Abstract:
A bracket assembly and method for positioning a cooling fan thermostat on a motorcycle engine so that the mounted thermostat is more responsive to actual changes in engine temperature. The bracket mounts on the engine&#39;s engine block near the base of the cylinders and positions the thermostat close to the cylinders&#39; cooling fins. This positioning leaves the thermostat well below the lines of air flowing from the fan and prevents the thermostat from cooling before lowering the engine temperature below the preset maximum level. This positioning also leaves the thermostat closer to the cylinders which are the most significant sources of heat in the engine, making the thermostat more convectively responsive to the engine&#39;s actual temperature.

Description:
BACKGROUND 
     The present invention is directed to the field of thermostat placement brackets. More particularly, the present invention is directed to a bracket assembly and method for positioning a cooling fan thermostat on a motorcycle engine. 
     Air-cooled motorcycle engines normally incorporate cooling fins on each cylinder in order to increase both the conductive and convective dissipation of waste heat. As a motorcycle travels, air flows over the cooling fins and increases the fins&#39; heat dissipating efficiency. However, this increase in efficiency lasts only as long as a constant airflow continues to pass over the cooling fins. When the motorcycle is traveling or idling at low speeds, airflow over the cooling fins is reduced or eliminated, significantly limiting the ability of the cooling fins to dissipate heat. If an engine is operated for extended periods, under extreme conditions, or in an environment that is enclosed or partially shielded from the wind, overheating and subsequent engine failure or damage can result. 
     In order to improve air flow and thereby improve heat dissipation from the surfaces of an engine&#39;s cooling fins, cooling fans are often installed as optional equipment on motorcycles. Such fans are typically operated with a thermostat and are positioned to draw in and blow air laterally across each of the engine&#39;s cylinders. If during operation, a motorcycle&#39;s forward movement produces sufficient air flow to remove most of the excessive waste heat generated, it is possible that no additional heat dissipation will be necessary. If however, air flow is reduced due to idling, insufficient speed, extreme conditions, or an obstruction, waste heat will likely be generated faster than it can be dissipated by the cooling fins working alone. Therefore, a cooling fan&#39;s thermostat will normally be set to operate the cooling fan as soon as the engine&#39;s temperature surpasses a preselected maximum temperature. Once the cooling fan begins to operate, air continues to blow across the cooling fins, convectively removing heat from the surfaces of the cylinder and cooling fins and until the thermostat senses that temperature has been reduced below the preselected maximum level. 
     In prior art engines, such as the engine  10  depicted in FIG. 2, a cooling fan assembly (not shown) houses a fan (not shown) positioned to draw air over the engine&#39;s cylinders  20 , the cylinders  20  being positioned on an engine block  22 . As depicted in the side view of the same engine in FIG. 3, the fan draws and blows air  14  against the cylinders  20  and over the cylinders&#39; cooling fins  18 . The fan is operated by a thermostat  23  placed on an air cleaner housing  12 . The thermostat  23  is placed at a position most proximate the cylinders  20  while still being positioned on the air cleaner housing  12 . As best understood with reference to FIG. 3A, this positioning puts the thermostat  23  in the line of the flowing air  14 . The thermostat  23  also remains separated from the engine block  22  and cylinders  20  by a substantial distance without having a direct structural interconnection. 
     Such previous configurations significantly limit the thermostat&#39;s temperature sensing ability. One result of the configuration is that heat must first convectively migrate the distance from the engine&#39;s cylinders  20  to the air cleaner housing  12  before it can be sensed by the thermostat  23 , significantly delaying the thermostat&#39;s response time in reacting to temperature changes of the engine  10 . Another result is that plastic and other materials which comprise the air cleaner housing  12  which surround the thermostat  23  tend to both insulate the thermostat  23  and dissipate ambient and radiant heat, further delaying the thermostat&#39;s response time to temperature changes and possibly subjecting the thermostat  23  to premature cooling. Such possible premature cooling can cause the cooling fan to shut off before the engine&#39;s temperature falls to below the preselected maximum level. Consequently, the lowered thermostat responsiveness of such previous designs inherently limits a fan&#39;s ability to effect engine cooling and to prevent overheating. 
     SUMMARY 
     The present invention is a bracket assembly and method for positioning a cooling fan thermostat on a motorcycle engine so that the mounted thermostat is more responsive to actual changes in engine temperature. A bracket mounts on the engine&#39;s engine block near the base of the cylinders and positions the thermostat close to the cylinders&#39; cooling fins. This positioning leaves the thermostat well below the lines of air flowing from the fan and prevents the thermostat from cooling before lowering the engine temperature below the preset maximum level. This positioning also leaves the thermostat closer to the cylinders which are themselves the most significant sources of heat in the engine, making the thermostat more convectively responsive to the engine&#39;s actual temperature. 
