Abstract:
A portable engine driven welder is provided that has a case enclosing an internal combustion engine and a welding generator, and a running gear that is attached to the case. The running gear includes a pair of rails and a pair of leading wheels connected to the rails toward the back wall of the case. A pair of trailing wheels is connected to the rails toward the front wall of the case. The leading and trailing wheels have different resiliency values with the leading wheels being more resilient or flexible than the trailing wheels. This allows the leading wheels to act like a suspension system for the portable engine driven welder and running gear by soaking up or absorbing impacts instead of transmitting them therethrough so as to reduce exposure of the portable engine driven welder to such impacts.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This utility patent application claims the benefit of and priority to U.S. provisional application 61/122,996, filed Dec. 16, 2008, entitled CART FOR A WELDER; WELDER/CART COMBINATION, which is herein expressly incorporated by reference in its entirety, for all purposes. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to engine driven welders and, more specifically, to engine driven welders having running gears to facilitate movement of such engine driven welders. 
     2. Discussion of the Related Art 
     A need to move welding equipment has been long recognized. Various running gears have been provided for suitably moving welding equipment around in a welding shop or other fabricating facility. Such facilities usually have substantially flat floor surfaces, whereby caster-like wheels have been successfully implemented into running gears for rolling the welding equipment across these flat floor surfaces. 
     At times, needs arise to transport welding equipment to jobsites, that is, away from the fabricating facilities which are purposefully set up for such welding-related tasks. In such instances, engine driven welders are often used because they are stand-alone welding machines that generate their own electrical current and therefore do not have to be plugged into a power source or outlet. Correspondingly, such engine driven welders, with their stand-alone capabilities can be moved to a jobsite. 
     Engine driven welders can be quite large and heavy, whereby they are at times installed upon a vehicle such as a work truck that is driven to the jobsite. Once the work truck is driven to the job site, the engine driven welder is often left mounted to the work truck and long weld cables are routed to a particular work piece to conduct a welding current, generated by the engine driven welder, to the work piece. Such long weld cables can be heavy and expensive. 
     Accordingly, efforts have been successfully made to improve engine driven welder technology so that smaller and lighter units had high enough welding performance output capability to make such engine driven welders portable, not only to the jobsites on work trucks, but also at least somewhat portable at the jobsites themselves. This allowed users to manually push or otherwise move the engine driven welders closer to the particular work pieces being welded, allowing the users to implement shorter weld cables which may reduce welder performance losses that can exist as a function of weld cable length (for the same weld cable diameter). 
     Attempts have been made to enhance portability of such engines driven welders by making them easier for the users to maneuver. For example, it is known to mount an engine driven welder to a cart or undercarriage that has suspension components and/or a steerable axle. Another known cart or undercarriage includes a closely spaced pair of wheels, with smaller wheels being provided toward a front of the undercarriage&#39;s base. An elongate push bar is connected to the base of the undercarriage and is located opposite the smaller front wheels in a manner that allows a user to lift the smaller front wheels by pushing down on the elongate push bar. Such carts or undercarriages have proven largely successful at increasing manual portability of engine driven welders. 
     Notwithstanding, devices that further improve manual portability of engine driven welders could prove desirable. 
     SUMMARY AND OBJECTS OF THE INVENTION 
     In light of the foregoing, a portable engine driven welder is provided that has a case enclosing an internal combustion engine and a welding generator, and a running gear that is attached to the case. The running gear includes a pair of rails and a pair of leading wheels connected to the rails toward the back wall of the case. A pair of trailing wheels is connected to the rails toward the front wall of the case. The leading and trailing wheels have different resiliencies, with the leading wheels being more resilient than the trailing wheels. This allows the leading wheels to act like a suspension system for the portable engine driven welder and running gear by soaking up or absorbing impacts instead of transmitting them therethrough so as to reduce exposure of the portable engine driven welder to such impacts, and making it easier for a user to push across uneven terrain. 
     In some aspects, the leading wheels are larger, for example, having larger diameters, than trailing wheels. The leading and trailing wheels can have central wheel segments with tires mounted thereto, and the tires on the leading wheels can have taller sidewalls heights. Some implementations have pneumatic tires and, in these implementations, the tires on the leading wheels can be inflated to a lower operating pressure or lower PSI (pounds per square inch) than the tires on the trailing wheels. Larger tire diameters, larger tires widths, taller sidewall heights, particular sidewall thickness dimensions, lower operating pressures, and/or other factors can contribute to the leading wheels having greater resiliency values than the trailing wheels. 
