Abstract:
Wheel assemblies for attachment to a carriage or a vehicle. The wheel assemblies can be configured for four wheel steering, locked in predetermined directions, or free pivoting. The wheel assemblies further include an apparatus for retracting and extending the wheels of the carriage to support the carriage on fixed length supports.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to a carriage for a mobile vehicle, and more particularly, to a carriage for a compact mobile crane. The carriage includes a plurality of retractable and extendable wheel assemblies each including a multi-mode steering system. 
     BACKGROUND OF THE INVENTION 
     Mobile cranes and other utility vehicles with wheels are well known in the prior art. The wheels provide such vehicles with support, mobility, and steering. When the vehicle includes a crane, some additional type of jacking system is generally attached to the carriage of the vehicle in order to lift the carriage in an upward direction until the wheels are no longer in contact with a support surface. This action provides a secure support footing for the crane to prevent the crane from sliding or rolling along the support surface when a load is lifted. In the prior art, separate steering and jacking systems have been employed to provide such mobile vehicles with steering and jacking capabilities. Unfortunately, the steering and jacking systems of the prior art tend to be highly complex, expensive to produce and maintain, and difficult to use. 
     SUMMARY OF THE INVENTION 
     In order to overcome the above deficiencies of the prior art, the present invention provides a multi-purpose wheel assembly for a mobile crane or other utility vehicle. Although described in detail below in conjunction with a mobile crane, it should be readily apparent that the wheel assembly of the present invention can be employed in a wide variety of other types of utility vehicles. 
     The wheel assembly of the present invention combines multi-mode steering and wheel retraction and extension in one assembly that can be easily attached to the carriage of a mobile crane. Unlike the prior art, separate jacking devices are not required to jack the carriage of the mobile crane in an upward direction. Rather, the wheel assembly includes a wheel retraction apparatus for retracting and extending the wheels of the wheel assembly relative to the carriage, and a fixed length king pin support housing. When the wheels are retracted by the wheel retraction apparatus, the carriage is lowered toward a support surface until a support pad on the king pin support housing contacts the support surface. As the wheels are retracted further, the wheels leave contact with the support surface, and the carriage is fully supported by the support pad and the king pin housing support. Conversely, when the wheels are extended downward by the wheel retraction apparatus beyond the support pad, the wheels contact the support surface and support the carriage, thereby allowing the carriage to be easily steered and moved along the support surface. 
     Three modes of wheel positioning can be selected using a single control element. A first mode of wheel positioning provides all wheel steering. In the present invention, at least two wheels can be selected for the all wheel steering mode. Regardless of the actual number of wheels that are selected, this first mode of wheel positioning will hereafter be referred to as “four wheel steering.” A second mode of wheel positioning provides fixed independent wheel directions allowing carriage travel parallel and/or perpendicular to the edge of a building, carriage travel in predetermined directions, and rotatable motion about the center of the carriage. A third mode of wheel positioning allows each wheel assembly to freely swivel in any direction. The control element also allows the wheel positioning mode of each wheel assembly to be independently selected from any of the three wheel positioning modes described above. For instance, if the carriage includes four of the wheel assemblies, the four wheel steering mode can be selected for two of the wheel assemblies, while the free swiveling mode can be selected for the other two wheel assemblies. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features of the present invention will best be understood from a detailed description of the invention and a preferred embodiment thereof selected for the purposes of illustration and shown in the accompanying drawings in which: 
     FIG. 1 is a side elevational view of a mobile roof crane which incorporates a plurality of the wheel assemblies of the present invention; 
     FIG. 2 is a front elevational view of a wheel retraction apparatus in accordance with the present invention; 
     FIG. 3 is a side elevational view of the wheel retraction apparatus; 
     FIG. 4 is a partial side elevational view of a wheel in a downward rolling position; 
     FIG. 5 is a partial side elevational view of a wheel in a retracted position allowing a king pin housing support to contact a support surface to support the carriage; 
     FIG. 6 is a fragmentary cross-sectional view of the king pin mounting assembly taken along line  6 — 6  of FIG. 3; 
     FIG. 7 is an exploded perspective view of the wheel steering apparatus; 
     FIG. 8 is a rear elevational view of the wheel steering apparatus; 
     FIG. 9 is a side elevational view of the wheel steering apparatus; 
     FIG. 10 is a plan view of the wheel steering apparatus; 
     FIG. 11 illustrates the multi-directional steering modes provided to the carriage by the wheel steering apparatus of the present invention; and 
     FIG. 12 is a side elevational view showing the wheel positions that allow movement parallel to a roof edge. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Although certain preferred embodiments of the present invention will be shown and described in detail, it should be understood that various changes and modifications may be made without departing from the scope of the present invention. The scope of the present invention will in no way be limited to the number of constituting components, the materials thereof, the shapes thereof, the relative arrangement thereof, etc., and are disclosed simply as an example of the preferred embodiment. The features and advantages of the present invention are illustrated in detail in the accompanying drawings, wherein like reference numerals refer to like elements throughout the drawings. 