     The bracket and/or the components of the bracket assembly may be made of a thermally conductive material. The bracket provides a single structural link between the engine block and the thermostat, permitting more efficient and conductive heat transfer between the engine and thermostat. Thus, the invention permits the thermostat to be both convectively and conductively more responsive to the engine temperature. 
     Some motorcycle engines have preexisting studs extending outward from the engine block near the bases of the cylinders. In such engines, a bracket assembly can be mounted by fitting a bracket over the existing stud and securing the bracket in position with a nut and washer. Many such engines have adjacently positioned screw caps which can interfere with the positioning of the bracket. Thus, some embodiments of the invention include shaved edges on the bracket and/or on some of the bracket assembly components to provide clearance against the cap screws. In some of these embodiments, one of the shaved edges can be positioned sufficiently proximate the screw cap to restrict undesired rotational movement of the bracket. 
     In other embodiments of the invention, a threaded mounting hole is added to an engine block if the engine lacks a stud near the base of its cylinders. These embodiments incorporate a threaded mounting bolt to fasten the bracket to the engine block. In some of these embodiments, a spacer is added to provide clearance between the bracket and engine block if such clearance is necessary to properly orient the bracket with respect to the cylinders. 
     Those skilled in the art will realize that this invention is capable of embodiments which are different from those shown and described below. It will be appreciated that details of the structure of this cooling fan thermostat bracket can be changed in various manners without departing from the scope of this invention. Accordingly, the drawings and Detailed Description of the Preferred Embodiments below are to be regarded as including such equivalent thermostat brackets as do not depart from the spirit and scope of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more complete understanding and appreciation of this invention and many of its advantages, reference should be made to the following, detailed description taken in conjunction with the accompanying drawings wherein: 
     FIG. 1 is a perspective view of typical motorcycle engine having a thermostat positioned on a thermostat bracket according to the invention; 
     FIG. 2 is a perspective view of a prior art motorcycle engine having a thermostat mounted to its air cleaner housing for comparison with the invention depicted in FIG. 1; 
     FIG. 3A is a front view of the motorcycle engine of FIG. 2, depicting the thermostat&#39;s relative positioning with respect to the line of airflow from the cooling fan and the engine&#39;s cylinders; 
     FIG. 3B is a front view of the motorcycle engine of the invention of FIG. 1 depicting the relative positioning of the thermostat with respect to the lines of air flowing from the cooling fan to the engine&#39;s cylinders according to one embodiment of the invention; 
     FIG. 4 is a side view of the motorcycle engine of FIG. 3B further depicting the bracket assembly&#39;s proximity to an adjacent screw cap on one lifter housing and the shaved edges at the bracket&#39;s attachment end for providing clearance and for restricting rotation of the bracket on its stud; 
     FIG. 5 is a side view of a bracket having shaved edges at its attachment end according to one embodiment of the invention; 
     FIG. 6 is an exploded view depicting the various components of the motorcycle thermostat bracket assembly of FIG. 4 according to one embodiment of the invention; 
     FIG. 7 is a side view of a motorcycle engine having an alternate thermostat bracket assembly for engines lacking a stud proximate the bases of the engine&#39;s cylinders; 
     FIG. 8 is a side view of the bracket used in the thermostat bracket assembly of FIG. 7; and 
     FIG. 9 is an exploded view depicting the various components of the motorcycle thermostat bracket assembly of FIG. 7, including a spacer positioned between the engine block and bracket according to one embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings, identical reference numerals and letters designate the same or corresponding parts throughout the several figures shown in the drawings. In drawings depicting slight variations of the invention design, corresponding part numbers include the lowercase letter a. 
     FIG. 1 depicts a typical 2-cylinder motorcycle engine  24  having a front cylinder  26  and a rear cylinder  28  positioned on an engine block  30 . Each cylinder  26  and  28  has a number of cooling fins  32  and  34  surrounding each cylinder for dissipating heat generated during engine operation. The cylinders  26  and  28  connect to the engine block  30  at their bases  36  and  38  ( 38  not shown in FIG. 1) and are proximately arranged in V-configuration (as shown). An air cleaner housing  42  is positioned to one side of the cylinders  26  and  28  and is separated from the cooling fins  32  and  34  by an intermediate space  44 , as best understood with reference to FIG.  3 B. As depicted in FIG. 3B, push rod housings  46  occupy the intermediate space  44 . Referring again to FIG. 1, a thermostat bracket assembly  40  of the invention is positioned on the engine block  30  between the cylinders  26  and  28  near the cylinders&#39; bases  36  and  38  ( 38  not shown in FIG. 1) on a stud  48  which extends outward from the engine block  30 . 
