Patent Publication Number: US-8984974-B2

Title: Pump transmission with PTO gear and independently clutched impeller

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Applicant claims priority based on Provisional Patent Application No. 60/870,086, filed Dec. 14, 2006, the entirety of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to transmissions capable of powering multiple devices from a single drive shaft, and more specifically to pumps and pump transmissions capable of powering an impeller shaft of a fluid pump and at least another device, and particularly to emergency vehicle pumps and transmissions of such variety. 
     2. Background Information 
     Transmissions capable of powering a primary device and at least another device are not new. Some transmissions, especially in the automotive or truck areas, include a drive for powering a primary device, such as an axle of the vehicle, and may also include a power take-off, commonly known as a PTO. A PTO device is designed to power an auxiliary device, drawing power from the main drive of the transmission. In some instances an auxiliary device itself might take power off from (or directly connect to) the main transmission, as opposed to coupling with an intermediate PTO device. A PTO device typically attaches to the main transmission and in turn powers an auxiliary device. Typically a transmission includes an internal gear, i.e., a “PTO gear”, to which the auxiliary device or to which the PTO device couples in order for the auxiliary device or the PTO device to be driven. 
     Pump transmissions, including pump transmissions of the fire-fighting variety have also been designed to power a primary device such as a pump, and at least another device, such as a booster pump or a compressor. One such system includes extending the impeller shaft out the opposite side of the gearbox of a pump transmission. One end of the impeller shaft is engaged with the pump impeller while the opposite end is available for use to power another device. In other systems, an additional gear may be included inside the gearcase to provide a power output. An example of such additional gearing is found in the patent to Hoffman, U.S. Pat. No. 4,587,862, issued May 13, 1986. In Hoffman, an input member 30 alternately powers an output member 32 or a pump shaft 18 by means of a sliding gear 70. A further example of a system that provides additional gearing is found in the patent to Eberhardt, U.S. Pat. No. 5,145,014, where the transmission powers a rotating pump shaft 18 and an air compressor 13. 
     In other firefighting pump transmission systems an opening is provided on the gearcase or housing of a primary transmission to receive a specially designed auxiliary transmission or device. A specially designed PTO device is used to couple the primary transmission to the auxiliary device. The auxiliary system may be equipped with a sliding clutch gear to engage or disengage a driven device. For instance, an auxiliary device such as a booster pump or compressor may typically be mounted to the housing or closely coupled to the housing of a firefighting pump transmission. An example of such a system is the model LDMH pump manufactured by W.S. Darley &amp; Company, Chippewa Falls, Wis. 
     SUMMARY 
     While the prior pump transmissions power a primary device and also allow for the powering of an auxiliary device or devices, they are limited such that in order to power a PTO gear within the casing of the transmission, the pump or impeller shaft must be powered. This has not been viewed as a problem but, rather, a fact of life or a necessary aspect of such devices. Heretofore there was little or no purpose in decoupling the pump from the PTO device since auxiliary devices used in conjunction with the pump or pump transmission require the pump. Indeed, auxiliary devices such as compressors or boosters require the pump and its water in order to operate. The present inventors have recognized, however, that running the PTO gear without running the impeller shaft would provide numerous benefits, such as prolonging pump life, allowing for running of an auxiliary device in situations where pump water is scarce or lacking, providing versatility options for a pump transmission to power a variety of devices that otherwise would not be justified running due to excessive pump wear, among many other benefits. The present inventors have also recognized that since the PTO gear may be driven independently from the pump, the particular features of the PTO gear can also be independent of the pump. For instance, the type and size of the PTO gear does not have to be influenced by the speed requirements or other particulars of the pump. A spur gear, instead of a helical gear may be used for the PTO gear. Different gear spacing and helix angles, the number of gear teeth, and other aspects of the gearing can be modified or used to accommodate compatibility with a variety of auxiliary and PTO devices. Advantageously, the PTO gear may be configured to engage with a Commercially Available (instead of a specially designed) PTO device. Thus, running the PTO gear without running the impeller shaft provides even further benefits. 
     Affixing a PTO device  50  (such as a Commercially Available PTO device) to the pump transmission  20  for powering an auxiliary device which is not useful or not critical to the operation of the pump would not make sense, for in order to run the auxiliary device would necessarily require driving the impeller shaft  40 . Preferably the impeller shaft is run only when required in order to preserve the useful life of the pump. Typically, the pump impeller is driven only a small percentage of the time an emergency vehicle is called to action in the field. As such, configuring the PTO device to operate independently of the impeller shaft provides further benefits. 
