Abstract:
A constant velocity flexible coupling for direct drive to the wheels of a low speed light duty wheeled vehicle or 4-wheel drive steer lawn tractor having discs which flexibly couple a drive shaft to a wheel flange.

Description:
CROSS REFERENCES TO CO-PENDING APPLICATIONS 
     This patent application is a continuation-in-part of Ser. No. 08/415,667 entitled &#34;Constant Velocity Flexible Coupling&#34; filed on Apr. 3, 1995, abandoned by the same inventor. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is for a constant velocity flexible coupling, and more particularly pertains to a flexible disc coupled mechanism similar in function to a universal drive joint for use in 4-wheel drive steer devices, such as a 4-wheel drive lawn mower or other such vehicles. 
     2. Description of the Prior Art 
     Four-wheel drive and steer mechanisms have been reserved for high end expensive commercial and industrial equipment ranging in the tens of thousands of dollars. The methods used to achieve power delivery through a pivoting steerable mechanism are effective and durable, but not in the same class as the smaller and more inexpensive and smaller lawn tractors intended for general consumer use. The cost is high and many do not even use CV-joints. Four-wheel drive farm tractors and utility tractors use designs far too expensive and are similar in design to units utilized in front wheel drive cars. 
     Another problem with prior art devices is that of offering a low speed flexible coupling that can function effectively up to 50° angles and yet fit in a relatively short (axial) space and require no sliding connections such as splines for absorbing axial reciprocation. The present invention uses no such spline devices and as such can be fabricated for a much more reasonable price. Four-wheel drive/steer mechanisms have been incorporated in some prior art lawn tractors, but steering and drive devices have limited the steering angle to a low range of steering at approximately 20°. 
     Although disc-type flexible joints are not new, the turning radius of single disc-type flexible joints are limited by the geometry of the single flexible disc. The present invention overcomes this problem by utilizing two flexible disc members coupled by an intermediate joint connector about which both discs flex. 
     Clearly, what is needed is an inexpensive, yet effective and durable drive steer coupling providing for an increased turn angle for use in small vehicles, such as provided by the present invention. 
     SUMMARY OF THE INVENTION 
     The general purpose of the present invention is a constant velocity flexible coupling for use in driving the wheels of a small wheeled vehicle that is powered and steered through each of its four wheels. 
     According to one embodiment of the present invention, there is provided a constant velocity flexible coupling. An output shaft of a differential unit couples to a first yoke which is connected to an inner flexible disc with optional reinforced metal inserts at the securation points. At 90° to the first yoke, an intermediate joint connector is fastened to the first disc. A second disc also attaches to the common joint connector and is parallel and opposite the first disc. A second yoke attaches to the second disc and is oriented 90° to the common joint connector and is aligned to the first yoke. The second yoke attaches to a shaft and a wheel flange which are secured to a pivotal wheel bearing housing which pivots about a mounting bracket secured to one end of differential housing members. 
     One significant aspect and feature of the present invention is a constant velocity flexible coupling which is simple in design and which is inexpensive. 
     Another significant aspect and feature of the present invention is the utilization of parallel flexible disc members coupled centrally by a joint connector in conjunction with yoke members oriented at 90° to the centrally located joint connector. 
     Yet another significant aspect and feature of the present invention is the flexing of discs about a central common joint connector. 
     Still additional significant aspect and feature of the present invention is the flexing of discs about the ends of yoke members. 
     An additional significant aspect and feature of the present invention is a constant velocity flexible coupling which turns and provides drive force at very severe angles such as up to 50°. 
     A further significant aspect and feature of the present invention is a constant velocity flexible coupling used in conjunction with a 4-wheel drive, 4-wheel steer lawn tractor or other such vehicles. 
     A still further significant aspect and feature of the present invention is the utilization of flexibly aligned discs to absorb axial reciprocation. The self-aligning tendencies of the discs which assist in returning a wheel to the straight ahead position when steering inputs are reduced or neutralized. 