     According to yet other aspects, larger diameter leading wheels can help the leading wheels roll over obstacles instead of having to be lifted up and over. Such configuration reduces the amount of times that, or reduces the extent to which, an operator has to push down on the engine driven welder in order to lift the leading wheels upwardly to climb over obstacles. The larger leading wheels may climb up at least some such obstacles by merely rolling over them. 
     In some aspects, the leading wheels have larger footprints or contact patches defined between them and the underlying ground surface than do the trailing wheels. The smaller contact patches of the trailing wheels may, in some instances, improve maneuverability of the engine driven welder by allowing a user to laterally or transversely skid the trailing wheels across the underlying ground surface in order to (re)point the engine driven welder in a desired travel direction. 
     According to yet other aspects, the rails can include front tapering segments that extend upward and angularly, tangentially or otherwise, in front of the leading wheels. Such front tapering segments may protect the leading wheels from impacting certain relatively tall obstructions. The front tapering segments may further provide skid or ramp-like structures than allow users to slide the engine driven welder up tall obstacles before the leading wheels can engage and roll over such obstacles. The front tapering segments may cooperate with the leading wheels, such that obstacles that would otherwise be contacted at or near a front axle height of the leading wheels, which would be difficult for the wheels to roll over, can be at least partially slid up, pushed up, glanced up, or skidded up, by way of the front tapering segments, so that such obstacle then contacts a lower portion of the leading wheels. This can make the obstacle easier to roll or climb over, at that point, by contacting portions of the leading wheels that are spaced further below their axis of rotation, which makes rotating the leading wheels easier. 
     The engine driven welder may also be provided with a running gear that has relatively few moving parts requiring maintenance. The engine driven welder and running gear may also be substantially devoid of structure(s) extending outwardly beyond a perimeter of the engine driven welder that would otherwise occupy space at a jobsite in an area around the engine driven welder. 
     Other various features and advantages of the invention will become apparent to those skilled in the art from the following detailed description and accompanying drawings. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the present invention, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A clear conception of the advantages and features constituting the present invention, and of the construction and operation of typical mechanisms provided with the present invention, will become more readily apparent by referring to the exemplary, and therefore non-limiting, embodiments illustrated in the drawings accompanying and forming a part of this specification, wherein like reference numerals designate the same elements in the several views, and in which: 
         FIG. 1  is a pictorial view of an engine driven welder and running gear of the present invention; 
         FIG. 2  is an exploded, pictorial, view of engine driven welder and running gear of  FIG. 1 ; 
         FIG. 3  is a side elevation view of a variant of the engine driven welder and running gear of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS. 1 and 2  show portable engine driven welders, e.g., welders  1 , each including a protective cage  50  and a running gear  100 . The welder  1  includes an internal combustion engine and a welding generator  7  that are housed within a case  10 . A suitable such welder  1  can include any of the Bobcat™, Legend®, and Trailblazer® Series from the Miller Electric Manufacturing Company, in Appleton, Wis. The case  10  includes a bottom wall  11 , a pair of sidewalls  12 ,  14  that extend upwardly from side edges of the bottom wall  11 . A back wall  16  extends between and interconnects the sidewalls  12 ,  14  at a back end of the case. A front wall  18  extends between and interconnects the sidewalls  12 ,  14  at a front end of the case. Front wall  18  houses the controls for the welder  1  and typically faces away from a direction of travel, so that they are less susceptible to impact-induced damage than they would be if they faced toward the travel direction. 
     Still referring to  FIGS. 1 and 2 , protective cage  50  is connected directly to the case  10  and includes back and front handles  56  and  58  that overlie outer perimeters of the back and front walls  16  and  18 , respectively. Crossbars  62  and  64  extend between the back and front handles  56  and  58 , connecting the back and front handle  56 ,  58  to each other, and above the sidewalls  12 ,  15 . In some embodiments, the protective cage  50  further includes hooks  60  for hanging or otherwise storing, for example, weld cables and/or other welding accessories. It is noted that the protective cage  50  need not cover the entire welder  1 , as illustrated. Instead, in some embodiments, a single handle  58  is provided, without the other handle  56  or crossbars  62 ,  64 . 
     Running gear  100  supports the welder  1  and its optional protective cage  50 , while facilitating movement of the welder  1  over uneven terrain, for example, in some embodiments, rolling up and over various obstacles. Running gear  100  includes a pair of rails  110 ,  120  and two pairs of wheels, namely, a pair of leading wheels  150  and a pair of trailing wheels  170 . 
