Abstract:
A caster supporting weight through biasing means utilizes an elastomeric material, such as polyurethane, to elastomerically support the weight transmitted through the caster. The components are concisely related to each other, the elastic material is protected against damage, including excessive weight supporting forces, and in an embodiment of the invention, vertical caster adjustment is possible without affecting its elastomeric weight bearing characteristics.

Description:
FIELD OF THE INVENTION  
         [0001]    A caster having a wheel pivotally supported upon arms wherein the arms are elastomerically biased to absorb shock and improve the caster rolling characteristics.  
         BACKGROUND OF THE INVENTION  
         [0002]    Heavy-duty casters are used to support relatively heavy loads transported by small lift trucks, material handling carts, and the like. By using biasing means to transmit the supported weight between the caster wheel and the caster body, the load bearing ability of the caster is improved resulting in smoother operation, ease of movement of the caster supported truck or vehicle, and improved truck travel operation due to caster wheel wear.  
           [0003]    Steel compression springs have been used to bias resiliently supported casters, but such springs as are necessary to achieve the desired resilient supported characteristics are relatively large and not readily adaptable to many caster installations wherein the overall vertical dimension available for the caster is limited, and the vertical profile of the caster assembly must be concise.  
           [0004]    Heretofore, it has not been possible to provide a low profile caster wherein the wheel is resiliently supported, the cost is relatively inexpensive, and the vertical caster dimension is relatively concise.  
         OBJECTS OF THE INVENTION  
         [0005]    It is an object of the invention to provide a heavy-duty resiliently supported caster wherein the resilient caster characteristics are achieved through a torque transmitting polyurethane material wherein high loads may be elastomerically absorbed.  
           [0006]    Another object of the invention is to provide a heavy-duty resiliently supported caster which is of a low vertical profile and may be installed in low profile environments without sacrifice of the elastomeric and shock absorbing weight characteristics of the caster.  
         SUMMARY OF THE INVENTION  
         [0007]    The caster in accord with the invention includes a support plate affixed to the truck, forklift, or other structure to be supported by the caster. The caster body is mounted to the support plate either in a fixed relationship, or in a rotative relationship by the use of ball bearings if the caster is to be of the “pivoted” type. Such caster choices are well known.  
           [0008]    The caster wheel is rotatably supported between a pair of pivoted caster arms mounted to the caster body. The upper end of the caster arms are attached to an insert which is part of the core of an elastomeric assembly wherein an elastic material, such as polyurethane, is bonded to an internal core, and is exteriorly bonded to a tubular housing, wherein a rotative relationship between the elastomeric material and the housing and the core is prevented.  
           [0009]    The housing, which is of a non-circular transverse cross section, as is the core, is attached to the caster body intermediate the caster arms. The caster arms are attached to the ends of the core insert by a non-circular torque transmitting configuration, and held in this relationship by bolts threaded into the core ends. Stop projections are defined on the caster arms for engaging the caster body with excessive deformation of the elastomeric material takes place during operation.  
           [0010]    The weight carried by the caster is transmitted through the elastomeric material in a torque transmitting manner, and in this way, the caster wheel is elastomerically related to the caster body to achieve the desired biased caster operation. As the ends of the elastic material are protected by the upper ends of the caster arms, the likelihood of damage to the elastomeric material is minimized, and the arrangement of components, as will be appreciated from the attached drawings, permits the entire caster assembly to be of a concise configuration and installable in applications wherein a low vertical profile is required.  
