Patent Publication Number: US-2023149754-A1

Title: Sandwiched power take-off (pto) for a vehicle

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     This application claims the benefit of and priority to (a) U.S. Provisional Patent Application No. 63/279,944, filed Nov. 16, 2021 and (b) U.S. Provisional Patent Application No. 63/335,681, filed Apr. 27, 2022, both of which are incorporated herein by reference in their entireties. 
    
    
     BACKGROUND 
     A fire apparatus can include an on-board pump system that pumps a fluid (e.g., water) from a water source (e.g., a water tank, a fire hydrant, etc.) to one or more outputs of the fire apparatus. Such pump systems are typically driven using an engine PTO or are positioned downstream of transmission. 
     SUMMARY 
     One embodiment relates to a fire apparatus. The fire apparatus includes a chassis, a cab coupled to the chassis, a pump system coupled to the chassis and positioned at least partially behind the cab, and a driveline. The pump system includes a pump. The driveline includes a prime mover positioned beneath the cab and coupled to the chassis, a transmission, and a sandwiched power take-off unit positioned between (a) the prime mover and (b) the transmission and the pump system. The sandwiched power take-off unit facilitates operating the pump independent of a gear selection of the transmission and a ground speed of the fire apparatus. 
     Another embodiment relates to a vehicle. The vehicle includes a vehicle accessory and a driveline. The driveline includes a prime mover, a transmission, and a sandwiched power take-off unit positioned between (a) the prime mover and (b) the transmission and the vehicle accessory. The sandwiched power take-off unit includes a main housing defining an aperture and an interior chamber, a main drive shaft disposed within the interior chamber, a power take-off drive shaft positioned external to the main housing, a gear train, and a clutch. The main drive shaft is driven by the prime mover. The power take-off drive shaft is coupled to the vehicle accessory. The gear train extends from the main drive shaft, through the aperture in the main housing, and to the power take-off drive shaft. The gear train includes a drive gear coupled to the main drive shaft, an output gear coupled to the power take-off drive shaft, and an intermediate gear positioned between the drive gear and the output gear. The clutch is positioned to facilitate selectively disconnecting the vehicle accessory from the main drive shaft. 
     Still another embodiment relates to a vehicle. The vehicle includes a vehicle accessory and a driveline. The driveline includes a prime mover, a transmission, and a sandwiched power take-off unit positioned between (a) the prime mover and (b) the transmission and the vehicle accessory. The sandwiched power take-off unit includes a main housing, a main drive shaft, a power take-off drive shaft, a gear train, an adapter plate, a first bearing, a second bearing, an auxiliary shaft, and a clutch. The main housing defines an interior chamber and has a support extending through the interior chamber. The main drive shaft is disposed within the interior chamber and extends through the support. The power take-off drive shaft is coupled to the vehicle accessory. The gear train includes a drive gear coupled to the main drive shaft, an output gear coupled to the power take-off drive shaft, and an intermediate gear positioned between the drive gear and the output gear. The adapter plate is coupled to an output of the prime mover. The adapter plate defines a central bore that receives an end of the main drive shaft without a bearing positioned therebetween. The first bearing is positioned between the main drive shaft and the drive gear. The second bearing is positioned between the main drive shaft and the support. The auxiliary shaft is received by the support. The intermediate gear is disposed on the auxiliary shaft. The clutch is positioned to facilitate selectively disconnecting the vehicle accessory from the main drive shaft. 
     This summary is illustrative only and is not intended to be in any way limiting. Other aspects, inventive features, and advantages of the devices or processes described herein will become apparent in the detailed description set forth herein, taken in conjunction with the accompanying figures, wherein like reference numerals refer to like elements. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a side view of a vehicle, according to an exemplary embodiment. 
         FIG.  2    is a side view of a vehicle, according to another exemplary embodiment. 
         FIG.  3    is a schematic drawing of a driveline of the vehicle, according to an exemplary embodiment. 
         FIG.  4    is a perspective view of a portion of the driveline of  FIG.  3    including a prime mover, a transmission, and a power divider positioned between the prime mover and the transmission, according to an exemplary embodiment. 
         FIGS.  5  and  6    are various schematic drawings of the portion of the driveline of  FIG.  4   , according to an exemplary embodiment. 
         FIG.  7    is a first cross-sectional view of the portion of the driveline of  FIG.  4   , according to another exemplary embodiment. 
         FIG.  8    is a second cross-sectional view of the portion of the driveline of  FIG.  7   , according to an exemplary embodiment. 
