Abstract:
A transmission having improved heat dissipation components is disclosed. The transmission includes a housing having housing walls defining an internal chamber and a rotatable input shaft extending through one of the housing walls into the internal chamber. Power transmission components are disposed in the internal chamber and rotatably driven by the input shaft. An output shaft extends through one of the housing walls from the internal chamber and is rotatably driven by the power transmission components. A lubricating fluid is disposed in the internal chamber and lubricates the power transmission components. A cooling shroud surrounds the housing and includes a cooling passageway in fluid communication with the internal chamber. The lubricating fluid flows out of the internal chamber into the cooling passageway, through the cooling passageway, and back into the internal chamber.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     Not Applicable. 
     STATEMENT CONCERNING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable. 
     BACKGROUND OF THE INVENTION 
     This invention relates to transmissions having external fluid coolers. 
     Transmissions such as industrial gear drives are capable of transmitting a large amount of mechanical power. Unfortunately, some of the transmitted power is converted to heat that may increase the transmission temperature to an unacceptably high level. Such temperatures may cause lubricating fluid within the transmission housing to deteriorate rapidly and ultimately lead to component wear or failure. 
     As such, many transmissions include heat dissipation components to prevent overheating. For example, some transmissions simply include a fan to provide convective cooling by blowing air over the external surfaces of the transmission housing. However, these heat dissipation systems, despite being structurally simple and relatively inexpensive, are typically ineffective for significantly decreasing the transmission temperature unless they are much larger than the transmission itself. 
     As another example, some transmissions include external radiators or heat pipes having internal chambers to accommodate the lubricating fluid and permit cooling outside of the transmission housing. Like the fan systems described above, relatively large radiators, e.g., those having a relatively large surface, are most effective for cooling a transmission. As such, the most effective heat dissipation components can significantly increase the space required for a transmission. 
     Considering the drawbacks of previous designs, a transmission having improved heat dissipation components is needed. 
     SUMMARY OF THE INVENTION 
     In one aspect, the present invention provides a transmission including a housing having housing walls defining an internal chamber and a rotatable input shaft extending through one of the housing walls into the internal chamber. Power transmission components are disposed in the internal chamber and rotatably driven by the input shaft. An output shaft extends through one of the housing walls from the internal chamber and is rotatably driven by the power transmission components. A lubricating fluid is disposed in the internal chamber and lubricates the power transmission components. A cooling shroud surrounds the housing and defines a gap between at least one of the housing walls. The cooling shroud includes a cooling passageway in fluid communication with the internal chamber. The lubricating fluid flows out of the internal chamber into the cooling passageway, through the cooling passageway, and back into the internal chamber. The transmission further includes a fan exhausting air through the gap cooling the at least one of the housing walls and the lubricating fluid flowing through the cooling passageway. 
     In some embodiments, the cooling shroud includes fan shroud surrounding the fan and a housing shroud surrounding the housing. 
     The foregoing and advantages of the invention will appear in the detailed description which follows. In the description, reference is made to the accompanying drawings which illustrate a preferred embodiment of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and: 
         FIG. 1  is a perspective view of a transmission including a cooling shroud according to the present invention; 
         FIG. 2  is an exploded perspective view showing a fan of the transmission of  FIG. 1 ; 
         FIG. 3  is a front view of the transmission of  FIG. 1  with the fan and a fan shroud removed; 
         FIG. 4  is a “flattened” schematic view of a housing shroud showing a fluid flow path there through; 
         FIG. 5  is a top sectional view of the fan shroud along line  5 - 5  of  FIG. 2 ; 
         FIG. 6  is a detail section view of the transmission along line  6 - 6  of  FIG. 2 ; 
         FIG. 7  is a detail section view of the transmission along line  7 - 7  of  FIG. 2 ; 
         FIG. 8  is a perspective view of a second embodiment of a transmission including a fan shroud according to the present invention; 
         FIG. 9  is a top sectional view of the fan shroud along line  9 - 9  of  FIG. 8 ; 
         FIG. 10  is a front view of a third embodiment of a transmission according to the present invention with the fan and the fan shroud removed; 
         FIG. 11  is a detail section view of the transmission of  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The particulars shown herein are by way of example and only for purposes of illustrative discussion of the embodiments of the invention. The particulars shown herein are presented to provide what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for the fundamental understanding of the invention. The description taken with the drawings should make apparent to those skilled in the art how the several forms of the present invention may be embodied in practice. 
