Abstract:
An excavator undercarriage frame is made to reduce the amount of machining necessary for supporting a swing bearing and ring gear on which an upper swing platform including the cab and operator&#39;s platform are mounted. The frame is made in two separate frame sections having top plates and formed peripheral skirts that nest together to form a planar support on which the base ring of a swing bearing and ring gear are mounted. The frame section plates are thin enough so that they will flex to conform to the base ring of the swing bearing, so it is not necessary to provide a machined surface for the swing bearing. The frame sections are welded together only around the peripheral edges and skirts, so that the distortion in the plates is substantially eliminated. The plates can be then bolted or secured directly to the bearing base ring, preferably using a clamp ring on the bottom of the frame plates and will provide an adequate support with the two plate thicknesses, and will be true and square without machining.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part of U.S. patent application Ser. No. 09/260,240, filed Mar. 2, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to an undercarriage frame structure for an excavator or power shovel that provides proper support for a bearing and ring gear of an excavator upper structure without machining the frame, resulting in reduced manufacturing costs. The frame is used for supporting additional components for mounting the tracks that propel the excavator, and auxiliary equipment such as a backfill blade. 
     In the prior art, mini excavators or small power shovels are widely used. These are track propelled vehicles that have an undercarriage mounting the track and accessory items, and including a frame with a horizontal surface on which a bearing and ring gear that supports a rotatable turntable plate is mounted. The turntable mounts a cab and operator&#39;s platform, as well as the excavator bucket. The existing undercarriage frame that mount the bearing and a ring gear typically is a very thick or heavy plate that has a machined surface on which the bearing support is mounted, in order to obtain a surface that is flat and perpendicular to the vertical axis of rotation. The plate is large and heavy, making it difficult to handle and time consuming to machine, which increases the manufacturing costs. Since the bearing support ring is quite heavy as well, any portion of the surface on the heavy plate that is out of true will cause the bearing to be inaccurately located. 
     Various types of frames have been advanced, but the need for machining has been a source of extra cost for years. 
     SUMMARY OF THE INVENTION 
     The present invention relates to an undercarriage for an excavator which supports a rotatable upper plate mounting a platform and a working implement, such as an excavator bucket, and provides a support for drive and propelling structure for the excavator. The undercarriage includes a frame having a support plate for supporting a swing bearing and ring gear used for mounting the upper plate and the excavator bucket, without machining subsequent to welding the frame together. 
     The frame is made up of two frame sections having flat top plates with integral depending skirts on the sides thereof. The plates and skirts will nest together, so that the plates that support the bearing are contiguous. The skirts of the plates are then welded together without any welding in the center plate portions of the frame sections. This minimizes any distortion of the plates, and leaves the center portions flat for mounting the bearing, including the ring gear. 
     To insure conformance of the top plates and to clamp the ring gear tightly, a reinforcing or backing ring is preferably placed on the bottom side of the top plates and the ring gear bearing bolts passed through the ring. The reinforcing ring, when needed, provides a flattening action on the bottom one of the frame plates and holds the lower plate planar. 
     Components for supporting the tracks and accessories such as a backfill blade can be mounted onto the frame without causing distortions in the plates. When the bearing and ring gear are bolted in place, the two plates, which have lower individual bending strength in the center portions than the present unitary thick plate, will permit slight shifting to conform to the bearing base without distorting the bearing so that the bearing will be held positively, and true without machining the upper surface of the frame. 
     The frame assembly or welding is made of two formed frame sections, each comprising a rolled steel plate and integrally die formed depending skirts. The frame sections can be formed quite precisely, and when welded together along the skirts, and the corners (but not on the flat plates forming the center) the frame sections will be securely held as an assembly without inducing unnecessary welding stresses and consequent distortions into the support area for the bearing and ring gear. The skirts of the frame sections also are welded to a bottom plate that forms a box section for rigidity. Cross tubes or sockets for holding the track supports are welded in the lower sides of the frame section skirts and also added rigidity. 
