Patent Publication Number: US-6659723-B2

Title: Fan for an engine driven generator

Description:
BACKGROUND OF INVENTION 
     The present invention relates generally to generator cooling, and more particularly, to an apparatus and method to stabilize a fan for cooling an engine driven generator. 
     Engine driven welding machines or welders generate considerable heat and noise during operation, which are undesired characteristics of the device. One source of heat generation in a welder is a generator which combines with other components to increase the temperature of the operating environment. Another undesirable byproduct of welder use is noise generation which occurs primarily due to the operation of a fan that cools the generator and an external engine that drives the generator. In a proper operating environment, the welder must have sufficient heat removed to keep the engine, generator, and other components at suitable operating temperatures. A failure to maintain the proper operating environment will result in the output of the welder becoming limited due to the rise in temperature, which is undesired. 
     Historically, noise emanates from the generator due to the rotation of the fan which operates to cool the generator. Prior art machines utilized different fans to produce airflows through the generator. Such fans were generally connected to a rotary shaft having a hub member at one end of the rotary shaft with a plurality of fan blades connected thereto. The fans were generally complete, unitary pieces with each of the fan blades and hub constructed from a metal, such as aluminum. Constructing the fan blades of a unitary metal material stabilized the fan during rotation and reduced vibrational noise. Some such prior art devices further include fins positioned on the fan blades that were spaced apart from one another and extend outwardly from the fan blades. 
     The prior cooling and noise reduction efforts for engine driven welding machine generators are not completely satisfactory. Constructing fan blades of metal materials such as aluminum and steel can be costly. Moreover, it is desirable to reduce noise generated by a welder to provide safer and user-friendlier operating conditions. Furthermore, excess noise due to vibration of the fan blades is also a concern. Rotation of the fan can result in increased noise levels at certain harmonic frequencies, which are a function of the size, shape, and materials that form the fan. 
     There is a need for an apparatus capable of reducing noise vibrations of a rotary fan during cooling of an engine driven welding machine generator in a more efficient manner than current fan configurations. It would therefore be desirable to have a more economical fan blade arrangement capable of preventing harmonic frequency vibrations from occurring in a fan. 
     BRIEF DESCRIPTION OF INVENTION 
     The present invention is directed to a system and method to cool an engine driven welding machine generator more economically and with reduced noise vibrations by stabilizing the fan blades about an annular lip of a hub rotated by a rotary shaft to overcome the aforementioned concerns. 
     The present invention includes a fan fixed to one end of a rotary shaft. Upon transmission of a driving force to the rotary shaft by a flywheel, the fan rotates to cool a generator, such as a generator of an engine driven welding machine. The fan is constructed of at least one fan blade segment that extends away from the rotating shaft and have a plurality of fins on the fan segments. Nearest protrusions are generally separated by respective arc distances such that at least two of the arc distances of the fan are unequal. A flex plate is also included to secure the fan blades to a hub. 
     In accordance with an aspect of the present invention, a fan is disclosed and includes a fan blade assembly having an inner arcuate end. The fan further includes a hub having an inner annular lip and an outer annular lip, the outer annular lip adapted to receive the inner arcuate end of the fan blade assembly. The fan also has a flexible plate having an aperture therethrough to receive the inner annular lip therein, the plate attached to the hub and fan blade assembly and configured to provide flexation to the fan blade assembly. 
     In accordance with another aspect of the present invention, a system for cooling an engine driven welding machine generator includes a rotary shaft having a first end rotatably attached to a generator housing. The rotary shaft is rotated by transmission of a driving force applied thereto by a flywheel through a flex plate. The system has a hub fastened to a second end of the rotary shaft and at least two fan blade segments configured to engage an outer annular lip of the hub. The flex plate is affixed to the flywheel and has at least two fan blade segments mounted thereto. The plate also has an aperture to receive an inner annular protrusion of the hub therein. 
     In accordance with the process of the present invention, a method to stabilize a fan for cooling an engine driven welding machine generator has two steps. One step includes positioning a number of fins to at least one fan segment such that adjacent fins have unequal spacing therebetween. The other step includes connecting the at least one fan segment between a hub and a plate. 
     Various other features, objects and advantages of the present invention will be made apparent from the following detailed description and the drawings. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     The drawings illustrate one preferred embodiment presently contemplated for carrying out the invention. 
     In the drawings: 
     FIG. 1 is an exploded perspective view of an engine driven generator. 
     FIG. 2 is a cross-sectional view of the engine driven generator. 