           [0011]    In an embodiment of the invention, stop arms are bolted to the core insert in a non-rotative relationship and these stop arms will bear against the caster body if excessive elastomer deformation occurs. The upper ends of the stop arms include a torque coupling receivable within a slot defined in the upper end of the caster arms and a toothed washer mounted upon the insert bolts cooperating with teeth defined in the outer surface of the caster arms permits the caster arms to be adjustably positioned relative to the caster body and support. In this manner, the vertical height of the caster can be easily adjusted to accommodate the caster to a particular installation without requiring major modification. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    The aforementioned objects of the invention and an understanding of various embodiments thereof will be appreciated from the following description and accompanying drawings wherein:  
         [0013]    [0013]FIG. 1 is a side elevational view of a caster in accord with the invention,  
         [0014]    [0014]FIG. 2 is an elevational view taken along Section  2 - 2  of FIG. 1,  
         [0015]    [0015]FIG. 3 is a detailed elevational sectional view taken through the elastomeric assembly along Section  3 - 3  of FIG. 2,  
         [0016]    [0016]FIG. 4 is an enlarged detail elevational sectional view of a caster arm upper end taken along Section  4 - 4  of FIG. 2,  
         [0017]    [0017]FIG. 5 is an elevational view of one of the caster arms used in the embodiment of FIG. 1,  
         [0018]    [0018]FIG. 6 is an elevational view of another embodiment of the caster invention wherein the vertical height of the caster is adjustable,  
         [0019]    [0019]FIG. 7 is an elevational sectional view as taken through Section  7 - 7  of FIG. 6,  
         [0020]    [0020]FIG. 8 is an elevational sectional view as taken along Section  8 - 8  of FIG. 7,  
         [0021]    [0021]FIG. 9 is an elevational view of the outer side of a stop dog used with the embodiment of FIG. 6,  
         [0022]    [0022]FIG. 10 is an elevational view of the inner side of the stop dog of FIG. 9, and  
         [0023]    [0023]FIG. 11 is an elevational view of the end of the elastomeric assembly as taken along Section  11 - 11  of FIG. 6. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]    The elevational view of FIG. 1 illustrates a typical example of the assembly of components producing a caster utilizing the inventive concepts. A support plate  10  is attached to the vehicle being supported by the caster, such as a small lift truck, material handling container, hand truck, or the like. This type of caster is particularly useful with small forklift trucks of the non-ridable type wherein relatively heavy loads are carried and the forklift truck vertical dimension is low.  
         [0025]    The caster body is represented at  12  and is attached to the support plate  10  by bearing structure at  14 . The bearing  14  may constitute merely a plate whereby the caster body  12  is rigidly attached to the support plate  10 , but in many instances, the bearing  14  will be of the anti-friction type wherein the caster body  12  is rotatably supported relative to the plate  10 , as is well known in the caster art. A grease fitting  16  serves to lubricate the bearing  14  if it is of the rotative type.  
         [0026]    A tubular box frame  18  of a length less than the width of the caster body  12  is attached to the caster body by bolts  20 . As will be appreciated from FIGS. 1 and 3, the box frame  18  defines a square void which closely receives the elastomer assembly  22 .  
         [0027]    The elastomer assembly  22  includes a tubular housing  24  which, in the disclosed embodiment, is of approximately a square transverse cross section and of a length as will be appreciated from FIG. 2. Internally, the elastomeric assembly core  26  is centrally located within the tubular housing  24  and is of a square configuration, FIG. 3, and is of a smaller dimension than the housing  24  such that the void between the housing  24  and core  26  can be filled with an elastomeric material  28 , such as polyurethane. The elastomeric polyurethane  28  is preferably bonded to the inside of the tubular housing  24  and the exterior configuration of the core  26  whereby relative limited rotation between the core  26  and tubular housing  24  is permitted by the elastomeric characteristic of the polyurethane, but such elastomeric deformation is resisted.  
         [0028]    The core  26  consists of a square tubular element  29  of an elongated configuration and a square insert  30  closely fits within the element  29  and is of a length greater than the element  29  as will be appreciated from FIG. 2. The ends of the insert  30  are represented at  32 , and coaxial threaded holes  34  are defined in each of the insert ends.  
         [0029]    A pair of identical caster arms  36  are mounted upon the insert  30 , each of the caster arms including an upper end  38  and a lower end  40 . As clearly indicated in FIG. 5, the caster upper end  38  includes a square hole  42 , and the lower end  40  includes a round hole  44 . A stop projection is integrally defined on the caster arms  36  forming the stop projection surface  46 . The caster wheel  48 , formed of metal or a synthetic material, is rotatably located between the caster arms  36  upon an axle  50 .  
         [0030]    As will be appreciated from FIG. 2, the length of the insert  30  is such that the insert end extensions  52 , which are of the square configuration of the entire length of the insert  30 , extend beyond the ends of the elastomer  28  and the housing  24 . Accordingly, the caster arms  36  are placed upon the insert extensions  52  by holes  42 , and bolts  54  threaded into insert holes  34  maintain the caster arms  36  in a non-rotatable relationship to the insert  30 .  