     Referring to  FIGS. 1-2 , a transmission  10  according to the present invention includes a housing  12  that rotatably supports an input shaft  14  and an output shaft  16  driven by the input shaft  14 . The housing  12  includes a housing walls  18  having a front surface  20  and right side surface  22  from which the input shaft  14  and the output shaft  16  extend, respectively. As such, the transmission  10  is a right angle shaft transmission. The output shaft  16  may also extend from a left side surface  24  of the housing  12 . Furthermore, the output shaft  16  may extend from a surface opposite the front surface  20 , i.e., a rear surface  26  of the housing  12 , to provide a parallel shaft transmission without departing from the scope of the invention. The housing walls  18  also include an upper surface  28  having a removable inspection cover (not shown). The upper surface  28  is adjacent the front surface  20 , the right side surface  22 , the left side surface  24 , and the rear surface  26 . As used herein, the term “adjacent” means that two surfaces share a common edge. In contrast and as used herein, the term “opposite” means that two surfaces do not share a common edge. 
     The input shaft  14  supports a fan  27  that draws air towards the transmission housing  12  as in the input shaft  14  rotates. The fan  27  can also be driven by the output shaft  16  or can be completely independent of the shafts  14  and  16  without departing from the scope of the invention. Regardless of the specific structure, the fan  27  exhausts air along the housing walls  18  to cool the housing  12  and thereby prevent the transmission  10  from overheating. Other components that further dissipate heat from the transmission  10  are described in further detail below. 
     As shown most clearly in  FIG. 2 , the housing walls  18  define an internal chamber  30  in which power transmission components  29  are disposed. The power transmission components  29  may be, e.g., bevel gears and helical gears. However, other types of gears, e.g., spur gears, worm gears, planetary gears, helical gears, combinations thereof, or even other types of power transmission components may be used without departing from the scope of the invention. In any case, the power transmission components provide the driving relationship between the input shaft  14  and the output shaft  16 . 
     The internal chamber  30  of the housing  12  also accommodates a lubricating fluid  32  that reduces transmission wear by absorbing heat generated by the transmission components. As such, the internal chamber  30  also preferably accommodates a pump  34  that delivers lubricating fluid  32  to a housing output port  36  for subsequent cooling. However, the lubricating fluid  32  may be directed to the output port  36  by other means, e.g., gravity, without departing from the scope of the invention. In any case, after cooling the lubricating fluid  32  returns to the internal chamber  30  through a housing input port  38 . 
     Referring now to  FIGS. 1-7 , the transmission housing  12  supports a radiator jacket or cooling shroud  40  having a cooling circuit or passageway through which the lubricating fluid  32  flows to cool. The shape of the cooling shroud  40  advantageously closely matches the external shape of the transmission housing  12 , and therefore the cooling shroud  40  does not significantly increase the space required for the transmission  10 . That is, the cooling shroud  40  includes a fan shroud  42  that surrounds the input shaft  14  and the fan  27  and a housing shroud  60  that surrounds the housing  12 . The fan shroud  42  and the housing shroud  60  are described in further detail in the following paragraphs, but it should be noted that as used herein, the term “surround” and variations thereof means a shroud is disposed proximate at least two opposite surfaces of another object. 
     The fan shroud  42  has a general open-bowl shape through which air is drawn by the fan  27  and directed towards the housing walls  18 . That is, air is drawn through an air input  43  and directed towards an air output  45  proximate the front surface  20  of the housing  12 . The air input  43  and the air output  45  are separated by diagonally extending walls that provide the open-bowl shape of the fan shroud  42 . The open-bowl shape of the fan shroud  42  is also formed by a right half  47  and a left half  49  that together surround the input shaft  14  and the fan  27 . The halves  47  and  49  may connect to each other by fasteners, or as shown in the figures, by diagonally extending weld lines  66 . 
