(19)
(11)EP 3 390 850 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
29.07.2020 Bulletin 2020/31

(21)Application number: 17767273.0

(22)Date of filing:  13.03.2017
(51)International Patent Classification (IPC): 
F16D 3/34(2006.01)
(86)International application number:
PCT/US2017/022121
(87)International publication number:
WO 2017/160733 (21.09.2017 Gazette  2017/38)

(54)

BI-DIRECTIONAL OVERRUNNING CLUTCH WITH OUTER SPRING FOR A DRIVE AXLE

BIDIREKTIONALE FREILAUFKUPPLUNG MIT ÄUSSERER FEDER FÜR EINE ANTRIEBSACHSE

ROUE LIBRE BIDIRECTIONNELLE À RESSORT EXTÉRIEUR POUR ESSIEU D'ENTRAÎNEMENT


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 16.03.2016 US 201615071751

(43)Date of publication of application:
24.10.2018 Bulletin 2018/43

(73)Proprietor: The Hilliard Corporation
Elmira NY 14902-1504 (US)

(72)Inventors:
  • HEATH, Kelly, P.
    Corning NY 14830 (US)
  • OCHAB, David, C.
    Horseheads NY 14845 (US)

(74)Representative: Murgitroyd & Company 
Murgitroyd House 165-169 Scotland Street
Glasgow G5 8PL
Glasgow G5 8PL (GB)


(56)References cited: : 
JP-U- S63 139 334
US-A1- 2005 067 248
US-A1- 2007 010 366
US-A1- 2005 067 248
US-A1- 2007 010 366
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description

    FIELD OF THE INVENTION



    [0001] The present invention is directed to clutches and, more particularly, to a bi-directional overrunning clutch for controlling torque transmission to a drive shaft of a wheeled machine.

    BACKGROUND OF THE INVENTION



    [0002] In recent years there has been a tremendous demand for adding motor propulsion to what had previously been manual propelled machines. One example of such a device is ride-on and walk-behind power equipment. Walk-behind devices were once solely push-propelled. However, recently more models have become self-propelled. Examples of such equipment are lawnmowers, lawn vacuums, snowblowers, trimmers, edgers, concrete and asphalt cutters and the like. A number of factors have driven the move to self-propulsion, such as a desire for larger equipment which requires less effort and allows for more detailed control. Speed of operation is another factor that has driven the increase demand for self-propelled equipment. Current self-propulsion systems for walk-behind equipment generally fall into two categories, simple and complex.

    [0003] In a simple type drive system, a drive shaft or belt is connected to a single drive axle which drives two wheels, one at each end of the axle. Because the wheels are on a common shaft, they rotate at the same rate. The principal deficiency with this type of device is that no differential rotation is permitted between the drive wheels. As a result, the machine is not efficient during cornering, which requires the outer wheel to travel a greater distance than the inner wheel. Because the outer wheel travels farther than the inner wheel in the same amount of time, the outer wheel should rotate faster than the inner wheel. When the outer and inner wheels are fixed to a common axle, however, that differential rotation is not permitted. The result is that either the inner wheel is driven faster or the outer wheel is driven slower than is optimum for the speed of the vehicle. In either case, cornering the equipment requires one of the wheels to slip or skid. That results in premature wear of the wheel.

    [0004] Difficulty with cornering and wheel slippage are two major disadvantages with using equipment having drive wheels fixed to a common axle. Additionally, effort by the operator must be provided to overcome the ground-engaging forces to allow one wheel to slip. Furthermore, wheel slippage can cause damage to the surfaces on which the equipment is operating, as well as accelerated tire wear. For instance, turning a lawnmower with this type of drive system damages the turf under the slipping wheel.

    [0005] Complex drive systems for self-propelled, walk-behind power equipment generally provide a differential between the pair of drive wheels. The differential permits independent or differential rotation of the drive wheels on an axle when the user corners. Many drive systems with differentials use some form of an overrunning clutch to transmit torque when needed to a driven shaft, while allowing a wheel to turn faster than the motor drive when necessary. One successful use of an overrunning clutch in an all terrain vehicle incorporates overrunning clutches where the wheel hub mounts to the axle, thus allowing each wheel to independently disengage when required.

    [0006] Conventional complex differentials and overrunning clutches are generally costly to manufacture and, thus, relegated to more expensive vehicles, such as cars and four wheel drive vehicles.

    [0007] A need exists for a less complex and less expensive bi-directional overrunning clutch that can be used in various self-propelled machines and light duty vehicles, such as snowblowers, lawn mowers, golf carts, and concrete and asphalt cutters.

    [0008] U.S. Patent Application Publication no. 2007/0010366A1 discloses a drive assembly that includes two interconnected roll cases, each with a set of casters configured to engage with cubes that are splined onto hubs of a shaft. A spring is associated with each caster in each set of casters and biases the individual caster radially inward toward the recesses.

    [0009] U.S. Patent No. 6,722,484 describes a bi-directional overrunning clutch that allows the motor to drive both wheels in either direction when proceeding in a straight line, and on corners allows the motor to drive the slower (inside) wheel, while allowing the outside wheel to turn faster, without the need for a complex differential. The clutch disclosed in U.S. Patent No. 6,722,484 has proven very satisfactory. However, there is still room for further improvement.

    SUMMARY OF THE INVENTION



    [0010] In a first aspect of the present invention, there is provided an overrunning clutch as claimed in claim 1 for controlling torque transmission to a pair of shaft segments of a drive axle in a wheeled machine. Optionally, the spring of each roller assembly comprises a garter spring encircling the rollers. The rollers may then be grooved, with the garter springs seated in the grooves, and the depth of the grooves being greater than the thickness of the garter springs.

    [0011] Optionally, the clutch further comprises at least one tongue on at least one of the roll cages received in a respective notch in the other of the roll cages, the notch having a greater circumferential length than the tongue, wherein the difference in the circumferential lengths of the tongue and the notch determines the amount of the limited relative rotation of the two roll cages.

    [0012] Optionally, the clutch further comprises at least one adapter positioned between the roll cages for proving the engagement between the roll cages, the adapter being configured to engage with at least some of the slots in each roll cage.

    [0013] Optionally, the rollers are evenly spaced around each roll cage, the recesses are evenly spaced around each hub, and the number of recesses is a whole multiple of the number of rollers.

