Abstract:
An automatic transmission adapted to receive a power take-off device at a rear portion thereof and kit for providing power take-off components. Due to size constraints around an automatic transmission, a rear mounted power take-off device avoids the difficulties common to side mounted power take-offs. The automatic transmission includes a transmission housing with a front and rear portion, an input member, at least one planetary gear set driven by the input member, at least one brake or clutch adapted to change a gear ratio output from the transmission. A driven gear on a second axis of rotation intermeshes an input gear on a first axis of rotation. A flange on the rear portion of the transmission is configured to receive the power take-off device.

Description:
RELATED APPLICATIONS  
       [0001]     This application claims priority to U.S. application Ser. No. 11/022,630, entitled “Rear Power Takeoff” filed on Dec. 28, 2004, to John M. Seipold and Kevin G. Meyer, and U.S. Provisional Patent Application No. 60/660,707, entitled “Transmission Assembly”, filed on Mar. 11, 2005 to Anthony R. Johnson, John M. Seipold, and Kevin G. Meyer. 
     
    
     TECHNICAL FIELD  
       [0002]     The present invention relates to automatic transmissions and, more particularly, to enabling automatic transmissions to receive power take-off devices.  
       BACKGROUND  
       [0003]     Conventional work machines can be used in many different applications, including those in the areas of construction, agriculture, landscaping, and mining. To perform these applications, work components are typically connected to work machine lift arms or other articulated members, which are actuated by the work machine&#39;s auxiliary hydraulic circuit. For example, an auxiliary hydraulic circuit may include an auxiliary pump configured to supply fluid to the articulated members to effectuate movement of the members.  
         [0004]     In some work machines, the transmission may be used to drive the auxiliary hydraulic circuit, such as a power take-off (“PTO”). The PTO drives the auxiliary pumps to assist in actuating the articulated members of the work machine. In many cases, the PTO is mounted directly to the transmission.  
         [0005]     For example, U.S. Pat. No. 6,080,081 to Sauermann et al. provides a PTO control and illustrates a countershaft transmission with a PTO mounted to a rear portion of the transmission. Due to the plurality of available shafts in a countershaft transmission, attaching a PTO to a rear portion of the transmission has been widely adopted.  
         [0006]     In contrast, automatic transmissions only use one shaft, which is in coaxial alignment with the input shaft, to drive the machine. For example, U.S. Pat. No. 4,944,193 to Harada et al. (“the &#39;193 patent”) discloses an automatic transmission. Power from the engine enters a torque converter, which outputs to a drive shaft of the transmission. A plurality of frictional clutches positioned axially of each other react to provide different gear ratios. The plurality of clutches and planetary gear sets eliminate the need for additional countershafts.  
         [0007]     Automatic transmissions, however, are preferred for many types of large truck and vocational truck applications. The automatic transmission provides improved shifting generally not available with the countershaft transmissions. The recreational vehicle operator is especially particular of the shift characteristics, demanding seamless, smooth shifting. The automatic transmission is capable of satisfying that demand. Similar particularity is growing in the long-haul and vocational vehicles industry, such as dump trucks and garbage trucks, where smooth shifts are desirable for driver comfort, control, and to decrease wear and damage due to hard shifts.  
         [0008]     As a result, a need existed for the placement of PTO&#39;s on automatic transmissions. To satisfy this need, PTO&#39;s were place on a side of the automatic transmission and directly driven by a large gear connected to the input shaft. The &#39;193 patent teaches a radially positioned PTO located on an outer side portion of the transmission housing.  
         [0009]     Many automatic transmissions have been adapted to receive more than one PTO, and include a plurality of PTO pads, or interfaces, designed to interface a PTO. PTO pad locations vary by transmission manufacturer. Generally, the PTO pads are located at eight o&#39;clock and one o&#39;clock with respect to the circumference of the transmission housing.  
         [0010]     However, large PTO&#39;s and corresponding large hydraulic pumps do not always fit on the PTO pads due to size restraints as a result of the frame rails, exhaust piping, cab constraints, large transmissions, and large engines. Often, to fit large PTO&#39;s, the engine must be repositioned, brackets built, and notches formed in vehicle components. Such drastic changes are undesirable as they affect the overall balance and structural integrity of the machine. Additionally, modifying original components is rarely preferred, and may result in denial of warranty claims.  
