Abstract:
An engine starting and stopping device includes a first roller selectively abutting the flywheel of an engine for rotation on a first shaft in response to rotation of the flywheel. A second roller abuts the first roller and rotates in response to rotation of the first roller. A second shaft and an overwind clutch couple the second roller with a third roller such that the third roller rotates in response to rotation of the second roller. The third roller abuts a spring housing and causes rotation of the spring housing in response to rotation of the third roller. A spring is housed within the spring housing and is loaded in response to rotation of the spring housing. The overwind clutch slips when the spring is loaded to a preselected level to protect the spring from overwinding. The spring is selectively unloaded to rotate the spring housing in an unloading direction. Rotation of the spring housing in the unloading direction causes rotation of the engine&#39;s crankshaft and startup of the engine.

Description:
This application is a continuation-in-part of U.S. application Ser. No. 09/709,859 filed Nov. 10, 2000, now U.S. Pat. No. 6,386,169, which is a continuation of U.S. application Ser. No. 09/183,425 filed Oct. 30, 1998, now U.S. Pat. No. 6,230,678. The entire contents of both prior applications are incorporated herein by reference. 
    
    
     BACKGROUND 
     The invention relates to a starting and stopping device for an internal combustion engine. More specifically, the present invention relates to a mechanism for starting the engine by unloading stored power in an elastic member. 
     SUMMARY 
     The present invention provides a starting device for use on an internal combustion engine that includes an engine housing, a crankshaft mounted for rotation within the engine housing, and a flywheel mounted to the crankshaft for rotation therewith. The starting device includes a rotatable spring housing. An energy storing mechanism, including at least one elastic member, is housed within the spring housing. The elastic member is loaded in response to the spring housing rotating in a loading direction, and the spring housing rotates in an unloading direction in response to unloading of the elastic member. 
     A movable bracket is mounted to the engine housing. First, second, and third rollers are supported for rotation. At least one of the rollers is supported by the movable bracket. 
     An actuation assembly selectively moves the movable bracket between an engaged position and a disengaged position. When the bracket is in the engaged position, rotation of the flywheel is converted through the rollers into rotation of the spring housing in the loading direction. However, when the bracket is in the disengaged position, rotation of the flywheel is not converted into rotation of the spring housing. 
     To cause startup of the engine, a coupling mechanism couples the spring housing with at least one of the flywheel and the crankshaft in response to the spring housing rotating in the unloading direction. 
     A ratchet wheel is preferably mounted to the spring housing for rotation therewith, and a pawl is preferably mounted to the movable bracket to engage the ratchet wheel and to resist rotation of the spring housing in the unloading direction. The pawl is removable from engagement with the ratchet wheel upon pivoting or otherwise moving the bracket to the disengaged position, thereby permitting the elastic member to unload. 
     Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims, and drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a lawnmower embodying the present invention. 
     FIG. 2 is a cross-section view of a portion of the lawnmower illustrated in FIG.  1 . 
     FIG. 3 is a view taken along line  3 — 3  in FIG.  2 . 
     FIG. 4 is a view taken along line  4 — 4  in FIG.  2 . 
     FIG. 5 is a view taken along line  5 — 5  in FIG. 4 showing the spring loading mechanism in an engaged position. 
     FIG. 6 is a view taken along line  5 — 5  in FIG. 4 showing the spring loading mechanism in a disengaged position. 
    
    
     Before one embodiment of the invention is explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including” and “comprising” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The use of “consisting of” and variations thereof herein is meant to encompass only the items listed thereafter. The use of letters to identify elements of a method or process is simply for identification and is not meant to indicate that the elements should be performed in a particular order. 
     DETAILED DESCRIPTION 
     FIG. 1 illustrates a lawnmower  10  comprising a deck  14 , a blower housing or stationary housing  18 , an engine  20  (FIG. 2) mounted to the deck  14  and supporting the stationary housing  18 , a set of wheels  22  supporting the deck  14  above the ground, and a handle assembly  26  extending up from the deck  14 . The lawnmower  10  also includes first and second manual actuators, which are a bail handle  30  and push button  34  in the illustrated embodiment, supported on the handle  26  at a location remote from the engine  20 . The bail handle  30 , or alternatively the push button  34 , is operatively interconnected with mechanisms in the engine  20  by way of a cable.  36 . As will be described below in more detail, the bail handle  30  and push button  34  must both be actuated in order to start up the engine  20 . The bail handle  30 , push button  34 , and cable  36  are part of the control system of the engine  20 . Alternatively, other types of manual actuators may be used, such as levers, knobs, removable keys, etc. 