         FIGS.  9 - 11    are side views of a vehicle, according to another exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Before turning to the figures, which illustrate certain exemplary embodiments in detail, it should be understood that the present disclosure is not limited to the details or methodology set forth in the description or illustrated in the figures. It should also be understood that the terminology used herein is for the purpose of description only and should not be regarded as limiting. 
     Overall Vehicle 
     According to the exemplary embodiment shown in  FIG.  1   , a vehicle, shown as fire apparatus  10 , is configured as a mid-mount quint fire truck having a tandem rear axle. A “quint” fire truck as used herein may refer to a fire truck that includes a water tank, an aerial ladder, hose storage, ground ladder storage, and a water pump. In other embodiments, the fire apparatus  10  is configured as a mid-mount quint fire truck having a single rear axle. A tandem rear axle may include two solid axle configurations or may include two pairs of axles (e.g., two pairs of half shafts, etc.) each having a set of constant velocity joints and coupling two differentials to two pairs of hub assemblies. A single rear axle chassis may include one solid axle configuration or may include one pair of axles each having a set of constant velocity joints and coupling a differential to a pair of hub assemblies, according to various alternative embodiments. In still other embodiments, the fire apparatus  10  is configured as a non-quint mid-mount fire truck having a single rear axle or a tandem rear axle. According to the exemplary embodiment shown in  FIG.  2   , the fire apparatus  10  is configured as a rear-mount, quint, single rear axle fire truck. In yet other embodiments, the fire apparatus  10  is configured as a rear-mount, quint or non-quint, single rear axle or tandem rear axle fire truck. In yet other embodiments, the fire apparatus does not include an aerial ladder (e.g., a pumper, a fire engine, etc.). In still other embodiments, the vehicle is not a fire truck, but is any other type of vehicle (e.g., a concrete mixer truck, a refuse truck, etc.) that can include a sandwiched PTO unit similar to the fire apparatus  10 , as described in greater detail herein. 
     As shown in  FIGS.  1  and  2   , the fire apparatus  10  includes a chassis, shown as frame  12 , having longitudinal frame rails that define an axis, shown as longitudinal axis  14 , that extends between a first end, shown as front end  2 , and an opposing second end, shown as rear end  4 , of the fire apparatus  10 ; a first axle, shown as front axle  16 , coupled to the frame  12 ; one or more second axles, shown as rear axles  18 , coupled to the frame  12 ; a first assembly or cab assembly, shown as front cabin  30 , coupled to and supported by the frame  12 ; a second assembly, shown as rear assembly  40 , coupled to and supported by the frame  12 ; and a powertrain, shown as driveline  100 , coupled to and supported by the frame  12 . 
     As shown in  FIGS.  1  and  2   , the front axle  16  and the rear axles  18  include tractive assemblies, shown as wheel and tire assemblies  20 . As shown in  FIGS.  1  and  2   , the front cabin  30  is positioned forward of the rear assembly  40  (e.g., with respect to a forward direction of travel for the fire apparatus  10  along the longitudinal axis  14 , etc.). According to an alternative embodiment, at least a portion of the cab assembly may be positioned behind the rear assembly  40  (e.g., with respect to a forward direction of travel for the fire apparatus  10  along the longitudinal axis  14 , etc.). The cab assembly may be positioned behind the rear assembly  40  on, by way of example, a rear tiller fire apparatus. In some embodiments, the fire apparatus  10  is a ladder truck with a front portion that includes the front cabin  30  pivotally coupled to a rear portion that includes the rear assembly  40  (i.e., the rear portion is towed by the front portion). 
     As shown in  FIGS.  1  and  2   , the rear assembly  40  includes a body assembly, shown as body  50 , coupled to and supported by the frame  12 ; a fluid driver, shown as pump system  60 , coupled to and supported by the frame  12 ; a chassis support member, shown as torque box  70 , coupled to and supported by the frame  12 ; a fluid reservoir, shown as water tank  80 , coupled to the body  50  and supported by the torque box  70  and/or the frame  12 ; and an aerial assembly, shown as aerial assembly  90 , pivotally coupled to the torque box  70  and supported by the torque box  70  and/or the frame  12 . In some embodiments, the rear assembly  40  additionally or alternatively includes an agent or foam tank (e.g., that receives and stores a fire suppressing agent, foam, etc.). In some embodiments, the rear assembly  40  does not include the torque box  70 , the water tank  80 , and/or the aerial assembly  90 . 