    [0014] Optionally, the clutch further comprises an input gear encircling the clutch housing, wherein the input gear includes teeth that are formed about an outer circumference of the input gear and wherein the inner cam surface is formed on or secured to an inner diameter of the input gear.

    [0015] Optionally, the clutch is mounted in a vehicle, the vehicle having a drive axle that includes two shaft segments, and wherein each shaft segment is drivingly engaged with one of the hubs, the vehicle including a motor with an output shaft that is engaged with the input gear for transmitting rotary motion to the input gear. The hubs may then include splined ends for engaging with mating splined ends on the shaft segments.

    [0016] Optionally, the input may comprise an input gear adapted to be engaged with an input shaft for transmitting rotation of the input shaft into rotation of the input gear, the input gear being engaged to the clutch housing to rotate the clutch housing with the input gear.

    [0017] Optionally, the clutch of the first aspect may include the features of any two or more of the mentioned second through eighth aspects, optionally including any or all of the mentioned optional features of the second and/or seventh aspects.

    [0018] In a second aspect, there is provided a wheeled machine having a power source and a primary drive axle with two shaft segments, and a bi-directional overrunning clutch according to any of the above-mentioned embodiments for transmitting torque and controlling torque transmission from the power source to the shaft segments of the primary drive axle.

    [0019] The foregoing and other features of the invention and advantages of the present invention will become more apparent in light of the following detailed description of the preferred embodiments, as illustrated in the accompanying drawings. As will be realized, the invention is capable of modifications in various respects, all without departing from the invention. Accordingly, the drawings and the description are to be regarded as illustrative in nature, and not as restrictive.

    BRIEF DESCRIPTION OF THE DRAWINGS



    [0020] For the purpose of the illustrating the invention, the drawings show a form of the invention which is presently preferred. However, it should be understood that this invention is not limited to the precise arrangements and instrumentalities shown in the drawings.

    FIG. 1 is a side view of a vehicle incorporating the present invention;

    FIG. 2 is a schematic illustration of the wheels, axle and clutch of the vehicle of FIG. 1 turning left;

    FIG. 3 is a schematic illustration of the wheels, axle and clutch of the vehicle of FIG. 1 turning right;

    FIG. 4 is an exploded view of an embodiment of a clutch assembly;

    FIG. 5 is a perspective view of the clutch assembly of FIG. 4;

    FIG. 6 is an end view of one embodiment of the clutch of FIG. 4, with an end cover removed, in a disengaged condition;

    FIG. 7 is a front view of the clutch in FIG. 6, with part of the housing cut away;

    FIG. 8 is an end view similar to FIG. 6 of the clutch of FIG. 4 in a forward-driving condition;

    FIG. 9 is an end view similar to FIG. 6 of the clutch in a condition where the vehicle is turning;

    FIG. 10 is a front view similar to FIG. 7 of the clutch in the condition of FIG. 9.

    FIG. 11 is a perspective view of an alternative clutch with one of the roll cages and hubs removed.

    FIG. 12 is a perspective view of the clutch of FIG. 11 showing both roll cages and hubs in place.


    DETAILED DESCRIPTION OF THE EMBODIMENTS



    [0021] Referring now to the drawings, wherein like reference numerals illustrate corresponding or similar elements throughout the several views, FIGS. 1 to 3 illustrate a vehicle 10, in this embodiment a snow-blower, that incorporates a bi-directional overrunning clutch according to the present invention. The vehicle 10 includes a drive axle 12 that is supported for rotation with respect to a frame 14 in a conventional manner. A motor 16 provides the power for a blower assembly 18 as well as power for propelling the vehicle 10 as will be described in greater detail. A handle 20 is connected to the frame 14 to provide for walk-behind operation of the vehicle.

    [0022] The drive axle 12 includes separate shaft segments 22, 24 that are connected to wheels 26, 28, respectively, for rotation therewith. Each of the shaft segments 22, 24 is also connected at an opposite, proximal end to a bi-directional overrunning clutch 30 that is engageable to the motor 16. The connection can be through any conventional means, but in the illustrated embodiment is a splined connection between each shaft segment 22, 24 and a hub 32, 34 of the bi-directional overrunning clutch 30.

    [0023] The bi-directional overrunning clutch 30 is constructed to transfer torque to the shaft segments 22, 24 for driving the wheels 26, 28. As will be described in greater detail, the construction of the clutch 30 facilitates turning of the vehicle 10 by allowing an outer wheel and the associated shaft segment to rotate faster than the inner wheel and associated shaft segment, which remain positively driven by the motor 16 through the clutch 30. Thus, the clutch 30 permits the outer wheel to independently rotate while the inner wheel continues to drive the machine. The drive axle 12 and wheels 26, 28 are shown in dashed line in FIGS. 2 and 3 being driven along a straight path to the left and in solid line being driven though turns. In the left turn illustrated in FIG. 2, wheel 26 is allowed to overrun clutch 30 while wheel 28 remains a positively driven wheel. In the right turn shown in FIG. 3, wheel 28 overruns while wheel 26 is positively driven by clutch 30.

    [0024] Referring to FIGS. 4 and 5, one embodiment of a clutch 30 suitable for use in the vehicle of FIGS. 1-3 includes a clutch housing 36 having a gear 38 mounted on or engaged to the outside of the clutch housing 36. The gear 38 has teeth 40 which, as will be well understood by one skilled in the art, are adapted to engage cooperatively formed teeth of a motor-driven gear (not shown) for transmitting rotation from a drive shaft of the motor 16 to the clutch housing 36. Also, while the gear 38 is shown as a separate component that is attached to the clutch housing 36, it should be readily apparent that the gear teeth 40 may be formed integral with the clutch housing 36. Alternatively, the gear 38 may be replaced by a sprocket, pulley, or other structure suitable to receive driving force or torque directly or indirectly from motor 16, and cause the clutch housing 36 to rotate.