         [0011]     To overcome the size constraints it is common to mount a PTO to a front of a vehicle. The front mounted PTO creates additional problems. For example, when mounted in the front location, the front bumper of the vehicle oftentimes must be extended to accommodate the usually large pumps. Further the radiators in such equipped vehicles frequently need to be cored or relocated to accommodate the mounting position of the hydraulic pump, which may result in decreased airflow to the radiator, a practice which may not be possible with the increased heat rejection of engines meeting stricter Environmental Protection Agency emissions laws. One option is to increase the size of the radiator. However, increasing the width makes the body larger, and increasing the height decreases the operator&#39;s field of vision. Consequently, the radiators must be made to extend lower, which cuts off the coupling between the crankshaft and forward mounted PTO&#39;s.  
         [0012]     U.S. Pat. No. 6,263,749 also attempts to overcome the size constraints by providing an extended shaft capable of operably coupling an extended shaft to a side-mounted PTO and a pump. Unfortunately, this configuration suffers from the same drawbacks as discussed above with side mounted PTO&#39;s in that the size constraints may prevent the ability to attach such a large device to the transmission.  
         [0013]     At least one additional problem common to all side mounted PTO&#39;s is the accessibility of the PTO pad. To attach the PTO to a side of the transmission may require either the removal of the transmission or the removal of the engine to gain access to the PTO pad. Neither option is desirable and both options are very expensive.  
         [0014]     The present invention is directed to overcoming one or more of the problems as set forth above.  
       SUMMARY OF THE INVENTION  
       [0015]     According to one exemplary aspect of the present invention, an automatic transmission includes a transmission housing with a front and rear portion, an input member configured to rotate about a first axis, at least one planetary gear set having a sun gear, a ring gear, and carrier gears disposed between the sun gear and the ring gear, the at least one planetary gear set being driven by the input member, at least one brake and/or clutch adapted to change a gear ratio output from the transmission, and an output member rotating about the first axis. An input drive gear connected to the input member rotates about the first axis. A driven gear intermeshes the input drive gear and rotates about a second axis offset and parallel to the first axis. A mounting arrangement on the rear portion of the transmission is adapted to receive an auxiliary device and defines an aperture in coaxial alignment with the second axis.  
         [0016]     According to another exemplary aspect of the present invention, a method of installing a power take-off shaft in an automatic transmission is provided. The transmission includes a transmission housing with a front and rear portion, an input member, at least one planetary gear set driven by the input member, and at least one brake or clutch adapted to change a gear ratio output from the transmission is provided. The method includes the steps of inserting the power take-off shaft into a bearing bore on the rear portion of the transmission housing and connecting one end of the power take-off shaft to a power take-off shaft receiver, inserting a bearing into the bearing bore on the rear portion of the transmission housing and onto the power take-off shaft, securing the power take-off shaft to the bearing, and securing the bearing to the transmission housing.  
         [0017]     According to yet another exemplary aspect of the present invention, a power take-off kit for an automatic transmission to enable application of a power-take off device from a rear portion of a transmission housing is provided. The automatic transmission includes a transmission housing with a front and rear portion, an input member configured to rotate about a first axis, at least one planetary gear set having a sun gear, a ring gear, and carrier gears disposed between the sun gear and the ring gear, the at least one planetary gear set being driven by the input member, at least one brake and/or clutch adapted to change a gear ratio output from the transmission, and an output member rotating about the first axis. An input drive gear connected to the input member rotates about the first axis. A driven gear intermeshes the input drive gear and rotates about a second axis offset and parallel to the first axis. A mounting arrangement on the rear portion of the transmission is adapted to receive an auxiliary device and defines an aperture in coaxial alignment with the second axis. The kit includes a power take-off shaft, a bearing, a first fastener for securing the power take-off shaft to the bearing, and a second fastener for securing the bearing to the transmission housing.  
         [0018]     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]      FIG. 1  is an isometric view of a transmission having a rear-mounted power take-off and hydraulic pump according to an exemplary embodiment of the present disclosure; and  
         [0020]      FIG. 2  is a cross-sectional isometric view of a transmission and driven assembly. 