     Each rail  110 ,  120  includes a horizontal leg that attaches to outer segments of the bottom wall  11  and an upright leg that extends perpendicularly down from an outer edge of the horizontal leg, whereby the rails  110 ,  120  define an L-shaped profile when viewed from a front or rear elevation. 
     Referring now to  FIGS. 1-3 , a length of the rails  110 ,  120  is less than a length of the case. The rails  110 ,  120  can be longitudinally centered under the case  10  so that the ends of the case  10  project beyond the corresponding ends of the rails  110 ,  120 . Perhaps best seen in the exploded view of  FIG. 2 , each of the rails  110 ,  120  includes a front tapering segment  112 ,  122  that extends angularly from a bottom edge of the rail  110 ,  120  toward the back wall  16  of the case  10 . At the other end of the rail  110 ,  120 , a rear tapering segment  114 ,  124  extends angularly from the bottom edge of the rail  110 ,  120  toward the front wall  18  of the case  10 . 
     The rear tapering segment  114 ,  124  can be longer than the front tapering segment  112 ,  122 , whereby the rear tapering segment  114 ,  124  may extend across more of the rail  110 ,  120  than the front tapering segment  112 ,  122 . For example, the rear tapering segment  114 ,  124  extends more than half-way along the length of the rail  110 ,  120 , from the back toward the front. In contrast, the front tapering segment  112 ,  122  extends less than half-way along the length of the rail  110 ,  120 , from the front toward the back. As for the relative lengths of the rear tapering segment  114 ,  124  as compared to those of the front tapering segment  112 ,  122 , in some embodiments, the rear tapering segment  114 ,  124  can be at least two times longer, or at least five times longer, than the front tapering segment  112 ,  122 . 
     Referring yet further to  FIGS. 1-3 , a maximum height segment  132 ,  134  may extend between the front and rear tapering segments  112 ,  122  and  114 ,  124 . The maximum height segment  132 ,  134  has a bottom edge that is substantially parallel to the upper edge of the rail  110 ,  120  defined at the corner between the horizontal and upright legs of the rail  110 ,  120 . In this regard, the maximum height segment  132 ,  134  can have a rectangular profile shape while the front and rear tapering segments  112 ,  122  and  114 ,  124  have angled or somewhat triangular profile shapes. 
     Referring now to  FIG. 2 , regardless of the particular configuration of the rails  110  and  120 , they may serve as mounting structures for supporting axles such as leading axle  140  and trailing axle  145 . Leading axle  140  is mounted toward the front tapering segments  112  and  122 , extending through aligned bores in the rails  110  and  120 , respectively. As seen in  FIG. 2 , the leading axle  140  can be located within the maximum height segments  132  and  134 , adjacent the front tapering segments  112  and  122 , while also being located adjacent the top edge of the maximum height segments  132  and  134  or near the horizontal legs of the rails  110  and  120 . 
     Referring still to  FIG. 2 , trailing axle  145  is mounted within the rear tapering segments  114 ,  124  extending through aligned bores in the rails  110  and  120 , respectively. Trailing axle  145  can be located, longitudinally, in about the middle of the rear tapering segments  114  and  124 , while being adjacent a lower edge of the rear tapering segments. 
     Referring now to  FIGS. 2 and 3 , a pair of leading wheels  150  is rotatably mounted to the leading axle  140 , and a pair of trailing wheels  170  is mounted to the trailing axle  145 . Regarding their particular placement along a length of the welder  1 , leading wheels  150  are connected to the rails  110  and  120  at locations upon the rails that are closer to the back wall  16  of the case  10  than they are to the front wall  18 . The leading wheels  150  can be positioned rather close to the back wall  16  of the case  10  so that the leading wheels  150  are longitudinally spaced from the back wall  16 , or a plane projecting therefrom, by a distance that is less than a radius of the leading wheels. The trailing wheels  170  are connected to the rails  110  and  120  at locations upon the rails that are closer to the front wall  118  of the case  10  than they are to the back wall  16 . 