     FIG. 3 is a cross-sectional view of the rotor assembly of FIG.  1 . 
     FIG. 4 is an exploded perspective view of the fan and hub assembly of FIGS. 1-3. 
     FIG. 5 is a rear perspective view of the fan assembly of FIG. 4 assembled. 
     FIG. 6 is a perspective view of a portion of the fan assembly of FIG.  4 . 
     FIG. 7 is a perspective view of the hub of FIG.  4 . 
     FIG. 8 is a perspective view of the plate of FIG.  4 . 
     FIG. 9 is a detailed view of the fan assembly of FIG. 4 connected between the hub and plate. 
     FIG. 10 is a partial cross-sectional view of the fan blade connection between the hub and plate. 
     FIG. 11 is a perspective view of a crush zone of the fan segment of FIG.  6 . 
     FIG. 12 is a partial cross-section view of a crush zone of the fan segment of FIG. 6 having a fan blade bolt threaded therethrough. 
     FIG. 13 is an underside view of the fan segment of FIG.  6 . 
    
    
     DETAILED DESCRIPTION 
     Referring to FIG. 1, an exploded view of an engine driven generator  10  is shown. The generator  10  has a housing  12  having a plurality of air vents  14  encircling the housing  12  and a starter hole cover  16 . A wire mesh  18  having a pair of spring connectors  19  encloses the air vents  14  and prevents foreign objects from entering into the generator  10 . The generator  10  also has external and internal components that are fixed in position by screws  20  and washers  22 . Internal components include an o-ring  24 , a support assembly  26  mounted to the housing  12 , a brush holder assembly  28 , a small stator  30 , a large stator  32 , and an air baffle  34 . Other internal components include a rotor assembly  36  having a rotor ring  38 , a rotor bearing  40 , and a fan assembly for generator cooling  42 . The fan assembly  42  has a flex plate or plate  44  that is fastened to the rotor  36  by fan blade screw  46 , a pair of washers  22 , and a fan blade nut  48 . The rotor  36  is connected to a flywheel  50  which is further coupled to an engine (not shown). Threaded apertures  52  of the flywheel  50  receive four flex plate corner screws  54  that pass through four corner apertures  56  of the plate  44 . 
     FIG. 2 provides a cross-sectional view of an assembled generator  10  of FIG.  1 . Air vents  14  permit airflow through the interior of housing  12  during fan  42  operation to cool the generator&#39;s internal components, such as the small stator  30 , large stator  32 , and rotor  36 . Flex plate corner screw  54  secures the plate  44  to the flywheel  50 . In operation, the plate  44  is configured to rotate with the flywheel  50 , which causes rotation of the fan  42 . The fan  42  has a hub  58  press fit to a rotary shaft  60  that also rotate with the flywheel  50 . 
     Referring now to FIG. 3, a cross-sectional view of the rotor assembly  36  is shown. The rotor assembly  36  has a rotary shaft  60  having a first end in which fan  42  is mounted thereto. The rotor assembly  36  also includes standard components known to those skilled in the art, such as a pair of rotational field assemblies  63  having laminated steel plates  64  and copper metal windings  66 . Other standard rotor components include wire connectors  68  connecting wires  70 , a pair of slip rings  72 , and a single slip ring  74 . Additionally, adjacent a second end  76  of the rotary shaft  60  the rotor  36  has a rotor ring  38  and a rotor bearing  40  which accommodate rotation of the rotary shaft  60 . 
     FIG. 4 shows an exploded view of the fan and hub assembly of FIG. 1 having the hub  58  connected to the rotary shaft  60  at one end. The second end  76  of the rotary shaft  60  is connected to the rotor bearing  40  to support the rotary shaft  60  when driving forces are applied to the rotary shaft  60 . The fan assembly  42  includes a plurality of fan blade segments  78 , each having a plurality of fins  94  attached to a base  92 , attached to the flex plate  44 . In a preferred embodiment, four fan blade segments  78  are concentrically located about the plate  44 , and in one embodiment are equally spaced from one another. Each of the fan blade segments  78  has an arcuate inner end  80  that is positioned between the hub  58  and plate  44 . A plurality of hub apertures  82  and inner plate apertures  84  each have a hub screw  86  passing therethrough to secure the hub  58  to the plate  44 , and in a preferred embodiment are arranged such that ten screws are uniformly and circularly spaced around the hub  58 . In an alternative embodiment, the hub  58  and plate  44  may have tapped apertures to permit fastening of the components to each other and the fan blade segments  78  without the need of a nut. Fan blade screws  46  pass through outer plate apertures  88  and fan blade apertures  90 . The fan blade apertures  90  are located in the base  92  of the fan blade segment  78 , and preferably number two per fan blade segment  78  to improve the fan assembly&#39;s stability. Fan blade screws  46  are preferably uniformly and symmetrically spaced about the hub  58  to fix each of the fan blade segments  78  concentrically about the hub  58 . 
