Abstract:
A positionable support device employs a motion restriction device retrofitted to an existing spring cylinder to adjust the amount of force exerted. In one embodiment, split ring is pressed against an actuating shaft of the spring cylinder with adjustable force. The force on the split ring causes frictional resistance to the motion of the shaft thereby reducing the force applied. This is useful in spring-loaded positioners which allow the object to be placed, and remain in a selected position. The spring cylinder may be gas-charged or spring-loaded support. Various types of friction adjustment units may be employed to result in a positionable support device which holds an object in a desired position.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The invention relates generally to a friction device for dampening the motion of a gas spring cylinder. 
         [0002]    Positionable support arms for mounting electronic peripheral devices, such as computer monitors or televisions to, among other things, a wall, column, ceiling, desktop or other support structure are well known in the prior art. Conventional support arms include a rigid elongated arm having a first end pivotally coupled to the support structure for pivoting movement about a generally horizontal first pivot axis and vertically between and upper and lower position. A mounting element is provided for coupling a device to a second end of the rigid arm, which typically provides for pivoting of the device about a second generally horizontal pivot point, and vertically to maintain the orientation of the device as the arm is moved between upper and lower positions. 
         [0003]    Some conventional support arm systems rely on frictional contact between moving parts of the rigid arm to hold a device in the desired position relative to the support structure. Such systems require that the frictional forces overcome the force of gravity acting on the support arm and the associated device. For example, the arm may include a frictional assembly at a pivot point including at least two planar surfaces where a nut, bolt and spring washer assembly provide tension to the assembly. 
         [0004]    Other conventional support arms of the prior art include springs, gas springs, also referred to as gas cylinders or pneumatic cylinders, or other biasing means to counterbalance at least a portion of the weight of an object supported by the support arm. This enables a user to move supported objects upwardly using less force than would be required to lift the object. 
         [0005]    In some applications it is desirable to provide a gas spring cylinder and to dampen the cylinder so that the support arm remains stationary when a user finishes moving the object being supported to a new position. Such “dampening” can be accomplished by providing additional frictional resistance on the cylinder shaft. It is also often desirable to provide means to adjust the amount of friction being exerted on the cylinder shaft, in order to accommodate different user preferences and objects of different weights. For example, U.S. Pat. No. 7,014,157, entitled “Friction Cylinder for a Support Device,” teaches a custom-built spring cylinder having a friction device located on the interior of the cylinder. 
         [0006]    There is a need for a more cost-effective means to dampen the movement of the shaft of a gas or spring cylinder. In addition, there is a need for an improved means for adjusting the amount of friction exerted on the shaft of a gas or spring cylinder. 
       SUMMARY OF THE INVENTION 
       [0007]    In one respect, the invention comprises a positional support comprising: a shaft capable of being extended and/or retracted; a spring cylinder attached to the shaft capable of applying an urging force on the shaft pushing it toward its extended position; and a motion resistance device externally attached to the spring cylinder for applying frictional resistance to any motion of the shaft. 
         [0008]    In another respect, the invention comprises a motion resistance device for retrofitting existing spring support having a spring cylinder that activates a shaft comprising: a frictional element in contact with the shaft for providing frictional resistance to the shaft; a collar having: a cup for enclosing and holding the frictional element against the shaft; at least one arm for attaching the collar to the spring cylinder; and friction adjustment unit for applying adjustable pressure to the frictional element. 
         [0009]    In yet another respect, the invention comprises a motion resistance device for retrofitting existing spring supports having a spring cylinder and a shaft comprising: a wedge-shaped frictional element in contact with the shaft for providing frictional resistance to the shaft; a collar having: a threaded outer surface; a tapered recess for receiving, enclosing and holding the wedge-shaped frictional elements against the shaft; at least one arm for attaching the collar to the spring cylinder; a friction adjustment unit for applying adjustable pressure to the frictional element; and a securing device for securing the at least one arm to the spring cylinder; wherein the friction adjustment unit applies adjustable force on the frictional element causing adjustable frictional resistance to movement of the shaft. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The present invention will hereinafter be described in conjunction with the appended drawing figures wherein like numerals denote like elements. 