     The track supports of the present device are slidably mounted in cross tubes on the frame assembly. The track supports will telescope for changing the width or tread of the tracks. A hydraulic cylinder is mounted between the tubes on the frame and extends laterally so when operated it will move the tracks laterally in or out as desired. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic side view of a typical excavator utilizing the undercarriage or chassis of the present invention; 
     FIG. 2 is a fragmentary schematic perspective view of the undercarriage assembly, showing the tracks in place, and with a backfill blade supported on the undercarriage frame assembly; 
     FIG. 3 is a perspective view of the undercarriage frame assembly shown in FIG. 2; 
     FIG. 4 is a top plan view of the frame assembly of FIG. 3; 
     FIG. 5 is a sectional view taken as on line  5 — 5  in FIG. 4; 
     FIG. 6 is a front elevational view of the frame assembly of FIG. 4; 
     FIG. 7 is an exploded view of the frame sections or components of the frame assembly, including support plates for a swing bearing race; 
     FIG. 8 is a bottom plan view of the undercarriage assembly of FIG. 3; and 
     FIG. 9 is an enlarged sectional view of a bearing assembly as supported on the frame of the present invention and taken on line  9 — 9  in FIG.  2 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A self-propelled power excavator or power shovel illustrated generally at  10  has an undercarriage  12  comprising a lower frame and drive assembly and an upper rotatable platform assembly  14  which supports a pivotally mounted two section boom  16  with a bucket  18  at the outer end thereof. The boom sections are operated with hydraulic actuators shown generally at  20  for moving the boom sections about horizontal pivots. The bucket  18  is also operated with a hydraulic cylinder  21 . An operator&#39;s cab area  22  moves with the upper rotatable platform assembly  14 , and includes a housing for an engine  24  to provide power. The platform assembly  14  is mounted to the undercarriage  12  through a swing bearing  26 . The undercarriage  12  supports ground engaging tracks  28  that would be driven from a suitable drive arrangement such as hydraulic motors operated from a pump driven by the engine  24 . 
     The excavator shown in FIG. 1 is a typical example of the type of excavator or power shovel that would utilize the undercarriage having a frame assembly made according to the present invention for supporting one race and a ring gear of the swing bearing  26 . 
     FIG. 2 is a schematic view of the undercarriage  12  with the platform assembly  14  removed. The tracks  28  are shown on opposite sides of the center frame assembly  30 , which will be described in detail, which mounts the swing bearing  26  on the center frame assembly  30 . The tracks  28  have conventional track support frames  35  which are attached to and supported on square tubes  34  that insert into tubes  51  of the center frame assembly. Tubes  34  are on both sides of the frame and can be telescoped laterally in and out through the use of a laterally extending hydraulic actuator  36  shown in FIG.  2  and in cross section in FIG.  5 . The actuator  36  and the track support tubes  51  are shown only schematically, but the actuator  36  connects to the track frames  35  and extends through clearance openings in the side walls of the center frame  30 . The actuator  36  has its base end connected to one frame  35  and the rod end is connected to the other frame  35  so that upon operating the actuator,  36  the tracks can be spread apart or moved together while telescoping tubes  34  slide in tubes  51 . 
     The track support frames  35  are made in a conventional manner, and include sprockets shown at  38  mounted onto the frames  35  and driven to a suitable drive motor, such as a hydraulic motor. Suitable tensioning devices  40  for keeping the tracks under tension also can be provided on the track frames  35 . 
     The undercarriage center frame assembly  30  can support a backfill blade  42 , which is mounted onto support arms  44  that attach to brackets  46  that, as will be explained, are welded onto the center frame assembly  30  during assembly. The blade  42  can be raised and lowered relative to the pivots between the arms  44  and the brackets  46  through the use of a hydraulic actuator shown at  48  which has a base end attached to the blade  42 , and a rod end attached to a bracket  50  that also is mounted on the center frame assembly  30 . 
     In prior art excavators, the undercarriage center frame assembly  30  is made of parts including a very heavy top plate that is immediately underneath the bearing assembly  26 , to support the bearing assembly. The conventional heavy top plate requires machining after components such as the brackets  46  and  50  and track support tubes  51  for the slide tubes  34  mounting the track assemblies are welded in place. 
