Abstract:
A transaxle for a small utility vehicle or implement, including a casing, at least one rotatable shaft disposed in and extending from the casing, at least one brake disc rotatably fixed to the rotatable shaft for rotation therewith, and at least one braking mechanism with at least a portion of the braking mechanism being externally mounted on the casing proximate the rotatable shaft. The braking mechanism includes at least one friction puck disposed proximate the brake disc, and a brake shaft including a cam surface having a longitudinal edge, wherein the brake shaft has an engaged position in which the longitudinal edge is in operative engagement with the friction puck and the friction puck is in pressing engagement with the brake disc and a disengaged position in which the longitudinal edge is out of operative engagement with the friction puck.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Application No. 60/283,242, filed Apr. 11, 2001. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The present invention relates to braking systems for use with small utility vehicles such as riding lawn mowers, lawn tractors and the like, specifically, disc braking systems. 
     2. Description of the Related Art 
     Typically, small utility vehicles and implements, such as riding lawn mowers, lawn tractors, and snow throwers, contain an internal combustion engine that supplies drive power in the form of rotary mechanical motion to the input of a transaxle. In some cases the transaxle then transfers this mechanical motion through a gearbox and then to a differential, which splits the rotary mechanical motion between two axles at the output of the transaxle. The axles each terminate with connections to wheels that engage the ground to drive the vehicle or implement. Braking systems are utilized with such vehicles to allow an operator to slow or stop motion of the vehicle, and to prevent runaway implements and resultant injuries. 
     Some previous braking systems have employed braking mechanisms that are mounted completely within the transaxle casings. A problem with such braking mechanisms is that the braking mechanisms must be assembled contemporaneously within the transaxle casings, and therefore any design changes in such braking mechanisms necessarily require additional complementary design changes in the transaxle casings. A further problem with these braking mechanisms is that the transaxle casings must be separated and the transaxle partially disassembled in order to access the braking mechanisms for servicing. In addition, locating the braking mechanisms within the transaxle casings increases the likelihood that the brake disc will be contaminated by oil, grease or other lubricants used to lubricate the gears and shafts within the transaxle, and may adversely affect brake performance. 
     Another previous braking mechanism utilizes a brake housing, which is mounted on the exterior of the transmission and includes a brake disc and brake pucks located externally of the transmission, and a brake lever, located on the exterior of a brake housing, which rotates to move a friction puck into braking engagement with the brake disc (U.S. Pat. No. 5,195,386). Such a braking mechanism structure allows the brake to be located externally of the transmission, but requires the use of several components for actuation of the brake, thereby raising the cost and complexity of the braking mechanism. Furthermore, such a structure requires additional assembly steps, thereby limiting the capability of the braking system being shipped with the transaxle and limiting the possibility of installation of the transaxle into a vehicle without requiring the vehicle manufacturer to conduct additional assembly of the transaxle, or the possibility of “drop-in” installation of a transaxle including the brake mechanism to a vehicle. 
     What is needed is a braking system for a small utility vehicle or implement that effectively stops, slows, or prevents motion of the vehicle. A further need is for a braking system that contains braking mechanisms mounted such that the braking mechanisms are readily accessible for servicing by not being internally disposed within the transaxle casing, cannot be contaminated by oil, grease, or other lubricants from within the transaxle casings, and can be shipped with the transaxle as a single unit to a final vehicle assembly location for “drop-in” installation to the vehicle. 
     SUMMARY OF THE INVENTION 
     The above-mentioned and described shortcomings are overcome by providing a braking mechanism which is mounted externally of the transaxle casing and which includes a removable cover, thereby providing access for servicing and preventing contamination by oil, grease, or other lubricants. Furthermore, the braking mechanism may include a portion formed with the transaxle casing such that the braking mechanism may be combined with the transmission into a single unit. 
     The present invention provides a transaxle for a small utility vehicle or implement, including a casing, at least one rotatable shaft disposed in and extending from the casing, at least one brake disc rotatably fixed to the rotatable shaft for rotation therewith, and at least one braking mechanism with at least a portion of the braking mechanism being externally mounted on the casing proximate the rotatable shaft. The braking mechanism includes at least one friction puck disposed proximate the brake disc, and a brake shaft including a cam surface having a longitudinal edge, wherein the brake shaft has an engaged position in which the longitudinal edge is in operative engagement with the friction puck and the friction puck is in pressing engagement with the brake disc and a disengaged position in which the longitudinal edge is out of operative engagement with the friction puck. 