     In accordance with the invention, then, the versatility of a firefighting pump transmission is enhanced by independently powering, from a common drive shaft, a PTO gear and an impeller shaft. Such arrangement allows for independent use of an auxiliary device without having to run the pump, and among other benefits, also accommodates use of a variety of auxiliary devices heretofore otherwise being impractical for use with a pump transmission. 
     In particular embodiments of the invention, the PTO gear is affixed to the transmission drive shaft. Also, a clutch is placed on the impeller shaft. In a particular aspect, the clutch is coupled to the transmission drive shaft via a clutch driving gear. A clutch driving gear is connected to the drive shaft and couples with a clutch gear of the clutch. Clutching devices of various types may be used, however, a multi-disk clutch placed on the impeller shaft is most advantageous. Mounting the “chuck” portion of the multi-disk clutch on the impeller shaft allows the impeller shaft to be powered “on” when the clutch is activated. Also in a particular aspect the clutch driving gear is connected adjacent to or in contact with the PTO gear, and both rotate together as the drive shaft turns. Each of these details provides particular advantages and can be implemented independently of the others. 
     The PTO gear attached to the drive shaft can be of any desired variety. A PTO gear of a spur gear is most advantageous, however. 
     Also in particular embodiments, a PTO device is attached to the transmission and is coupled with the PTO gear situated inside a casing of the transmission. Particular aspects include mounting the PTO device to a side of the casing (i.e., avoiding a mounting to the front or rear of the casing). 
     Advantageously, in particular embodiments the transmission of the present invention accommodates or includes a mounting of a “Commercially Available PTO device” as described further below. In additional aspects, an optional drive-line is used in conjunction with the transmission. Also in particular aspects, a device powered by the PTO gear mounts remotely from the transmission. In particular aspects, a drive shaft or a hydraulic adapter are included with the PTO device. 
     In additional aspects the impeller shaft includes a spline feature for mounting of an auxiliary device. In particular aspects, such auxiliary device includes a brake or a hydraulic pump. In additional aspects the transmission includes a lubrication system and pump for lubricating and cooling transmission components. 
     In particular embodiments in accordance with a further aspect of the invention, the problem of independently powering a PTO gear and an impeller shaft from a single drive shaft of a firefighting pump transmission is solved by affixing the PTO gear to the drive shaft and clutching the impeller shaft. In particular aspects, clutching of the impeller shaft includes attachment of a clutch driving gear to the drive shaft adjacent the PTO gear. Further optional aspects include mounting a PTO device to the transmission and coupling the PTO device with a drive line to power a remote auxiliary device. 
     The above summary provides that the powering of the PTO gear is not dependent on the powering of the pump (i.e., the impeller shaft need not move in order to drive the PTO gear). The concept may be alternatively stated in terms of selectively powering the impeller shaft while powering the PTO gear. Indeed, powering of the PTO gear is independent of powering the impeller shaft. 
     The above summary of the present invention is not intended to describe each illustrated embodiment or every implementation or aspect of the present invention. The figures and detailed description that follow more particularly exemplify these embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a firefighting pump transmission embodying the principles of the present invention. 
         FIG. 2  is a further perspective view of the transmission of  FIG. 1  having portions removed for clarity. 
         FIG. 3  is a further perspective view of the transmission of  FIG. 1  having portions removed for clarity. 
         FIG. 4  is a section view taken along line  4 - 4  of  FIG. 1 . 
         FIG. 5  is a perspective view of the transmission of  FIG. 1  equipped with a pump and having plate removed. 
         FIG. 6  is a partial perspective exploded view of a pump transmission embodying the principles of the present invention. 
         FIG. 7  is an exploded perspective view of the transmission of  FIG. 1 . 
         FIG. 8  is a bottom perspective view of a PTO device known in the prior art. 
         FIG. 9  is a perspective view of a pump and transmission and PTO device embodying the principles of the present invention. 
         FIG. 10  is a perspective view of a pump and transmission having a PTO device embodying the principles of the present invention and where a portion of the housing is removed for illustration. 
         FIG. 11  is a perspective view of a firefighting pump transmission embodying the principles of the present invention and having an impeller cap removed. 
         FIG. 12  is a section view taken along line  12 - 12  of  FIG. 11 . 
         FIG. 13  is a perspective view of a firefighting pump transmission embodying the principles of the present invention. 
         FIG. 14  depicts a type of pump and pump transmission known in the prior art. 
         FIG. 15  is a perspective view of a firefighting pump transmission embodying principles of the present invention. 