     Referring to FIG. 1, there is illustrated a side elevational view of a mobile roof crane  12  including a plurality of wheel assemblies  10  in accordance with the present invention. Each wheel assembly  10  is attached to the carriage  14  of the mobile roof crane  12  and includes at least one wheel  34 . The mobile roof crane  12  also includes a boom assembly  16 , boom support assembly  18 , winch  24 , cable  26 , and counterweight  28 . In this application, the wheel assemblies  10  allow the crane to be easily steered and rolled into position for lifting a load  30  to the roof  32  of a structure. 
     Each wheel assembly  10  includes a wheel retraction apparatus  40  (FIGS. 2 and 3) for selectively retracting and extending the wheels  34  relative to the carriage  14 , and a fixed length king pin housing support  52 . The king pin housing support  52  supports the weight of the carriage  14  when the wheels  34  are in a retracted state. A support pad  38  is attached to a lower end of the king pin housing support  52 . The upper end of the king pin housing support  52  is rotatably attached to a mounting bracket  42 . The mounting bracket  42  is attached to the carriage  14 . 
     In operation, before the load  30  is lifted by the mobile roof crane  12 , the wheels  34  of each wheel assembly are retracted toward the carriage  14  by the wheel retraction apparatus  40 . As the wheels  34  are retracted, the carriage  14  is lowered toward the roof  32  until the support pads  38  attached to the king pin housing supports  52  come into contact with the roof  32 . As the wheels  34  are retracted further, the wheels  34  are lifted from the roof  32 , and the carriage  14  is fully supported by the support pad  38  and the king pin housing support  52 . Conversely, when the wheels  34  are extended downward by the wheel retraction apparatus  40  beyond the support pad  38 , the wheels  34  contact the roof  32  and support the carriage  14 , thereby allowing the mobile roof crane  12  to be easily steered and displaced on the roof  32 . 
     The features of a wheel assembly  10  and the wheel retraction apparatus  40  are illustrated in greater detail in FIGS. 2 and 3. FIG. 2 provides a partial front elevational view of the wheel retraction apparatus  40 , while FIG. 3 provides a partial side elevational view of the wheel retraction apparatus  40  with one wheel  34  removed for clarity. Phantom dotted lines indicate the movement of the wheels  34  from extended to retracted locations. 
     The wheel assembly  10  includes the mounting bracket  42 , a direction control plate  44 , a selector plate  46 , a control element  48 , a steering arm  50 , the king pin housing support  52 , the support pad  38 , and the wheel retraction apparatus  40 . 
     The wheel retraction apparatus  40  includes wheel axles  54  for rotatably supporting the wheels  34 , axle arms  56 , an axle arm shaft  58 , a trunnion nut  60 , trunnion bolts  62 , a jack screw  64 , a jack screw head  66 , a trunnion lock nut  68 , a trunnion block  70 , trunnion block bolts  72 , trunnion plates  74 , and mounting plates  76 . 
     Referring to FIGS. 2 and 31 the mounting bracket  42  allows the wheel assembly  10  to be conveniently attached to the carriage  14 . The direction control plate  44  is rigidly attached to the mounting bracket  42 , while the king pin housing support  52  is rotatably attached to the mounting bracket  42 . The selector plate  46  is rigidly attached to the king pin housing support  52 , so that any rotation of the selector plate  46  causes a direct rotation of the king pin housing support  52 . The steering arm  50  is freely rotatable about the king pin housing support  52 . 
     The mounting plates  76  are fixed to, or integrally formed with, the king pin housing support  52 . The trunnion block  70  is rotatably attached to the trunnion plates  74  using trunnion block bolts  72  or other suitable hardware. The trunnion plates  74  are attached to the king pin housing support  52  by the mounting plates  76 . A first end of the jack screw  64  passes through and is rotatably attached to the trunnion block  70 . The location of the trunnion block  70  relative to the jack screw head  66  is maintained by the trunnion lock nut  68 . The second end of the jack screw  64  is threadedly attached to the trunnion nut  60 . Again, the trunnion nut  60  is rotatably attached to the axle arms  56  using trunnion bolts  62  or other suitable hardware. 
