Abstract:
A modular, self-contained, bi-directional wheel clutch unit selectively attachable and detachable as a unit to and from an axle, the unit including a rotatable wheel-driving hub including a casing portion, a clutch cage disposed in the casing portion and surrounded thereby and which has a plurality of circumferentially-distributed openings, a rotatably driven cam element disposed in the casing portion and surrounded by the clutch cage and which has a plurality of discrete surfaces thereon, and a plurality of rollers rotatably disposed within the casing portion and within the clutch cage openings. The rollers are located between the casing portion and the cam element discrete surfaces and have an engaged position wherein the cam element and the hub are in binding engagement through the rollers and the hub is rotatably driven by the cam element, and a disengaged position wherein the hub is freely rotatable relative to the cam element.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]    This application claims the benefit under 35 U.S.C. § 119 (e) of U.S. Provisional Application No. 60/293,332, filed May 24, 2001. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to clutches useful for lawn and garden implements, specifically bi-directional overrunning clutches.  
           [0004]    2. Description of the Related Art  
           [0005]    Lawn and garden implements, for example, mowers, tillers and snow throwers, often comprise a transaxle through which power from an engine is transmitted to ground-engaging wheels attached to axles extending from the transaxle for propelling the implement. These implements are often difficult to steer, owing to their weight, size, or the particular way in which the geartrain of the transaxle is designed. As to their geartrain design, many transaxles are provided with a solid axle which transmits an equal amount of torque to each of the pair of ground-engaging wheels, and during a turn, the wheel at the inside of the turn rotates at the same speed as the wheel at the outside of the turn; the wheel at the inside of the turn must be skidded on the ground to some degree, a considerable degree for sharp turns, in order to negotiate the turn. Controlling the implement can thus be a problem for some operators having insufficient strength or weight to force the implement through the turn as desired.  
           [0006]    Previous attempts to address this problem include providing the transaxle with a differential, which allows the two ground-engaging wheels to rotate at different speeds, as is well known in the art. Through use of a differential, the wheel at the inside of the turn is not skidded on the ground during the turn; rather it slows down, while the wheel at the outside of the turn correspondingly speeds up. Differential arrangements, while improving the amount of control during cornering, add considerable cost to the transaxle. Moreover, even if the implement is provided with a differential-equipped transaxle, a not insubstantial amount of force is still required to initiate the turn and hold the implement therethrough. Thus, transaxles having differential arrangements do not provide satisfactorily controllable implements for all operators.  
           [0007]    Another possible approach is the use of clutches to control the implement by powering or disengaging power from the ground engaging wheels, thereby providing a limited means for steering the implement. Some clutches which provide such control include means for selective disengagement of the input and output members (see, e.g., U.S. Pat. Nos. Re. 25,229, 2,951,568, and 3,429,408) or, specifically, include a spring which expands to produce engagement between the input and output members (see, e.g., U.S. Pat. Nos. 3,040,855 and 5,029,689). Previous wheel clutches may also use left and right hand grip-mounted triggers to engage and disengage the clutches. Such systems do provide means for simple engagement and disengagement of the clutches and limited power steering capabilities, but do not provide an intuitive, passive means for easily controlling the turning of the implement.  
           [0008]    Another alternative has been steering mechanisms which use bi-directional overrunning clutches at each wheel. One such clutch is the Bi-Directional Clutch, designed and manufactured by the Motion Control Division of Hilliard Corporation of Elmira, N.Y. A change in the direction and/or speed of the implement causes the bi-directional clutch to sense the change and to allow overrunning of its connected wheel. Sensing the change in direction and speed is accomplished with a roller ramp design which allows a roller (maintained within a roll cage) to move between an outer race and multiple flat cams to engage and disengage the engine and transaxle. This clutch must be assembled directly to the axle, piece-by-piece, such as would occur when the implement is originally manufactured. Thus, as a practical matter, this clutch may only be added to an implement by the original equipment manufacturer, thereby preventing the operator of the implement from easily adding the clutch to an existing implement.  
         SUMMARY OF THE INVENTION  
         [0009]    The inventive wheel clutch unit is modular, self-contained, and is assembled as a unit to the axle of a walk-behind machine, such as a lawnmower or a snow thrower. Furthermore, the clutch is bi-directional, similar to previous bi-directional overrunning clutches; however, unlike the previous overrunning clutches, the inventive modular and self-contained clutch unit does not need to be assembled to an implement component-by-component or by the implement manufacturer. The modular, self-contained clutch may be assembled separately and added to an existing implement after the final assembly and sale to a consumer. Additionally, a consumer may add the clutch to his implement since no assembly of the clutch itself is required by the consumer. The use of a self-contained and modular wheel clutch unit expands the addition of an overrunning clutch to anytime, including after the implement has been sold to the consumer, and by anyone, including the consumer.  