     The center frame  30  of the present invention is constructed to avoid the need for machining support surfaces for the bearing assembly  26 . As shown in FIGS. 3,  4 ,  5  and  6 , the frame assembly  30  includes a base frame weldment  52  that is constructed in a manner such that it avoids the need for machining the upper surface. The frame weldment  52  is made of three basic parts, as shown in FIG. 7, including a formed top frame section  54 , a lower frame section  56  which mates with the top frame section and which is welded thereto, and then a bottom cover plate  58 , which is supported on and welded to the lower frame section  56 . 
     First referring to the top frame section  54 , it can be seen that it has a top plate  60  with an opening  62  in the center, and formed guides  63  that are used for holding or stopping desired parts. The plate  66  of frame section  54  has integrally formed downwardly sloping front and rear skirts or wall members  64  and  66  and side skirt members  68 . At the corners of the top plate  60 , there are recesses  70  cut out, when the edges of the skirt are formed. The lower edges  72  and  74  of the skirt  68  are formed in an irregular pattern for clearance and welding. 
     The lower frame section  56  has a plate  76  made to be contiguous with and below the top plate  60  of the top frame section  54 . Plate  76  has a center opening  78  with guides  80  that match the opening  62  and the guides  64 . The frame section  56  has a slightly smaller size than the top frame section  54 , so that it will nest inside of the skirts or side walls  64 ,  66  and  68  and plates  60  and  76  engage or nest flat against each other. The lower plate  76  has a front skirt member  82  that is integrally die formed to depend from the plate  76 . A rear skirt member  84  is integral with and also depends from the rear edge of the plate  76 . The side edges of the lower plate  76  have integral depending skirts  86  thereon, which have peripheral edges  88  and  90  that are different in configuration and span a greater front to rear length than the edges  72  and  74  of skirts  68  the top frame section  54 . The depending side skirts  68  and  86  on the upper sides of the frame section in FIG. 7 can be seen through the openings  62  and  78 . Thus as shown skirts bound the periphery of the plates, but in some instances only two skirts will work. 
     The top and lower frame sections  54  and  56  will nest together, as stated, and it can be seen that the skirts of frame section  54  overlie and mate with the skirts of frame section  56 . The skirts of frame section  54  are shorter than the skirts of frame section  56  when the plates  60  and  76  are contiguous or rest against each other with holes or openings  62  and  78  in registry. This leaves edges of skirts  64 ,  66  and  68  for welding to skirts  82 ,  84  and  86 . 
     As can be seen a plurality of holes  92  are provided in both of the plates  60  and  76 , and the holes  92  will also align when the frame sections are nested together. The top frame section  54  and the lower frame section  56  are nested together, and the top frame section skirts will be resting on or very closely adjacent the lower frame section skirts. They are welded together along the peripheral edges of the top skirt, including in the corners and recesses  70 . There is no welding on the plates  60  and  76  in the preferred form. 
     Once the top frame section  54  and the lower frame section  56  are nested, the track supports and bottom cover plate  58  are assembled and welded in place. Bottom plate  58  has a planar center portion  100 , and upstanding flanges  102  that will fit outside the lower edge portions  104  of the skirts  82  and  84 , respectively. The parts are welded together so that the frame  30  has box section rigidity. 
     Before the bottom plate  58  is welded in place, the supports  51 , that are inverted channels are placed in recesses  88  and  90  of the side skirt  86  of lower frame section  56 , and are welded in place along the edges of the recesses so that they are held by the skirts of this lower frame section  56 . When the bottom plate  58  is welded into place, the weldment forms tubular openings  110  and  112  (see FIG. 3) in which the track support assemblies can be mounted using the telescoping tubes  34 . 
     When the top frame section  54  and the lower frame section  56  are welded together, the plates  60  and  76  are contiguous. They can be clamped together when welding takes place so that they touch along substantially their entire surfaces, and the holes  92  in each of the plates are aligning. This also then aligns the openings  78  and  62 . This is shown in FIG.  3 . 