     According to an exemplary embodiment, the pump system  60  includes a housing that supports a pump that is configured to drive fluid (e.g., water, agent, etc.) from a fluid source (e.g., the water tank  80 , the agent tank, an external source such as a fire hydrant, etc.) to one or more fluid outlets of the fire apparatus  10  (e.g., a structural hose outlet along the body  50 ; a deluge gun, cannon, or turret; a hose reel; etc.). According to an exemplary embodiment, the pump system  60  is a midship mounted pump system that (i) is located at or proximate the middle of the fire apparatus  10  (e.g., between the front axle  16  and the rear axle(s)  18 ) and (ii) is part of the driveline  100  of the fire apparatus  10 . 
     A fire apparatus  400  is shown in  FIGS.  9 - 11    according to an alternative embodiment. The fire apparatus  400  may be substantially similar to the fire apparatus  10 , except as otherwise specified herein. In the fire apparatus  400 , the pump system  60  is positioned at least partially beneath or below the front cabin  30  (e.g., partially beneath the cabin, entirely beneath the front cabin). In some embodiments, a footprint of the front cabin  30  partially encompasses or contains the pump system  60  (e.g., such that a portion of the pump system  60  extends beyond the footprint of the front cabin  30 ). In other embodiments, the footprint of the front cabin  30  entirely or completely encompasses or contains the pump system  60 . Accordingly, the front cabin  30  may be supported above or otherwise disposed over at least a portion of the pump system  60 . 
     In some embodiments, the pump system  60  may be at least partially supported within a cavity (e.g., along a centerline of fire apparatus  400 , etc.) defined by the longitudinal frame rails  402  of the fire apparatus  400 . The pump system  60  may at least partially extend above the frame rails  402 . The front cabin  30  may be configured to accommodate the positioning of the pump system  60  at least partially above the frame rails  402 . For example, a bottom portion of the front cabin  30  may include a raised portion or raised floor that protrudes into the occupant compartment and defines an area (e.g., cavity, chamber, tunnel, etc.) configured to receive at least a portion of the pump system  60 . This may include a portion extending in longitudinally along a centerline of the front cabin  30  (e.g., a tunnel, shroud, doghouse, etc.) and/or a portion or raised floor extending laterally along a rear portion of the front cabin  30  (e.g., a rear seat box, EMS compartment, storage receptacle, etc.). 
     The pump system  60  may be positioned such that a main portion of the pump system  60  (e.g., a fire pump and a gear case, etc.) is positioned under the rear portion of front cabin  30 . To facilitate the positioning of pump system  60  under the front cabin  30 , a rear wall of the front cabin  30  may include a central cutout portion that extends upward from a bottom edge and is sized to conform to or otherwise receive a portion of the pump system  60  (e.g., a pump housing, etc.). To further accommodate the positioning of pump system  60 , the left and right sides of the front cabin  30  may define a cutout portion  410  at their respective bottom rear corners. The cutout portion  410  is provided to permit a portion of a fluid routing system of the pump system  60  to be supported under the front cabin  30 . 
     In some embodiments, the front cabin  30  is movably (e.g., tiltably, slidably, removably, etc.) coupled to the frame  12 . The front cabin  30  may be selectively repositionable between a first or transit position (shown in solid lines in  FIG.  9   ) and a second or service position (shown in dashed lines in  FIG.  9   ). The front cabin  30  may be repositionable using one or more actuators (e.g., hydraulic cylinders, electric linear actuators, etc.). In the service position, systems positioned beneath the front cabin  30  (e.g., the pump system  60 , etc.) are more accessible from above the frame  12  than would otherwise be if the front cabin  30  was in the transit position. Movably supporting the front cabin  30  relative to the frame  12  facilitates relatively unrestricted or otherwise convenient access to systems (e.g., the pump system  60 , etc.) that may be supported at least partially under the front cabin  30 . 