     It should be noted that although the invention is illustrated as embodied in a lawnmower  10 , the invention may be embodied in other devices powered by either a four-stroke or two-stroke cycle internal combustion engine. In some applications it may be desirable to have a two-step engine starting sequence. In other applications, it may be that only a single manual actuator, such as a push button or bail handle, is actuated to start the engine  20 . 
     During operation of the lawnmower  10 , the bail handle  30  must be moved to a start position  38  (FIG. 1) near the end of the handle assembly  26  to keep the engine  20  operating. The bail handle  30  is biased to move to a rest position (see FIG. 1) once let go by the operator. This causes the ignition circuit of the engine  20  to be grounded and shutdown of the engine  20  to be initiated. In order to move the bail handle  30  to the start position  38 , the push button  34  must first be depressed and held while the bail handle  30  is moved. Depressing the push button  34  disengages a lock on the bail handle  30  or on another movable member in the engine starting mechanism (discussed in further detail below) that is required to start the engine  20 . Alternatively, the bail handle  30  and push button  34  may be configured such that the bail handle  30  must first be moved to the start position  38  to enable the push button  34  to be actuated, in which case actuation of the push button  34  starts the engine  20 . 
     Turning now to FIG. 2, the engine  20  includes a crankshaft  42  that rotates in a known manner to drive a cutting blade positioned under the deck  14  of the lawnmower  10 . The crankshaft  42  may be vertically-oriented as in the illustrated embodiment such that the cutting blade is attached directly to the lower end of the crankshaft  42 . Alternatively, it can be oriented horizontally or non-vertically. Mounted to the top end of the crankshaft  42  are a flywheel  46  and a starter cup  50 . A nut  54  may be threaded onto the end of the crankshaft  42  to secure the starter cup  50  and flywheel  46  to the top end of the crankshaft  42 , as illustrated. 
     A shaft  56  is fixed to the stationary housing  18  (as by welding or integral forming), and extends down inside the housing  18 . A recoil starter pulley  58  is rotatably mounted to the shaft  56  above the flywheel  46 , crankshaft  42 , and starter cup  50  by way of a one-way clutch  60 . A starter pull rope  62  is wound around the starter pulley  58 . The one-way clutch  60  couples the starter pulley  58  with an arbor  70 , such that pulling the starter rope  62  rotates the starter pulley  58  and the arbor  70  in a starting direction  74  (FIG.  3 ). 
     A plurality of dogs  78  are pivotably mounted to the lower end of the arbor  70  and engage the starter cup  50  upon rotation of the arbor  70  in the starting direction  74  to thereby couple the recoil pulley  58  and crankshaft  42  for rotation together. The dogs  78  and cup  50  are therefore part of a centrifugal coupling mechanism between the arbor  70  and the crankshaft  42 . Alternatively, the dogs  78  may be mounted to the starter cup  50 , and may be spring-biased toward engagement with the arbor  70 . Under such an arrangement, the dogs  78  would retract against the bias of the springs to uncouple the recoil pulley  58  from the crankshaft  42  once the crankshaft  42  has reached a predetermined rotational speed. 
     The two-stroke or four-stroke cycle of the engine  20  is started in response to rotation of the crankshaft  42  and flywheel  46  in the starting direction  74 , and the crankshaft  42  and flywheel  46  continue to rotate in the starting direction  74  during operation of the engine  20 . A recoil spring is housed within the recoil pulley  58  to rewind the starter rope  62  onto the starter pulley  58  once the engine  20  is started. 
     Also mounted around the arbor  70  above the crankshaft  42  and flywheel  46  is a spring housing  82 . A second unidirectional clutch  86  permits rotation of the spring housing  82  in a spring loading direction  90  (FIG. 3) with respect to the arbor  70 , but couples the arbor  70  and spring housing  82  together for rotation in the starting direction  74 . An elastic member or spring  94 , which is a coil of spring steel in the illustrated embodiment, is housed within the spring housing  82 . The spring housing  82  has an open top that is covered partially by a portion of an engine housing  98 . 
     The portion of the engine housing  98  also extends down into the spring housing  82 , and there defines two eyelets  102 . The inner end  104  of the spring  94  describes a hook  108  that releasably interconnects with one of the eyelets  102 . The outer end  110  of the spring  94  is mounted to the spring housing  82  with a bolt, hook, or the like. The spring  94  wraps around the inner portion of the engine housing  98  and is loaded in response to the spring housing  82  rotating in the loading direction  90 . 
     The spring housing  82  rotates with respect to the engine housing  98  in the starting direction  74  in response to unloading of the spring  94 . The rewind pulley  58  does not rotate when the spring  94  is unloading, because the unidirectional clutch  60  does not couple the arbor  70  and the rewind pulley  58  for rotation together when the arbor  70  rotates in the starting direction  74 . Because the second unidirectional clutch  86  transforms rotation of the spring housing  82  in the starting direction  74  into rotation of the arbor  70  in the same direction, the dogs  78  engage the starter cup  50  as described above. The engine  20  may, therefore, be started in response to the spring  94  becoming unloaded. 