    [0025] Referring now also to FIGS. 6 to 10, the clutch housing 36 includes an inner cam surface 42, for transferring rotation of the clutch housing 36 to other components of the clutch 30 as will be described in greater detail below.
    The clutch 30 further includes a pair of roller assemblies 44, 46 having rollers 48 arranged in two sets, preferably of four rollers each, although other number of rollers can be used in the present embodiment. Each of the roller assemblies 44, 46 also includes a roll cage 50, 52 for rotatably supporting the rollers 48. Each of the roll cages 50, 52 includes spaced slots or recesses 54 formed on an outer side of the cage 50, 52. The slots 54 are sized to receive the rollers 48. Each cage 50, 52 receives one set of rollers 48.

    [0026] As best seen in FIGS. 7 and 10, the roll cages 50, 52 are connected at their inner ends by a boss or tongue 56 on one roll cage engaging in a notch 58 in the other roll cage. Preferably, there are at least two tongues 56 and respective notches 58, evenly spaced around the circumference of the roll cages 50, 52. Each tongue 56 is shorter in the circumferential direction than its associated notch 58, allowing a small amount of relative rotation between the two roll cages 50, 52, while the tongue 56 remains engaged in the notch 58. The amount and purpose of this limited rotation will be explained below.

    [0027] Each of the hubs 32, 34 is formed on its exterior surface with a scalloped surface 60 consisting of part-cylindrical or curved recesses 62 that extend parallel to the axis of the clutch 30. The recesses 62 are dimensioned to receive the rollers 48 but permit rotation. The number of recesses 62 in each hub 32, 34 is a multiple of the number of rollers 48 in each set, so that in a resting position all of the rollers 48 are seated in respective ones of the recesses 62.

    [0028] Each roll cage 50, 52 is encircled by a garter spring 64 that lies in grooves 66 in the rollers 48 in that roll cage. In the resting position, the garter springs 64 bear on the bottoms of the grooves 66 and hold the rollers 48 seated in the recesses 62 in the hubs 32, 34. The grooves 66 are sufficiently deep that the rollers 48 project outwards beyond the garter springs 64.

    [0029] As shown in the drawings, the hubs 32, 34 have splines 68 formed on an inner surface thereof for receiving splined ends of the shaft segments 22, 24. Of course, the hub may instead include a stub shaft portion with outer splines for engaging with inner splines on a shaft segment. Other types of well-known connections can be substituted for the illustrated splines. The splined connection secures the hubs 32, 34 to the shaft segments 22, 24 such that each of the hubs 32, 34 rotates in combination with one of the shaft segments 22, 24.

    [0030] Referring again to FIG. 7, each of the hubs 32, 34 includes at an outer end, opposite the end with the tongue(s) 56 and/or notch(es) 58, a second portion 70 having an outer surface that is preferably reduced in diameter with respect to that of the scalloped surface 60. The reduced diameter portion 70 is preferably sized to extend through a central opening 72 in one of opposite covers 74. The covers 74 are fastened to the clutch housing 36 to form a closed whole, which may contain grease or other lubricant and may be sealed by O-rings or similar components between the two hubs 32, 34 and between each hub and one of the covers 74.

    [0031] The operation of the bi-directional overrunning clutch 30 will now be described in more detail. Although the drawings illustrate the incorporation of the bi-directional overrunning clutch in a walk-behind single axle snowblower 10, it will become quite apparent from the following discussion that the present invention is not limited to use with only a snowblower. Instead, the present invention can be used with any suitable machine that has a drive axle with two shaft segments that are driven from a common motor or other power supply.

    [0032] FIGS. 6 and 7 illustrate the bi-directional overrunning clutch prior to engagement. As shown, the rollers 48 of both roller assemblies 44, 46 are located between forward and reverse portions of the cam surface 42. More specifically, as shown in FIG. 6, the contour of cam surface 42 includes a plurality of peaks 80 and valleys 82. The number of valleys 82 is equal in number to the number of rollers 48 in each set. In the resting position, the rollers 48 are located within the valleys 82 with the cam surface 42 tapering inward toward the roll cage on either side of the rollers 48 (generally referred to herein as tapered portions 84). The valleys 82 are sufficiently deep that when a roller 48 is in the middle of a valley 82 the roller 48 can move radially outwards far enough to pass over the cusp between adjacent recesses 62 in the scalloped surface 60. The peaks 80 are sufficiently high that even when the rollers 48 are fully seated in recesses 62 in the scalloped surface 60, the rollers cannot pass under the peaks 80, but instead wedge on the tapered portions 84.

    [0033] For ease of manufacture and assembly, the cam surface 42 preferably has n-fold rotational symmetry about the main axis of the clutch, where there are n rollers 48 in each roll cage, and preferably has mirror symmetry about any plane including the axis and passing through the center of a peak 80 or valley 82, and the roll cages 50, 52 and hubs 32, 34 have the same symmetry. The clutch can then be assembled without requiring any specific alignment of the components. A configuration in which there are an even number of tongues 56 and respective notches 58, and each roll cage 50, 52 has half the tongues 56 and half the notches 58, with tongues and notches alternately on each roll cage 50, 52, for example, each roll cage 50, 52 has one tongue 56 and one notch 58, diametrically opposite each other, allows for easy assembly using identical parts for both roll cages. However, because the roll cages cannot rotate relative to the housing more than the width of one valley, that level of symmetry is not essential, and may be departed from for other reasons. For operational purposes, it is believed that at least three rollers 48 on each roller assembly 44, 46 are desirable, and at least two pairs of a tongue 56 and a notch 58 are desirable, to ensure stable operation. A larger number of either or both of those features may be desirable, especially for clutches carrying large torques.

    [0034] The cam surface 42, hubs 32, 34, and rollers 48 provide the bi-directional overrunning capabilities as will be discussed hereinafter. Cam surfaces and roll cages in overrunning clutches are well known in the art. See, e.g., above-mentioned U.S. Pat. No. 6,722,484, U.S. Pat. No. 5,971,123, and also U.S. Pat. No. 4,373,407 to Okubo. A detailed discussion of the features of a cam surface is therefore not needed.