     As shown in  FIGS.  1  and  2   , the aerial assembly  90  includes a turntable assembly, shown as turntable  92 , pivotally coupled to the torque box  70 ; a platform, shown work platform  94 , coupled to the turntable  92 ; a ladder assembly, shown as aerial ladder assembly  96 , having a first end (e.g., a base end, a proximal end, a pivot end, a platform end, etc.) pivotally coupled to the turntable  92 , and an opposing second end (e.g., a free end, a distal end, an implement end, etc.); and an implement, shown as work basket  98 , coupled to the opposing second end of the aerial ladder assembly  96 . In some embodiments, as shown in  FIG.  2   , the aerial assembly  90  does not include the work basket  98 . In some embodiments, the work basket  98  is replaced with or additionally includes a nozzle (e.g., a deluge gun, a water cannon, a water turret, etc.) or other tool/implement. By way of example, the nozzle may be connected to a water source (e.g., the water tank  80 , an external source, a fire hydrant, etc.) with a conduit extending along the aerial ladder assembly  96  (e.g., along the side of the aerial ladder assembly  96 , beneath the aerial ladder assembly  96 , in a channel provided in the aerial ladder assembly  96 , etc.). By pivoting the aerial ladder assembly  96  into a raised position, the nozzle may be elevated to expel water from a higher elevation to facilitate suppressing a fire. According to an exemplary embodiment, the aerial assembly  90  (e.g., the turntable  92 , the work platform  94 , the aerial ladder assembly  96 , the work basket  98 , etc.) is controllable (e.g., rotatable, pivotable, extendable, etc.) such that the aerial assembly  90  is selectively repositionable into a plurality of operating positions or orientations. 
     Driveline 
     According to an exemplary embodiment, the driveline  100  is configured to (i) propel the fire apparatus  10  and (ii) drive the pump system  60 . As shown in  FIGS.  3 - 5 ,  7 , and  8   , the driveline  100  includes a primary driver, shown as prime mover  110 , and an energy storage device, shown as energy storage  120 . In some embodiments, the driveline  100  is a conventional driveline whereby the prime mover  110  is an internal combustion engine and the energy storage  120  is a fuel tank. The internal combustion engine may be a spark-ignition internal combustion engine or a compression-ignition internal combustion engine that may use any suitable fuel type (e.g., diesel, ethanol, gasoline, natural gas, propane, etc.). In some embodiments, the driveline  100  is an electric driveline whereby the prime mover  110  is an electric motor and the energy storage  120  is a battery system. In some embodiments, the driveline  100  is a fuel cell electric driveline whereby the prime mover  110  is an electric motor and the energy storage  120  is a fuel cell (e.g., that stores hydrogen, that produces electricity from the hydrogen, etc.). In some embodiments, the driveline  100  is a hybrid driveline whereby (i) the prime mover  110  includes an internal combustion engine and an electric motor/generator and (ii) the energy storage  120  includes a fuel tank and/or a battery system. 
     As shown in  FIGS.  3 - 5 ,  7 , and  8   , the driveline  100  includes a transmission device (e.g., a gearbox, a continuous variable transmission (“CVT”), etc.), shown as transmission  130 , and a first power divider, shown as sandwiched PTO unit  200 , positioned between (i.e., sandwiched between) the prime mover  110  and the transmission  130 , and coupled to the pump system  60 . According to an exemplary embodiment, the prime mover  110  is positioned beneath the front cabin  30  and, therefore, the sandwiched PTO unit  200  is at least partially positioned beneath the front cabin  30 . According to an exemplary embodiment, the sandwiched PTO unit  200  is configured to receive an input from the prime mover  110  and provide (i) a first output to the transmission  130  to drive the fire apparatus  10  and (ii) a second output to the pump system  60  to drive a pump thereof. In other embodiments (e.g., non-fire apparatus implementations, etc.), the second output of the sandwiched PTO unit  200  is provided to another type of vehicle system or vehicle accessory (e.g., an accessory drive, a compressor, etc.) other than the pump system  60 . According to an exemplary embodiment, the transmission  130  has a variety of configurations (e.g., gear ratios, etc.) and provides different output speeds relative to an input received thereby from the sandwiched PTO unit  200 . 