     
    
     DETAILED DESCRIPTION  
       [0021]     Reference will now be made in detail to embodiments of the invention, examples of which are illustrated in the accompanying drawings.  
         [0022]      FIG. 1  illustrates a transmission  10  of an engine  12 . The engine  12  may be, for example, an internal combustion engine or any other type of engine known in the art. The engine  12  and the transmission  10  may be mounted within an engine compartment of a work machine (not shown) and may be configured to supply power to elements of the work machine by any conventional means.  
         [0023]     The transmission  10  may be connected to the engine  12  through any conventional means. In an exemplary embodiment, an input shaft, or input member  14  of the transmission  10  directly couples an output shaft of the engine  12  using, for example, a conventional torque converter (not shown).  
         [0024]     A power take-off (“PTO”)  16  useful in supplying power to a pump assembly  18  mounts to a rear side of the transmission  10 , specifically to a rear side  20  of the transmission case, or housing  22 . The PTO  16  operates to drive the pump assembly  18  to supply hydraulic fluid to elements (not shown) of the work machine. In one embodiment, the pumping assembly  18 , rather than the PTO  16 , mounts directly to the rear portion  20  of the transmission  10  with a pump adapter. In such an embodiment, the pumping mechanism operates to supply hydraulic power to elements of the work machine, whenever the transmission  10  receives power. It is recognized that any type of auxiliary device, such as the PTO, the pump, or an electric motor/generator can be attached to the transmission housing  22 .  
         [0025]      FIG. 2  illustrates a cross-sectional view of the transmission  10 . The transmission  10  includes a first and second section  24  and  26  divided by a wall  28 . On the first section  24  an input drive gear  32  directly couples the input shaft  14  such that the input drive gear  32  rotates at the same rotational speed as the input shaft  14  while the engine  12  is operating. The planetaries are positioned on the second section  26 .  
         [0026]     The input drive gear  32  drives a driven assembly  34  to transfer power from the engine  12  to the PTO  16 . The driven assembly  34  may be a PTO drive shaft  36  connected to a driven gear  38 , or alternatively, the PTO drive shaft  36  may be connected to a charge pump  40 , which is driven by the driven gear  38  through a splined receiver  41 . The driven assembly  34  is displaced from and parallel to a first axis  30  (See  FIG. 1 ). The driven gear  38  rotates about a second axis  39 . The PTO drive shaft  36  is configured with a spline  42 , or the like, on a first end  44  to receive the PTO  16  so as to provide power thereto. Similarly, the PTO drive shaft  36  is splined on a second end  46  to connect to the charge pump  40  or the driven gear  38 . The driven gear  38  passes through the wall  28  and is supported by bearings  43 . The input drive gear  32  and the driven gear  38  may be sized and configured so as to drive the PTO  16  of the work machine at a desired rate. One skilled in the art will recognize that there are numerous gear ratios that can be accomplished by changing the size of the input drive gear  32  and the driven gear  38 .  
         [0027]     The transmission further includes a series of three planetary gear sets, clutches, brakes, and other automatic transmission components for automatic transmissions. The planetary gear sets rotate about the first axis  30 , as is well known in the art. Similarly, the clutches and brakes function similar to clutches and brakes of other well-known automatic transmissions. The transmission includes two rotating clutches and three brakes. The input drives the sun gear of the first planetary, and a carrier of the third planetary drives the output member.  
         [0028]     The charge pump  40  provides hydraulic power to elements throughout the transmission  10  for lubrication and/or clutch and brake engagement. The charge pump  40  is a gear pump to draw fluid from a sump  48  through a suction line  50 . One skilled in the art will recognize that various types of charge pumps  40  exist and are well known in the art. It is envisioned that any type of charge pump  40  may be used in the current described configuration. The fluid leaves the charge pump  40  at a predetermined pressure to the oil filter (not shown) and through control valves to actuate the various clutches and brakes, and to lubricate the internal transmission components.  