    [0035] In the neutral or resting position shown in FIG. 6, the hubs 32, 34 are not engaged to the clutch housing 36 because the rollers 48 are not wedged between the clutch housing 36 and the hubs 32, 34. However, because the garter springs 64 hold the rollers 48 into the recesses 62 of the scalloped surfaces 60 of the hubs 32, 34, the roll cages 50, 52 are connected to the hubs 32, 34, causing each roll cage 50, 52 to move with its respective hub 32, 34. As a result, any relative motion between the clutch housing 36 and the hub 32 or 34 will cause the respective roll cage 50 or 52 to index or position the rollers 48 for engagement. Hence, although the resting position of the rollers shown in FIG. 6 theoretically provides no direct torque transfer between the input gear 38 and the hubs, in reality, positive drive occurs essentially instantaneously upon any movement. For example, in the embodiment illustrated, engagement occurs with as little as 8 degrees of rotation.

    [0036] Referring now to FIG. 8, the bi-directional clutch is shown with the roller assembly in its forward-engagement position. As discussed above, when the drive system of the vehicle 10 is engaged for forwardly driving the vehicle, the motor 16 causes the clutch housing 36 to rotate with respect to the frame 14 of the vehicle 10 in the direction of the arrow in FIG. 8. Because the hubs 32, 34 are engaged to the wheels 26, 28 through the shaft segments 22, 24, the hubs initially do not move. However, as explained above, the roll cages 50, 52 are connected by the rollers 48, held in place by the garter springs 64, to rotate with the hubs 32, 34. As a result, the rollers 48 wedge between the forward tapered portions 84 of the cam surface 42 and the hub 32, 34. The wedging of the rollers 48 provides a path for the transmission of torque from the input gear 38 through the rollers 48 to the hubs 32, 34, and thus to the shafts 22, 24. This represents the forward-engagement position of the bi-directional clutch which permits the motor-driven rotation of the hubs 32, 34 and the associated shaft segments 22, 24 and wheels 26, 28.

    [0037] In this forward-engagement position shown in FIG. 8, the tongues 56 are in the middles of the notches 58, identically to the position shown in FIG. 7, because the two roll cages 32, 34 have moved in step with one another from the position of FIG. 6 to the position of FIG. 8, so that the two roll cages 50, 52 are not engaged with each other. This alignment is determined by the positions of the slots 54 that contain the rollers 48, relative to the tongues 56 and notches 58, as long as the rollers 48 of both roller assemblies 44, 46 are wedged on the tapered portions of the cam surface 42 of the housing 36.

    [0038] The above-described construction of the bi-directional clutch 30, however, also allows the shaft segments 22, 24 to separately overrun (disengage) from the forward-engagement position. This is particularly important during turning where it is beneficial to permit one wheel (i.e., the outer wheel) to turn faster than the other wheel (i.e., the inner wheel), while the motor 16 continues to drive the slower wheel, and thus to propel the vehicle 10. This prevents scuffing and resultant wear of the slower moving wheel. More importantly, the overrunning greatly reduces the effort required to steer the vehicle. The present invention achieves this goal in the drive axle 22, 24 by allowing each hub 32, 34 to overrun separately, i.e. to rotate independent from the clutch housing 36, when the hub 32, 34 rotates faster than the clutch housing 36.

    [0039] The overrunning condition of the clutch 30 during the turning of the vehicle 10 is illustrated in FIGS. 9 and 10. As described previously, in the forward-engagement position shown in FIG. 8, the rollers 48 of both hubs 32, 34 are wedged between the forward tapered portions 84 of the cam surface 42 and the scalloped surfaces 60 of the hubs 32, 34. When the vehicle 10 is directed into a right turn in the forward driven mode as shown in FIG. 3, the hub 34 engaged with the left-hand shaft segment 24 will tend to turn faster than the hub 32 engaged with the right-hand shaft segment 22. As a result, the motor 16 will continue to drive the right-hand hub 32, shaft segment 22, and wheel 26, but the other hub 34 and the associated shaft segment 24 will overrun the clutch, carrying the associated roller assembly 46 forward.

    [0040] The movement of roller assembly 46 relative to roller assembly 44 and housing 36 will stop when the tongues 56 engage the ends of the notches 58 as shown in FIG. 10, preventing further movement of the roller assembly 46 relative to the roller assembly 44. The difference in the circumferential length of the tongues 56 and notches 58 is chosen so that with the roller assembly 44 still wedged against the tapered portion 84 of the cam surface 42, the rollers 48 of roller assembly 46 are positioned in the centers of the valleys 82 of cam surface 42. As the wheel 28 continues to drive the hub 34 taster than the hub 32 and the housing 36, the cusps at the rear edges of the recesses 62 in the scalloped surface 60 will push against the rollers 48 in roller assembly 46. Because those rollers are in the valleys 82, they are retained only by the garter spring 64. The rollers 48 will therefore be lifted outwards, allowing the cusps to pass underneath, and will then drop into the next recess 62. This will happen repeatedly, as long as the vehicle 10 is turning and the wheel 28 is moving faster than the wheel 26.

    [0041] It is expected that any audible click as the rollers drop into the recesses 62 will in practice be imperceptible over the normal noise of operation of vehicle 10, especially if motor 16 is an internal combustion engine.

    [0042] Upon reentering a straight path following the turn, the rotational speed of the overrunning shaft segment will equalize with the rotational speed of the driven shaft segment and the clutch housing 36. The equalization of the relative speeds causes the rollers 48 to once again wedge between the tapered portion 84 of the cam surface 42 of the clutch housing 36 and the respective hub 32, 34 in the forward-engagement position, whereupon both axles are again driven by the input gear 38.

    [0043] Because of the symmetry of the clutch 30, an exactly similar mirror-image process will occur during a left turn, as shown in FIG. 2.

    [0044] Referring again to FIGS. 6 and 8, the cam surface 42 includes reverse-engagement surfaces, which are the tapered portions 84 opposite the forward-engagement surfaces associated with the forward-engagement position shown in FIG. 8. As a result, the clutch is bi-directional, permitting it to be reversibly driven, and functions in reverse exactly the same way as it functions in forward motion. For example, if the vehicle 10 in the illustrated embodiment is designed with a reverse gear, upon shifting to reverse, the input gear would turn the opposite way from the illustrated embodiment of FIG. 8. Thus, the rollers would engage with the tapered portions 84 associated with the reverse-engagement position. The bi-directional clutch 30 according to the present embodiment permits torque transfer (driving) equally in such a reverse direction. Furthermore, as with the forward driving of the vehicle, the present invention also permits overrunning in the reverse direction.