     The skirts  86 , as can be seen, have clearance openings for components, as well as for the channel shaped supports  51  and  53 , and the edges  72  and  74  of the skirts  68  are recessed around clearance openings. Welding is along the edges  72  and  74  so that the skirts  68  and the skirts  86  are securely held together all along the periphery of the skirts  68 . Welding continues between the skirts along all four corners as shown at  114  (FIG.  3 ), so that all edges of the skirts  68  are held in place. The welding at the front, continues down along the edges  116  to provide strength. There are weld lines along the lower edges of skirts  64  and  66  to weld to the front and rear skirt  82  and  84  of lower frame section  56 , including along the side edges, so that the parts are securely welded together at the skirt portions, but the top plates  60  and  76  are not welded. The flanges  102  of bottom plate  58  are welded to the lower edge portions  104  of skirts  82  and  84 . 
     The front skirts  64  and  82  have openings  122  that are used for mounting additional parts, and these are left unwelded, but if desired, openings can be provided so that welds can be made along the edges of openings. However, no welding is done in the center portions of the plates  60  and  76 . 
     The conventional plates that are provided on the center frame are extremely heavy, and had to be machined to support a bearing ring. The heavy top plate did not have depending skirts, and was supported on a welded frame assembly. The support plate had a thickness of 1.58 cm, or in the range of ⅝ inch. The plates in the formed frame section of the present invention, comprising the upper and lower frame sections  54  and  56  are each usually in the range of 0.635 cm or ¼ inch. 
     Referring to FIG. 9, an enlarged view through the bearing assembly is provided, and it can be seen that the upper plate  60  and the lower plate  76  have aligning bores  92  therein, around the openings  62  and  78 . The bearing assembly  32  includes the inner bearing race or base ring  130  that is an annular ring and which has teeth  132  forming a ring gear thereon, against which a pinion gear  134  that is mounted for driving with a motor  136  will drive. The pinion  134  is mounted on the platform plate  144  of the upper platform assembly  14 , so that as the pinion  134  is rotated, the upper platform assembly will rotate relative to the ring  130  through the outer race  138  forming part of the bearing assembly  26 . As can be seen, the outer race is supported in place on the inner race or base ring  130  with a series of balls  140 . 
     The vertical height of the inner race or base ring  130  may be in the range of 32 mm or about 1 ¼ inches. A heavy reinforcing ring  143  (for example in the range of ⅝″ thick) is placed below lower plate  76 , aligned with base ring  130 . The reinforcing ring is annular and extends around the openings  62  and  78  and has bolt holes in a circle to match holes  92  as shown in FIG.  7 . The ring  130  and reinforcing ring  193  are then clamped tightly against the upper surface of the upper plate  60  and the lower surface of lower plate  76  with bolts  142  that pass through the aligning openings  92  in plates  60  and  76  and can be tightened using a nut on the bottom of the reinforcing ring  143 . 
     Since the plates  60  and  76  are relatively thin, compared to the heavy bearing ring and reinforcing ring, the plates can shift or flatten slightly if necessary to seat the bearing inner race or base ring  130  securely, as it is clamped, and provide good alignment for the two portions of the bearing. The tightening of the bolts  142  clamps plate  60  against the bearing ring and the reinforcing ring  143  clamps plate  76  against plate  60 . The reinforcing ring  143  distributes compression forces across the bottom of plate  76  to make the plate  76  less likely to bulge between the bolts  142 . 
     If the plates  60  and  76  are slightly wavy (rolled steel plate having a good finish is used for the frame sections  54  and  56 ) the waviness can be accommodated since the plates will conform because they can individually flex slightly as the bolts  142  are tightened down. 
     The outer race  148  of bearing  26  is fastened to platform plate  144  forming a part of the upper platform, using capscrews  146  that thread into bores in the bearing race  138  as shown. 
     The center frame is thus easily formed, and welded as an assembly, and can be used for mounting the bearing and ring gear assembly without machining. The welding is omitted from within the peripheral edges of plates  60  and  76  where the skirts join. The frame sections are die formed and the plates can be held flat with the heavy bearing ring and the reinforcing ring, while the integral skirts are also held to close tolerances so they nest precisely. 
     It should be noted that housing lock brackets  160  and  161  can be welded to the front and rear skirts and a catch bracket  162  can be welded to the bottom cover plate. 
     Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.