     Having thus described embodiments of the present invention, it is the principal object of the present invention to provide a constant velocity flexible coupling. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects of the present invention and many of the attendant advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, in which like reference numerals designate like parts throughout the figures thereof and wherein: 
     FIG. 1 illustrates a perspective view of a constant velocity flexible coupling, the present invention; 
     FIG. 2 illustrates an exploded view of the inner drive components which align between the mounting bracket and the wheel bearing housing; 
     FIG. 3 illustrates the alignment of FIGS. 4A-4B and of FIGS. 5A-5B; 
     FIGS. 4A-4B illustrate a side view of constant velocity flexible couplings utilized at opposing ends of a differential drive assembly; 
     FIGS. 5A-5B illustrate a top view of a differential assembly and opposing flexible couplings of FIGS. 4A-4B. 
     FIG. 6 illustrates a cutaway view of the constant velocity flexible coupling 10 in a turn to the left; 
     FIG. 7 illustrates the members of FIG. 6 where discs 36 and 38 have advanced 90° in rotation; and, 
     FIG. 8 illustrates the utilization of a plurality of constant velocity flexible couplings with a 4-wheel drive/steer tractor. 
     FIG. 9 illustrates a perspective view of the first alternative embodiment. 
     FIG. 10 illustrates a cross sectional view of the first alternative embodiment. 
     FIG. 11 illustrates a cutaway view of the constant velocity flexible coupling 10 in a turn to the left incorporating flexible coupling discs 160 and 161. 
     FIG. 12 illustrates a perspective view of the second alternative embodiment. 
     FIG. 13 illustrates a front view of a constant velocity flexible interface, the third alternative embodiment. 
     FIG. 14 illustrates an end view of the constant velocity flexible interface. 
     FIG. 15 illustrates a cross-sectional view of the constant velocity flexible interface. 
     FIG. 16 illustrates a cutaway view of the constant velocity flexible coupling in a turn to the left incorporating the constant velocity flexible interface. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 illustrates a perspective view of a constant velocity flexible coupling 10 secured to a housing member 12 and a shaft member 14 of a differential drive later illustrated in the following FIGS. Visible in FIG. 1 is a mounting bracket 16 having a planar vertical member 18, a horizontally aligned planar top member 20 generally in the shape of a triangle, and a similarly shaped horizontally aligned planar bottom member 22. A wheel bearing housing 24, which functions also as a pivot bracket, pivotally aligns and secures over and about the outer ends of the mounting bracket top member 20 and bottom member 22 respectively. The one piece wheel bearing housing 24 includes a plurality of planar members including a vertically aligned planar member 26, an angled planar member 28 extending upwardly and inwardly from the vertically aligned planar member 26, an L-shaped planar bell crank member 30 being pivotally secured to the top member 20 of the mounting bracket 16, an angled planar member 32 extending downwardly and inwardly from the vertically aligned planar member 26 and a planar member 34 being pivotally secured to the bottom member 22 of the mounting bracket 16. The differential drive housing member 12 secures through the vertical planar member 18 of the mounting bracket 16. Shaft 14 rotates members located between the mounting bracket 16 and the wheel bearing housing 24 including an inner flexible disc 36 and an outer flexible disc 38 of rubber, polyurethane, urethane elastomers, polymers or other suitable materials. A wheel flange 35 having a plurality of studs 37a-37n aligns in a bearing 39 secured to the wheel bearing housing 24. An exploded view of these component members is illustrated in FIG. 2 and an assembled view is illustrated in FIG. 4B. 