     As shown in  FIG.  3   , the driveline  100  additionally includes a second power divider, shown as transfer case  140 , coupled to the transmission  130 ; a first drive shaft, shown as front drive shaft  150 , coupled to a first or front output  142  of the transfer case  140 ; a first differential, shown as front differential  152 , coupled to the front drive shaft  150  and the front axle  16 ; a second drive shaft, shown as rear drive shaft  160 , coupled to a second or rear output  144  of the transfer case  140 ; and a second differential, shown as rear differential  162 , coupled to the rear drive shaft  160  and the rear axle(s)  18 . According to an exemplary embodiment, the transfer case  140  is configured to facilitate driving both the front axle  16  and the rear axle(s)  18  with the prime mover  110  to facilitate front and rear drive (e.g., an all-wheel-drive vehicle, a four-wheel-drive vehicle, etc.). In some embodiments, the transfer case  140  facilitates selectively engaging rear drive only, front drive only, and both front and rear drive simultaneously. In some embodiments, the transmission  130  and/or the transfer case  140  facilitate selectively disengaging the front axle  16  and the rear axle(s)  18  from the prime mover  110  (e.g., in a neutral mode of operation). In some embodiments (e.g., in electric driveline configurations, in hybrid driveline configurations, etc.), the driveline  100  does not include the transmission  130 . In such embodiments, the sandwiched PTO unit  200  may be directly coupled to the transfer case  140 . In some embodiments, the driveline  100  does not include the transfer case  140 . In such embodiments, the transmission  130  may directly drive the front drive shaft  150  (i.e., a front-wheel-drive vehicle) or the rear drive shaft  160  (i.e., a rear-wheel-drive vehicle). In some embodiments, the driveline  100  does not include the front drive shaft  150  or the front differential  152  (e.g., a rear-wheel-drive vehicle). In some embodiments, the driveline  100  does not include the rear drive shaft  160  or the rear differential  162  (e.g., a front-wheel-drive vehicle). 
     Sandwiched PTO Unit 
     Traditionally, water pumps on fire apparatuses have been driven using a rear engine power take-off (“REPTO”) or water pumps have been positioned along the driveline downstream of the transmission. However, REPTOs are limited in torque and horsepower output. Also, an arrangement with the water pump positioned downstream of the transmission requires a gear box or pump transfer case to be able to shift between a pump mode and a drive mode, which can complicate the driveline because of the addition of components and cause potential vibrations due to unfavorable layouts driven by packaging and driveline length constraints. Also, such arrangements can extend the length of the driveline. 
     According to an exemplary embodiment, the sandwiched PTO unit  200  reduces overall pump driveline components and simplifies the driveline by removing a pump transfer case and making the driveline angles more manageable. The sandwiched PTO unit  200  may also permit shortening the overall length of the driveline  100  relative to prior drivelines, allowing for shorter vehicle lengths. According to an exemplary embodiment, the sandwiched PTO unit  200  facilitates operating the pump of the pump system  60  independent of a gear selection of the transmission  130  and a ground speed of the fire apparatus  10 , while operating at a higher torque and horsepower output. By way of example, the sandwiched PTO unit  200  may accommodate driving or being configured to drive more than a 1500 gallon-per-minute (“gpm”) pump (e.g., greater than a 1,500 gpm pump; up to a 2,000 gpm pump; at least a 2,000 gpm pump, greater than an 2,000 gpm pump; etc.), while traditional pump drive designs can max out at 1,500 gpm pumps or less. In addition, the sandwiched PTO unit  200  accommodates engines or primary drivers that have either a clockwise or counterclockwise output. 
     As shown in  FIGS.  4 - 8   , the sandwiched PTO unit  200  includes a first housing, shown as main housing  202 , defining an interior chamber, shown as main chamber  204 ; a second housing, shown as pump output housing  206 , extending from the main housing  202 ; a first PTO drive shaft, shown as main drive shaft  210 , disposed within and extending through the main chamber  204 ; a pump output or second PTO drive shaft, shown as pump drive shaft  260 , at least partially disposed within, supported by, and extending from the pump output housing  206 ; and a gear train, shown as pump gear train  220 , including a plurality of gears that couple the main drive shaft  210  to the pump drive shaft  260  by coupling to the main drive shaft  210 , extending through an opening, shown as gear aperture  208 , defined by the main housing  202 , and coupling to the pump drive shaft  260 . 
     As shown in  FIGS.  4 - 8   , the plurality of gears of the pump gear train  220  include a first gear, shown as drive gear  230 , coupled to (e.g., disposed along) the main drive shaft  210 ; a second or intermediate gear, shown as idler gear  240 , coupled to the drive gear  230  (e.g., in a meshing engagement); and a third or final gear, shown as output gear  250 , coupled to the idler gear  240  (e.g., in a meshing engagement) and the pump drive shaft  260  (e.g., disposed along the pump drive shaft  260 ). In other embodiments, the pump gear train  220  includes a different number of gears (e.g., two gears, four gears, etc.). As shown in  FIGS.  5  and  7   , the main drive shaft  210  includes a first end, shown as input end  212 , coupled to an output (e.g., a crankshaft, etc.), shown as prime mover output  112 , of the prime mover  110  and an opposing second end, shown as output end  214 , coupled to an input, shown as transmission input  132 , of the transmission  130 . Accordingly, driving the main drive shaft  210  with the prime mover  110  facilitates driving (i) the transmission  130  and, thereby, the fire apparatus  10  (e.g., the transfer case  140 , the front drive shaft  150 , the front axle  16 , the rear drive shaft  160 , the rear axle(s)  18 , etc.) and (ii) the pump gear train  220  and, thereby, the pump drive shaft  260  and the pump of the pump system  60 . 