     The present invention further provides a braking mechanism for a transaxle in a small utility vehicle with at least a portion of the braking mechanism being externally mounted to the transaxle. The braking mechanism includes a brake disc, at least one friction puck disposed proximate the brake disc, and a brake shaft including a cam surface having a longitudinal edge, wherein the brake shaft has an engaged position in which the longitudinal edge is in operative engagement with the friction puck and the friction puck is in pressing engagement with the brake disc and a disengaged position in which the longitudinal edge is out of operative engagement with the friction puck. 
     The present invention further provides a transmission for a vehicle including a casing, at least one rotating shaft extending from the casing, a brake disc rotatably fixed to the rotating shaft for rotation therewith, and at least one braking mechanism. The braking mechanism includes a brake housing with at least a portion of the brake housing being externally mounted on the casing, at least one friction puck disposed proximate the brake disc, and a brake shaft including a cam surface having a longitudinal edge. The brake shaft has a first, rotated position in which the longitudinal edge is in operative engagement with the friction puck such that the friction puck is in pressing engagement with the brake disc, and a second position wherein the longitudinal edge is not in operative engagement with the friction puck and the cam surface is disposed parallel to the friction puck. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     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: 
     FIG. 1 is a sectional plan view of a hydrostatic transaxle for a zero turn mower including a first embodiment brake assembly according to the present invention in which a portion of the brake housing is integrally formed with the transaxle casing; 
     FIG. 2A is an enlarged sectional plan view of the upper portion of FIG. 1; 
     FIG. 2B is an enlarged sectional plan view of the lower portion of FIG. 1; 
     FIG. 3 is a sectional side view of the hydrostatic transmission of FIG. 1; 
     FIG. 4 is a side view of the hydrostatic transmission of FIG. 1 along line  4 — 4  thereof; 
     FIG. 5 is a side view of a first embodiment of one of the brake assemblies according to the present invention; 
     FIG. 6 is a view of one of the wheel-mounting flanges of the transmission, along line  6 — 6  of FIG. 1; 
     FIG. 7 is a sectional view of one of the drive disconnect mechanism of the transmission, along line  7 — 7  of FIG. 1; and 
     FIG. 8 is an exploded view of a second embodiment of the inventive brake assembly. 
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views. Although the drawings represent embodiments of the present invention, the drawings are not necessarily to scale and certain features may be exaggerated in order to better illustrate and explain the present invention. The exemplifications set out herein illustrate two embodiments of the invention and such exemplification is not to be construed as limiting the scope of the invention in any manner. 
     DETAILED DESCRIPTION 
     For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments 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. 
     FIG. 1 shows a partial view of zero turn radius mower  20  having frame  22  and ground engaging drive wheels  24 , one of which is shown in ghosted lines. Frame  22  includes left hand frame rail  26  and right hand frame rail  28 . Between left and right hand frame rails  26  and  28  is disposed transaxle assembly  30  in accordance with the present invention. Transaxle  30  includes T-shaped axle housing  32  and two hydrostatic transmission modules  34   a  and  34   b . Hydrostatic transmission modules  34   a  and  34   b  are mirror images of one another, and their structure and operation are described in U.S. Pat. No. 6,301,885 and U.S. patent applications Ser. Nos. 09/498,692, filed Feb. 7, 2000, and Ser. No. 09/671,796, filed Sep. 27, 2000, all of which are assigned to Tecumseh Products Company, the disclosures of which are each expressly incorporated herein by reference. 
     Transaxle assembly  30  further includes left hand axle  36  and right hand axle  38  which abut within axle drive housing  32 , but are not rotatably coupled together. The outboard ends of each of axles  36  and  38  are provided with splines  40  on which are fitted flanges  42  to which wheels  24  are attached. Nut  44  secures flange  42  onto the end of axles  36  and  38 , and bolts  46  project through holes provided in flanges  42  and a center portion (not shown) of drive wheels  24 . Nuts (not shown) threadedly engage bolts  46  to secure wheels  24  to flanges  42  in the conventional manner. 