     FIG. 2 illustrates an exploded view of the inner drive components which align between the mounting bracket 16 and the wheel bearing housing 24 of FIG. 1 where all numerals correspond to those elements previously described. A joint connector 40 secures between the flexible inner and outer discs 36 and 38. Opposing cylindrical members 42 and 44, including central bores 42a and 44a respectively, are mutually secured by a central connecting rod member 46 to form the joint connector 40. The inner and outer flexible discs 36 and 38 secure to the joint connector 40 by a plurality of fasteners. Fasteners 48 and 50 extend through opposing holes 52 and 54 in the outer flexible disc 38 to frictionally engage one end of bores 42a and 44a of the joint connector 40. In a like and similar fashion, fasteners 56 and 58 extend through holes 60 and 62 in the inner flexible disc 36 to frictionally engage the unoccupied end of bores 42a and 44a of the joint connector 40. Inner and outer yokes 64 and 66 align and secure to the inner and outer flexible discs 36 and 38 at points 90° from the attachment of the cylindrical members 42 and 44. Yoke 64 includes a central bore 68 and opposing outer bores 72 and 74. A yoke bushing 76 having a fastener bore 78 and a central bore 80 aligns and secures, such as by a weldment, to the bore 68 of the yoke 64. Yoke bushing 76 accommodates the end of the shaft member 14 illustrated in FIG. 1. Spacers 82 and 84 having central bores 86 and 88 align and secure, such as by weldment, to outer bores 72 and 74 respectively on the inner yoke 64. Fasteners 90 and 92 extend through holes 94 and 96 of the inner flexible disc 36 to frictionally engage holes 86 and 88 of the yoke spacers 82 and 84, thus securing the yoke 64 to the inner flexible disc 36. A hole 98 is centrally located in the inner flexible disc 36 to accommodate the yoke bushing 76 and the end of shaft 14, if required. The outer flexible disc 38 secures to the outer yoke 66 in much the same manner and fashion. Yoke 66 includes a central bore 100 and opposing outer bores 102 and 104. A shaft 106 aligns and secures, such as by a weldment, to the central bore 100. Shaft 106 aligns in a bearing 39 on the wheel bearing housing 24 illustrated in FIGS. 4A-4B. Spacers 108 and 110 having central bores 112 and 114 align and secure, such as by a weldment, to the outer bores 102 and 104 respectively of the outer yoke 66. Fasteners 116 and 118 extend through holes 120 and 122 in the outer flexible disc 38 to frictionally engage holes 112 and 114 of the yoke spacers 108 and 110, thus securing the yoke 66 to the outer flexible disc 38. 
     FIG. 3 illustrates the alignment of FIGS. 4A-4B and FIGS. 5A-5B. 
     FIGS. 4A-4B illustrate a side view of a constant velocity flexible coupling 10 incorporated into use with a differential drive assembly 124. Another constant velocity drive assembly 126 constructed in a fashion similar to the constant velocity flexible coupling 10 is located opposing the constant velocity flexible coupling 10 on the opposing end of the differential drive assembly 124 where all numerals correspond to those elements previously described. Constant velocity drive assembly 126, being similar in construction to constant velocity drive assembly, is not described for purposes of brevity. 
     Shaft 14 extends from the end of the housing member 12 into the central bore 80 of the yoke busing 76 and is secured therein by a nut and bolt assembly 130 extending through the fastener bore 78 and a corresponding bore 132 in the end of the shaft member 14, thus coupling the differential drive assembly 126 to the inner components of the constant velocity flexible coupling 10. Shaft 106 extends from the outer yoke 66 through and is supported by the wheel bearing housing mounted bearing 39 and further extends through and secures to the wheel flange 35 to couple the outer components of the constant velocity flexible coupling 10 to the wheel flange 35 and the wheel bearing housing 24. The upper portion of the wheel bearing housing 24 pivotally secures to the top planar member 20 of the mounting bracket 16 by engagement of an upper pivot bolt and washer assembly 134 with the top planar bell crank member 30 of the wheel bearing housing 24. In a similar fashion the lower portion of the wheel bearing housing 24 pivotally secures to the bottom planar member 22 of the mounting bracket 16 by engagement of a lower pivot bolt and washer assembly 136 with the lower planar member 34 of the wheel bearing housing 24. A control link 138 pivotally secures to the bell crank member 30 by a pivot member 140 and extends to connect to the opposing constant velocity flexible coupling 126 to provide for simultaneous steering of constant velocity flexible couplings 10 and 126 when connected to the steering mechanism of a vehicle such as a small rider lawn mower or other vehicle in which the invention is utilized. 