         [0029]     In an exemplary embodiment of the present invention, the driven assembly  34  is disposed below the first axis  30  (See  FIG. 1 ) of the transmission  10 . In particular, the driven assembly  34  and the PTO  16  may be disposed in a lower side quadrant of the transmission  10 . It is envisioned, however, that the driven assembly  34 , and the PTO  16  may be positioned at any location within the transmission housing  22 . It is preferable, however, that the driven assembly  34 , specifically the charge pump  40 , be positioned where access is facilitated. In the illustrated embodiment, the driven assembly  34  is located below a horizontal plane  52  for easy access after the oil has been drained and an oil pan removed. If the driven assembly  34  is positioned at a location above the horizontal plane, it is envisioned that access holes, compartments, or lids may be used to facilitate access thereto.  
         [0030]     As discussed above, the PTO drive shaft  36  may be a separate shaft with respect to the driven gear  38  and the charge pump  40 . Advantageously, the PTO drive shaft  36  may be an optional component. Specifically, the transmission  10  can be manufactured and sold without the optional PTO drive shaft  36 . Rather than having to buy a completely new transmission, a kit may be acquired containing the optional PTO drive shaft  36 , a bearing  56 , and two snap rings  58  and  60 . One snap ring  58  secures the bearing  56  to the transmission housing  22  and the other snap ring  60  secures the PTO drive shaft  36  to the bearing  56 . The PTO  16  fastens to a flange  54  on the rear portion  20  of the transmission  10 . It is noted that any kind of mounting arrangement can used for attaching the PTO  16 , or other auxiliary device, to the transmission housing  22 . For example, the mounting arrangement may be any kind of bolt pattern provided in the transmission housing  22 , as is well known to SAE standards.  
         [0031]     To install the PTO drive shaft  36  post sale, the customer, dealer, or mechanic simply removes a PTO cover  62 , inserts the first end  44  of the PTO drive shaft  36  into the bearing  56 , secures the PTO drive shaft  36  to the bearing  56  with the snap ring  60 , or other fastening device, such as a bolt, screw, clamp, clip, press, or permanent structure, and slides the spline of the second end  46  of the PTO drive shaft over a splined output member  64  of the charge pump  40  or receiver  41  of the driven member  38 . It is noted that the PTO drive shaft  36  may be pressed into the bearing  56 . It is further noted that the act of pressing the PTO drive shaft  36  into the bearing  56  may be equivalent to securing the PTO drive shaft  36  to the bearing  56 . The snap ring  56  is configured to prevent significant axial movement of the PTO drive shaft  36  with respect to the bearing  56 . The bearing  56  is pressed, or installed into a transmission bearing bore  66  of the housing  22 , and secured with the snap ring  58 , or other fastening device, such as a bolt, screw, clamp, clip, press, or permanent structure. It is noted again that the act of pressing the bearing  56  into the transmission bearing bore may be equivalent to securing the bearing  56  to the bearing bore  66 . It may be necessary to heat the bearing bore  66  before installing the bearing  56  therein. The bearing bore  66  and flange  54  define an aperture with an axis coaxially aligned with the second axis  39 . It is envisioned that the bearing  56  may be secured to the PTO drive shaft  36  and subsequently inserted into the bearing bore  66  and connected to the charge pump receiver  64  or receiver  41  of the driven gear  38 .  
         [0032]     The spline  42  on the first end  44  of the PTO drive shaft  36  is configured to receive the PTO  16 . It is noted that the splines  42  may be internal or external, and may be any shape.  
       INDUSTRIAL APPLICABILITY  
       [0033]     Work machines known to use automatic transmissions of the type disclosed in the present invention have tight constraints due to the large size of the engine, the large size of the transmission, distance between the frame rails, exhaust routing pipes, and heavy duty suspension and steering components. On-highway trucking applications, as well as vocational vehicles, such as dump trucks, recreational vehicles, cement mixers, and garbage trucks are typical examples of the type of vehicle typical for application of the present invention. The transmission provides power to move the vehicle and the ability to mount a power take-off device to the rear of the transmission. Positioning the PTO  16  at the rear side  20  of the transmission  10  helps eliminate the need for machine modifications.  
         [0034]     The PTO drive shaft  36  may be sold as an optional unit to decrease overall costs for users not in need of a rear-mounted PTO. The PTO drive shaft  36  may, however, be sold and purchased and easily installed at a later date if the user determines that a need exists. Additional components such as bearings and snap rings, or other fastening devices, may be used to hold the PTO drive shaft in position.  
         [0035]     It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the scope or spirit of the invention. Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only.