     
    
    
     While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not necessarily to limit the invention to the particular embodiments or aspects described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention and as defined by the appended claims. 
     DETAILED DESCRIPTION 
     Among the pumps and pump transmissions known in the prior art are those referenced above in the background section and the device shown in  FIG. 14 . The  FIG. 14  device shows a pump/pump transmission  200 . An input shaft (which is a shaft positioned opposite output shaft  210 ) enters the housing of the transmission  220  at a front portion of the transmission  220 . An auxiliary transmission  230  is mounted to the side of the transmission  220 . The auxiliary transmission  230  powers a smaller pump  240  which is fed by a hose  250 . In this prior system, pump  240  operates as a booster for the pump/pump transmission  200 , achieving higher pressures than the pump  200  would otherwise achieve. 
     The auxiliary transmission  230  is equipped with a sliding clutch gear (not shown) to engage or disengage the PTO driven device  240 . In the illustrated case, the driven device (auxiliary) is the smaller pump  240 . The PTO driven device  240  might alternatively be a compressor. The transmission  230  is a two-gear transmission that mounts to the side of main transmission  220  and operates as a power-take-off PTO device. 
     Within the housing  260  of pump/pump transmission  200 , a gear (not shown) of transmission  230  couples with a “drive gear” that is mounted on input shaft  210 . The drive gear powers both PTO device  230  and an idler gear which in turn powers a third gear within housing  260  to power the impeller shaft of pump and transmission  200 . As the drive gear turns, both the PTO device  230  and the main impeller shaft within housing  260  are powered. There are also other known types of firefighting pump transmissions that use a PTO to power an auxiliary device where the PTO is powered together with the impeller shaft. 
     The known firefighting pump transmissions lack versatility because the impeller shaft must be powered in order for the PTO gear or the auxiliary device to be powered. As noted above, it remained for the present inventors to recognize that having a PTO gear powered independently of the impeller shaft would provide numerous benefits, as detailed hereinabove. Indeed, the transmissions referenced in the background and in  FIG. 14  may power an auxiliary device, yet such transmissions are limited as compared to the present invention. 
     Referring to  FIGS. 1-13 , a transmission embodying the principles of the present invention is generally depicted with reference to numeral  20 . In one aspect, transmission  20  is a fluid pump transmission and includes a housing  22 . Transmission  20  operates with a pump of a firefighting variety and may be used on a firetruck or other emergency response vehicle. Housing  22  is preferably made from cast metal such as iron, preferably aluminum. Housing  22  is a single-piece construction and may attach to or include a bottom  23 . Housing  22  receives a drive shaft  34  which enters housing  22  in conventional fashion. Drive shaft  34  connects to a clutch driving gear  30  within housing  22  (See  FIGS. 2-4 ). Clutch driving gear  30  is operatively coupled to an impeller shaft  40 . Transmission  20  further includes a PTO gear  32  affixed to drive shaft  34 . In accordance with the invention, the versatility of firefighting pump transmission  20  is enhanced by independently powering, from a common drive shaft  34 , the PTO gear  32  and the impeller shaft  40 . In one particular aspect, impeller shaft  40  is selectively powered by means of a clutch, such as clutch  38 . While drive shaft  34  and gears  32  and  30  may rotate together, clutch  38  allows for impeller shaft  40  to remain idle. When clutch  38  is activated, impeller shaft  40  rotates. 
     Preferably clutch  38  couples clutch driving gear  30  with impeller shaft  40 . Clutch  38  includes a clutch gear  36 . Clutch driving gear  30  engages with clutch gear  36 . While other varieties may be used, preferably clutch driving gear  30  is a helical gear matched to a corresponding helical gear  36 . Together clutch driving gear  30  and clutch gear  36  form a pump gear set  44  (See  FIG. 2 ). The number of teeth used on gear set  44  may be altered to achieve a desired drive shaft-to-impeller shaft ratio. Gear set  44  may include multiple gears, however use of a pair of gears such as gear  30  and clutch gear  36  is preferred. It may be appreciated that the particular gear set  44  may be established to have a rotational output speed which matches an optimal impeller rotation speed of a given pump  60  which may be engaged with impeller shaft  40 . 