           [0011]      FIG. 1  is a side elevational view showing the adjustable support device  30  of the present invention in use; 
           [0012]      FIG. 2  is an exploded view showing the adjustable support device  30  of the present invention; 
           [0013]      FIG. 3  is a perspective view showing the adjustable support device  30  of the present invention fully assembled; 
           [0014]      FIG. 4  is an enlarged sectional view taken along line  4 - 4  of  FIG. 3 ; 
           [0015]      FIG. 5  is an exploded view showing an alternative embodiment of the adjustable support device of the present invention which is attached to a spring support; 
           [0016]      FIG. 6  is a perspective view showing an alternative embodiment of the adjustable support device  130  of the present invention fully assembled; and 
           [0017]      FIG. 7  is an enlarged sectional view taken along line  7 - 7  of  FIG. 6 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0018]    The ensuing detailed description provides preferred exemplary embodiments only, and is not intended to limit the scope, applicability, or configuration of the invention. Rather, the ensuing detailed description of the preferred exemplary embodiments will provide those skilled in the art with an enabling description for implementing the preferred exemplary embodiments of the invention. It being understood that various changes may be made in the function and arrangement of elements without departing from the spirit and scope of the invention, as set forth in the appended claims. 
         [0019]    To aid in describing the invention, directional terms are used in the specification and claims to describe portions of the present invention (e.g., upper, lower, left, right, etc.). These directional definitions are merely intended to assist in describing and claiming the invention and are not intended to limit the invention in any way. In addition, reference numerals that are introduced in the specification in association with a drawing figure may be repeated in one or more subsequent figures without additional description in the specification in order to provide context for other features. 
         [0020]      FIG. 1  is a side elevational view showing one embodiment of an adjustable support device  30  of the present invention in use as part of a positioner  6  for holding a computer monitor  4 . 
         [0021]    In this preferred embodiment, a computer monitor  4  is being supported and held at a pre-selected position by a positioner  6 . Positioner  6  has a base  8 , which is attached to a fixed surface  2 , and mount  14 , which is connected to monitor  4 . A first arm  10  is pivotally connected to base  8  at a first pivot  16  and also to mount  14  at a third pivot  20 . A second arm  12  is also pivotally connected to base  8  at a second pivot  18 , and to mount  14  at a fourth pivot  22 . First and second arms  10 ,  12  are intended to remain approximately parallel to each other throughout the normal range of motion of the positioner  6 . 
         [0022]    An adjustable support device  30  attaches diagonally at or near pivots  18 ,  20 . Adjustable support device  30  includes a cylinder  24 , a shaft  26  extending from the cylinder  24 , and a motion resistance device  28  for resisting extension or retraction of shaft  26 . The adjustable support device  30  provides a compressive force that opposes the force exerted on the positioner  6  by the weight of the monitor  4 . As will be explained in greater detail herein, the motion resistance device  28  provides frictional resistance against movement of the shaft  26  and is designed to keep the monitor  4  stationary after user adjusts the position of the monitor  4  and has released it. 
         [0023]      FIG. 2  is an exploded view showing the adjustable support device  30  of the present invention. In this embodiment, the adjustable support device  30  includes a standard, pre-manufactured gas cylinder, which comprises a shaft  26  that is slidably contained within a cylinder  24 . The cylinder  24  includes a pressurized gas and piston arrangement (not shown) which urges the shaft  26  outwardly from the cylinder. In alternate embodiments, other means of providing a compressive force could be provided, such as a spring, for example. The shaft  26  includes an attachment end  38 , which is intended to engage the pivot  18  (see  FIG. 1 ). 
         [0024]    In accordance with the present invention, the adjustable support device  30  also includes a motion resistance device  28 , which is designed to be installed over the shaft  26  and external to the cylinder  24 . This allows the motion resistance device  28  to be used with a standard gas cylinder instead of requiring a custom designed and built gas cylinder, and enables the motion resistance device  28  to be retrofitted to a standard gas cylinder. 