     According to the exemplary embodiments shown in  FIGS.  5  and  7   , the sandwiched PTO unit  200  includes a clutch, shown as pump clutch  270 , that provides a clutched pump output design. Such clutched pump output designs reduce noise pollution and reduce wear on the pump driveline components (e.g., bearings, gears, chains, etc.) by completely disengaging the pump system  60  from the prime mover  110  when the pump is not in use. 
     As shown in  FIG.  5   , the clutched pump output design is an external clutch design where the pump clutch  270  is positioned between the pump drive shaft  260  of the sandwiched PTO unit  200  and the pump of the pump system  60  (e.g., the pump clutch  270  is positioned outside of the main housing  202  of the sandwiched PTO unit  200 , the pump clutch  270  is positioned downstream of the pump gear train  220 , etc.). Accordingly, the pump clutch  270  in the external clutch design can be disengaged when the pump is not in use to decouple the pump drive shaft  260  from the pump system  60  so that the pump system  60  is not unnecessarily driven by the sandwiched PTO unit  200  when the pump is not in use. 
     As shown in  FIG.  7   , the clutched pump output design is an internal clutch design where the pump clutch  270  is positioned (i) within the main chamber  204  of the main housing  202  of the sandwiched PTO unit  200  and (ii) upstream of the pump drive shaft  260  and the pump gear train  220  (e.g., between the main drive shaft  210  and the pump gear train  220 ). Accordingly, the pump clutch  270  in the internal clutch design can be disengaged when the pump is not in use to decouple the pump gear train  220 , the pump drive shaft  260 , and the pump system  60  from the main drive shaft  210  such that (i) the pump system  60  and (ii) the pump gear train  220  and the pump drive shaft  260  of the sandwiched PTO unit  200  are not unnecessarily driven when the pump is not in use. 
     As shown in  FIG.  7   , the sandwiched PTO unit  200  includes a first adapter, shown as prime mover adapter plate  280 , a dampening element, shown as dampener  290 , a connector or coupler, shown as connector sleeve  300 , and a second adapter, shown as transmission adapter plate  310 . The prime mover adapter plate  280  defines (i) a first interface, shown as prime mover interface  282 , coupled to the prime mover output  112 , (ii) a second interface, shown as dampener interface  284 , that receives and couples to a portion of the dampener  290 , and (iii) a first aperture, shown as central bore  286 , that receives the input end  212  of the main drive shaft  210 . The dampener  290  includes (i) a first portion, shown as adapter plate portion  292 , received by and coupled to the dampener interface  284  of the prime mover adapter plate  280  and (ii) a second portion, shown as sleeve portion  294 , that defines a second aperture, shown as central bore  296 , that receives a portion of the connector sleeve  300 . According to an exemplary embodiment, the dampener  290  is configured to dampen vibrational forces generated by the prime mover  110  such that such vibrational forces are mitigated or eliminated and do not propagate throughout the sandwiched PTO unit  200  (e.g., which reduces rattling of the gears, reduces component wear, etc.). 
     As shown in  FIG.  7   , the connector sleeve  300  includes (i) a first portion, shown as dampener interface  302 , that extends into the central bore  296  of the dampener  290  to couple the dampener  290  to the connector sleeve  300 , (ii) a second portion, shown as shaft interface  304 , the engages with a portion of the main drive shaft  210  positioned along a length thereof (e.g., a portion proximate a middle of the main drive shaft  210  but closer to the input end  212  thereof) to couple the main drive shaft  210  to the connector sleeve  300 , and (iii) a third portion, shown as clutch interface  306 , that engages with a housing, shown as clutch housing  272 , of the pump clutch  270  to couple the pump clutch  270  to the connector sleeve  300 . The connector sleeve  300  defines a central passage, and similarly the dampener  290  defines the central bore  296 , through which the input end  212  of the main drive shaft  210  extends such that (i) the input end  212  is positioned on an upstream or prime mover side of the dampener  290  and the connector sleeve  300  and (ii) the output end  214  of the main drive shaft  210  is positioned on a downstream or transmission side of the dampener  290  and the connector sleeve  300 . As shown in  FIG.  7   , the transmission adapter plate  310  couples the output end  214  of the main drive shaft  210  to the transmission input  132  of the transmission  130 . 