     As shown most clearly in  FIG. 5 , the walls of the halves  47  and  49  are defined by an inner layer  44  and an outer layer  46  that are preferably shaped sections of sheet metal, although other materials may be used without departing from the scope of the invention. In any case, the inner layer  44  and the outer layer  46  are spaced apart to define the cooling passageway there between. Of course, the edges of the inner layer  44  and an outer layer  46  are sealed, e.g., by weld lines  48 , to prevent lubricating fluid  32  leaks. 
     The right and left halves  47  and  49  of the fan shroud  42  each define separate sections of the cooling passageway through which the lubricating fluid  32  passes. For example, lubricating fluid  32  enters the right half  47  through a shroud input port  54  disposed near the upper surface  28  of the transmission housing  12  and connected to the housing output port  36 . The shroud input port  54  delivers lubricating fluid  32  to an input passage  56  of the cooling passageway defined between the inner and outer layers  44  and  46  of the right half  47 . The input passage  56  delivers lubricating fluid  32  to a fan shroud output port  58  disposed near the bottom corner of the front surface  20  and the right side surface  22  of the transmission housing  12 . The fan shroud output port  58  delivers lubricating fluid  32  to the housing shroud  60 . 
     Similarly, lubricating fluid  32  from the housing shroud  60  enters the left half  49  through a fan shroud input port  62  disposed near the bottom corner of the front surface  20  and the left side surface  24  of the transmission housing  12 . The fan shroud input port  62  delivers lubricating fluid  32  to an output passage  64  of the cooling passageway defined between the inner and outer layers  44  and  46  of the left half  49 . The output passage  64  delivers lubricating fluid  32  to a shroud output port  68  disposed near the upper surface  28  of the transmission housing  12  and connected to the housing input port  38 . 
     The right and left halves  47  and  49  of the fan shroud  42  may connect to the transmission housing  12 , the housing shroud  60 , or both in various manners. For example, the edges of the fan shroud  42  may be welded to the housing shroud  60 . However and as shown in the figures, the outer sheet metal layer  46  preferably forms several mounting feet  50  that accommodate fasteners  52 , e.g., bolts and spacers, to connect the fan shroud  42  to the transmission housing  12 . 
     Referring now to  FIGS. 2-7  and as briefly described above, the housing shroud  60  receives lubricating fluid  32  from the fan shroud  42  to further dissipate heat from the transmission  10 . The housing shroud  60  has a general saddle shape (i.e., the housing shroud  60  is positioned proximate the upper surface  28  and side surfaces  22  and  24  of the housing  12 ) that extends between the front surface  20  and the rear surface  26  of the transmission housing  12 . In addition, the cooling passageway follows a serpentine path over the general saddle shape of the housing shroud  60 , and as such the housing shroud  60  has a relatively large surface area over which the lubricating fluid  32  dissipates heat. Furthermore, the housing shroud  60  is spaced apart from the surfaces  22 ,  24 , and  28  of the transmission housing  12  to define a gap  75  there between. Air exhausted by the fan  27  passes through the gap  75  and convectively cools the housing walls  18  and the lubricating oil  32  within the housing shroud  60 . 
     Like the fan shroud  42 , the housing shroud  60  is defined by an inner layer  70  and an outer layer  72  (e.g., separate sheet metal layers connected by weld lines  74 ) that form part of the cooling passageway there between. The inner and outer layers  70  and  72  also form three panels  76 ,  92 , and  106  that provide the serpentine shape of the cooling passageway. As shown in the figures, the panels  76 ,  92 , and  106  are preferably integrally connected to each other (i.e., formed by the same inner and outer layers  70  and  72 ). However, the panels  76 ,  92 , and  106  may be formed from separate layers without departing from the scope of the invention. 
     Each of the shroud panels  76 ,  92 , and  106  defines part of the serpentine shape of the cooling passageway that directs lubricating fluid  32  back and forth between the front surface  20  and the rear surface  26  of the housing  12 . For example, the first or right side surface shroud panel  76  disposed proximate the right side surface  22  of the housing  12  defines an S-shaped section of the serpentine flow path. This S-shaped section is formed by the following components and features of the first panel  76 . 