     Each of the fan blade segments  78  has a plurality of fins  94  for generating airflow during rotation of the fan assembly  42 . The fins  94  have a tapered end concluding at a reduced inner diameter  94   a  to accommodate hub  58  and a squared-off end  94   b  (shown in FIG. 6) to maximize airflow. In a preferred embodiment, the fan assembly  42  includes four arcuately shaped fan blade segments  78  formed of an elastomer material that combine to form a circle. In another embodiment, the plate  44  is constructed of steel and fan blade segments  78  are comprised of nylon with each of the segments  78  having four fins  94  integrally molded to the fan blade base  92 . In other embodiments, the fan blade segments  78  can be configured of more or less than four components, and the fan blade segments  78  can be constructed of plastic materials other than nylon. 
     FIG. 5 provides a rear view of an assembled fan assembly  42  showing the plate  44  mounted to the hub  58  and fan blade segments  78 . Hub screws or bolts  86  connect the plate  44  to the hub  58 . Similarly, fan blade screws or bolts  46  secure the fan blade segments  78  to the plate  44 . The four corner apertures  56  are used to connect the plate  44  to the flywheel  50 , which supports and drives the generator rotor  36 . The assembly forms a lightweight and inexpensive circular fan assembly for efficiently cooling a generator with reduced external noise generation. 
     Referring now to FIG. 6, one of the arcuately-shaped fan blade segments  78  of FIG. 4 is shown. The base  92  preferably has a pair of metal sleeves  93  having apertures  90  therethrough for fastening the fan blade segment  78  to the plate  44 . Crush zones  95  are adjacent and generally parallel to the metal sleeves  93  and extend upwardly therefrom. The annular crush zones  95  are configured to compress during mounting of the plate  44  to the fan blade segment  78 . Preferably, the crush zones  95  are formed of the same elastomer material as the fan blade segment  78 . The crush zones  95  prevent looseness or movement between each of the fan segments  78  and the surfaces that the fan segments are mounted to at tolerance limit conditions. Metal sleeves  93  prevent damage to the base  92  of the fan blade segment  78  during fastening of the fan blade screw  46  to the fan blade nut  48 . Contiguous fins  94  of the fan blade segment  78  have an arc distance  96  therebetween such that each of the arc distances between successive fins are unequal which has been found to reduce resonant noise vibrations. Such vibrations can occur at particular harmonic rotational frequencies of the fan. In particular, the harmonic frequencies will depend on the size, shape, and materials used to construct the fan. 
     In one embodiment, the fan blade segments  78  are formed identically and have unequal arc distances between successive fins  94 . However, other fan blade fin arrangements are contemplated wherein at least two of the defined arc distances  96  between the fins  94  of one fan blade segment  78  or differing fan blades are unequal. Likewise, although the fan blade segment  78  preferably includes two fan blade apertures  90  for securing the segment  78  to the plate  44 , single or multiple apertures can be utilized. 
     The inner arcuate end  80  of the fan blade segment  78  is designed to fit snuggly against the hub to provide stabilization between the hub and plate during operation. In one embodiment, the fins  94  are perpendicular to the base  92 . Other fin arrangements having the fins  94  at acute or obtuse angles to the base  92  are contemplated within the present invention. 
     A perspective view of the hub  58  of FIG. 4 is shown in FIG.  7 . The ten hub apertures  82  are concentrically located around a lower face  98  of the hub  58 . The hub  58  has an outer annular protrusion or lip  100  for receiving the tapered ends  80  of the fan blade segments  78 . Each of the fan blades engages a portion of a side wall  102  of the outer annular lip  100  such that the fins of the fan blade segments are essentially radially aligned from a center  104  of the hub  58 . The hub  58  also has an inner annular protrusion or lip  106  configured to engage the plate  44  along a side surface  108 . Inner annular lip  106  receives structural support from plate  44  during rotation of the fan assembly  42 . Preferably, the inner annular lip  106  is circularly shaped, although other geometric shapes can be implemented if desired. 