     MODE OF OPERATION 
     FIGS. 5A-5B illustrate a top view of the differential assembly 124 and opposing constant velocity flexible couplings 10 and 126 secured to each end. The static steering mode of operation is illustrated in dashed lines indicating straight ahead steering. Actuation of the control link 138 to the right by a vehicle steering mechanism, as in a turn to the left, causes the bell crank 30 to be positioned, as illustrated in solid lines, thus causing the wheel bearing housing 24 to pivot about the upper and lower pivot bolt and washer assemblies 134 and 136 of FIGS. 4A-4B. Pivoting of the wheel bearing housing 24 causes the inner flexible disc 36, of FIGS. 4A-4B, and the outer disc 38 to flex. Flexing about various component members occurs as the wheel flange 35 is propelled by the differential drive assembly 124 as illustrated in FIGS. 6 and 7. 
     FIG. 6 illustrates a cutaway view of the constant velocity flexible coupling 10 in a turn to the left illustrating the flexing of the inner and outer flexible discs 36 and 38 where the joint connector 40 is positioned in horizontal alignment at a point in time during rotation. In the straight ahead and in the turn, steering mode power is delivered from the shaft 14, through the yoke 64 and its respective spacers 82 and 84, through the inner flexible disc 36, through the joint connector 40, through the outer flexible disc 38, through the yoke 66 and its respective spacers 108 and 110, and finally through shaft 106 to the wheel flange 35. As the flexible discs 36 and 38 rotate, and as a turning action is imitated by the control link 138 of FIGS. 5A-5B, the shafts 14 and 106 are removed from concentric alignment to be angularly displaced from each other thereby causing the flexible discs 36 and 38 to flex and distort in a mirror image-like fashion about a vertical axis while the joint connector 40 is horizontal, such as exhibited and seen from a view line 142 where the vertical axis of the outer disc 38 is described as a line extending through the zone from the spacer 108 to the spacer 110 where contact with the flexible disc 38 is made or, in other words, from the 12 o&#39;clock position to the 6 o&#39;clock position on the disc 38. A similar vertical axis exists between the zone where spacers 82 and 84 align to the flexible disc 36. As can be seen from the illustration, discs 36 and 38 flex about these vertical axii, thus flexing the flexible discs 36 and 38 between the respective ends of the cylindrical members 42 and 44 of the joint connector 40. 
     FIG. 7 illustrates the members of FIG. 6 where the flexible discs 36 and 38 have advanced 90° in rotation with respect to FIG. 6 where all numerals correspond to those elements previously described. Illustrated in particular is the flexing of the inner and outer flexible discs 36 and 38 about the vertically aligned joint connector 40 with respect to the horizontally aligned yokes 64 and 66 at a point in time where flexible disc rotation is advanced 90° with respect to the flexible disc position illustrated in FIG. 6. At this point of rotation, where the joint connector 40 is positioned vertically, the flexible discs exhibit mirror-like image flexings where the discs 36 and 38 are flexed about vertical axii defined as a line through the outer ends of the cylindrical members 42 and 44 where the cylindrical members 42 and 44 meet the disc 38, the 12 o&#39;clock and 6 o&#39;clock position, and a line through the inner ends of the cylindrical members 42 and 44 where the cylindrical members 42 and 44 meet the disc 36, the 12 o&#39;clock and 6 o&#39;clock positions. Flexing of the flexible discs 36 and 38 exhibit different degrees of flexing between the positions illustrated in FIGS. 6 and 7 as the discs are rotated between the 0° and 90° positions and, of course, are repeated in various degrees of flex throughout the remaining 270° of rotation to provide a constantly flexing flexible coupling and to absorb axial reciprocation of component members. As steering input is relieved or reduced, the discs 36 and 38, being sprung and flexed, return to the flat disc memory position, thus returning the wheel bearing housing 24 into straight ahead steering alignment as opposed to most other constant velocity joints which do not automatically return to a neutral straight ahead positioning. 