     As shown in  FIG.  7   , the clutch housing  272  of the pump clutch  270  contains a plurality of clutch plates, shown as clutch plates  274 . According to an exemplary embodiment, when the pump clutch  270  is engaged, the clutch plates  274  couple the clutch housing  272 , and therefore, the connector sleeve  300 , to the drive gear  230  such that rotation of the connector sleeve  300  is imparted to the pump gear train  220  and the pump drive shaft  260  to drive the pump system  60  with the prime mover  110 . In one embodiment, the clutch plates  274  are spring biased into a disengaged position and the pump clutch  270  is fluidly operated to overcome the spring bias such that the clutch plates  274  engage with the drive gear  230 . In some embodiments, the main drive shaft  210  defines an internal passage that fluidly connects the pump clutch  270  to a fluid source (e.g., a fluid pump, a hydraulic pump, etc.) where the fluid source provides a fluid (e.g., a hydraulic fluid, etc.) to the pump clutch  270  to overcome the spring bias and engage the pump clutch  270 . In other embodiments, the pump clutch  270  receives fluid in another suitable manner and/or is otherwise activated/engaged. 
     According to an exemplary embodiment, when the prime mover  110  provides an input to the sandwiched PTO unit  200  via the prime mover output  112  and the pump clutch  270  is disengaged, the prime mover output  112  drives the prime mover adapter plate  280 , the prime mover adapter plate  280  drives the dampener  290 , the dampener  290  drives the connector sleeve  300 , the connector sleeve  300  drives the main drive shaft  210  and the clutch housing  272  (but not the pump gear train  220 ), and the main drive shaft  210  drives the transmission adapter plate  310  and the transmission input  132  such that the prime mover adapter plate  280 , the dampener  290 , the connector sleeve  300 , the main drive shaft  210 , the transmission adapter plate  310 , and the transmission input  132  rotate together so that the prime mover  110  drives the transmission  130  but not the pump gear train  220 , the pump drive shaft  260 , or the pump system  60 . 
     According to an exemplary embodiment, when the prime mover  110  provides an input to the sandwiched PTO unit  200  via the prime mover output  112  and the pump clutch  270  is engaged, the prime mover output  112  drives the prime mover adapter plate  280 , the prime mover adapter plate  280  drives the dampener  290 , the dampener  290  drives the connector sleeve  300 , the connector sleeve  300  drives the main drive shaft  210  and the clutch housing  272 , the main drive shaft  210  drives the transmission adapter plate  310  and the transmission input  132 , the clutch housing  272  drives the clutch plates  274 , the clutch plates  274  drive the drive gear  230 , the drive gear  230  drives the idler gear  240 , the idler gear  240  drives the output gear  250 , the output gear  250  drives the pump drive shaft  260 , and the pump drive shaft  260  drives the pump system  60  such that the prime mover adapter plate  280 , the dampener  290 , the connector sleeve  300 , the main drive shaft  210 , the transmission adapter plate  310 , the transmission input  132 , the pump clutch  270 , the pump gear train  220 , and the pump drive shaft  260  rotate together so that the prime mover  110  drives the transmission  130  and the pump system  60 . 
     As shown in  FIGS.  7  and  8   , the main housing  202  includes a support, shown as support rib  207 , extending from the main housing  202  and into the main chamber  204  thereof. As shown in  FIG.  7   , the support rib  207  supports a first bearing, shown as main drive shaft bearing  216 , positioned along the main drive shaft  210  proximate the output end  214  of the main drive shaft  210  (such that the main drive shaft  210  extends through the support rib  207 ). According to the exemplary embodiment, the main drive shaft  210  does not include a similar bearing positioned proximate the input end  212  of the main drive shaft  210 . Rather, the drive gear  230 , the idler gear  240 , and the output gear  250  are cut to have a specific helical angle pattern such that the loading imparted onto the main drive shaft  210  and, therefore, onto the prime mover output  112  by the pump gear train  220  is substantially straight down, and not laterally into the prime mover output  112 , such that a bearing proximate the input end  212  of the main drive shaft  210  is not necessary to support the loading. Eliminating the need for a bearing proximate the input end  212  of the main drive shaft  210  permits reducing the overall length of the sandwiched PTO unit  200  and, thereby, the overall length of the driveline  100  (e.g., such that the fire apparatus  10  can have a shorter wheel base). By way of example, adding a bearing proximate the input end  212  of the main drive shaft  210  would require extending the length of the sandwiched PTO unit  200  approximately four to six inches to accommodate proper packaging of an additional bearing with the remaining components of the sandwiched PTO unit  200 . 