     A first or right side surface shroud input port  78  is disposed near the bottom corner of the front surface  20  and the right side surface  22  of the transmission housing  12 . The input port  78  receives lubricating fluid  32  from the fan shroud  42  and delivers lubricating fluid  32  to a first leg  80  of the cooling passageway. The first leg  80  connects to a second leg  82  of the cooling passageway near the rear surface  26  of the transmission housing  12 . An internal wall, e.g., a weld line  84  connecting the housing shroud inner and outer layers  70  and  72  separates a majority of the first leg  80  and the second leg  82 . 
     The second leg  82  connects to a third leg  86  of the cooling passageway near the front surface  20  of the transmission housing  12 . A first shroud opening  88  separates a majority of the second leg  82  and the third leg  86 . The output shaft  16  extends through the first shroud opening  88  and, of course, air may escape from the air gap  75  through the first shroud opening  88 . The third leg  86  delivers lubricating fluid  32  to a first or right side surface shroud output port  90  disposed near the top corner of the rear surface  26  and the right side surface  22  of the transmission housing  12 . 
     The first panel  76  connects to the second or upper surface shroud panel  92  proximate the upper surface  28  of the housing  12 . The second panel  92  defines a U-shaped section of the serpentine flow path. This U-shaped section is formed by the following components and features of the second panel  92 . 
     A second or upper surface shroud input port  94  is disposed near the top corner of the rear surface  26  and the right side surface  22  of the transmission housing  12 . The second or upper surface shroud input port  94  connects to the first output port  90  and receives lubricating fluid  32  therefrom. The second port  94  also delivers lubricating fluid  32  to a fourth leg  96  of the cooling passageway. The fourth leg  96  is preferably separated from the third leg  86  of the first panel  76  by an internal wall, e.g., a weld line  98  connecting the housing shroud inner and outer layers  70  and  72 . 
     The fourth leg  96  connects to a fifth leg  100  near the front surface  20  of the transmission housing  12 . A second shroud opening  102  separates a majority of the fourth leg  96  and the fifth leg  100 . The removable inspection cover may be accessed through the second shroud opening  102  and, of course, air may escape from the air gap  75  through the second shroud opening  102 . The fifth leg  100  delivers lubricating fluid  32  to a second or upper surface shroud output port  104  disposed near the top corner of the rear surface  26  and the left side surface  24  of the transmission housing  12 . 
     The second panel  92  connects to a third or left side surface shroud panel  106  proximate the left side surface  24  of the housing  12 . The third panel  106  defines an inverted S-shaped section of the serpentine flow path. This inverted S-shaped section is formed by the following components and features of the first panel  106 . 
     A third or left side surface shroud input port  108  is disposed near the top corner of the rear surface  26  and the left side surface  24  of the transmission housing  12 . The third input port  108  connects to the second shroud output port  104  and receives lubricating fluid  32  therefrom. The third input port  108  delivers lubricating fluid  32  to a sixth leg  110  of the cooling passageway. The sixth leg  110  is preferably separated from the fifth leg  100  of the second panel  92  by an internal wall, e.g., a weld line  111  connecting the housing shroud inner and outer layers  70  and  72 . 
     The sixth leg  110  connects to a seventh leg  112  of the cooling passageway near the front surface  20  of the transmission housing  12 . A third shroud opening  114  separates a majority of the sixth leg  110  and the seventh leg  112 . The output shaft  16  may extend through the third shroud opening  114  and, of course, air may escape from the air gap  75  through the third shroud opening  114 . 
     The seventh leg  112  connects to an eighth leg  116  of the cooling passageway near the rear surface  26  of the transmission housing  12 . An internal wall, e.g., a weld line  118  connecting the housing shroud inner and outer layers  70  and  72 , separates a majority of the seventh leg  112  and the eighth leg  116 . The eighth leg  116  delivers lubricating fluid  32  to a third or left side surface shroud output port  120  disposed near the bottom corner of the front surface  20  and the left side surface  24  of the transmission housing  12 . 
     As briefly described above, the third output port  120  connects to the fan shroud input port  62  to deliver lubricating fluid  32  to the output passage  64  of the fan shroud left half  49 . The output passage  64  then directs the lubricating fluid  32  to the shroud output port  68  connected to the housing input port  38  to return the fluid  32  to the internal chamber  30  of the transmission housing  12 . 