     FIG. 8 is a perspective view of the plate  44  of FIG.  4 . Apertures  56 ,  84 , and  88  permit the connection of the hub, fan blades, and flywheel together as previously discussed. The flex plate  44  is configured to deform or compensate for non-perpendicular alignments between the rotary shaft  60  and an engine crankshaft (not shown) during fan rotation. A circular opening or aperture  110  defines an inner edge or surface  112  of the plate that abuts at least a portion of the side surface  108  of the inner annular lip  106  to stabilize the hub  58 . Although a circular opening or aperture  110  is preferred, other geometrical shapes can be implemented with the present invention if the inner annular lip  106  of the hub  58  is geometrically contoured to match the shape of the aperture  110 . 
     Referring now to FIG. 9, a detailed view of the fan blade segment  78  of FIG. 4 is shown with the tapered end  80  of one fin  94  abutting the side wall  102  of the hub  58 . The fan blade segment  78  has a contact pad  114  (shown in FIG. 10) adjacent to the inner arcuate end  80  of the fan blade segment  78  to limit the contact area between the segment  78  and the flex plate  44 . 
     FIG. 10 is a partial cross-sectional view of the fan blade connection between the plate  44  and hub  58 . A crush zone  115  compresses during fastening of the hub screw  86  which causes the base  92  of the fan blade segment  78  to contact an upper surface  118  of the plate  44  to stabilize the fan blade. The tapered end  80  of the fan blade segment  78  fits snugly against an underside  120  of the outer rim  100  and side wall  102  of the hub  58  to further stabilize the fan and avoid looseness of the fan blade segments  78 . 
     Referring now to FIG. 11, a partial view of the base  92  of a fan blade segment  78  including an annular crush zone  95  is shown. The crush zone  95  extends above a pair of generally planar surfaces  122 , and can be crushed toward the planar surfaces upon assembly of the fan blade to the hub and plate. A raised collar  124  includes the planar surfaces  122  and provides support for the crush zone  95  during fan assembly. 
     FIG. 12 provides a partial cross-sectional view of a fan blade screw  46  connecting the fan blade segment  78  to the plate  44 . As fan blade screw  46  crushes the annular crush zones  95 , metal sleeves  93  limit the crushing of the crush zones  95  to prevent the head  126  of the fan blade screw  46  from contacting the planar surfaces  122  of the raised collar  124 . 
     An underside view of the fan blade segment  78  is shown in FIG. 13. A second contact pad  128  surrounds apertures  90  and is configured to combine with contact pad  114  to prevent the plate from contacting an underside surface  130  of the fan blade segment during fan assembly. Preferably, contact pad  114  includes three crush zones  115  that assist with preventing looseness of the fan blades. In alternative embodiments, each fan blade segment  78  may have more or less than three crush zones  115  connected to the contact pad  114 . 
     In accordance with an aspect of the present invention, a fan comprises a fan blade assembly having an inner arcuate end. The fan includes a hub having an inner annular lip and an outer annular lip, with the outer annular lip adapted to receive the inner arcuate end of the fan blade assembly. The fan blade assembly may include a plurality of fan blade segments, each mounted to a flexible plate with a gap therebetween. The flexible plate has an aperture therethrough to receive the inner annular lip therein, and is attached to the hub and fan blade assembly. The plate is configured to provide flexibility to the fan blade assembly. 
     In accordance with another aspect of the present invention, a system for cooling an engine driven welding machine generator includes a rotary shaft having a first end rotatably attached to a generator housing and being rotated by transmission of a driving force applied thereto by a flywheel. The system has a hub fastened to a second end of the rotary shaft and at least two fan blade segments configured to engage an outer annular lip of the hub. The system further includes a plate affixed to the flywheel and having the at least two fan blade segments mounted thereto. The plate has an aperture to receive an inner annular protrusion of the hub therein. 
     In accordance with the process of the present invention, a method to stabilize a fan for cooling an engine driven welding machine generator includes the steps of positioning a number of fins to at least one fan segment such that adjacent fins have unequal spacing therebetween and connecting the at least one fan segment between a hub and a plate. Alternatively, the method may also include the step of segmenting at least one fan segment into a plurality of fan segments and concentrically positioning the fan segments around the hub with a given spacing therebetween. 
     The present invention has been described in terms of the preferred embodiment, and it is recognized that equivalents, alternatives, and modifications, aside from those expressly stated, are possible and within the scope of the appending claims.