     As drive shaft  34  spins, clutch driving gear  30  spins which in turn spins clutch gear  36  to operate impeller shaft  40  when clutch  38  is activated. Pump  60  includes impeller  41 . When impeller shaft  40  turns, impeller  41  turns. When clutch  38  is deactivated, clutch gear  36  spins freely upon shaft  40  and rides on bearings  47 . Clutch  38  is preferably of a well known multi-disk variety having disk plates  42 . Clutch  38  includes a chuck portion  43  which is securely mounted to impeller shaft  40 . As the clutch gear  36  spins, so do some of the plates  42 . When clutch  38  is activated, plates  42  bind upon or within chuck  38 , thereby causing chuck  38  and impeller shaft  40  to turn. The speed of rotation of impeller shaft  40  is dependent in part on the speed of rotation of drive shaft  34  and the gearing ratio of gear set  44 . It may be appreciated that the speed of rotation of impeller  40  may be different from the speed of rotation of drive shaft  34 . 
     As referenced above, transmission  20  includes a PTO gear  32  affixed to drive shaft  34 . PTO gear  32  is affixed to shaft  34  so that it rotates as shaft  34  spins, and further preferably does not slide along shaft  34  but remains in a set position. While other varieties may be used, preferably PTO gear  32  is of a spur gear variety and is positioned within housing  22 . PTO gear  32  allows for gearing the pump  60  and the PTO device  50  (See  FIGS. 8-10 ) independently. More preferably, PTO gear  32  is configured to engage with a Commercially Available power take-off, or PTO  50 . A “Commercially Available” PTO device is one that mounts to a standard PTO opening of a casing, particularly such devices that mount to openings having a six or eight bolt pattern as defined under Society of Automotive Engineers Standard SAE J704, as well as openings having a ten bolt pattern for mounting on an Allison transmission. One non-limiting example of a spur gear  32  for use in conjunction with the invention includes a gear  32  which matches to fit a receiving gear  54  (See  FIG. 8 ) of PTO  50  where the PTO receiving gear  54  is also a spur gear. It may be appreciated that gear  32  may be configured to match other types of receiver gears, yet is preferably configured to operate with Commercially Available PTO devices. Other non-limiting examples of Commercially Available PTO  50  devices that may be used with the invention include Chelsea and Muncie (not shown) varieties. Together, gear  32  and receiver gear  54  form a PTO gear set  46  (See  FIG. 10 ). The number of teeth used on gear set  46  may be altered to achieve a desired drive shaft-to-PTO output shaft ratio. Gear set  46  may include multiple gears, however use of a pair of gears such as gear  32  and receiver gear  54  is preferred. It may be appreciated that the particular gear set  46  may be established to have a rotational output speed which matches an optimal rotational speed of a given accessory device (accessory device not shown). Non-limiting examples of some accessory devices include booster pumps, compressors, foam concentrate pumps, generators or other devices. 
     Preferably housing  22  defines a PTO port  48  (See  FIG. 5 ). PTO port  48  allows for access to the inner space of housing  22  where clutch driving gear  30  and PTO gear  32  operate. Preferably port  48  is positioned adjacent clutch driving gear  30  and PTO gear  32 . Preferably housing  22  includes a substantially flat mounting face  24 . Face  24  is situated on an exterior of housing  22  and preferably about a perimeter  26  of the PTO port  48 . Preferably perimeter  26  is dimensioned to match a perimeter  26 ′ of PTO  50  (See  FIG. 8 ). Preferably mounting face  24  includes at least one bolt hole  28 , and more preferably includes at least six bolt holes  28  as shown, and most preferably includes holes or openings having a six or eight bolt pattern as defined under Society of Automotive Engineers Standard SAE J704 or openings having a ten bolt pattern for mounting on an Allison transmission or similar casing. When PTO device  50  is not mounted to transmission  20 , plate  52  is mounted to housing  22  which covers PTO port  48  and clutch driving gear  30  and PTO gear  32 . Bolts  29  are used to mount plate  52  to housing  22 . While other sizes and varieties are possible, preferably plate  52  is a generally rectangular, planar body which defines and lies on a plane oriented substantially parallel to a longitudinal axis A (see  FIG. 4 ) of drive shaft  34 . Preferably mounting face  24  defines a plane oriented substantially parallel to a longitudinal axis A of drive shaft  34 . The plane preferably also runs parallel with the gear flanks of the PTO gear  32  (in the case where PTO gear is a spur gear). It may be appreciated that where mounting face  24  defines a plane oriented substantially parallel to a longitudinal axis A of drive shaft  34 , a mounting of a PTO  50  thereupon provides for a preferred and improved engagement between receiver gear  54  and spur gear  32 . Were such orientation not substantially parallel, receiver gear  54  might otherwise be skewed or out of alignment when engaged with gear  32  or when attempting to couple gear  54  and gear  32 . Further, port  48  is positioned on a side of transmission  20  as generally shown. 