    [0045] Another aspect of the bi-directional clutch according to the present embodiment is that it permits backdriving, which has particular importance in situations where it is necessary or desirable to prevent the wheels from rotating faster than the input gear 38. For example, when the vehicle 10 is being operated on a descending slope, the speed of the wheels 26, 28 may tend to go faster than the speed of the input gear 38. In a vehicle with conventional single direction overrunning clutches, the wheels would then overrun and the machine would be free-wheeling (uncontrolled). In the clutch 30 shown in the drawings, if both wheels 26, 28 overrun the speed of the input gear 38, the tongues 56 and notches 58 will not engage to restrain the movement of the roller assemblies 44, 46. Therefore, both roller assemblies will advance until the rollers 48 engage the reverse-engagement tapered portions 84 of the cam surface 42. In that position, the wheels 26, 28 are backdriving torque into the motor 16, which can act as a brake on the wheels. The shift of the roll cage 42 to the reverse-engagement clutch position therefore provides for controlled operation of the vehicle 10 on a descending slope, forcing the wheels 26, 28 to rotate at the same relative speed as the rotational speed of the clutch housing 36 and input gear 38.

    [0046] In that state, it may be seen that the overrunning clutch will still operate to permit one wheel to disengage from the motor 16 on a turn, but now the faster-moving (outside) wheel is back-driving the motor 16, while the slower-moving wheel is disengaged.

    [0047] The embodiment of clutch shown in the drawings is a compact design which would work well in conventional two-wheel drive walk behind and light duty machines and vehicles where overrunning is needed on the primary drive axle. The invention, however, is also equally applicable for providing positive drive for heavy duty machines and vehicles, such as 2 and 4 wheel drive vehicles.

    [0048] The present invention can be used with many types of drive devices where overrunning of the primary shaft segments is necessary. The clutch of the present invention is also not limited to use with single-axle walk behind equipment, but may be used for controlling a driven axle on multiple axle machinery, as well as ridden vehicles such as a golf cart, for example.

    [0049] Whenever the clutch 30 is under load, at least one set of rollers 48 is wedged between the hub 32, 34 and the tapered portions of the cam surface 42. The housing 36 and input gear 38 are thus wedged to at least one of the output shafts 22, 24, and are supported by the bearings for the output shafts 22, 24. A separate bearing to support the clutch 30 and input gear 38 is therefore not needed, which can afford a considerable simplification and economy in the construction of the clutch assembly. However, additional bearings to support the clutch housing 36 and input gear 38 can of course be provided, and may be desired especially in heavier duty embodiments.

    [0050] In the described embodiment, each roller assembly 44, 46 is encircled by a garter spring 64 that biases the rollers 48 inwards, into engagement with the hub 32, 34. However, coil springs or other forms of spring may be used, including separate springs for each roller. Other mechanisms may be used, provided that the rollers 48 are biased or urged inwards sufficiently that in the unengaged position the rollers 48 remain in engagement with the hubs 32, 34, but in the turning position the rollers 48 of the wheel that is overrunning can index from one groove 62 to the next.

    [0051] Referring now also to FIGS. 11 and 12, while the above invention has been described as being applicable to the clutch arrangement shown in the figures, it can also be readily incorporated into a split roll cage assembly such as the one shown in US Patent 8,919,513, which is incorporated herein by reference in its entirety. As shown in FIG. 11 (which corresponds to FIG. 3A of the mentioned US Patent 8,919,513), instead of a tongue 56 on one roll cage 50 engaging in a notch 58 in the other roll cage 52, the slots 154 in each roll cage 150 that receive the rollers 148 are open at the end facing towards the other roll cage. A coupler or adaptor 160 is placed between the two roll cages. The coupler 160 includes a hub 162 with a plurality of teeth 164 extending radially outward from the hub 162. The second roll cage 150, which engages the other side of the coupler 160, is omitted from FIG. 11 to allow a clear view of the coupler, but may be identical to the roll cage that is shown.

    [0052] The number of teeth 164 preferably matches the number of slots 154 and the number of rollers 148 in each roll cage 150. The width in the circumferential direction of the portion of a tooth 164 within a slot 154 of the roll cages 150 is slightly less than the width of the slot 154 of the roll cages 150 such that a gap exists. This gap is designed to permit the same limited relative rotation between the two roll cages 150 as discussed above for the tongue 56 and notch 58. However, because the tooth 164 has clearances for limited rotation within the slots 154 of both roll cages 150, the clearance within each slot provides half the total relative rotation of the two roll cages. A person skilled in the art would be readily capable of combining the scalloped hub surfaces described above with the adaptor 160 of FIG. 11.

    [0053] Although the present invention has been described and illustrated with respect to the exemplary embodiments thereof, it should be understood by those skilled in the art that the foregoing and various other changes, omissions and additions may be made therein and thereto, without departing from the scope of the present invention.


    Claims

    1. A bi-directional overrunning clutch (30) for controlling torque transmission to shaft segments of a primary drive axle (12) of a wheeled machine, the bi-directional overrunning clutch comprising:

    a clutch housing (36) adapted to be engaged to and rotated by an input, the clutch housing having an inner cam surface (42) on it;

    a pair of hubs (32, 34) each adapted to engage an end of a respective shaft segment of a drive axle for rotation therewith, each hub having a plurality of axially-extending recesses (62) on an outer surface;

    a pair of roller assemblies (44, 46) disposed within the clutch housing, each roller assembly including a set of rollers (48) positioned around at least a portion of one of the hubs, a roll cage (50, 52) having a plurality of slots (54), each roller being located within a slot, the roll cage being located about at least a portion of the respective hub, the roll cages (50, 52) engaging each other for limited relative rotation such that when one roller assembly is in one of the forward-engagement position and the reverse-engagement position, the other roller assembly cannot move into the opposite direction of the forward-engagement position and the reverse-engagement position,

    characterised in that each roller assembly further comprises a single spring (64) tending to urge all the rollers radially inwards to seat in respective ones of the recesses in the respective hub; with each roller assembly (44, 46) being located adjacent to the inner cam surface, the inner cam surface adapted to provide wedging engagement of the rollers between the inner cam surface and the respective hub when the roll cage is rotated in a first direction relative to the clutch housing into the forward-engagement position and when the roll cage is rotated in a second direction relative to the clutch housing into the reverse-engagement position, the second direction of rotation being opposite the first, the inner cam surface defining a released position of the rollers between said forward-engagement position and said reverse-engagement position in which radially outward movement of the rollers is permitted against the action of the spring to free the rollers from the recesses in the respective hub to permit relative rotation of the hub and the respective roller assembly.