     A spring loading mechanism is illustrated in FIGS. 2-4. The spring loading mechanism includes a bracket  114 , first and second shafts  118 ,  122  mounted to the bracket  114 , and first, second, and third rollers  126 ,  130 ,  134 . As used herein, “rollers” means either the resilient (e.g., rubber) friction rollers illustrated or toothed members such as gears. Also included in the spring loading mechanism is a locking mechanism that includes a ratchet wheel  138  (FIGS. 2 and 4) mounted under the spring housing  82  and a pawl  142  mounted to the bracket  114  and in engagement with the ratchet wheel  138 . 
     As seen in FIGS. 2 and 4, the first and second shafts  118 ,  122  are supported for rotation with respect to the bracket  114  by bearings or bushings  146 . The first roller  126  is fixed to the first shaft  118 , and the second roller  130  is fixed to the second shaft  122 . Alternatively, the first shaft  118  may be fixed to the bracket  114  and the first roller  126  be rotatable about the first shaft  118 . The second shaft  122  is supported by bearings or bushings  150  in support arms  151  that are mounted to the engine housing  98 . The bracket  114  is therefore pivotable about the second shaft  122 . The pivot axis for the bracket  114  is therefore coaxial or collinear with the axis of rotation of the second shaft  122  in the illustrated embodiment. In alternative embodiments, a pivot axis for the bracket  114  may be provided that is non-coaxial with respect to the axis of rotation of the second shaft  122  (e.g., as shown in phantom at  152  in FIG.  3 ). This would permit both rollers  126 ,  134  to disengage the flywheel  46  and spring housing  82 . 
     The third roller  134  is coupled to the second shaft  122  by way of a friction clutch or overwind clutch  154 , the significance of which will be discussed below. The overwind clutch  154  includes a nut threaded onto the second shaft  122  and a Belleville washer and a flat washer sandwiched between the nut and the third roller  134 . A shoulder  158  (FIG. 4) may be provided on the second shaft  122  to provide a bearing surface against which the third roller  134  is pressed as the nut is tightened. Provided the friction limit in the overwind clutch  154  is not exceeded, the third roller  134  will rotate with the second shaft  122  in response to rotation of the second roller  130 . The second shaft  122  may be termed a “coupling shaft.” 
     It should be noted that the overwind clutch  154  could alternatively be used to couple the second roller  130  to the second shaft  122  or to couple the first roller  126  to the first shaft  118 . The overwind clutch  154  will reduce the likelihood that the spring  94  will overwind, provided the overwind clutch  154  is operatively positioned substantially anywhere between the spring  94  and the crankshaft  42 . Therefore, the specific position of the overwind clutch  154  illustrated should not be regarded as limiting. 
     Turning to FIGS. 5 and 6, the bracket  114  is pivotable between an engaged position (FIG. 5) and a disengaged position (FIG.  6 ). The third roller  134  is in contact with the spring housing  82  whether the bracket  114  is in the engaged or disengaged position. The cable  36  and a return spring  162  are interconnected to the end of the bracket  114  opposite the pivot axis. The bracket  114  may be pivoted to the disengaged position in response to actuation of one or both of the manual actuators  30 ,  34  through the cable  36 . 
     During operation of the engine  20 , the bail handle  30  is maintained in the start position  38 , which holds the bracket  114  in the disengaged position. When the bail handle  30  is released, the first roller  126  is moved into engagement with the flywheel  46  under the influence of the return spring  162 . As seen in FIG. 5, the coastdown rotation of the flywheel  46  in the starting direction  74  causes the first roller  126  to rotate in the opposite direction (counterclockwise in the illustrated embodiment), which causes the second and third rollers  130 ,  134  to rotate opposite (e.g., clockwise) the direction of rotation of the first roller  126 . 
     The third roller  134 , through its engagement with the spring housing  82 , causes the spring housing  82  to rotate in the loading direction  90 , which is opposite the starting direction  46  or counterclockwise. Rotation of the spring housing  82  in the loading direction  90  winds the spring  94  around the inner portion of the engine housing  98  and loads the spring  94 . The pawl  142  engages the ratchet wheel  138  and prevents the spring  94  from unloading. 
     As the spring  94  winds tighter, the resistance is transmitted back through the third roller  134 , overwind clutch  154 , second shaft  122 , second roller  130 , and first roller  126  to the flywheel  46  and crankshaft  42 . This has a braking effect on the flywheel  46  and crankshaft  42  and helps bring them to a stop. If the load in the spring  94  exceeds a predetermined amount, the torque transmitted from the second shaft  122  to the third roller  134  will become high enough to overcome the frictional forces in the overwind clutch  154 , thereby decoupling the flywheel  46  and crankshaft  42  from the spring housing  82  and protecting the spring  94  from overwinding and potentially being damaged. 