           [0010]    The present invention provides a modular, bi-directional wheel clutch unit adapted to be assembled to the driving axle of a walk-behind machine including a rotatable wheel-driving hub including a casing portion, a clutch cage disposed in the casing portion and surrounded thereby and which has a plurality of circumferentially-distributed openings, a rotatably driven cam element disposed in the casing portion and surrounded by the clutch cage and which has a plurality of discrete surfaces thereon, and a plurality of rollers rotatably disposed within the casing portion and within the clutch cage openings. The rollers are located between the casing portion and the cam element discrete surfaces and have an engaged position wherein the cam element and the hub are in binding engagement through the rollers and the hub is rotatably driven by the cam element, and a disengaged position wherein the hub is freely rotatable relative to the cam element. The wheel clutch unit is self-contained and is selectively attachable and detachable as a unit to and from the axle of the machine.  
           [0011]    The present invention further provides, in combination, a walk-behind machine having an engine, an axle rotatably driven by the engine, and a pair of ground engaging wheels, one the wheel located at each end of the axle, and at least one unitized wheel clutch unit. The clutch unit includes a rotatable wheel-driving hub detachably fixed to a the wheel and including a casing portion, a clutch cage disposed in the casing portion and surrounded thereby and having a plurality of circumferentially-distributed openings, a cam element detachably fixed to the axle and disposed in the casing portion, and a plurality of rollers rotatably disposed within the casing portion and within the clutch cage openings. The cam element is surrounded by the clutch cage and having a plurality of discrete surfaces thereon. The rollers are located between the casing portion and the cam element discrete surfaces, and have an engaged position wherein the cam element and the hub are in binding engagement through the rollers and the hub is rotatably driven by the cam element, and a disengaged position wherein the hub is freely rotatable relative to the cam element. The wheel clutch unit is self-contained and is selectively attachable and detachable as a unit to and from the axle of the machine.  
           [0012]    The present invention further provides a modular, bi-directional wheel clutch unit adapted to be assembled as a unit to the driving axle of a walk-behind machine including a rotatable casing, a clutch cage disposed in and surrounded by the casing and which has a plurality of openings along a circumference of the clutch cage, a rotatably driven cam element disposed in the casing and surrounded by the clutch cage, and a plurality of rotatable elements rotatably disposed within the casing and within the clutch cage openings. The cam element has a plurality of discrete surfaces thereon. The rotatable elements are located between an interior surface of the casing and the cam element discrete surfaces, the casing being selectively driven by the cam element through selective engagement of the casing with the cam element. The wheel clutch unit is self-contained and is selectively attachable and detachable as a unit to and from the axle of the machine.  
           [0013]    The present invention further provides in combination, a walk-behind machine including an engine, an axle driven by the engine, and a pair of ground-engaging wheels, one the wheel at each end of the axle, and a modular, bi-directional wheel clutch assembly assembled as a unit to the axle. The clutch assembly includes a rotatable casing, a clutch cage disposed in and surrounded by the casing and which has a plurality of openings along a circumference of the clutch cage, a rotatably driven cam element disposed in the casing and surrounded by the clutch cage with the cam element having a plurality of discrete surfaces thereon, and a plurality of rollers rotatably disposed within the casing and within the clutch cage openings. The rollers are located between an interior surface of the casing and the cam element discrete surfaces, the casing being selectively driven by the cam element through selective engagement of the casing with the cam element. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein:  
         [0015]    [0015]FIG. 1A is a perspective view of an implement which includes a pair of the inventive wheel clutches, the implement shown as a lawnmower;  
         [0016]    [0016]FIG. 1B is a perspective view of an implement which includes a pair of the wheel clutches, the implement shown as a snow thrower;  
         [0017]    [0017]FIG. 1C is a rear view of an implement which includes a pair of the wheel clutches;  
         [0018]    [0018]FIG. 2 is a perspective view of the wheel clutch as viewed from its outboard end;  
         [0019]    [0019]FIG. 3 is a perspective view of the wheel clutch as viewed from its inboard end;  
         [0020]    [0020]FIG. 4 is an exploded view of the wheel clutch; and  
         [0021]    [0021]FIG. 5 is a sectional view of the wheel clutch of FIG. 2 taken along line  5 - 5 . 
     
    
       [0022]    Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates an embodiment of the invention and such exemplification is not to be construed as limiting the scope of the invention in any manner.  
