through aligned apertures in hand grip end40and socket38. When a nut44and washer46are tightened on the end of bolt42, hand grip end40is substantially affixed to movable body portion36of first compliant mechanism28.

In the embodiment shown inFIG.3, bolt42does double duty as it extends beyond first compliant mechanism28to rigidly affix a portion of a second compliant mechanism48to the inner side of first compliant mechanism28. Second compliant mechanism48movably mounts bail26adjacent hand grip24in a manner that will be described more fully hereafter. However, in embodiments of the invention in which the implement control formed by bail26is not used and there is no second compliant mechanism48, bolt42shown inFIG.3will be shorter and the nut44and washer46will directly engage against the inner side of first compliant mechanism28rather than the inner side of second compliant mechanism48.

Referring now toFIG.5hereof, the centerline39of socket38of movable body portion36of first compliant mechanism28is aligned with a narrow web50which connects the movable and fixed body portions28,48of first compliant mechanism28together to unify them into a unitary structure. A first relatively long, open ended, front slot52is placed forward of web50and extends through the thickness of first compliant mechanism28. A second relatively short, open ended, rear slot54is placed rearward of web50and also extends through the thickness of first compliant mechanism28. Second slot54has an open end that comprises a relatively small slit56while the first slot has an open end that is much larger.

Referring toFIG.3, movable body portion36of first compliant mechanism28has a front end58. The opposite sides of front end58include two reduced diameter portions60that extend laterally outwardly from opposite sides of front end58. Reduced diameter portion60on the inward side of front end58of movable body portion36of first compliant mechanism28will be received within a front circular opening62on second compliant mechanism48. This helps locate second compliant mechanism48on first compliant mechanism28.

As best shown inFIG.4, front end58of movable body portion36of first compliant mechanism28has a vertical bore64extending downwardly from the top thereof. A small cylindrical magnet66can be inserted into and pushed downwardly into bore64until magnet66rests atop an inwardly extending ledge (not shown) within bore64as shown inFIG.4. Magnet66can be retained in this position by a pair of flexible detents (not shown) on opposite sides of bore64which allow magnet66to pass as it is inserted through bore64but which then snap over on top of magnet66once magnet66has reached the ledge. Other ways of attaching magnet66to front end58of movable body portion36of first compliant mechanism28could be used.

Referring now toFIGS.3and4, the top of a front end of fixed body portion30of first compliant mechanism28includes an upwardly open pocket68. An electrically operated sensor, such as, but not limited to, a Hall sensor70, is installed in a horizontal slideway72at the top of pocket68as best shown inFIG.4. Two apertures74also shown inFIG.4are disposed respectively on either side of slideway72. Once Hall sensor70is fully inserted in slideway72, two screws76are threaded into apertures74. When screws76are so installed, portions of the heads of screws76will abut against opposite sides of Hall sensor70to retain Hall sensor70in slideway72as best shown inFIG.3.

FIG.5illustrates first compliant mechanism28in a neutral position in which it has not been deformed or flexed by force applied to hand grip24. If the operator wishes to adjust the traction speed of mower4and is gripping hand grip24, the operator need only push forwardly on hand grip24. This will cause front end58of movable body portion36of first compliant mechanism28to flex or pivot generally downwardly towards fixed body portion30in the direction of arrow A inFIG.5. This motion is permitted by front slot52in first compliant mechanism28which will narrow somewhat as hand grip24is pushed forwardly and by rear slot54which will expand somewhat as hand grip24is pushed forwardly.

Conversely, the operator cannot meaningfully move hand grip24in the opposite or rearward direction from neutral. This is prevented by the very narrow slit56that forms the opening on rear slot54. Slit56will substantially immediately closed upon such rearward motion of hand grip24. Thus, in a unidirectional variable speed traction drive embodiment of the invention under consideration here, movable body portion36of first compliant mechanism28becomes rigid almost immediately upon any motion of hand grip24in a rearward direction from neutral. In other bidirectional, variable speed traction embodiments, slit56that forms the open end of rear slot54could be much wider to allow movable body portion36of first compliant mechanism28to flex meaningfully rearwardly when hand grip24is moved rearwardly out of neutral.