     It should be noted that the arrangement of the flywheel  46 , first roller  126 , and second roller  130  causes the spring loading mechanism to be self-actuating. In other words, as the spring  94  tightens in the spring housing  82 , the first roller  126  must transmit more and more torque to the second roller  130  to continue loading the spring  94 . Because of the arrangement of parts, the first roller  126  will attempt to crawl in the counterclockwise direction (as seen in FIG. 5) around the second roller  130 , which causes the first roller  126  to be pressed tighter and tighter against the flywheel  46 . The resulting increase in normal force between the flywheel  46  and the first roller  126  permits the first roller  126  to transmit more torque to the spring housing  82  through the second roller  130 , second shaft  122 , and third roller  134  up to the point where the overwind clutch  154  slips or the flywheel  46  and crankshaft  42  rotation stops. 
     In light of the self-energizing nature of the spring loading mechanism, the return spring  162  only has to be strong enough to bring the first roller  126  into contact with the flywheel  46  with enough normal force to transmit the initial rotations to the spring housing  82 . Once spring loading is initiated, the return spring  162  does not have to provide increasing normal force between the first roller  126  and the flywheel  46 , as that is automatically accomplished with the self-energizing arrangement of parts described above. 
     It should also be noted that only one of the rollers  126 ,  130 ,  134  need be movable to engage and disengage one of the other rollers, the flywheel  46 , or spring housing  82  to interengage and disengage the flywheel  46  and spring housing  82 . In alternative embodiments, for example, the first roller  126  alone may be mounted to the movable bracket  114  and the second roller  130 , second shaft  122 , and third roller  134  may be supported independent of the bracket  114  at a fixed location. In other alternative embodiments, the first roller  126  could be rotatable mounted at a fixed location in engagement with the flywheel  46 , and the second roller  130 , second shaft  122 , and third roller  134  may be carried by a movable bracket and movable into and out of engagement between the first roller  126  and the spring housing  82 . 
     In still another alternative embodiment, the three rollers  126 ,  130 ,  134  may all be in fixed locations, with the first roller  126  engaging both the flywheel  46  and the second roller  130 , and the third roller  134  engaging the spring housing  82 . In such an alternative construction, the movable bracket  114  may engage and disengage a clutch that couples the second and third rollers  130 ,  134  for rotation together. 
     Startup of the engine  20  is accomplished by actuating the push button  34  and the bail handle  30  (or one or more other manual actuators). This causes the cable  36  to tighten and pivot the bracket  114  clockwise as seen in FIGS. 5 and 6. This removes the pawl  142  from the ratchet wheel  138  and permits the spring  94  to unload. The resulting rotation of the spring housing  82  in the starting direction  74  is transmitted to the flywheel  46  and crankshaft  42  through the arbor  70 , dogs  78 , and cup  50 . The engine  20  is capable of sustaining rotation of the flywheel  46  and crankshaft  42  once the crankshaft  42  has started rotating. 
     The hook  108  on the inner end  104  of the spring  94  slides out of the eyelet  102  in the engine housing  98  once the spring  94  has substantially entirely unloaded. This prevents the spring  94  from bending back on itself at the inner end  104  and snapping. In this regard, the hook and eyelet  10 ,  102  arrangement is essentially a one-way clutch, and may be replaced with other suitable one-way clutches. 
     In an alternative embodiment, the bracket  114  may be pivoted by an automatic spring loading mechanism that pivots the rollers  126 ,  130 ,  134  into engagement with the flywheel  46  and spring housing  82  during operation of the engine  20  rather than during engine coastdown. The automatic spring loading mechanism would also remove the rollers  126 ,  130 ,  134  from engagement with one or both of the flywheel  46  and spring housing  82  once the spring  94  is sufficiently loaded. Also, the overwind clutch  154  would let the third roller  134  slip with respect to the second shaft  122  once the spring  94  is loaded to a selected amount. 
     While it is preferred that the first roller  126  include a resilient roller portion that is easily engageable and disengageable with the flywheel  46 , the first roller  126  may also include a toothed portion (e.g., above or below the resilient roller portion). The second roller  130  may be a toothed member, such as a gear, that meshes with the toothed portion of the first roller  126 . A ring gear may be mounted around the outside of the spring housing  82 , or gear teeth otherwise may be provided on the outside of the spring housing  82 . The third roller  134  may also be a toothed member that meshes with the gear teeth on the outside surface of the spring housing  82 . The first, second, and third rollers  26 ,  30 ,  34  may therefore include different combinations of gears and resilient rollers than that shown in the accompanying drawings.