     The outward extension of the stud  48  can be best understood in FIG.  3 B. The stud  48  extends outward from the engine block  30  between the cylinders  26  and  28  and adjacent the cylinder&#39;s bases  36  and  38 . A thermostat bracket assembly  40  of the invention is mounted to the engine block  30  on the stud  48 . The components of the bracket assembly  40  are depicted in the exploded view of FIG.  6 . The bracket assembly  40  is constructed around a bracket  50  having an attachment end  52  and a positioning end  54  that includes a flat attachment surface  72 . The bracket  50  is itself depicted in FIG.  5 . 
     An attachment hole  56  extends through the attachment end  52  of the bracket  50 . When the bracket  50  is mounted on the engine block  30 , the stud  48  extends through the attachment hole  56 , the bracket  50  being secured in place with an inside washer  58 , outside washer  60 , and a nut  62 . The stud  48 , bracket  50 , and other components of the bracket assembly  40  are ideally constructed of one or more thermally conductive materials such as steel, copper, or aluminum, in order to permit the flow of conductive heat from the engine block  30  to the positioning end  54  of the bracket  50 . The positioning end  54  of the bracket  50  includes two positioning holes  64  for attaching a thermostat assembly  66 . 
     The thermostat assembly  66  includes a thermostat  68  having a flat positioning surface  70  and having a plastic attachment tab  74 . The thermostat assembly  66  also includes a thermostat mount  75  having a through hole  76  for connecting to the thermostat  68  and two connecting holes  78  for attaching to the bracket assembly  50 . When assembled, the thermostat  68  connects to the thermostat mount  75  with the plastic attachment tab  74  extending through the through hole  76 . The plastic attachment tab  74  is typically made of plastic or another formable material and is melted to lock the thermostat  68  in place after being inserted into the through hole  76  (as shown in FIG.  4 ). The thermostat assembly  66  connects to the bracket  50  by aligning connecting holes  78  of the thermostat mount  75  to positioning holes  64  extending through the attachment surface  72  in the bracket  50  so that the flat positioning surface  70  rests flat against the attachment surface  72 . Positioning screws  80  extend through both the positioning holes  64  and connecting holes  78  and are fastened with positioning nuts  82 , securing the thermostat assembly  66  to the bracket  50 . 
     Some engines, such as the one depicted in FIGS. 1 and 4, have one or more lifter blocks  86  and  88  positioned adjacent the stud  48  extending from the engine block  30 . As is the case with the engine  24  depicted in FIGS. 1 and 4, one or more of the lifter blocks  86  and  88  may be sufficiently close to the stud  48  to potentially interfere with the mounting of the thermostat bracket  50 . For example, on the engine  24  of FIGS. 1 and 4, both the forward lifter block  86  and the rear lifter block  88  are proximate to the stud  48 . Each lifter block  86  and  88  has screw caps  92  positioned at each corner. As seen in FIG. 1, an intermediate gap  90  separates the base  36  of the front cylinder  26  from the forward lifter block  86 , permitting the bracket  50  and washers  58  and  60  to fit substantially flush with the engine block  30  when mounted on the stud  48 . However, a much smaller intermediate gap (not shown) exists between the rear lifter block  88  and the base  38  of the rear cylinder  28 . 
     As best understood by comparing FIG. 1 with FIG. 4, the result of this positioning is that the rear lifter block  88  has one screw cap  94  that can block the mounting of the bracket  50  and washers  58  and  60  on the stud  48 . For this reason, the bracket  50  has a first shaved lower edge  96  at its attachment end  52  to provide clearance from the most adjacent screw cap  94 . The inside washer  58  and outside washer  60  have similarly shaved respective edges  98  and  100  to also allow for clearance with the adjacent screw cap  94 . In some designs, such as that depicted in FIGS. 1 and 4, the first shaved lower edge  96  of the bracket  50  can be sufficiently close to the adjacent screw cap  94  that the first shaved lower edge  96  is used to prevent undesired rotation of the bracket  50  about the stud  48 . 
     The intermediate gap  90  separating the base  36  of the front cylinder  26  from the forward lifter block  86  increases the clearance between the stud  48  and the adjacent forward lifter block  86 . In some engine models, this intermediate gap  90  may be sufficiently small to permit the forward lifter block  86  to interfere with the mounting of the bracket  50 , though it is generally not sufficiently small to permit interference with the mounting of the washers  58  and  60 . To prevent potential interference from the forward lifter block  86 , a second shaved lower edge  97  is positioned at the bracket&#39;s attachment end  52  to provide the necessary clearance for mounting. 