     T-shaped housing  32  includes upper housing portion  48  and lower housing portion  50  which are attached to each other and interface along a substantially horizontal parting line. Upper and lower portions  48  and  50  of housing  32  define gear train enclosing portion  52  and longitudinal central leg or portion  54  through which axle  38  extends, as best shown in FIG.  1 . 
     Each of hydrostatic transmission modules  34   a ,  34   b  respectively includes a housing comprising upper portion  60   a ,  60   b  and lower housing portion  62   a ,  62   b . Housing portions  60   a ,  60   b  and  62   a ,  62   b  are respectively identical except for being mirror images of one another. Disposed within each of hydrostatic transmission modules  34   a ,  34   b  is center section or block  64   a ,  64   b , respectively. Center sections or blocks  64   a  and  64   b  are mirror images of each other, the structure of one of which is detailed in above-incorporated U.S. Pat. No. 6,301,885. Each of the hydrostatic transmission modules include axial piston pump  66  and axial piston motor  68  mounted to its center section or block  64 . Referring to FIG. 3, each of pumps  66  is provided with input shaft  70  to which is affixed drive pulley  72  and fan  74 . Pulleys  72  are driven by the mower engine (not shown) and are rotated in the same direction to impart constant-speed rotating motion to pumps  66 . 
     Each of pumps  66  is of variable displacement, and the displacement, and direction of fluid flow between the pump and its respective motor, is controlled by swash plate assembly  76  (FIG.  4 ). The operation of axial piston pump and motor combinations is generally well known in the art. The swash plate assembly is adjusted through pivoting movement of lever  78  (FIG. 3) provided on each of hydrostatic transmission modules  34   a  and  34   b . Levers  78  may be provided with a neutral adjustment mechanism and return spring as described in above-incorporated U.S. patent application Ser. No. 09/671,796. As shown in FIG. 3, each of levers  78  pivots its swash plate assembly approximately 21° from its neutral position in the forward and reverse directions for controlling the pump displacement and direction of fluid flow to the motor. As is well known in the art, at the pump neutral position substantially zero fluid flow is provided to the motor, and the motor is then not driven in either direction. Fluid flow from the pump to the motor through one conduit within block  64  will drive the motor in a forward rotating direction; and fluid flow from the pump to the motor through another conduit within the block will drive the motor in the reverse rotating direction. Each of rotatable motors  68  drives a transmission output shaft  80  radially supported within a bearing  81 , a portion of which extends axially from the transmission module housing, the end of each transmission output shaft  80  being provided with splines  82 , as best shown in FIGS. 2A and 2B. 
     With reference now to FIG. 2A, it can be seen that the end of transmission output shaft  80  of hydrostatic transmission module  34   a  is provided with a cylindrical, axially-extending recess into which the cylindrical end of first axle drive input shaft  84  is piloted. The piloted end of input shaft  84  is smaller in diameter than the adjacent portion of shaft  84 , which is provided with splines  86  and is of the same diameter as output shaft  80 . Internally splined collar  88  is provided which at all times engages splines  82  of transmission output shaft. Collar  88  is biased by spring  92  into an engaged position in which its internal splines also engage splines  86  of input shaft  84  to effect coupling between the hydrostatic transmission module  34   a  and first axle drive input shaft  84 . Referring to FIG. 7, collar  88  is provided with an external circumferential groove into which tines  91  of fork  90  are slidably received. Fork  90  pivots about axis  94  to move collar  88  between its engaged position (shown), in which it overlaps splines  86  and splines  82 , and against the force of spring  92  to a disengaged position in which the collar is entirely received on splines  82  of transmission output shaft  80 . In the collar disengaged position, transmission module  34   a  is mechanically disengaged from the gear train and its axle  38 , and shafts  80  and  84  freely rotate relative to one another through their piloted connection. With collar  88  in its disengaged position, axle  38  may rotate freely for easy manual maneuvering of mower  20 , a feature which may prove extremely useful in the event of hydrostatic component failure. 
     The end of first axle drive input shaft  84  located opposite that which is piloted into transmission output shaft  80  is provided with external splines  96  onto which is fitted the internal splines of brake disk  98  (FIG.  2 A). Brake disk  98  may move axially on shaft  84  along the interfitting splines and comprises part of brake assembly  100  which has a housing formed of first brake housing portion  102 , which is integral with upper housing portion  48  of T-shaped housing  32 , and second brake housing portion  104 , which is bolted to the first brake housing portion. Brake pads  106  and  107  are respectively contained within first and second brake housing portions  102  and  104  and slidably engage opposite sides of brake disk  98 . Planar, rectangular support members (not shown) made of a metal such as steel, may be located between the brake pads and their respective housing portions to help evenly distribute the load on the pads. Brake control rod  108  extends along a direction perpendicular to the axis of shaft  84  and is provided with a flat surface which, when the brake is not engaged, is substantially parallel with the surface of brake disk  98  which engages brake pad  106 . 