     FIG. 8 illustrates the use of opposing and similar constant velocity flexible couplings 10 and 126 mounted on differential drive assembly 124 with a 4-wheel steer/drive tractor 144 in a left turn where all numerals correspond to those elements previously described. 
     FIG. 9 illustrates a perspective view of the first alternative embodiment where all numerals correspond to those elements previously described. A disk-shaped constant velocity flexible coupling 160 made of a polymer urethane elastomer, such as K-Prene or other suitable polymer, includes a plurality of raised bosses 162a-162n and a plurality of extended metal inserts 164a-164n. Flexible coupling disc 160 can be used in place of both the inner flexible disc 36 and the outer flexible disc 38 of the present invention as previously described. The flexible coupling disc 160 has a centrally located hole 166 to accommodate the yolk bushing 76 and the end of the shaft 14, if required, as shown in FIG. 2. Also illustrated in this FIG. are areas 174a-174n which are located equal distance between raised bosses 162a-162n. 
     FIG. 10 illustrates a cross sectional view of the flexible coupling disc 160 where all numerals correspond to those elements previously described. Illustrated in particular is the assembly of the metal inserts 164a-164n which extend from the upper portion 168 to the lower portion 170 of the raised bosses 162a-162n. Metal inserts 164a-164n are permanently secured to the inner wall 172 of the flexible coupling disc 160. The taper of the raised bosses 162a-162n prevents stress on the polymer urethane elastomer when flexed which further prevents the polymer urethane elastomer from pulling away from the metal inserts 164a-164n by shifting the stress to the areas 174a-174n shown in FIG. 11. 
     FIG. 11 illustrates the members of FIG. 6 where the flexible coupling discs 160 and 161 have advanced 90° in rotation with respect to FIG. 6 where all numerals correspond to those elements previously described. Illustrated in particular is the flexing of the flexible coupling discs 160 and 161 about the vertically aligned joint connector 40 with respect to the horizontally aligned yokes 64 and 66 at a point in time where flexible disc rotation is advanced 90° with respect to the flexible disc position illustrated in FIG. 6. At this point of rotation, where the joint connector 40 is positioned vertically, the flexible discs exhibit mirror-like image flexings where the flexible coupling discs 160 and 161 are flexed about vertical axii defined as a line through the outer ends of the cylindrical members 42 and 44 where the cylindrical members 42 and 44 meet the flexible coupling disc 161, the 12 o&#39;clock and 6 o&#39;clock position, and a line through the inner ends of the cylindrical members 42 and 44 where the cylindrical members 42 and 44 meet the flexible coupling disc 160, the 12 o&#39;clock and 6 o&#39;clock positions. Flexing of the flexible coupling discs 160 and 161 exhibit different degrees of flexing between the positions illustrated in FIGS. 6 and 7 as the discs are rotated between the 0° and 90° positions and, of course, are repeated in various degrees of flex throughout the remaining 270° of rotation to provide a constantly flexing flexible coupling and to absorb axial reciprocation of component members. As steering input is relieved or reduced, the flexible coupling discs 160 and 161, being sprung and flexed, return to the flat disc memory position, thus returning the wheel bearing housing 24 into straight ahead steering alignment as opposed to most other constant velocity joints which do not automatically return to a neutral straight ahead positioning. Also illustrated in FIG. 11 is the transfer of stress from the raised bosses 162a-162n to the central area 174a-174n when the flexible coupling discs are flexed. 