Together, magnet66and Hall sensor70provide a motion sensing device that can infinitely determine the degree of motion of movable body portion36relative to fixed body portion30. This motion is caused by the operator moving hand grip24forwardly to set or select a desired forward traction speed. The motion information provided by Hall sensor70is sent to an electronic controller on mower4. The electronic controller then varies the operational speed of the traction drive in concert with how far hand grip24has been pivoted forwardly by the operator out of a neutral position thereof.

Referring now toFIGS.3and6, second compliant mechanism48has a fixed body portion78that includes a lateral passage80that receives bolt42that secures movable body portion36of first compliant mechanism28to hand grip24. In addition, reduced diameter portion60of front end58of movable body portion36of first compliant mechanism28is inserted into circular opening62of fixed body portion78of second compliant mechanism48. When nut44and washer46are tightened on bolt42, fixed body portion78of second compliant mechanism48will be drawn towards and clamped tightly against the inner side of movable body portion36of first compliant mechanism28as best shown inFIG.2. Thus, as movable body portion36of first compliant mechanism28flexes during motion of hand grip24to control the traction drive, second compliant mechanism48will move with movable body portion36of first compliant mechanism28with bail26maintaining a fixed orientation relative to hand grip24.

Second compliant mechanism48has a movable body portion82which includes an upwardly facing, generally cylindrical socket84that receives the downwardly facing, generally cylindrical end86of one side of bail26. Once bail end86is inserted into bail socket84, a laterally extending fastener (not shown) passes through aligned apertures in bail end86and bail socket84to secure bail26to movable body portion82of second compliant mechanism48. When the pair of second compliant mechanisms48are mounted on the pair of first compliant mechanism28and the opposite ends86of bail26are inserted into bail sockets84on the pair of laterally spaced second compliant mechanisms48, bail26will be disposed in an implement disengaged position spaced away from hand grip24as best shown inFIG.2.

Referring now toFIG.6hereof, the centerline85of bail socket84of movable body portion82of second compliant mechanism48is aligned with a narrow web88that connects the fixed and movable body portions78,82of second compliant mechanism48together to unify them into a unitary structure. A first relatively long, open ended, front slot90is placed forward of web88and extends through the thickness82of second compliant mechanism48. A second relatively long, open ended, rear slot92is placed rearward of web88and also extends through the thickness of first compliant mechanism28. First slot90has an open end that comprises a relatively small slit94while second slot92has an open end that is much larger.

As further shown inFIG.6, fixed body portion78of second compliant mechanism48includes an upwardly open switch housing96that receives the case of an on/off type electrical switch98. Switch98has a plunger100that is outwardly biased by an internal spring within the case. Plunger100when fully extended from the case in the off position of switch98is in contact with or spaced close to a rear wall102of movable body portion82of second compliant mechanism48. In order to change the state of switch98from off to on, the rear wall of movable body portion82of second compliant mechanism48must be moved rearwardly inFIG.6to depress plunger100relative to the case of switch98sufficiently to change the state of switch98to on. When switch98is placed into the on state, the controller of mower4will receive an activation signal and will engage the operation of the implement, e.g. start the blade(s) of mower4rotating when outdoor power equipment unit2comprises a mower4as shown inFIG.1.

The motion of movable body portion82of second compliant mechanism48which is needed to actuate switch98is caused by the operator closing bail26from its usual position spaced away from hand grip24to an implement engaged position adjacent to or in contact with hand grip24. The force applied by bail26to movable body portion82of second compliant mechanism48is sufficient to flex movable body portion82of second compliant mechanism48about web88relative to fixed body portion78of second compliant mechanism48. This will cause rear wall102of movable body portion82of second compliant mechanism48to flex or pivot generally downwardly/rearwardly towards switch98in the direction of arrow B inFIG.6. This motion is permitted by rear slot92in second compliant mechanism48which will narrow somewhat as bail26is pulled rearwardly and by front slot90which will expand somewhat as bail26is pulled rearwardly. The amount of motion allowed upon the closing of bail26will be sufficient to change the state of switch98from off to on to thereby start the operation of the implement.

One material which can be used to manufacture first compliant mechanism28and/or second compliant mechanism48or any other compliant mechanism described in this application is a thermoplastic polyester elastomer such as DuPont Hytrel7246.