     To actuate the brake, brake control rod  108  is rotated in either direction about its longitudinal axis, and the edge at either lateral side of the rod&#39;s flat surface is brought into abutment with the support member, and forces the same, and pad  106  into frictional engagement with disk  98 . Disk  98  may move slightly along splines  96  and into frictional engagement with pad  107 . The movement of pad  107  is limited by second brake housing portion  104 , and disk  98  therefore becomes tightly clamped between pads  106  and  107 , preventing rotation of shaft  84  and thus axle  38 . Normally, hydrostatic transmissions do not require mechanical braking to slow or stop the tractor or mower driven thereby; merely reducing the pump displacement to or toward zero (at neutral) is usually sufficient to effect braking. Brake assembly  100  may be used as a parking brake, however, and may be used to prevent movement of mower  20  when collar  88  is in its disengaged position. The structure and operation of first embodiment brake assembly  100  is otherwise as described further hereinbelow with regard to second embodiment brake assembly  100 A. 
     First axle drive input shaft  84  is supported within housing  32  by means of bearings and is surrounded by shaft seals to prevent the leakage of lubricating oil therefrom. Located between the opposite ends of shaft  84  are splines  110  which engage the internal splines of spur gear  112 . Jack shaft  114  is also supported by bearings within housing  32  and has spacer  116  and a compound gear comprising large diameter gear portion  118  and integral small diameter gear portion  120  rotatably disposed thereabout. Large diameter gear portion  118  is intermeshed with spur gear  112  and is driven thereby. Small diameter gear portion  120  is intermeshed with first axle drive gear  122  which is rotatably fixed via splines  124  to axle  38  for driving the right hand drive wheel  24  attached to the end thereof. It will now be understood by those of ordinary skill in the art that hydrostatic transmission module  34   a  receives rotary input through its input shaft  70  and through pivotal manipulation of its swash plate assembly  76  effects, when collar  88  is in its engaged position, rotation of axle  38  in forward and reverse directions at variable speeds through a gear train comprising gears  112 ,  118 ,  120  and  122 . 
     Referring now to FIG. 2B, it is shown that motor  68  of hydrostatic transmission module  34   b  is similarly provided with output shaft  80  into which an end of second axle drive input shaft  126  is piloted, shafts  80  and  126  being selectively rotatably engaged through collar  88  and splines  128  and  82 , as described above. In the manner described above, output shaft  80  of hydrostatic transmission module  34 b and second axle drive input shaft  126  may be disengaged through rotation of fork  90 , which urges collar  88  rightward as shown against the biasing force of spring  92 . Like first axle drive input shaft  84 , an end of second axle drive input shaft  126  is provided with splines  96  on which a brake disk  98  is disposed, and another brake assembly  100  as described above is provided for preventing rotation of shaft  26 . 
     Second axle drive input shaft  126  is supported within housing  32  by bearings and is surrounded by shaft seals, like shaft  84 . At a location between its opposite ends, second axle drive input shaft  126  is provided with splines  130  which are engaged with the internal splines of a spur gear  132 . Jack shaft  134 , which is identical to jack shaft  114  and is similarly supported within housing  32  by bearings, has spacer  136  and a compound gear comprising integral large and small diameter gear portions  138 ,  140 , respectively, rotatably disposed thereabout. Large diameter gear portion  138  is intermeshed with spur gear  132 , and small diameter gear portion  140  is intermeshed with second axle drive gear  142 , which is rotatably fixed via splines  144 , to left hand axle  36  for driving the left hand side drive wheel  24 . It will now be understood by those of ordinary skill in the art that hydrostatic transmission module  34   b  receives rotary input through its input shaft  70  and through pivotal manipulation of its swash plate assembly  76  effects, when collar  88  is in its engaged position, rotation of axle  36  in forward and reverse directions at variable speeds through a gear train comprising gears  132 ,  138 ,  140  and  142 . 
