Abstract:
A swivel assembly for connecting a load such as a television receiver to a support includes a swivel stem having a cylindrical head, a reduced diameter cylindrical middle body, and a mounting base. The stem is supported by a retainer assembly including thrust washers engaging the top and the bottom of head. An adjustment is provided for maintaining the thrust washers securely engaged with the head of the stem.

Description:
FIELD OF THE INVENTION 
   This invention relates to a swivel assembly used to attach a load, such as a television receiver, to a support member in a manner to permit the load to rotate. 
   BACKGROUND OF THE INVENTION 
   One use of a swivel assembly of the type contemplated by this invention is to rotatably support a television receiver on a support arm adjacent a hospital bed. Such swivel assemblies may be hollow to permit electrical cables to extend along the center axis of the swivel assembly from the television receiver. Swivel assemblies are known in the art, but these are typically difficult to assemble at a hospital or other site and have an undesirable looseness, leading to a backlash condition which permits the load to wobble. Therefore, there is need for an improved swivel assembly that provides a swivel joint for rotatably supporting a television receiver or other load with minimal or no looseness or backlash. 
   SUMMARY OF THE INVENTION 
   A swivel assembly for connecting a load such as a television receiver includes a swivel stem having a cylindrical head, a reduced diameter cylindrical middle body, and a mounting base. The stem is supported by a retainer assembly including a pair of thrust washers engaging respectively the top of said head and the bottom of the head. An adjustment is provided for maintaining the thrust washers securely engaged with the head of the stem at a tension which enables the swivel stem to be rotated about a fixed axis and to avoid a backlash condition that would enable the load to wobble. 
   Other aspects and advantages of this invention will become apparent from the following description and the drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an isometric view of a swivel support assembly in accordance with this invention mounted on a support arm for a television receiver. Only a fragment of the support arm is illustrated. 
       FIG. 2  is an end elevational view of the swivel support assembly and the support arm of  FIG. 1 . Only a fragment of the support arm is illustrated. 
       FIG. 3  is side elevational view of the swivel support assembly of  FIG. 1 , omitting the support arm to avoid a confusion of lines. 
       FIG. 4  is an exploded perspective view of the swivel support assembly, the support arm, and a clevis shown in phantom associated with a television receiver (not shown). Only a fragment of the support arm is illustrated. 
   

   DETAILED DESCRIPTION 
   With reference to the drawings, a swivel assembly, generally designated  10  is shown in  FIGS. 1 through 3  mounted on and supported by the nose  12  of television support arm  14 . As shown best in  FIG. 4 , the support arm nose  12  is generally U-shaped, having a flat bottom wall  16  and flat side walls  18 . The support end of the nose  12  includes a U-shaped mounting slot  20  centrally of the bottom wall  16  and a through bore  22  spaced from the mounting slot  20  for a rear threaded fastener member  24 , which may be a cap screw. 
   As also shown best in  FIG. 4 , a one-piece swivel stem  30  having a rectangular mounting base  32  is designed to be connected by a clevis pin (not shown) to a clevis attachment assembly  34 , shown in phantom, mounted on the top of a television receiver (not shown), or any other load. 
   In addition to the mounting base  32 , the swivel stem  30  has a cylindrical head  38  and a reduced diameter cylindrical middle body  40 . The mounting base  32 , the head  38 , and the middle body  40  are mutually coaxial, and the head  38  has a ring-shaped bottom surface  42  forming an outwardly-extending shoulder at the top of the middle body  40 . Here it may be noted that the swivel stem  30 , made hollow by the through bore  36 , may be essentially identical to other swivel stems used in the past for supporting television receivers on support arms. 
   In accordance with this invention, the swivel stem  30  is rotatably supported on the support arm nose  12  by a retainer assembly, generally designated  50 , comprising a bottom retainer plate  52 , a lower washer support or plate assembly, generally designated  54 , and a top retainer plate  56 . 
   The bottom retainer plate  52  has a circular aperture  58  of sufficiently large diameter that the head  38  of the swivel stem  30  can be extended therethrough, a front circular bore  60 , and a rear circular bore  62 . 
   A front retainer plate  64  and a rear retainer plate  66  constitute the lower washer support assembly  54 . The front and rear retainer plates  64  and  66  are abutted end-to-end to one another and have semicircular recesses  68  and  70 , respectively, that form a circular, upwardly-facing, ring-shaped washer nest  72  around a circular aperture  74 . A split, lower thrust washer  76  is supported within the washer nest  72 . Both the nest  72  and the lower thrust washer  76  have an inner diameter only slightly larger than the outer diameter of the middle portion  40  of the stem  30 . Accordingly, when the retainer assembly  50  is fully assembled, the bottom surface  42  of the stem head  38  will be engaged and supported by the lower thrust washer  76 . 
   The lower thrust washer  76 , which may be nylon, is too small to pass over the head  38  or the mounting base  32  of the swivel stem  30 . Accordingly, during assembly of the retainer assembly  50 , the lower thrust washer  76 , since it is split, can be bent or otherwise deformed as needed to encircle the middle stem body  40 . Thereafter, the front and rear retainer plates  64  and  66  may conveniently be inserted between the lower thrust washer  76  and the bottom retainer plate  52 . 