         [0031]    Weight placed upon the support plate  10  is transferred through the elastomer  28  to the caster arms  36  and wheel  48 . This weight bearing of the caster tends to rotate the core  26  relative to the housing  24 , and such rotation is resisted by the elastomeric material  28  which deforms in a rotatable manner about the axis of the insert  30 . Of course, such rotation is limited and the flexible and elastomeric character of the elastomer  28  provides a resilient biasing support of the wheel  48  capable of resisting shock and uneven floor surfaces. Excessive weight applied to the caster causes engagement of the caster arm stop surface  46  with the underside of the body  12  so as not to overstress the elastomeric material.  
         [0032]    The disclosed arrangement of components permits high forces to be resiliently supported in a relatively low profile caster.  
         [0033]    The caster embodiment shown in FIGS.  6 - 11  has many similarities to the previously described caster and similar components are indicated by primed reference numerals.  
         [0034]    In the embodiment of FIGS.  6 - 11 , the elastomeric assembly  22 ′ is identical to that previously described but this embodiment uses a pair of stop dogs  58 , the opposite sides of one of which is shown in FIGS. 9 and 10. The caster uses two stop dogs  58  which are mirror images of each other, and each stop dog includes an inner side  62  and an outer side  64 . A bolt hole  66  extends through the stop dogs and on the inner side  62 , a square countersunk recess  68  is formed concentric with respect to the bolt hole  66 . The recess  68  does not extend completely through the associated stop dog as will be appreciated from FIGS. 7 and 9.  
         [0035]    Each of the stop dogs  58  includes a pair of spaced studs or projections  70  extending from side  64  as will be appreciated from FIG. 9. The studs  70  are in radial alignment with each other with respect to the center of the associated bolt hole  66 , and are used to establish a torque transmitting coupling with the caster arms as later described.  
         [0036]    The caster arms  72  are located upon each side of the caster and each includes an offset  74  to accommodate the greater width of the caster resulting from the use of the stop dogs  58 . Each caster arm  72  includes an axle  76  upon which the caster wheel  78  is mounted.  
         [0037]    As will be noted from FIGS. 6 and 7, a vertical slot  80  is defined in the upper end of each caster arm  72 . The length of the slot  80  is greater than the separation between the studs  70  on a common stop dog, and the studs  70  are received within a slot  80  as will be appreciated in FIGS. 6 and 7. A plurality of teeth or serrations  82  are defined on the outer side of each caster arm  72  adjacent the slot  80 , and the caster arms are attached to the caster body  12 ′ by the bolts  84  which pass through the bolt holes  66  and are threaded into the ends of the insert  30 ′. A toothed or serrated washer  86  of a rectangular configuration is engaged by the head of the bolt  84  which engages the caster arm teeth  82  wherein tightening of the bolts  84  prevent vertical movement of the caster arms  72  with respect to the caster body  12 ′.  
         [0038]    When adjusting the vertical height of the caster assembly shown in FIGS.  6 - 11 , the bolts  84  are loosened to such an extent that the washers  86  are not engaging the teeth  82  of the caster arms  72 . Accordingly, the length of the slots  80  will permit the caster arms to be moved vertically as the studs  70  slide within the slots  80 . Upon tightening of the bolts  84 , the washers  86  engage the teeth  82  and force the caster arms  72  towards the insert ends  32 ′. As the square insert end extensions  52 ′ are closely received within the caster arm recesses  68 , the caster arms are torsionally coupled to the core insert  30 ′, and the reception of the stop dog studs  70  into the caster arm slots  80  produces a torque transmitting coupling between the stop dogs and caster arms which permits the torque forces imposed on the caster arms to be transmitted to the elastomeric assembly  22 ′, and in this manner, vertical adjustment of the height of the caster is possible without adversely affecting the elastic characteristics of the elastomeric assembly  22 ′. As the stop dogs  58  rotate with the caster arms  72 , excessive movement of the caster arms upwardly is terminated by engagement of the stop surfaces  60  with the caster body  12 ′.  
         [0039]    It will be appreciated that various modifications to the inventive concepts may be apparent to those skilled in the art without departing from the spirit and scope of the invention. Terms such as “upper” and “lower” as used in the claims are only for the purpose of defining relative relationships and are not to be considered limiting.