     It will now be appreciated by those of ordinary skill in the art that in the event a hydrostatic transmission component failure, either or both of transmissions  34   a  and  34   b  may be operatively disconnected from its respective axle drive input shaft  84  or  126 , and mower  20  may thus be easily moved without having to remove the failed hydrostatic transmission module or disconnecting a drive wheel  24  from its respective axle  36  or  38 . Further, either or both of the brakes associated with axle drive input shafts  84  and  126  may be actuated for slowing, stopping or preventing movement of mower  20 . 
     Hydrostatic transmission modules  34   a  and  34   b  are each attached to axle drive housing  32  only through one bolted connection, shown at  154  and  156 , and portions of transmission output shaft bearings  81  which are slidably fitted into counterbores  158  of housing  32 . Hydrostatic transmission module  34   a  and  34   b  may be individually and separately removed and replaced without removal of the other transmission module from transaxle  30 , or of axle drive housing  32  or either of drive wheels  24  from mower  20 . 
     Referring again to FIG. 1, axle  38  is rotatably supported by bearing  146  provided at the end of longitudinal center portion or leg  54  of T-shaped axle housing  32 . That end of the housing center portion  54  is attached to right hand frame rail  28  by means of bolts  160  (FIG.  4 ). Axle  38  is also supported within housing  32  by a bearing located adjacent its splines  124  and gear  122 , and is there surrounded by a shaft seal. Left hand axle  36  is also supported within housing  32  by a bearing located adjacent its splines  144  and gear  142 , and is there surrounded by a shaft seal. External to housing  32 , axle  36  is supported by pillow block  148  which is attached to left hand frame rail  26 , axle  36  and pillow block  148  being received within notch  150  provided in frame rail  26 . A plurality of bolts (not shown) fix the pillow block to the left hand frame rail. A torque strap  152  (FIGS. 1 and 2A) may be provided to secure either the forward or rearward end of gear train enclosing portion  52  of housing  32  to frame  22  to counteract any tendency for transmission  30  to rotate about the axis of rotation of axles  36  and  38 . 
     Referring to FIG. 8, second embodiment brake assembly  100 A is shown as including first housing portion  102 A and second brake housing portion  104 A connected together by bolts  162 . Brake assembly  100 A differs from brake assembly  100  in that brake assembly  100 A may be completely detached from transaxle housing  32  or attached easily by a pair of bolts  164 . Within housing portions  102 A and  104 A is brake disc  98 A having first and second brake pads  106 A and  107 A on either side thereof. Adjacent brake pad  107 A are rigid shims  166 , which may be utilized to distribute the load exerted when brake rod  108 A is rotated into engagement therewith. Brake rod  108 A is inserted in brake housing portion  102 A such that upper portion  168  extends above first brake housing portion  102 A wherein upper portion  168 , specifically square end  170  is inserted through actuator  172  and attached thereto by bolt  174 . With such a connection, when actuator  172  is moved, brake rod  108 A will also rotate such that it may engage brake pad  107 A to effectuate a braking action. Biasing actuator  172  into a non-rotated position is spring  176  which receives brake rod  108 A and is attached to actuator  172  at tang  178  and pin  180  extending into housing portion  102 A. 
     In operation, actuator  172  rotates via an actuation mechanism external to brake assembly  100 A and then rotates brake rod  108 A through engagement of square portion  170  and bolt  174 . As brake rod  108 A is rotated, flat surface  182  of rod  108 A rotates from a position parallel to rigid shims  166  to a position wherein longitudinal edge  184  of rod  108 A comes into engagement with brake shims  166 . As longitudinal edge  184  contacts shims  166 , shims  166  are pushed into abutment with brake pad  107 A, with brake pad  107 A then moving toward brake disc  98 A. Brake disc  98 A is structured and arranged such that it may move axially along axle  38  to which it is splined, thus when brake pad  107 A comes into contact with brake disc  98 A, brake disc  98 A moves axially toward brake pad  106 A. As brake shaft  108 A is further rotated and longitudinal edge  184  pushes shims  166  into brake pad  107 A, brake disc  98 A moves closer toward brake pad  106 A until the two abut. At that point, both brake pads  106 A and  107 A are in braking engagement with brake disc  98 A, thus braking action is realized. 
     While this invention has been described as having exemplary designs, the present invention may be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains.