Abstract:
Articulated casters ( 14, 16 ) of low-cost design are provided which include an apertured base ( 18 ) with a plurality of caster wheels ( 20, 22, 24 ) coupled with the base and pivotal about respective upright axes. An upright pivot arm ( 26 ) having a lower end ( 60 ) and an upper load-supporting end, with the lower end ( 60 ) extending through the base aperture and being pivotally connected to the base via a pivot assembly ( 28 ). The assembly ( 28 ) includes an open-top housing ( 64 ) which receives the pivot arm lower end ( 60 ), as well as a connection assembly ( 74 ) securing the housing ( 64 ), base ( 18 ), and pivot arm ( 26 ) in order to permit relative pivotal movement between the pivot arm ( 26 ) and base ( 18 ).

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention is broadly concerned with improved articulated casters designed to support heavy loads. The invention is particularly beneficial in facilitating traversal of the load over sloped or uneven surfaces, or when obstacles are encountered. More particularly, the invention is concerned with an articulated caster assembly having an inexpensive yet rugged pivot assembly for pivotally interconnecting an upright pivot arm and the base of a caster assembly.  
         [0003]     2. Description of the Prior Art  
         [0004]     Casters are well known devices that assist in the mobility of a great variety of equipment and other loads. They are used in industry, in the home, in the medical field, and in general wherever it is desirable to efficiently move objects over surfaces. While casters function well on smooth surfaces, they tend to operate less efficiently when used on uneven surfaces or when obstructions are encountered. In order to overcome this problem, articulated casters have been developed which are better adapted to maneuver over uneven surfaces and/or obstructions.  
         [0005]     U.S. Pat. No. 5,507,069 describes a type of articulated caster of three-wheeled tricycle design. The casters of the &#39;069 patent include a central upstanding pivot arm extending through the caster base and pivotally connected thereto. The upper end of the arm is designed to support loads. The pivot assembly described in this patent makes use of a ball joint housed within a slotted carrier. Such a pivot assembly, while useful for its intended purpose, is very costly to manufacture, requiring multiple fabrication steps.  
         [0006]     There is accordingly a need in the art for improved articulated casters which afford a desirable degree of pivotal movement so as to traverse without difficulty uneven surfaces and the like, while at the same time having pivot coupling assemblies which are durable and inexpensive to manufacture from the standpoints of materials used and fabrication steps.  
       SUMMARY OF THE INVENTION  
       [0007]     The present invention overcomes the problems outlined above, and provides an improved articulated caster characterized by reduced manufacturing costs and high operational deficiencies. According to one aspect of the present invention, the articulated caster generally includes a caster assembly, an upright pivot arm, and a pivot assembly. The caster assembly includes a base and at least three spaced apart caster wheels that are attached to and cooperatively support the base so that the caster assembly is self-supporting. The upright pivot arm has a lower end and an upper end adapted for connection with a load. The pivot assembly operably couples the lower end of the arm with the base. The pivot assembly includes an open-top housing receiving the lower end of the pivot arm. The pivot assembly further includes a connection assembly interconnecting the housing, base, and pivot arm in order to permit relative pivotal movement between the pivot arm and base about generally transverse first and second pivot axes.  
         [0008]     Another aspect of the present invention concerns a carriage including a load-supporting component and two or more spaced apart wheeled supports, at least one of which is an articulated caster. The articulated caster is constructed as previously described.  
         [0009]     In preferred forms, the pivot assembly housing is substantially quadrate in plan configuration, presenting opposed sidewalls and opposed end walls. The preferred pivot arm is of mating, square tubular design and is received between the housing sidewalls. The connection assembly includes a pair of low-cost bolt and nut connectors securing the base and end walls of the housing and defining a first pivot axis. Additionally, a second coupler connects the housing sidewalls and the lower end of the pivot arm to define a second horizontal pivot axis transverse to the first pivot axis.  
         [0010]     Other aspects and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments and the accompanying drawing figures. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     Preferred embodiments of the invention are described in detail below with reference to the attached drawing figures, wherein:  
         [0012]      FIG. 1  is a perspective view of a load-supporting carriage incorporating articulated casters constructed in accordance with a preferred embodiment of the present invention;  
         [0013]      FIG. 2  is a fragmentary, perspective, exploded view of the components of one of the articulated casters depicted in  FIG. 1 , with the articulated casters preferably being similarly constructed;  
         [0014]      FIG. 3  is a fragmentary vertical sectional view of the carriage, particularly illustrating the construction of the articulated caster depicted in  FIG. 2 ;  
         [0015]      FIG. 4  is a fragmentary side view in partial vertical section of the carriage, particularly showing the articulated caster depicted in  FIGS. 2 and 3 ;  
         [0016]      FIG. 5  is a fragmentary side view of the carriage, specifically showing the articulated caster as the carriage travels on a sloped surface;  
         [0017]      FIG. 6  is a front view of the carriage and illustrating the articulated caster as the carriage traverses a side-sloped surface;  
         [0018]      FIG. 7  is a fragmentary side view of the carriage, particularly showing the articulated caster as the carriage travels over an uneven surface; and  
         [0019]      FIG. 8  is a perspective view of an articulated caster constructed in accordance with another preferred embodiment of the present invention. 
     
    
       [0020]     The drawing figures do not limit the present invention to the specific embodiments disclosed and described herein. The drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the preferred embodiments.  
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0021]     Turning now to the drawings, a wheeled carriage  10  is depicted in  FIG. 1  and generally includes an elongated, somewhat tray-shaped load-bearing component  12  and a pair of fore and aft articulated casters  14  and  16 . The casters  14 ,  16  are identical, and therefore only caster  14  will be described in detail. Broadly speaking, the caster  14  (see.  FIG. 2 ) includes a base  18  supported by a total of three caster wheels  20 ,  22 , and  24 , an upright pivot arm  26 , and a pivot assembly  28  serving to interconnect the pivot arm  26  and base  20  to provide an articulated connection therebetween.  
         [0022]     In more detail, the base  18  is somewhat triangular in shape and presents three wheel-mounting apices  30 ,  32 , and  34 . The base  18  has a generally central opening  36  and depending strengthening webs  37 . A pair of opposed depending triangular support legs  38  and  40  extend downwardly from the underside of base  18  and have aligned apertures  42 . As best illustrated in  FIG. 3 , the base  18  is designed such that the wheels  20  and  24  are beneath component  12 , whereas wheel  22  is situated outboard of this component.  
         [0023]     The caster wheels  20 - 24  are identical and each includes a mount  44  configured to mate with a corresponding base apex  30 ,  32 , or  34 , with fasteners  45  interconnecting the base apices and mounts. A swivel coupler  46  is secured to the underside of each mount  44  and a pair of opposed support arms  48  and  50  depend from the swivel coupler  46 . A wheel  52  is secured between the arms  48  and  50  via fastener  54 . It will thus be appreciated that the wheels  20 - 24  are independently pivotal about respective, upright pivot axes.  
         [0024]     The base  18  and wheels  20 - 24  cooperatively form a caster assembly that is self-supporting and particularly effective in supporting, along with other similarly constructed caster assemblies, extraordinarily large loads. The illustrated caster assembly is similar to that disclosed and claimed in U.S. patent application Ser. No. 10/886,369, entitled ARTICULATED CASTER, filed Jul. 6, 2004; and U.S. patent application Ser. No. 11/277,538, entitled ARTICULATED CASTER, filed contemporaneously herewith; both of which are assigned of record to the assignee of the present application and are hereby incorporated by reference herein. However, those ordinarily skilled in the art will appreciate that certain principles of the present invention are applicable to other caster assembly designs. For example, although the illustrated design is most preferred, the caster assembly may be provided with more caster wheels than illustrated, the base can have alternative shapes, etc.  
         [0025]     The illustrated pivot arm  26  is a rigid metallic part having an upper connection flange  56  and a depending arm member  58 . The member  58  is of square tubular configuration and terminates in a lowermost tubular section  60  of reduced cross-sectional area, which is interfitted within the member  58 . The section  60  carries a transversely extending bushing  62  forming a through passageway. Other suitable pivot arm designs are entirely within the ambit of the present invention, as will be subsequently described.  
         [0026]     The illustrated pivot assembly  28  differs significantly from that disclosed in the incorporated applications. More specifically, the pivot assembly  28  includes an open-top housing  64  of generally quadrate plan configuration, presenting opposed sidewalls  66  and opposed end walls  68 . As best seen in  FIG. 2 , the sidewalls  66  have aligned apertures  70 , and likewise the end walls have aligned apertures  72 . The overall pivot assembly  28  further includes a connection assembly  74  serving to secure the housing  64 , base  18 , and pivot arm  26  in order to permit relative pivoting movement between the pivot arm  26  and base  18  about generally horizontal and transverse pivot axes.  
         [0027]     The housing  64  is located between the lower ends of the support legs  38  and  40  with the apertures  42  thereof in alignment with the end wall apertures  72  of the housing. A pair of short bolt and nut assemblies  76  (bolt  76   a , washer  76   b , bushings  76   c , and nut  76   d ) are used to secure the housing  64  to the legs  38  and  40 , and to permit the housing to rotate about a pivot axis defined by the bolts  76   a . Again referring to  FIG. 2 , it will be seen that the lowermost tubular section  60  of arm  58  is received within the confines of housing  64 , with the bushing  62  in alignment with sidewall apertures  70 . A longer bolt and nut assembly  78  (bolt  78   a , washers  78   b , and nut  78   c ) extends through the sidewall apertures  70  and  62  in order to secure the housing  64  to pivot arm  26  and to allow the pivot arm to rotate about an axis defined by the bolt  78   a . It will be noted in this regard that the pivot axes defined by the assemblies  76  and  78  are substantially coplanar and orthogonal; these axes are also below the upper surface of base  18 . However, the principles of the present invention are equally applicable to axes that do not intersect (e.g., are vertically offset) and/or are not perpendicular relative to one another. Moreover, as perhaps best depicted in  FIGS. 5 and 6 , the axes are preferably spaced below the rotational axes of wheels  20 - 24  (assuming the surface is level or only slightly inclined). In other words, the pivot axes provided by the assembly  28  are preferably closer to the surface than the wheel axes. As noted in the incorporated applications, this arrangement provides tremendous stability to the carriage  10 .  
         [0028]      FIG. 4  illustrates the carriage  10  during movement thereof along a substantially even and flat surface  80 . In such a situation, three casters  20 ,  22 , and  24  are aligned and there is essentially no relative pivoting between arm  26  (and hence load-bearing component  12 ) and base  18 . When the carriage  12  encounters an inclined surface  82  ( FIG. 5 ), the pivot assembly  28  comes into play to maintain the component  12  in the desired orientation (e.g., a substantially horizontal orientation) through articulation of the caster assemblies  14  and  16 . In detail, the base  18  pivots about the axis defined by bolts  76   a  to accommodate the sloped surface. Likewise, when the carriage  10  encounters a side sloped surface  84  ( FIG. 6 ), the base  18  pivots about the axis defined by bolt  78   a  to again maintain the component  12  in a substantially horizontal orientation. The base  18  may simultaneously pivot about both of the horizontal axes when an obstruction is encountered or an uneven surface  86  is traversed. In this case, the base  18  will pivot about both of the axes respectively defined by the bolts  76   a  and bolt  78   a  ( FIG. 7 ).  
         [0029]     The articulated casters of the present invention, making use of the open-top housing  64  secured to base  18  and to the lower end of pivot arm  26 , provide a number of advantages as compared with prior art caster designs. For example, use of the pivot housing requires the pivot arm  26  to be only of simple square configuration versus prior art forked designs requiring multiple cutting, machining, welding, and/or casting operations to fabricate. Indeed, the housing  64  can readily be fabricated using a single laser cutting operation providing the rectangular configuration and the mounting apertures. Prior pivot block designs require at least four machining operations to give sizing and drilling of the center and end mounting apertures. Such pivot block units also require threading of the end holes. This is eliminated in the present invention where the housing apertures are unthreaded. The present pivot arm/pivot assembly is smaller and has a higher strength:weight ratio. Moreover, if it is desired to increase the strength of the pivot assembly, housing  64  can easily be increased in height without affecting the remainder of the caster assembly.  
         [0030]     Because of the use of the articulated casters  14  and  16 , the carriage is particularly effective in supporting large loads for traversal on uneven or inclined surfaces or across obstacles (such as debris on the surface). If desired, the carriage can be provided with more or less casters than depicted. Furthermore, each pivot arm can be associated with a gang of casters if desired. Another suitable but alternative carriage design is depicted in U.S. patent application Ser. No. 11/277,546, entitled QUAD-CASTER CARRIAGE WITH FORKLIFT ATTACHMENT, filed contemporaneously herewith, assigned of record to the assignee of the present application, and hereby incorporated by reference herein.  
         [0031]     The principles of the present invention are equally applicable to other pivot assembly designs. For example,  FIG. 8  illustrates another caster  14   a  constructed in accordance with another preferred embodiment of the present invention. The caster  14   a  is in many respects identical with previously described caster 14 , and accordingly like components will be numbered as set forth above. However, the caster  14   a  differs in the construction of the pivot assembly  28   a . In this instance, the assembly  28   a  includes a depending pivot arm  26   a  which is formed of solid block metal and having a through-aperture for receiving the screw and nut assembly  78 . Also, in this embodiment, the housing  64  is replaced by a solid extruded metallic tubing  64   a  of rectangular shape and having apertured end walls  68   a  and apertured sidewalls  66   a . It will be appreciated that this pivot assembly is less expensive than the design depicted in  FIG. 2 , inasmuch as the arm  26   a  can be fabricated from inexpensive bar stock, while the housing  64   a  can be easily cut from a length of conventional tubing stock.  
         [0032]     The preferred forms of the invention described above are to be used as illustration only, and should not be utilized in a limiting sense in interpreting the scope of the present invention. Obvious modifications to the exemplary embodiments, as hereinabove set forth, could be readily made by those skilled in the art without departing from the spirit of the present invention.  
         [0033]     The inventor hereby states his intent to rely on the Doctrine of Equivalents to determine and assess the reasonably fair scope of the present invention as pertains to any apparatus not materially departing from but outside the literal scope of the invention as set forth in the following claims.