     
    2. The bi-directional overrunning clutch (30) according to claim 1, wherein the spring of each roller assembly (44, 46) comprises a garter spring (64) encircling the rollers (48).
     
    3. The bi-directional overrunning clutch (30) according to claim 2, wherein the rollers (48) are grooved, the garter springs (64) are seated in the grooves (66), and the depth of the grooves is greater than the thickness of the garter springs.
     
    4. The bi-directional overrunning clutch (30) according to any preceding claim, further comprising at least one tongue (56) on at least one of the roll cages (50, 52) received in a respective notch (58) in the other of the roll cages, the notch having a greater circumferential length than the tongue, wherein the difference in the circumferential lengths of the tongue and the notch determines the amount of the limited relative rotation of the two roll cages.
     
    5. The bi-directional overrunning clutch (30) according to any preceding claim, further comprising at least one adapter (160) positioned between the roll cages (50, 52) for providing the engagement between the roll cages, the adapter being configured to engage with at least some of the slots (54) in each roll cage.
     
    6. The bi-directional overrunning clutch (30) according to any preceding claim, wherein the rollers (48) are evenly spaced around each roll cage (50, 52), the recesses (62) are evenly spaced around each hub (32, 34), and the number of recesses is a whole multiple of the number of rollers.
     
    7. The bi-directional overrunning clutch (30) according to any preceding claim, further comprising an input gear (38) encircling the clutch housing, wherein the input gear includes teeth (40) that are formed about an outer circumference of the input gear and wherein the inner cam surface (42) is formed on or secured to an inner diameter of the input gear.
     
    8. The bi-directional overrunning clutch (30) according to claim 7, wherein the clutch is mounted in a vehicle, the vehicle having a drive axle (12) that includes two shaft segments (22, 24), and wherein each shaft segment is drivingly engaged with one of the hubs (32, 34) , the vehicle including a motor (16) with an output shaft that is engaged with the input gear for transmitting rotary motion to the input gear.
     
    9. The bi-directional overrunning clutch (30) according to claim 8, wherein the hubs (32, 34) include splined ends for engaging with mating splined ends on the shaft segments (22, 24).
     
    10. The bi-directional overrunning clutch (30) according to any of claims 1-6, wherein the input comprises an input gear (38) adapted to be engaged with an input shaft for transmitting rotation of the input shaft into rotation of the input gear, the input gear being engaged to the clutch housing (36) to rotate the clutch housing with the input gear.
     
    11. A wheeled machine having a power source and a primary drive axle with two shaft segments, and a bi-directional overrunning clutch (30) according to any of the preceding claims for transmitting torque and controlling torque transmission from the power source to the shaft segments of the primary drive axle.
     
    12. The wheeled machine according to claim 11, wherein the machine is a two wheel drive snowblower (10) or lawn mower.
     
    13. A vehicle having a motor and a primary drive axle with two shaft segments, and a bi-directional overrunning clutch (30) according to any of claims 1-10 for transmitting torque and controlling torque transmission from the power source to the shaft segments of the primary drive axle.
     
    14. The vehicle according to claim 13 wherein the vehicle is a golf cart.
     


    Ansprüche

    1. Eine bidirektionale Freilaufkupplung (30) zum Steuern von Drehmomentübertragung auf Wellensegmente einer primären Antriebsachse (12) einer Radmaschine, wobei die bidirektionale Freilaufkupplung Folgendes beinhaltet:

    ein Kupplungsgehäuse (36), das angepasst ist, um sich mit einem Eingang in Eingriff zu befinden und von diesem gedreht zu werden, wobei das Kupplungsgehäuse eine innere Nockenlauffläche (42) darauf aufweist;

    ein Paar Naben (32, 34), die jeweils angepasst sind, um zur Drehung damit in ein Ende eines entsprechenden Wellensegments einer Antriebsachse einzugreifen, wobei jede Nabe eine Vielzahl von sich axial erstreckenden Aussparungen (62) auf einer äußeren Oberfläche aufweist;

    ein Paar Rollenanordnungen (44, 46), die innerhalb des Kupplungsgehäuses angeordnet sind, wobei jede Rollenanordnung Folgendes umfasst: einen Satz Rollen (48), die um mindestens einen Abschnitt einer der Naben positioniert sind, einen Rollenkäfig (50, 52), der eine Vielzahl von Schlitzen (54) aufweist, wobei sich jede Rolle innerhalb eines Schlitzes befindet, wobei sich der Rollenkäfig um mindestens einen Abschnitt der entsprechenden Nabe befindet, wobei die Rollenkäfige (50, 52) zur begrenzten relativen Drehung ineinander eingreifen, sodass, wenn sich eine Rollenanordnung in einer von der Vorwärts-Eingriffsposition und der Rückwärts-Eingriffsposition befindet, die andere Rollenanordnung sich nicht in die entgegengesetzte Richtung der Vorwärts-Eingriffsposition und der Rückwärts-Eingriffsposition bewegen kann,

    dadurch gekennzeichnet, dass jede Rollenanordnung ferner eine einzelne Feder (64) beinhaltet, die dazu tendiert, all die Rollen radial nach innen zu drücken, um in entsprechenden der Aussparungen in der entsprechenden Nabe zu sitzen; wobei sich jede Rollenanordnung (44, 46) der inneren Nockenlauffläche benachbart befindet, wobei die innere Nockenlauffläche angepasst ist, um einen Keileingriff der Rollen zwischen der inneren Nockenlauffläche und der entsprechenden Nabe bereitzustellen, wenn der Rollenkäfig in eine erste Richtung relativ zu dem Kupplungsgehäuse in die Vorwärts-Eingriffsposition gedreht wird, und wenn der Rollenkäfig in eine zweite Richtung relativ zu dem Kupplungsgehäuse in die Rückwärts-Eingriffsposition gedreht wird, wobei die zweite Richtung der Drehung der ersten entgegengesetzt ist, wobei die innere Nockenlauffläche eine freigegebene Position der Rollen zwischen der Vorwärts-Eingriffsposition und der Rückwärts-Eingriffsposition definiert, in der die Bewegung der Rollen radial nach außen gegen die Wirkung der Feder ermöglicht ist, um die Rollen aus den Aussparungen in der entsprechenden Nabe zu lösen, um die relative Drehung der Nabe und der entsprechenden Rollenanordnung zu ermöglichen.


     
    2. Bidirektionale Freilaufkupplung (30) gemäß Anspruch 1, wobei die Feder jeder Rollenanordnung (44, 46) einen Schraubenfederring (64) beinhaltet, der die Rollen (48) umgibt.
     
    3. Bidirektionale Freilaufkupplung (30) gemäß Anspruch 2, wobei die Rollen (48) gerillt sind, die Schraubenfederringe (64) in den Rillen (66) sitzen und die Tiefe der Rillen größer als die Dicke der Schraubenfederringe ist.
     
    4. Bidirektionale Freilaufkupplung (30) gemäß einem der vorhergehenden Ansprüche, ferner beinhaltend mindestens eine Zunge (56) an mindestens einem der Rollenkäfige (50, 52), die in einem entsprechenden Einschnitt (58) in dem anderen der Rollenkäfige aufgenommen ist, wobei der Einschnitt eine größere Umfangslänge als die Zunge aufweist, wobei die Differenz zwischen den Umfangslängen der Zunge und des Einschnitts das Ausmaß der begrenzten relativen Drehung der zwei Rollenkäfige bestimmt.
     
    5. Bidirektionale Freilaufkupplung (30) gemäß einem der vorhergehenden Ansprüche, ferner beinhaltend mindestens einen Adapter (160), der zum Bereitstellen des Eingriffs zwischen den Rollenkäfigen zwischen den Rollenkäfigen (50, 52) positioniert ist, wobei der Adapter konfiguriert ist, um in mindestens einige der Schlitze (54) in jedem Rollenkäfig einzugreifen.
     
    6. Bidirektionale Freilaufkupplung (30) gemäß einem der vorhergehenden Ansprüche, wobei die Rollen (48) um jeden Rollenkäfig (50, 52) in gleichmäßigen Abständen angeordnet sind, wobei die Aussparungen (62) um jede Nabe (32, 34) in gleichmäßigen Abständen angeordnet sind, und die Anzahl an Aussparungen ein ganzes Vielfaches der Zahl an Rollen ist.
     
    7. Bidirektionale Freilaufkupplung (30) gemäß einem der vorhergehenden Ansprüche, ferner beinhaltend ein Eingangsrad (38), das das Kupplungsgehäuse umgibt, wobei das Eingangsrad Zähne (40) umfasst, die um einen äußeren Umfang des Eingangsrads gebildet sind, und wobei die innere Nockenlauffläche (42) auf einem Innendurchmesser des Eingangsrads gebildet oder daran befestigt ist.
     
    8. Bidirektionale Freilaufkupplung (30) gemäß Anspruch 7, wobei die Kupplung in einem Fahrzeug montiert ist, wobei das Fahrzeug eine Antriebsachse (12) aufweist, die zwei Wellensegmente (22, 24) umfasst, und wobei jedes Wellensegment mit einer der Naben (32, 34) antreibend in Eingriff steht, wobei das Fahrzeug einen Motor (16) mit einer Ausgangswelle umfasst, die mit dem Eingangsrad in Eingriff steht, um Drehbewegung auf das Eingangsrad zu übertragen.
     
    9. Bidirektionale Freilaufkupplung (30) gemäß Anspruch 8, wobei die Naben (32, 34) keilverzahnte Enden zum Engreifen in passende keilverzahnte Enden auf den Wellensegmenten (22, 24) umfassen.
     
    10. Bidirektionale Freilaufkupplung (30) gemäß einem der Ansprüche 1-6, wobei der Eingang ein Eingangsrad (38) beinhaltet, das angepasst ist, um zum Übertragen der Drehung der Eingangswelle in eine Drehung des Eingangsrads mit einer Eingangswelle in Eingriff zu kommen, wobei das Eingangsrad mit dem Kupplungsgehäuse (36) in Eingriff steht, um das Kupplungsgehäuse mit dem Eingangsrad zu drehen.
     
    11. Eine Radmaschine, die Folgendes aufweist: eine Leistungsquelle und eine primäre Antriebsachse mit zwei Wellensegmenten, und eine bidirektionale Freilaufkupplung (30) gemäß einem der vorhergehenden Ansprüche zum Übertragen von Drehmoment und Steuern der Drehmomentübertragung von der Leistungsquelle auf die Wellensegmente der primären Antriebsachse.
     
    12. Radmaschine gemäß Anspruch 11, wobei die Maschine eine Schneefräse (10) oder ein Rasenmäher mit Zweiradantrieb ist.
     
    13. Ein Fahrzeug, das Folgendes aufweist: einen Motor und eine primäre Antriebsachse mit zwei Wellensegmenten und eine bidirektionale Freilaufkupplung (30) gemäß einem der Ansprüche 1-10 zum Übertragen von Drehmoment und Steuern der Drehmomentübertragung von der Leistungsquelle auf die Wellensegmente der primären Antriebsachse.
     
    14. Fahrzeug gemäß Anspruch 13, wobei das Fahrzeug ein Golfwagen ist.
     


    Revendications

    1. Un embrayage à roue libre bidirectionnel (30) pour commander une transmission de couple à des segments arbres d'un essieu moteur primaire (12) d'une machine à roues, l'embrayage à roue libre bidirectionnel comprenant :

    un carter d'embrayage (36) conçu pour être mis en prise avec et mis en rotation par un élément d'entrée, le carter d'embrayage ayant sur lui une surface de came interne (42) ;

    une paire de moyeux (32, 34) conçus chacun pour se mettre en prise avec une extrémité d'un segment arbre respectif d'un essieu moteur pour une rotation avec celle-ci, chaque moyeu ayant une pluralité de renfoncements s'étendant axialement (62) sur une surface externe ;