   Front retainer plate  64  has a threaded front bore  78  aligned with the front bore  60  of the bottom retainer plate  52  and the rear retainer plate  66  has a threaded rear bore  80  aligned with the rear bore  62  of the bottom retainer plate  52 . 
   The top retainer plate  56  overlies the swivel stem head  38  and has a centrally-located bore  86  surrounded by an upwardly-extending, downwardly-facing washer pocket  88  overlying the swivel stem head  38  which receives a second, upper, thrust washer  90 , which may also be made from nylon. The lower surface of the upper washer  90  is engaged with the top surface of the stem head  38 . Thus, it will be appreciated that the stem head  38  is sandwiched between upper and lower thrust washers  90  and  76 , which are lodged within washer nests or pockets. 
   Top retainer plate  56  also has a front bore  82  and a rear bore  84 . These are respectively vertically aligned with the front bores  78  and  60  in the front retainer plate  64  and the bottom plate  52  and the rear bores  80  and  62  in the rear retainer plate  66  and the bottom plate  52 . 
   A front threaded fastener  94 , which may also be a cap screw, extends upwardly through the aligned front bores  60 ,  78  and  82 , and has a head  96  engaged with the bottom surface of a retainer clip  98  that extends upwardly through the mounting slot  20  and bears upwardly against the bottom retainer plate  52 , and also bears upwardly against lower surface portions of the bottom wall  16  along margins of the mounting slot  20 . The retainer clip  98  has a central bore  92  aligned with the front bores  60 ,  78  and  82  through which the front threaded fastener  94  also extends. The mid-portion of the front threaded fastener  94  is threadedly connected to the front plate  64  due to the threaded connection with the threaded front bore  78  therein. The aforementioned rear threaded fastener  24  has a head  25  that bears upwardly against the bottom wall  16  of the support arm  14  and the fastener  24  extends vertically through the aligned rear bores  62 ,  80  and  84  as well as the aligned support arm bore  22 , and is threaded to the rear plate  66  by virtue of its engagement with the threads of the rear bore  80  in the rear plate  66 . The heads  25  and  96  of the respective threaded fasteners  24  and  94  may comprise Allen heads having internal, axial hexagonal sockets (not shown) at their lower ends for engagement by an Allen wrench (not shown). 
   As is evident from the foregoing description and the drawings, the swivel assembly  10  is clamped to the bottom support wall  16  of the support arm  14  in part by the retainer clip  98  in association with the front threaded fastener  94  and in part by the head  25  of the rear cap screw  24  which engages the bottom surface of the support wall  16 . 
   A front adjusting nut  100  threaded onto the upper end of the front threaded fastener  94  bears downwardly against the top surface of the upper retainer plate  56 . The front threaded fastener  94  may have a button head  96  to provide clearance for the swivel stem  30  and any parts (not shown) supported thereby. Similarly, a rear adjusting nut  102  threaded onto the upper end of the rear threaded fastener  94  also bears downwardly against the top surface of the upper retainer plate  56 . The adjusting nuts  100  and  102  may be acorn nuts as illustrated in the drawings to cover the upper ends of the threaded fasteners  24  and  94 . 
   When the swivel assembly  10  is first installed on the support arm  14 , the threaded fasteners  24  and  94  are rotated so as to draw the rear and front plates  64  and  66 , respectively, tightly against the bottom plate  52  so that the bottom plate  52  lies flush against the bottom wall  18  of the support arm  14 . This creates a rigid connection between the support arm  14 , the front and rear plates  64  and  66 , and the bottom plate  52 . 
   To pre-load or pre-tension the swivel assembly  10 , the acorn nuts  100  and  102  are rotated to bear downwardly on the top plate  56  to a finger tightness, whereupon the swivel stem head  38  is trapped between the two nylon washers  76  and  90 . The foregoing assembly can be carried out in a factory or on site at a hospital or other location. Thereafter, when a load such as a television set is connected to the swivel stem base  32 , the acorn nuts  100  and  102  can be tightened to the extent that the swivel stem  30  is rotatable without looseness or backlash. 
   After extended use, the swivel assembly  10  could become loose and exhibit a backlash. This can easily be eliminated by the simple expedient of rotating the acorn nuts  100  and  102  to bear further downwardly on the top plate  52 , and thereby reestablish the desired degree of tightness between the swivel stem head  38  and the washers  76  and  90 . 
   Although the threaded fasteners  24  and  94  are illustrated as comprising Allen head cap screws and used with acorn nuts  100  and  102 , it will be evident that other threaded fasteners, such as threaded rods, screws or bolts (not shown), with appropriate heads and/or nuts (not shown) may be used instead to achieve the purposes of this invention. In practice, ¼ 20 socket head cap screws have been used, but fasteners having other sizes and thread fineness could be used. 
   The parts of the swivel assembly  10  may be made from metal. The stem may be made from aluminum and the retainer plates from cold rolled steel, but other materials may be used. 
   Electrical cables (not shown) from a television receiver can be extended upwardly through the central bore  36  in the swivel stem  30 , around the clevis pin (not shown) received in the transverse bore  106  in the base  32  of the swivel stem  30  and outwardly through the central bore  86  in the top retainer plate  56 , and then along the support arm  14 . 
   Although the presently preferred embodiment of this invention has been described, it will be understood that within the purview of the invention various changes may be made within the scope of the following claims.