Each compliant mechanism28,48could be used in an outdoor power equipment unit2without using the other. For example, in another embodiment of the invention depicted inFIGS.7and8hereof, first compliant mechanism28has been removed in favor of a first non-compliant mechanism28′ for mounting hand grip24to handle. Each first non-compliant mechanism28′ is duplicated on both side tubes20when hand grip24extends across the full width of handle18. Since first non-compliant mechanism28′ is similar to first compliant mechanism28, the reference numerals used to refer to the same components of first compliant mechanism28will be used to refer to the corresponding components of first non-compliant mechanism28′ with a single prime designation following the reference numeral.

First non-compliant mechanism28′ has a substantially rigid fixed body portion30′ and a substantially rigid movable body portion36′ having overall shapes and functions similar to their compliant counterparts30,36. As best shown inFIG.8, fixed body portion30′ has a cavity104that includes aligned apertures106in spaced side walls108of cavity104. A protrusion or plug110on an underside of a rear portion of movable body portion36′ fits down into cavity104. Plug110has a through bore112that is aligned with apertures106in side walls108of cavity104when movable body portion36′ is assembled onto fixed body portion30′. A rigid pivot pin114then passes through apertures106and bore112. Pivot pin114can be secured by a bolt (not shown) on one end of pivot pin114to provide a mechanical pivot connection between fixed body portion30′ and movable body portion36′.

As shown inFIG.7and in addition to pivot pin114, a mechanical compression spring116normally biases movable body portion36′ in a direction that places hand grip24in a neutral position in which the speed of the traction drive is zero. The neutral position could be established by a physical stop (not shown) between fixed body portion30′ and movable body portion36′ that limits further pivotal motion of hand grip24rearwardly.

When the operator pushes forwardly on hand grip24to control the speed of the traction drive, the movable body portion36′ will pivot downwardly about pivot pin114to compress spring116against fixed body portion30′. Magnet66and Hall sensor70are present in this embodiment and will function as in the first embodiment ofFIGS.2-6to control the traction speed depending upon the degree of downward pivoting of movable body portion36′ relative to fixed body portion30′. When the operator releases hand grip24, the compression built up in spring116will return hand grip24to its neutral position.

Second compliant mechanism48as disclosed inFIGS.1-6is still used in the embodiment ofFIGS.7and8to support bail26for pivotal motion relative to hand grip24. Second compliant mechanism48is clamped against the side of movable body portion36′ of first non-compliant mechanism28′ by bolt42which passes through aperture80in second compliant mechanism48. In addition, the opening62in the nose of second compliant mechanism48is still received on the reduced diameter portion60′ (hidden inFIG.8) on the inward side of front end58′ of movable body portion36′ of first non-compliant mechanism28′. This helps prevent any rotation of second compliant mechanism48relative to first non-compliant mechanism28′ about the axis of bolt42. Second compliant mechanism48as used in the embodiment ofFIGS.7and8works identically to its operation in the embodiment ofFIGS.1-6.

In a further variation, first compliant mechanism28could be used with second compliant mechanism48being removed and being replaced by a non-compliant mechanism which includes a rigid pivot and mechanical spring.

Referring now toFIG.9, an additional embodiment of this invention comprises a first non-compliant mechanism28″ which is duplicated and mounted on each side tube20of handle assembly18. First non-compliant mechanism28″ ofFIGS.9and10is a modified version of the first non-compliant mechanism28′ ofFIGS.7and8. Since first non-compliant mechanism28″ is similar to first non-compliant mechanism28′, the reference numerals used to refer to the same components of first compliant mechanism28′ will be used to refer to the corresponding components of first non-compliant mechanism28″ with a double prime designation following the reference numerals.

In this embodiment, there are no second compliant mechanisms48for providing pivotal motion of bail26. Instead and referring toFIG.10, the bottom of each side of bail26has an outwardly turned circular end that forms a rigid pivot pin118. Each pivot pin118is rotatably received in a circular aperture of bushing120on movable body portion36″ of each first non-compliant mechanism28″. This pivotally journals the opposite ends of bail26directly on the pair of laterally spaced first non-compliant mechanisms28″,28″ mounted on side tubes20,20of handle18.

As further shown inFIG.10, a coil122of a torsion spring124is concentrically installed around a pivot pin118. One leg126of torsion spring124is hooked around a rear portion of one side of bail26. The other leg128of torsion spring124will abut against a fixed portion of movable body portion36″ of the adjacent first non-compliant mechanism28″ to which the one side of bail26is journalled.