     FIGS. 3B and 4 demonstrate certain advantages of the invention that are apparent when compared with previous designs such as that of FIG.  3 A. When assembled, the thermostat bracket assembly  40  positions the thermostat  68  between the bases  36  and  38  of the cylinders  26  and  28  and closely adjacent the cooling fins  32  and  34 . Thermostat wires  84  are routed behind the air cleaner housing  42  and allow the thermostat  68  to operate the fan. As best understood with reference to FIG. 3B, this positioning of the thermostat  68  substantially reduces the intermediate space  102  between the thermostat  68  and engine cylinders  26  and  28 , which are the most significant sources of heat in the engine  24 . The thermostat bracket  50  itself also improves heat relation by forming a direct structural link between the engine block  30  and the thermostat  68 , permitting the relation of conductive heat. Thus, the thermostat bracket  40  improves the communication of both conductive and convective heat between the engine block  30 , cylinders  32  and  34 , and the thermostat  68 , making the thermostat  68  more responsive to radiant heat resulting from increased engine temperatures. 
     The thermostat positioning depicted in FIG. 3B also allows the fan to cool the cylinders  26  and  28  without cooling the thermostat  68 . FIG. 3B depicts lines of flowing air  104  being blown over the cooling fins  32  and  34 . Due to the positioning of the thermostat  68  near the cylinders&#39; bases  36  and  38 , most of the flowing air  104  passes above the thermostat  68 . The bracket&#39;s location allows the thermostat  68  to continue operating the fan without the thermostat itself being significantly affected by the effects of the flowing air  104 . This minimizes the effect that the air  104  has on the thermostat&#39;s responsiveness, and may permit the fan to continue cooling the engine  24  for longer periods than previous configurations. 
     It will be appreciated that variations of the disclosed bracket design are also possible. For example, some models of motorcycle engines do not include a stud extending from the engine block near the bases of the engine&#39;s cylinders. Sufficient vertical clearance for the addition of a bracket to the engine block may be similarly lacking. Some models may also include lifter blocks which, due to their relative spacing, present no potential interference problems for mounting a thermostat bracket. Such engines lend themselves to slight variations in configurations of thermostat bracket assemblies without departing from the intended scope of the invention. 
     For example, FIG. 7 depicts a motorcycle engine  24   a  lacking a stud that extends from its engine block  30   a  between the cylinders  26   a  and  28   a . In order to properly mount the thermostat bracket  40   a  between the cylinders  26   a  and  28   a , a threaded mounting hole  106  must be added to the engine block  30   a . A threaded mounting bolt  108  is then be added to the bracket assembly  40   a  to attach the bracket  50   a  to the engine  24   a . An exploded view of such a bracket assembly  40   a  is depicted in FIG.  9 . The threaded bolt  108  extends through the attachment hole  56   a  of the bracket&#39;s attachment end  52   a . This allows the bracket  50   a  to be secured to the engine block  30   a  by screwing the threaded bolt  108  into the threaded mounting hole  106 . An inside washer  58   a  and an outside washer  60   a  are on either side of the attachment hole  56   a.    
     Some engines may not provide sufficient vertical clearance above the engine block  30   a  to enable the bracket  40   a  to fit near the bases of the cylinders  26   a  and  28   a . Such engines may require the use of a spacer  110 , to provide additional clearance between the bracket  50   a  and engine block  30   a . An additional spacer washer  112   a  may be positioned between the spacer  110  and engine block  30   a  in order to provide additional stability for the spacer  110 . 
     An additional variation of the engine  24   a  depicted in FIG. 7 includes increased spacing of the lifter blocks  86   a  and  88   a  away from the thermostat bracket  50   a . As shown, the spacing between the lifter blocks  86   a  and  88   a  and the thermostat bracket  50   a  is sufficiently large to prevent the blocks  86   a  and  88   a  from interfering with the proper mounting of the bracket  50   a . Therefore, it is not necessary to include shaved lower edges on the attachment end  52   a  of the bracket  50   a . The accordingly modified bracket  50   a  is depicted in FIG.  8  and incorporated into the assembled unit as shown in FIG.  7  and FIG.  9 . 
     Those skilled in the art will recognize that the various features of this invention described above can be used in various combinations with other elements without departing from the scope of the invention. Thus, the appended claims are intended to be interpreted to cover such equivalent thermostat brackets which do not depart from the spirit and scope of the invention.