     As shown in  FIG.  7   , the drive gear  230  defines an aperture, shown as central bore  232 , through which the main drive shaft  210  extends and that receives a second bearing, shown as drive gear bearing  236 . According to an exemplary embodiment, the drive gear bearing  236  permits relative rotation between the main drive shaft  210  and the drive gear  230  when the pump clutch  270  is disengaged. 
     As shown in  FIG.  8   , the support rib  207  supports an auxiliary shaft, shown as idler shaft  244 . The idler gear  240  defines an aperture, shown as central bore  242 , through which the idler shaft  244  extends and that receives a third bearing, shown as idler gear bearing  246 . According to an exemplary embodiment, the idler gear bearing  246  permits rotation of the idler gear  240  about the idler shaft  244 . As shown in  FIG.  8   , the idler shaft  244  defines an internal passage that couples to a conduit, shown as lubrication conduit  248 , which is coupled to a lubrication pump. According to an exemplary embodiment, the lubrication pump is configured to provide lubrication (e.g., oil) to the internal passage of the idler shaft  244 , which directs the lubrication to the idler gear  240  to keep the idler gear  240  (and the drive gear  230  and/or the output gear  250 ) properly lubricated. As shown in  FIGS.  7  and  8   , the output gear  250  defines an aperture, shown as central bore  252 , that receives a portion of the pump drive shaft  260  to couple the output gear  250  thereto. As shown in  FIG.  8   , the sandwiched PTO unit  200  includes fourth bearings, shown as pump drive shaft bearings  262 , supported by the pump output housing  206  and coupled to and supporting the pump drive shaft  260 . 
     As utilized herein, the terms “approximately,” “about,” “substantially”, and similar terms are intended to have a broad meaning in harmony with the common and accepted usage by those of ordinary skill in the art to which the subject matter of this disclosure pertains. It should be understood by those of skill in the art who review this disclosure that these terms are intended to allow a description of certain features described and claimed without restricting the scope of these features to the precise numerical ranges provided. Accordingly, these terms should be interpreted as indicating that insubstantial or inconsequential modifications or alterations of the subject matter described and claimed are considered to be within the scope of the disclosure as recited in the appended claims. 
     It should be noted that the term “exemplary” and variations thereof, as used herein to describe various embodiments, are intended to indicate that such embodiments are possible examples, representations, or illustrations of possible embodiments (and such terms are not intended to connote that such embodiments are necessarily extraordinary or superlative examples). 
     The term “coupled” and variations thereof, as used herein, means the joining of two members directly or indirectly to one another. Such joining may be stationary (e.g., permanent or fixed) or moveable (e.g., removable or releasable). Such joining may be achieved with the two members coupled directly to each other, with the two members coupled to each other using a separate intervening member and any additional intermediate members coupled with one another, or with the two members coupled to each other using an intervening member that is integrally formed as a single unitary body with one of the two members. If “coupled” or variations thereof are modified by an additional term (e.g., directly coupled), the generic definition of “coupled” provided above is modified by the plain language meaning of the additional term (e.g., “directly coupled” means the joining of two members without any separate intervening member), resulting in a narrower definition than the generic definition of “coupled” provided above. Such coupling may be mechanical, electrical, or fluidic. 
     The term “or,” as used herein, is used in its inclusive sense (and not in its exclusive sense) so that when used to connect a list of elements, the term “or” means one, some, or all of the elements in the list. Language such as the phrase “at least one of X, Y, and Z” and “at least one of X, Y, or Z,” unless specifically stated otherwise, is understood to convey that an element may be either X; Y; Z; X and Y; X and Z; Y and Z; or X, Y, and Z (i.e., any combination of X, Y, and Z). Thus, such language is not generally intended to imply that certain embodiments require at least one of X, at least one of Y, and at least one of Z to each be present, unless otherwise indicated. 
     References herein to the positions of elements (e.g., “top,” “bottom,” “above,” “below”) are merely used to describe the orientation of various elements in the FIGURES. It should be noted that the orientation of various elements may differ according to other exemplary embodiments, and that such variations are intended to be encompassed by the present disclosure. 
     It is important to note that the construction and arrangement of the fire apparatus  10  and the systems and components thereof as shown in the various exemplary embodiments is illustrative only. Additionally, any element disclosed in one embodiment may be incorporated or utilized with any other embodiment disclosed herein.