    une paire d'ensembles à rouleaux (44, 46) disposés à l'intérieur du carter d'embrayage, chaque ensemble à rouleaux incluant un jeu de rouleaux (48) positionnés autour d'au moins une portion d'un des moyeux, une cage de cylindres (50, 52) ayant une pluralité de fentes (54), chaque rouleau étant situé à l'intérieur d'une fente, la cage de cylindres étant située autour d'au moins une portion du moyeu respectif, les cages de cylindres (50, 52) se mettant en prise l'une avec l'autre pour une rotation relative limitée de telle sorte que quand un ensemble à rouleaux est dans une position parmi la position de mise en prise avant et la position de mise en prise arrière, l'autre ensemble à rouleaux ne peut pas se déplacer jusque dans la direction opposée de la position de mise en prise avant et la position de mise en prise arrière,

    caractérisé en ce que chaque ensemble à rouleaux comprend en sus un ressort unique (64) tendant à pousser tous les rouleaux radialement vers l'intérieur afin qu'ils se placent dans des renfoncements respectifs parmi les renfoncements dans le moyeu respectif ; chaque ensemble à rouleaux (44, 46) étant situé de façon adjacente à la surface de came interne, la surface de came interne étant conçue pour fournir une mise en prise par coinçage des rouleaux entre la surface de came interne et le moyeu respectif quand la cage de cylindres est mise en rotation dans une première direction relativement au carter d'embrayage jusque dans la position de mise en prise avant et quand la cage de cylindres est mise en rotation dans une deuxième direction relativement au carter d'embrayage jusque dans la position de mise en prise arrière, la deuxième direction de rotation étant opposée à la première, la surface de came interne définissant une position dégagée des rouleaux entre ladite position de mise en prise avant et ladite position de mise en prise arrière dans laquelle un déplacement des rouleaux radialement vers l'extérieur est permis contre l'action du ressort afin de libérer les rouleaux des renfoncements dans le moyeu respectif pour permettre une rotation relative du moyeu et de l'ensemble à rouleaux respectif.


     
    2. L'embrayage à roue libre bidirectionnel (30) selon la revendication 1, où le ressort de chaque ensemble à rouleaux (44, 46) comprend un ressort jarretière (64) encerclant les rouleaux (48).
     
    3. L'embrayage à roue libre bidirectionnel (30) selon la revendication 2, où les rouleaux (48) sont rainurés, les ressorts jarretières (64) sont placés dans les rainures (66), et la profondeur des rainures est supérieure à l'épaisseur des ressorts jarretières.
     
    4. L'embrayage à roue libre bidirectionnel (30) selon n'importe quelle revendication précédente, comprenant en sus au moins une languette (56) sur au moins une des cages de cylindres (50, 52) reçue dans une encoche respective (58) dans l'autre des cages de cylindres, l'encoche ayant une longueur circonférentielle supérieure à la languette, où la différence entre les longueurs circonférentielles de la languette et de l'encoche détermine la quantité de la rotation relative limitée des deux cages de cylindres.
     
    5. L'embrayage à roue libre bidirectionnel (30) selon n'importe quelle revendication précédente, comprenant en sus au moins un adaptateur (160) positionné entre les cages de cylindres (50, 52) pour fournir la mise en prise entre les cages de cylindres, l'adaptateur étant configuré pour se mettre en prise avec au moins certaines des fentes (54) dans chaque cage de cylindres.
     
    6. L'embrayage à roue libre bidirectionnel (30) selon n'importe quelle revendication précédente, où les rouleaux (48) sont espacés de façon égale autour de chaque cage de cylindres (50, 52), les renfoncements (62) sont espacés de façon égale autour de chaque moyeu (32, 34), et le nombre de renfoncements est un multiple entier du nombre de rouleaux.
     
    7. L'embrayage à roue libre bidirectionnel (30) selon n'importe quelle revendication précédente, comprenant en sus un engrenage d'entrée (38) encerclant le carter d'embrayage, où l'engrenage d'entrée inclut des dents (40) qui sont formées autour d'une circonférence externe de l'engrenage d'entrée et où la surface de came interne (42) est formée sur ou fixée à un diamètre interne de l'engrenage d'entrée.
     
    8. L'embrayage à roue libre bidirectionnel (30) selon la revendication 7, où l'embrayage est monté dans un véhicule, le véhicule ayant un essieu moteur (12) qui inclut deux segments arbres (22, 24), et où chaque segment arbre est mis en prise de façon entraînante avec un des moyeux (32, 34), le véhicule incluant un moteur (16) avec un arbre de sortie qui est mis en prise avec l'engrenage d'entrée pour transmettre un mouvement rotatif à l'engrenage d'entrée.
     
    9. L'embrayage à roue libre bidirectionnel (30) selon la revendication 8, où les moyeux (32, 34) incluent des extrémités cannelées pour se mettre en prise avec des extrémités cannelées d'accouplement sur les segments arbres (22, 24).
     
    10. L'embrayage à roue libre bidirectionnel (30) selon n'importe lesquelles des revendications 1 à 6, où l'élément d'entrée comprend un engrenage d'entrée (38) conçu pour être mis en prise avec un arbre d'entrée pour transmettre une rotation de l'arbre d'entrée en une rotation de l'engrenage d'entrée, l'engrenage d'entrée étant mis en prise avec le carter d'embrayage (36) afin de mettre en rotation le carter d'embrayage avec l'engrenage d'entrée.
     
    11. Une machine à roues ayant une source d'alimentation et un essieu moteur primaire avec deux segments arbres, et un embrayage à roue libre bidirectionnel (30) selon n'importe lesquelles des revendications précédentes pour transmettre un couple et commander une transmission de couple de la source d'alimentation aux segments arbres de l'essieu moteur primaire.
     
    12. La machine à roues selon la revendication 11, où la machine est une souffleuse à neige (10) ou une tondeuse à gazon à deux roues motrices.
     
    13. Un véhicule ayant un moteur et un essieu moteur primaire avec deux segments arbres, et un embrayage à roue libre bidirectionnel (30) selon n'importe lesquelles des revendications 1 à 10 pour transmettre un couple et commander une transmission de couple de la source d'alimentation aux segments arbres de l'essieu moteur primaire.
     
    14. Le véhicule selon la revendication 13 où le véhicule est une voiturette de golf.
     




    Drawing





























    Cited references

    REFERENCES CITED IN THE DESCRIPTION



    This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

    Patent documents cited in the description