     Clutch driving gear  30  and PTO gear  32  may have different diameters and different teeth arrangements. Preferably PTO gear  32  is a spur gear adapted to match with a receiver gear  54  of a PTO  50 . Having different gear sets  44 ,  46  allows for using a common drive shaft  34  to operate impeller  40  while simultaneously (or alternatively) operating PTO  50 . It may be appreciated that an accessory device (not shown) such as an air compressor, or a generator, or a secondary pump, or other device, including devices that may be useful on a emergency vehicle such as a fire truck, may be operated from power take-off area  51  (see  FIG. 1 ). It may be appreciated that operation of accessory device is made possible, or at least easier, due to the ability to incorporate a PTO gear set  46  (See  FIG. 10 ) which is different from impeller-clutch gear set  44 . Particularly, lower (or higher) spin ratios of a PTO output shaft  56  may be achieved as desired. It may be appreciated that additional gear or gears (not shown) may be included within PTO device  50  to accommodate variation of output spin of PTO output shaft  56 . Also, a clutch or clutch set (not shown) may be used with or within PTO device  50  to selectively engage or disengage power to an accessory device. In this manner the accessory device may be shut down while powering impeller shaft  40 , thus providing further versatility. 
     Advantageously, use of a Commercially Available PTO device accommodates use of an accessory device to be remotely positioned due to the ability to drive a PTO drive line (schematically represented and designated as “DL” in  FIG. 8 ) which may extend outward or away from PTO  50  and housing  22 . Drive-line DL may include a shaft  56 ′ attached to or comprising output shaft  56 , and may be equipped with a U-joint or yoke elements, or may include a hydraulic coupling. For instance, an accessory may be generally positioned in the region designated by numeral  62  (or some other region whether on the housing  22  or to a component of a firetruck or other structure). Such orientation allows freedom from having to configure a mounting directly to housing  22 , or other relatively close coupling to transmission  20 . 
     A situation unique to this present pump transmission arrangement arises where the impeller shaft  40  or pump  50  is not activated. When the PTO gear  32  runs, water circulation from the pump  50  is otherwise not available for cooling. Thus, the gears of the PTO device  50 , as well as the PTO gear  32  and the other gears and elements within the housing  22  require cooling and/or lubrication. A lubricant is thus circulated under pressure to and from the housing  22 . Further shown in  FIG. 4  is an oil or lubricant pump  64 . Oil pump  64  pressure-feeds or lubricates the PTO gear and bearings. An oil filter  76  is preferably provided. A radiator  69  (See  FIG. 15 ) is also used to cool the lubricant such as a lubricating oil or automatic transmission fluid. With such lubrication system, cooling may be achieved even where the impeller shaft  40  is not engaged. Alternatively, cooling may be accomplished by circulating lubricant through a heat exchanger (not shown). Filter  76  connects with lubricant tube  78  which re-circulates lubricant from the housing  22  back to oil pump  64 . Lubricant exits fitting  65  (See  FIG. 6 ,  FIG. 15 ) to an optional heat exchanger or radiator  69  for cooling of the lubricant. Lubricant may return to a fitting, for example a fitting  67  (see  FIG. 1 ) for passage to bearings and gears generally at the impeller shaft  40  location. 
     Further as shown in  FIGS. 11-13 , impeller shaft  40  is preferably provided with an external spline  70 . Brake  66  may be mounted to spline  70 . Brake  66  allows for braking of shaft  40  to prevent shaft  40  from rotating when clutch  38  is disengaged. It may be appreciated that wire  68  is used to engage clutch  38  and/or brake  66 . Preferably brake  66  is engaged when clutch  38  is disengaged and vice versa. Preferably, shaft  40  also includes internal spline  72 . Spline  72  may also receive a hydraulic pump (not shown) or hydraulic pump adapter (not shown). Preferably hydraulic pump adapter is an SAE “A”  9  tooth spline. It may be appreciated that impeller cap  74  may be removed for installing the above brake  66  and/or hydraulic components. It may be appreciated that the hydraulic pump may also act as a brake to prevent shaft  40  from rotating when clutch  38  is disengaged. It may also be appreciated that internal spline  72  may operate equipment in addition to brakes or hydraulic pumps and functions as an additional power driving location. 
     The foregoing merely illustrates the principles of the invention. For example, although a multi-disk clutch  38  is mounted to the impeller shaft  40 , it may be possible to use other clutch mechanisms to selectively turn “on” clutch  40 . 
     It will thus be appreciated that those skilled in the art will be able to devise numerous alternative arrangements that, while not shown or described herein, embody the principles of the invention and thus are within its spirit and scope.