     The axle arms  56  pivot about the axle arm shaft  58  which is attached to the mounting plates  76 . The axle arms  56  pivot about the axle arm shaft  58  in response to the rotation of the jack screw  64 . For example, when the jack screw  64  is rotated in a first direction such that the trunnion nut  60  and the axle arm  56  are displaced in an upward direction, the wheel axles  54  and associated wheels  34  on the other end of the axle arm  56  are displaced away from the carriage  14  in a downward direction. As shown in FIG. 4, this causes the wheels  34  to engage the roof  32 , thereby lifting the king pin housing support  52  and the attached support pad  38  away from the roof  32 . Correspondingly, when the jack screw  64  is rotated in a second, opposing direction, the trunnion nut  60  and the axle arms  56  are displaced in a downward direction, thereby displacing the wheel axles  54  and associated wheels  34  on the other end of the axle arm  56  toward the carriage  14  in an upward direction. As shown in FIG. 5, this action displaces the wheels  34  toward the carriage  14  until the support pad  38  on the king pin housing support  52  engages the roof  32 . 
     FIG. 6 is a fragmentary cross-sectional view of a king pin mounting assembly  94  taken along line  6 — 6  of FIG.  3 . The king pin mounting assembly  94  is used to rotatably couple the king pin housing support  52  to the carriage  14 . A bolt  200  fixedly attaches a king pin  202  to the mounting bracket  42 . The mounting bracket  42  is attached to the carriage  14  (see e.g., FIG.  7 ). Cylindrical bearings  204  are attached to the inner surface of the king pin housing support  52 , between the king pin housing support  52  and the king pin  202 . The cylindrical bearings  204  allow the king pin housing support  52  to rotate about the king pin  202 . A thrust bearing assembly  206  and a thrust washer  208  are located between the mounting bracket  42  and the king pin housing support  52 . The thrust bearing assembly  206  and the thrust washer  208  support the load from the king pin housing support  52  while providing low friction during the rotation of the king pin housing support  52 . A king pin washer  210  is attached to the lower end of the king pin  202  by a bolt  212 . An inner stop  215  of the king pin housing support  52  engages the king pin washer  210 , thereby retaining the king pin housing support  52  on the king pin  202 . 
     The direction control plate  44 , selector plate  46 , control element  48 , and steering arm  50  are also illustrated in FIG.  6 . The direction control plate  44  is welded, bolted, or otherwise rigidly attached to the mounting bracket  42 . The selector plate  46  is attached to the king pin housing support  52  by keys  214 . The steering arm  50  rotates about the king pin housing support  52  and is vertically restrained between a flange  216  and the selector plate  46 . The control element  48  is held in position by means of a spring  270 , a pin  272 , and three detent notches  274 . The spring  270  and the pin  272  are positioned within a hole formed in the selector plate  46 . The spring  270  biases the pin  272  in an outward direction so that as the control element  48  is rotated, the pointed end of the pin  272  is forced into one of the three detent notches  274 , thereby selectively securing the control element in three different positions. In FIG. 6, the control element  48  is shown rotated in a downward direction, engaging the notch  104  in the steering arm  50 . As detailed below, when in this configuration, the control element  48  actuates the four wheel steering mode of the wheel steering apparatus of the present invention. 
     FIG. 7 is an exploded perspective view of the wheel steering apparatus  90  for a rear wheel assembly  10 R of the carriage  14 . Each rear wheel assembly  10 R is provided with a similar steering apparatus  90 . Also shown are a king pin housing support  52  and a portion of the carriage  14 . The king pin housing support  52  is rotatably attached to the carriage  14  by the king pin mounting assembly  94 . Additional views of the components of the wheel steering apparatus  90  are provided in FIGS. 2,  3  and  6 . 
     Three modes of wheel positioning can be selected using the single control element  48 . The control element  48  is pivotally attached to the selector plate  46 . The selector plate  46  is rigidly attached to the king pin housing support  52  so that any rotation of the selector plate  46  causes a direct rotation of the king pin housing support  52 . 
     The direction control plate  44  is rigidly attached to the carriage  14 . The direction control plate  44  includes a plurality of fixed notches  100 ,  101 , and  103  that are configured to selectively receive the control element  48  to control the orientation of the wheels  34 . Although three fixed notches  100 ,  101 , and  103  are shown, it should be clear that any number of fixed notches may be employed. Also, the orientation of the fixed notches may be adjusted to provide specific wheel directions. A rear steering arm  102  includes a notch  104  for selectively receiving the control element  48  to activate the four wheel steering mode. A rear steering tie rod  116  and a rear transfer tie rod  122  are pivotally attached to the rear steering arm  102 . Each front and rear wheel assembly  10 F and  10 R of the mobile roof crane  12  includes at least the control element  48 , selector plate  46 , and the direction control plate  44 . 
     In a first mode of wheel positioning, the control element  48  is pivoted to engage the notch  104  in the rear steering arm  102  (see also FIGS. 8,  9  and  10 ). This activates a four wheel steering mode. In the four wheel steering mode, the steering tie rod  116  provides rotary motion to the rear steering arm  102  which in turn rotates the king pin housing  52  and the wheels  34 . As further illustrated in FIGS. 8,  9 , and  10 , the rotary motion of the rear steering arm  102  additionally imparts a rotary motion to a corresponding front steering arm  120  through a linkage assembly. 