     Like the fan shroud  42 , the housing shroud  60  may connect to the transmission housing  12 , the fan shroud  42 , or both in various manners. For example, the housing shroud  60  may be welded to the fan shroud  42 . However and as shown in the figures, the housing shroud  60  preferably connects to the housing  12  via fasteners  52 , some of which also connect the fan shroud  42  to the housing  12 . In this case, spacers of the fasteners  52  separate the panels  76 ,  92 , and  106  from the housing walls  18  to form the gap  75  there between. 
     In operation, the lubricating fluid  32  flows out of the internal chamber  30  of the transmission housing  12  through the housing output port  36  and into the input passage  56  of the fan shroud right half  47 . The lubricating fluid  32  then flows through the serpentine section of the cooling passageway formed by the housing shroud panels  76 ,  92 , and  106 . The housing shroud  60  delivers the lubricating fluid  32  to the output passage  64  of the fan shroud left half  49 . The lubricating fluid  32  then flows back into the internal chamber  30  of the housing  12  through the housing input port  38 . Of course, the fan  27  simultaneously exhausts air into the air gap  75  to cool the housing walls  18  and the lubricating fluid  32  flowing through the cooling passageway provided by the cooling shroud  40 . 
     The structure of the cooling shroud  40  may vary from the above description without departing from the scope of the invention. For example, the housing shroud  60  may provide a flow path for the lubricating fluid  32  having a different shape than the serpentine flow path described above. Nevertheless, such a housing shroud  60  preferably has a relatively large surface area over which the lubricating fluid  32  dissipates heat. 
     As another example, the weld lines  98  and  118  and the shroud openings  88 ,  102 , and  114  may be shorter than those as shown and described. However, these features preferably extend over the majority of the length between the front and rear surface  20  and  26  to provide a relatively large surface area for relatively high heat transfer with the air gap  75 . 
     As yet another example, right and left halves  47  and  49  of the fan shroud  42  may be formed from common inner and outer layers  44  and  46 . In this case, the input passage  56  and the output passage  64  of the fan shroud  42  may be separated by an internal wall, e.g., a weld line  66  connecting the inner and outer layers  44  and  46 . 
     As yet another example and referring now to  FIGS. 8 and 9 , a second embodiment of a transmission  210  according to the present invention includes a fan shroud  242  having a general U-shape as viewed from above. Like the fan shroud  42  described above, the fan shroud  242  includes an inner layer  244  and an outer layer  246  (e.g., shaped sections of sheet metal) that define fluid cooling passageways  256  and  264  there between. However, the fan input  243  includes a plurality of small input slits  247  through which air enters the fan shroud  242 . 
     As yet another example and referring now to  FIGS. 10 and 11 , a third embodiment of a transmission  310  according to the present invention includes a housing shroud  360  having additional panels to further dissipate heat from the transmission  310 . That is, the housing shroud  360  includes panels  376 ,  392 , and  406  as described above as well as inner panels  376 ′,  392 ′, and  406 ′ disposed in the air gap  375  adjacent the transmission housing walls  318 . The inner panels  376 ′,  392 ′, and  406 ′may provide the same general saddle shape as the outer panels  376 ,  392 , and  406  as described above. As such, the inner panels  376 ′,  392 ′, and  406 ′ may nearly double the amount of lubricating fluid  32  within the housing shroud  360  at a given time. Furthermore, the inner panels  376 ′,  392 ′, and  406 ′ include inlet and outlet ports  422  and  424  that receive and deliver lubricating fluid  32 , respectively, such that the inner panels  376 ′,  392 ′, and  406 ′ provide a second serpentine cooling path. Alternatively, the inner panels  376 ′,  392 ′, and  406 ′ may include multiple ports at various locations that provide a greater amount of fluid exchange between the inner panels  376 ′,  392 ′, and  406 ′ and the outer panels  376 ,  392 , and  406 . In any case, air exhausted by the fan cools lubricating fluid  32  in both the inner panels  376 ′,  392 ′, and  406 ′ and the outer panels  376 ,  392 , and  406 . 
     Exemplary embodiments of the invention have been described in considerable detail. Many modifications and variations to the embodiments described will be apparent to a person of ordinary skill in the art. Therefore, the invention should not be limited to the embodiments described, but should be defined by the claims that follow.