Normally, the bias of spring124will serve to move bail26to its neutral position spaced away from hand grip24as shown inFIG.9. When bail26is pivoted to its closed position adjacent to or in contact with hand grip24, torsion spring124will be wound up to store force therein. When the operator releases bail26, this stored up force in torsion spring124will return bail2to its neutral position. Torsion spring124can be used on just one pivot pin118on one side of bail26or can be duplicated and used on both pivot pins118on both sides of bail26.

In the embodiment ofFIGS.9and10, the second compliant mechanism48disclosed inFIGS.1-8is no longer needed to pivotally mount bail26in view of the mounting(s) provided by pivot pin118and spring124. However, a modified second compliant mechanism48″ is still used with respect to the operation of bail26. Since second compliant mechanism48″ is similar to second compliant mechanism48ofFIGS.1-8, the reference numerals used to refer to the same components of second compliant mechanism48will be used to refer to the corresponding components of second compliant mechanism48″ with a double prime designation following the reference numerals.

As shown inFIG.9, second compliant mechanism48″ comprises a fixed body portion78″ that is clamped to the inward side of movable body portion36″ of first non-compliant mechanism28″. Referring toFIG.10, this is accomplished by bolt42which passes through an aperture80″ in second compliant mechanism48″ to pull fixed body portion78″ of second complaint mechanism48″ tightly against first non-compliant mechanism28″ when a nut (not shown) on the free end of bolt42is tightened. In addition, the opposite sides of a rear end130of movable body portion36″ of first non-compliant mechanism28″ include two reduced diameter portions60″ that extend laterally outwardly from opposite sides of rear end130. The reduced diameter portion60″ on the inward side of rear end130(not visible inFIG.10) will be received within a rear circular opening62″ on second compliant mechanism48″. The engagement of reduced diameter portion60″ in opening62″ helps prevent any rotation of second compliant mechanism48″ relative to first non-compliant mechanism28″ about the axis of bolt42.

Fixed body portion78″ of second compliant mechanism48″ still includes a switch housing96″ that receives the case of an on/off type electrical switch98″. Switch98″ has a plunger100″ that is outwardly biased by an internal spring within the case. Second compliant mechanism48″ has a movable body portion82″ that can flex relative to fixed body portion78″ by virtue of an elongated slot92″ that permits such flexure. A rear wall102″ of movable body portion82″ is slightly spaced from or in slight contact with plunger100″ of switch98″. Second compliant mechanism48″ is used on only one side of bail26as it not needed on the other side of bail26.

As shown inFIGS.9and10, when bail26is in its neutral or implement disengaged condition, bail26is spaced forwardly of movable body portion82″ of second compliant mechanism48″. The upper portion of movable body portion82″ includes a forwardly facing U-shaped cradle132which is shaped to receive a rearward portion of one leg134of bail26. When the operator pivots bail26from its neutral position towards hand grip24, the first lost motion portion of its travel takes up the space between bail26and cradle132. Once bail leg134seats itself within cradle132, further motion of bail26towards hand grip24causes movable body portion82″ of second compliant mechanism48″ to flex or pivot generally downwardly/rearwardly towards switch98in the direction of arrow B″ inFIG.10. The amount of such flexure is sufficient to depress plunger100″ and thereby actuate switch98″ to begin the operation of the powered implement, e.g. the blades of mower4.

The use of either or both of the first and second compliant mechanisms28,48to mount traction drive and implement controls on the handle of a walk outdoor power equipment unit2is an advance in the art. It avoids the cost of using numerous rigid pivots and mechanical springs in the limited spaces available for the controls at the top of handle assembly18. In addition, while the embodiment ofFIGS.9and10use rigid pivots and mechanical springs to mount the traction drive and implement controls, it still retains the use of a compliant mechanism48″ arranged in a lost motion manner relative to bail26to operate switch98″. This allows bail26to have a larger throw or arc of movement relative to hand grip24, i.e. bail26when its neutral position is spaced further away from hand grip24, as shown by comparing the positons of bail26relative to hand grip24as shown inFIGS.2and9.

Various modifications of this invention will be apparent to those skilled in the art. For example, the use of a hand grip24and bail26that span the full width of handle assembly18and which are mounted by duplicate first and second compliant mechanisms to side tubes20is only one preferred embodiment of such controls. Hand grip24and bail26could be mounted only to one side tube20and extend only partially across the width of handle assembly18.

Various other modifications will be apparent to those skilled in the art. Accordingly, the scope of this invention is to be limited only by the appended claims.