     Referring specifically to  FIG. 3 , the leading wheel  150  is positioned along the length of the rail  110  such that the front tapering segment  122  extends angularly in front of the leading wheel  150 . When viewed from a side elevation, the bottom edge of front tapering segment  122  extends from, or appears to intersect, a lower portion of the leading wheel  150 , for example, a lower ½, a lower ⅓, or a lower ⅕ of the leading wheel  150 . The leading wheel  150  can also extend entirely across the maximum height segments  130  of rail  110 , extending from the intersection with the front tapering segment  122 , and extends partway across a front-most portion of the rear tapering segment  124 . In this configuration, the front and rear tapering segments  122  and  124  emerge from behind the leading wheel  150  at different heights, with the rear tapering segment  124  emerging from higher up on the leading wheel  150 . It is, of course, understood that although such placement is discussed only in terms of the right side or the rail  110  side of the welder  1  and running gear  100 , the same is equally applicable to the other side, that is, the left side or rail  120  side of welder  1  and running gear  100 . 
     Referring again to  FIGS. 1-3 , leading wheels  150  are larger in diameter than the trailing wheels  170 . For example, outside diameters of the leading and trailing wheels  150  and  170  can be about 14.5 inches and 10.25 inches, respectively, although it is noted that other diameters are contemplated in which the leading wheels  150  are, preferably, larger than the trailing wheels  170 . 
     The leading and trailing wheels  150  and  170  may be adapted to at least partially provide desired handling and/or other performance characteristics to the running gear  100  while moving welder  1 . For example, the leading wheels  150  can have greater resiliencies than the trailing wheels  170 . In this regard, leading wheels  150  can be softer or more pliable and therefore more easily compressible, deflectable, and/or otherwise deformable than the trailing wheels  170 . Accordingly, a pliability differential may be defined between the leading and trailing wheels  150  and  170 . This allows the front wheels  150  to perform suspension-like duties for the running gear  100  and welder  1  by resiliently isolating them from, or floating them over, discontinuous surface characteristics of the underlying terrain while moving across such terrain. 
     Still referring to  FIGS. 1-3 , the pliability differential between the leading and trailing wheels  150  and  170  can be suitably accomplished in any of a variety of ways. For example, in some embodiments, the leading and trailing wheels  150  and  170  include central wheel segments  152  and  172 , respectively, and tires  155  and  175  are mounted to the central wheel segments  152  and  172 . The pliability differential between the leading and trailing wheels  150  and  170  can be achieved by adapting the tires  155  and  175 , accordingly. 
     In some embodiments, the tires  155  and  175  can be solid tires, that is, being a solid web of material that radiates outwardly from the central wheel segments  152  and  172  or otherwise having substantially no void space within their interiors. For such solid tire versions, tires  155  of leading wheels  150  can be either made from a more pliable material tires  175  of trailing wheels  170 , or can have a thicker radial cross-section (greater diameter) of the same material as trailing wheel tires  172 , such that the additional material provides more overall compressive capability to the leading wheels  150 . 
     As another example, the tires  155  and  175  can be pneumatic or gas filled instead of solid. In these versions, the pliability differential may be established by filling the leading tires  155  to a lower operating pressure than the trailing tires  175  and/or configuring the leading tires  155  to provide greater pliability than their trailing tire  175  counterparts. In other words, leading tires  155  can have thinner sidewalls transverse dimensions, thinner outer circumferential surfaces, and/or taller sidewall heights or taller sidewall profiles, when compared to those of trailing tires  175 . Any of such characteristics may contribute to the leading tires  155  being more pliable than the trailing tires  175 . For example, in some embodiments, leading tires  155  are rated for and filled to an operating pressure of about 38 PSI, while the trailing tires  175  are rated for a filled to an operating pressure of about 50 PSI. In these embodiments, the trailing tires  175  define operating pressures that are at least about 30% greater than, optionally at least about 25% greater than or 20% greater than, operating pressures of the leading tires  155 . Referring further to  FIGS. 1-3 , the softer or more pliable leading wheels  150  will conform to and grip an underlying terrain or obstacle to a greater extent than the trailing wheels  170 . Such leading wheel  150  grip superiority can be further enhanced by providing a larger footprint or contact patch than the trailing wheels  170 , with a contact patch being defined as an interface area between the wheels  150 ,  170  and an underlying surface of the terrain. The larger contact patch of leading wheels  150  can be a function of the more pliable material characteristics of the leading wheels  150 , whereby they conform and spread out over the terrain across a larger area. However, in preferred embodiments, the larger contact patch of leading wheels  150  is also a function of a larger geometric size of the leading wheels  150 , for example, width and/or diameter, when compared to the trailing wheels  170 . 
     While the invention has been shown and described with respect to particular embodiments, it is understood that alternatives and modifications are possible and are contemplated as being within the scope of the present invention. Many changes and modifications could be made to the invention without departing from the spirit thereof. The scope of these changes will become apparent from the appended claims.