       DETAILED DESCRIPTION  
       [0023]    For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended.  
         [0024]    Implement  20  is shown in FIGS. 1A and 1B, and schematically in FIG. 1C, and is representatively shown as lawnmower  24  (FIG. 1A) or snow thrower  22  (FIG. 1B). Implement  20  is similar to the implement disclosed in U.S. patent application Ser. No. 09/785,431, filed Feb. 16, 2001, the disclosure of which is expressly incorporated herein by reference, except as otherwise described herein. As shown in FIGS.  1 A- 1 C, implement  20  includes engine  26 , frame  28  attached to engine  26  and enclosing a transmission means, working device  30 , handle  32 , and a pair of wheels  38 . Implement  20  also includes an intuitive, passive steering mechanism by which the operator may easily control turning of the implement. Working device  30 , as shown in FIG. 1A, is a mower deck assembly including rotating blades within a housing and driven by a shaft operatively connected to the output shaft of the engine, as is known. In a second embodiment, shown in FIG. 1B, working device  30  is a auger assembly including a chute for throwing the snow to the side of the cleared area and an auger mounted on a rotating shaft and housed within a shroud, with the shaft being operatively connected to the output shaft of the engine, as is known.  
         [0025]    As shown schematically in FIG. 1C, solid axle  40  is operatively connected to, or a component of, transmission  42 , which may be of any suitable type of transmission or transaxle. For example, transmission  42  may be of the known type and basic design exemplified by commercially available 1300, 2500 or 2600 Series transaxles manufactured by Tecumseh Products Company. Alternatively, transmission  42  may include a friction disk or a hydrostatic pump and motor arrangement, such as that disclosed in U.S. Pat. Nos. 6,301,885 and 6,378,300, assigned to the assignee of the present invention, the complete disclosures of which are incorporated herein by reference. Transmission  42 , whether a transmission or a transaxle, drives axle  40  and may be operatively connected to a reduction gear train to reduce the speed of the output of transmission  42  relative to axle  40 .  
         [0026]    It should be noted that handles  32  may include a single grip structure for grasping, as shown in FIG. 1B, or consist of two separate grip portions for grasping, as shown in FIG. 1A. Either structure is suitable for including lever  36  used to facilitate rotation of axle  40  through engagement of a primary drive mechanism (not shown), such as transmission  42 , when lever  36  is held down. Alternatively, a bail (not shown) may used in place of lever  36  to engage the primary drive mechanism. A cable (not shown) is connected to lever  36  or the bail for activation of transmission  42 .  
         [0027]    A pair of wheel clutches  44  are provided on axle  40 , each wheel clutch  44  operatively coupling a wheel  38  to its respective end of axle  40 . Wheel clutch  44  may be assembled separately then connected to axle  40  by the implement manufacturer or by someone other than the implement manufacturer after the assembly of implement  20  is complete. Referring to FIGS. 2 and 3, each wheel clutch  44  includes hub  48  having peripheral flange  50  with a plurality of apertures  56  therein for connection to a ground engaging wheel  38 . Surrounding each aperture  56  is a boss  57  integral with flange  50 . Also included as a part of hub  48  is casing portion  52  fixed to or integral with flange  50  and reinforced by ribs  54  between casing portion  52  and flange  50 .  
         [0028]    Shown extending beyond flange  50  is extension  60  of sleeve  58 ; sleeve  58  is disposed within casing portion  52  and cooperates with a wheel clutch cam, as described hereinbelow. Extension  60  has a pair of diametrically opposed apertures  104  therein for receipt of pin  41  (FIG. 1C) through a diagonal hole in axle  40  to connect each wheel clutch  44  to axle  40 . The use of pins is well-known for the attachment of a wheel to an axle; in previous implements, the wheels are rotatably fixed to the axle via the pin, and may be free to rotate relative thereto by extending the pin through the axle hole only. In the embodiment shown, wheel  38  is fixed to wheel clutch  44 , via peripheral flange  50 , with wheel clutch  44  being attached to axle  40 ; thus wheel  38  is selectively engaged with axle  40  when wheel clutch  44  is engaged and is disengaged from axle  40  when wheel clutch  44  is disengaged.  
         [0029]    Referring to FIG. 5, disposed between sleeve  58  and hub  48 , in recess  110  of hub  48 , is bearing  62 , which allows sleeve  58  and hub  48  to rotate relative to each other; bearings  62  also support the majority of the weight of implement  20  on axle  40 . On the inboard side of wheel clutch  44  is retainer  70  press-fitted into casing portion  52  and enclosing wheel clutch  44 . Retainer  70  further includes an aperture therein for receiving bushing  66 . Bushing  66  includes extending portion  68  and is rotatably supported on axle  40  extending therethrough. Extending portion  68  has pin  64 , which has one end maintained within extending portion  68  and the other end received in a hole in frame  28 , to provide a connection to frame  28  and to prevent rotation of bushing  66  relative to implement frame  28 .  