     In a second mode of wheel positioning, the control element  48  is rotated to engage a notch  100 ,  101 , or  103  in the direction control plate  44 . This causes the wheels  34  to be pointed and locked in a specific direction. For example, notch  100  will provide wheel alignment for a sideways direction, notch  103  will provide a straight forward or backward direction, and notch  101  will provide a wheel alignment causing rotation of the carriage  14  about its center. 
     In a third mode of wheel positioning, the control element  48  is rotated and secured in a direction parallel to the selector plate  46  as shown in FIG. 2, allowing the king pin housing support  52  and the wheels  34  to swivel and rotate in any direction. The control element  48  is secured in a fixed direction by the spring  270 , pin  272 , and one of the detent notches  274  as shown in FIG.  6 . 
     The wheels  34  (FIG. 1) can be provided with a power source  300  to turn each wheel  34  individually. Also, the wheels  34  can be provided with a brake system  302  to stop/prevent the wheels  34  from turning. The brakes can be operated from a single location using a lever  304  that keeps the brakes locked unless an operator pulls on the lever to release the brakes. This provides a safety feature to prevent the carriage from rolling unless an operator desires carriage motion. In addition, turning of the carriage can be assisted by simultaneously powering wheel assemblies on opposing sides of the carriage in opposite directions. 
     FIGS. 8,  9 , and  10  illustrate the wheel steering apparatus  110  of the mobile roof crane  12  in the four wheel steering mode. The steering apparatus  110  includes a steering wheel  112 , a steering gearbox  114 , a steering arm  113 , steering tie rods  116 , rear steering arms  102 , front steering arms  120 , rear transfer tie rods  122 , front transfer tie rods  123 , and transfer arms  124 . Also shown are the front wheel assemblies  10 F and the rear wheel assemblies  10 R. 
     The rear steering arms  102  and the front steering arms  120  are engaged in the four wheel steering mode by rotating and securing each of the control elements  48  in a corresponding notch  104 . Referring to FIG. 10, when the notches  104  on the front and rear control arms  120 ,  102  are engaged by the control elements  48 , the steering apparatus  110  is connected to the king pin housing supports  52  of the two front wheel assemblies  10 F and the two rear wheel assemblies  10 R. 
     Wheel direction in the four wheel steering mode is controlled by the steering wheel  112 . Specifically, a clockwise or counterclockwise rotation of the steering wheel  112  results, via the steering gearbox  114 , in a corresponding rotation of the steering arm  113  in a counterclockwise or clockwise direction. The steering arm  113  pulls/pushes the steering tie rods  116  which in turn cause rotation of the rear steering arms  102  and displacement of the rear transfer tie rods  122  in a first direction. The displacement of the rear transfer tie rods  122  causes a rotation of the transfer arms  124 , a reverse displacement of the front transfer tie rods  123 , and a rotation of the front steering arms  120  in a direction opposite to that of the rear steering arms  102 . Thus, the steering apparatus  110  provides an automatic synchronous turning motion such that as the rear steering arms  102  rotate in a clockwise direction, the front steering arms  120  simultaneously rotate in a counterclockwise direction. Similarly, when the rear steering arms  102  rotate in a counterclockwise direction, the front steering arms  120  rotate in a clockwise direction. 
     FIG. 11 is a plan view showing the steering modes available for providing multi-directional movement of the mobile roof crane  12 . For specific direction control, the control element  48  in each wheel assembly  10  is engaged in one of the notches  100 ,  101 , and  103  in the direction control plate  44 . In FIG. 11, position  130 A shows the wheels  34  locked in a straight forward position, position  130 F shows the wheels  34  locked in a position causing rotation of the carriage  14  about its center, and positions  130 G and  130 H show the wheels  34  locked in a position for sideways motion. The four wheel steering mode provided by the steering apparatus  110  is illustrated in positions  130 B,  130 C,  130 D and  130 E. 
     FIG. 12 is a side elevational view of the mobile crane  12  wherein the wheels  34  are arranged in positions that allow movement of the mobile roof crane  12  parallel to a roof edge  258 . In this configuration, the mobile roof crane  12  can be used to move a load  30  along a building face  260 . 
     The foregoing description of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and many modifications and variations are possible in light of the above teaching. For example, the wheel assemblies  10  have been shown in use on a mobile roof crane  12 . However, the wheel assemblies  10  can be employed in a wide variety of other types of utility vehicles. Such modifications and variations that may be apparent to a person skilled in the art are intended to be included within the scope of this invention as defined by the accompanying claims.