     FIG. 12 illustrates a perspective view of the second alternative embodiment where all numerals correspond to those elements previously described. A constant velocity flexible coupling disk 176 which is constructed similar to the first alternative embodiment and additionally includes a plurality of recessed areas 178a-178n correspondingly aligned to areas 174a-174n. Recessed areas 178a-178n lead to a lesser disk thickness than the corresponding adjacent disk thickness, which increases the flexibility of the flexible coupling disk 176 when flexed. The location of recessed areas 178a-178n also reduces the tendency of the urethane disk to separate from metal inserts 164a-164n when stressed without compromising the durability of the flexible coupling disk. 
     FIG. 13 illustrates a front view of a constant velocity flexible interface 210, the third alternative embodiment, which is constructed of urethane or like material and having an inner portion 212 which extends outwardly from the center to two opposing outer portions 214 and 216. The inner portion 212 has a relatively thick wall 218 and the outer portions 214 and 216 have relatively thin walls 220 and 222. The relatively thin walls 220 and 222 of outer portions 214 and 216 form opposing annular lips 232 and 234 as shown in FIG. 13. 
     The constant velocity flexible interface 210 incorporates mounting plates 224 and 226 constructed of steel or like material, which connect a differential axle 228 and a wheel axle 230 to the outer portions 214 and 216 of the constant velocity flexible interface 210. The method of securation will later be described in detail in conjunction with FIG. 14. 
     FIG. 14 illustrates an end view of the constant velocity flexible interface 210, where all numerals correspond to those elements previously described. Illustrated in detail is mounting plate 224 having a recessed planar area 236, a curved area 238 and an angled straight section 240 with respect to planar area 236. Located in the center of planar area 236 is a cylindrical axle mount sleeve 242 which is welded or otherwise suitably secured to the mounting plate 224. A plurality of screws 244a-n secure mounting plate 224 to the outer portion 214 of the constant velocity flexible interface 210 (not shown). The method of securation will later be described in detail in conjunction with FIG. 15. 
     FIG. 15 illustrates a cross-sectional view of the constant velocity flexible interface 210 where all numerals correspond to those elements previously described. Shown in detail is the method of securation of mounting plates 224 and 226 to the outer portions 214 and 216, respectively, of the constant velocity flexible interface 210. Mounting plate 226 has a recessed planar area 246, a curved area 248, an angled straight section 250, and an axle mount sleeve 252 identical to that of mounting plate 224. Screws or like fasteners pass through holes 254 and 256 in the axle mount sleeves 242 and 252 and respectively secure the differential axle 228 and wheel axle 230 thereto. Annular wedge plates 258 and 260 are aligned on the interior of annular lips 232 and 234 respectively and mounting plates 224 and 226 are then positioned over the exterior of annular lips 232 and 234 as shown in FIG. 16. A plurality of screws 244a-244n then pass through annular wedge plates 224 and 226 and annular wedge plates 258 and 260. When screws 244a-244n are torqued in the geometry of the annular wedge plates 258 and 260 in conjunction with the geometry of the angled straight portions 240 and 250 of mounting plates 224 and 226 the frictional engagement forces annular capture of opposing annular lips 232 and 234. 
     FIG. 16 illustrates a cutaway view of the constant velocity flexible coupling 262 in a turn to the left incorporating the constant velocity flexible interface 210, where all numerals correspond to those elements previously described. The constant velocity flexible coupling 262 is constructed using many of the principles taught in the preferred embodiment and includes a housing member 264, shaft member 266, mounting bracket 268, vertical member 270, bottom member 272, wheel bearing housing 274, vertical planar member 276, angled planar member 278, wheel flange 280, studs 282a-282n, bearing 284 and shaft 286 which operate similarly to the preferred embodiment. 
     Various modifications can be made to the present invention without departing from the apparent scope hereof.