         [0030]    With reference to FIGS. 4 and 5, wheel clutch  44  is manufactured as a compact and modular assembly, which may be easily attached to axle  40 , as described above. Starting at the inboard side of wheel clutch  44 , retainer  70  has outer surface  76 , which interfaces with first inner surface  108  of casing portion  52  through a press-fit arrangement, and inner surface  74 , which is in sliding engagement with outer surface  72  of bushing  66 . Bushing  66  further has flat inner surface  82  facing flat outer surface  80  of wheel clutch cage  78 .  
         [0031]    Wheel clutch cage  78  is a single piece and has annular portion  79  and a plurality of extensions  81  extending therefrom, with a plurality of openings  83  between extensions  81 . Rotatably disposed within each opening  83  is one roller  84 , which may rotate in the space provided by opening  83 . Additionally, each roller  84  rotates against one flat surface  88  of wheel clutch cam  86 , which is positioned within wheel clutch cage  78 . Wheel clutch cam  86  is hexagonal in shape, thereby using six rollers  84  for operation. Between cage  78  and wheel clutch cam  86  are thrust bearing  114  (FIG. 5) and wave washer  112  (FIG. 5) which create rotational drag on cage  78  relative to rotating cam  86 , which is rotatably fixed to axle  40 . This drag urges rollers  84  to edges  87  of surfaces  88 , thereby bringing rollers  84  into binding engagement with surface  106  of race  96  (FIG. 4) and surfaces  88  of cam  86 . Inner surface  92  of cam  86  interfaces with surface  94  of sleeve  58  through cam  86  and sleeve  58  being brazed, thereby fixing them together.  
         [0032]    Rollers  84  are prevented from moving radially outward and away from axle  40  by retaining ring  85 . Each roller  84  has annular groove  89  therein and wheel clutch cage  78  has its own annular groove  91 ; both grooves  89  and  91  are aligned when the rollers  84  are in the openings  83  such that ring  85  is located therein. By using ring  85  and groove  89 , each roller  84  is still capable of rotation but is unable to move radially away from axle  40 .  
         [0033]    Surrounding wheel clutch cage  78  is race  96  which has surface  98  abutting inner surface  100  of casing portion  52 . Lastly, bearing  62  is received at the outboard end of wheel clutch  44  in recess  110  in hub  48  to complete the assembly of wheel clutch  44 . As noted above, the two bearings  62  also carry the majority of the weight of implement  20  relative to axle  40 .  
         [0034]    Wheel clutch  44  further includes retaining ring  102  placed in recess  101  in sleeve  58  to prevent axial outward movement of bearing  62 . It should be noted that wheel clutch  44  has a modular configuration and does not need to be assembled to axle  40  piece by piece for operation.  
         [0035]    In operation, wheel clutch  44  may engage axle  40  in either the forward or reverse directions. Engagement occurs when rollers  84  move to edges  87  of surfaces  88 , through the drag caused by thrust bearing  114  and wave washer  112 , as described above. This action causes rollers  84  to be “locked” into position between race  96  and wheel clutch cam  86 , thereby bringing race  96  and casing portion  52  into engagement with cam  86  through rollers  84 , and thus wheel clutch  44  into engagement with axle  40 . Each surface  88  has two edges  87  at the ends thereof, thus rotation of shaft  40  in either direction will cause rollers  84  to move toward an edge  87  associated with the surface  88  upon which roller  84  is rotating. Disengagement of wheel clutch  44  occurs when rollers  84  are allowed to freely rotate between the edges of surfaces  88 , or roller  84  will rotate away from an edge  87  when the hub casing  52  and race  96  are urged to rotate faster than cam  86 . As can be seen, the design provides for ease of engagement and disengagement of wheel clutch  44  since mere movement of implement  20  is required for engagement and disengagement of wheel clutch  44 . This allows for overrunning of the associated wheel  38  such that as implement  20  is turned, the wheel clutch  44  on the wheel  38  at the inside of the turn will disengage or partially disengage while the other wheel clutch  44  is engaged with its respective wheel  38 , thereby continuing power to that wheel  38  and propelling implement  20  through the turn.  
         [0036]    While this invention has been described as having an exemplary structure, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to platform any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to platform such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.