         [0025]    The motion resistance device  28  comprises a split ring having two halves  32   a ,  32   b , which are positioned on opposing sides of the shaft  26 . A collar  36  encloses the split ring halves  32   a ,  32   b  and holds them in position against the shaft  26 . The collar  36  includes a cylindrical cup  40 , sized to slide over the split ring halves  32   a ,  32   b  and the shaft  26 , and two opposing arms  44   a ,  44   b  that extend from an open end of the cup  40 . Each of the arms  44   a ,  44   b  has a respective protrusion  48   a ,  48   b  that extends inwardly from the end of its respective arm  44   a ,  44   b  in a substantially perpendicular direction. The length of the arms  44   a ,  44   b  and the position and shape of the protrusions  48   a ,  48   b  are designed to engage a groove  50  of cylinder  24 , which retains collar  36  in position over split ring halves  32   a ,  32   b  and onto cylinder  24 . Groove  50  is provided in many standard gas cylinders. 
         [0026]    The cup  40  also includes an opening  42 , which is shaped to allow the attachment end  38  and shaft  26  pass through. Accordingly, in this embodiment, the opening  42  includes a circular-shaped center portion  41  that is positioned between opposing rectangular end portions  43   a ,  43   b.    
         [0027]    A strap  46  is preferably slid over the arms  44   a ,  44   b , which holds the arms  44   a ,  44   b  tightly against cylinder  24 , and therefore, prevents protrusions  48   a ,  48   b  from releasing from the groove  50 . Arms  44   a ,  44   b , protrusions  48   a ,  48   b , groove  50  and strap  46  are collectively identified in  FIG. 3  as a securing device  52 . Other alternative means, such as screws, rivets, fittings or other fasteners, for example, could be used to secure the collar  36  to the cylinder  24 . 
         [0028]    The amount of frictional resistance that the motion resistance device  28  provides against movement of the shaft  26  is determined by the force exerted by the split ring halves  32   a ,  32   b  against the shaft  26 . In order to enable the motion resistance device  28  to be used in a wide variety of applications, it is preferable that the amount of frictional resistance be adjustable. In this embodiment, the force exerted by the split ring halves  32   a ,  32   b  against the shaft  26  can be varied by adjusting a screw  54  that is threaded into a recess  56  on the side of the cup  40 . As screw  54  is threaded into the recess  56 , it presses split ring halves  32   a ,  32   b  more tightly against shaft  26 , thereby increasing the amount of frictional resistance acting on the shaft  26 . 
         [0029]      FIGS. 3 and 4  show the adjustable support device  30  of the present invention fully assembled. Arms  44   a ,  44   b  of collar  36  are held against cylinder  24  with strap  46 . Cup  40  is shown here completely enclosing split ring halves  32   a ,  32   b.    
         [0030]      FIGS. 5 through 7  show an alternate embodiment of the adjustable support device  130  of the present invention. In this embodiment, elements shared with the first embodiment are represented by reference numerals increased by factors of 100. For example, the cylinder  24  in  FIGS. 2-4  corresponds to cylinder  124  in  FIGS. 5-7 . Some features of this embodiment that are substantially identical to corresponding features in the first embodiment and were described with respect to the first embodiment are numbered in  FIGS. 5-7  but are not specifically referred to in the specification. 
         [0031]    As in the previous embodiment, this embodiment also employs arms  144   a ,  144   b  having protrusions  148   a ,  148   b , which fit into groove  150  of cylinder  124 , and strap  146  encircles the arms  144   a ,  144   b  and secures them to cylinder  124 . 
         [0032]    In this embodiment, a collar  136  having a threaded portion  161  and a tapered cup  140  is provided. The tapered cup  140  is of a truncated conical shape and includes a circular opening  168  sufficiently large in size to allow the passage of the shaft  126 . Two tapered split ring halves  132   a ,  132   b  (also of a truncated conical shape when paired) are provided and are complimentary in shape to the tapered cup  140 . A cap  166 , having internal threads  163  formed thereon, is designed to thread onto the threaded portion  161  of the collar  136  and retain the split ring halves  132   a ,  132   b  around the shaft  126  and within the tapered cup  140 . 
         [0033]    In this embodiment, the amount of friction applied by the split ring halves  132   a ,  132   b  against the shaft  126  can be adjusted by tightening or loosening the cap  166  (i.e., by rotating the cap  166  clockwise or counterclockwise, respectively, relative to the collar  136 ). A shoulder portion  170  of the cap  166  rests against the split ring halves  132   a ,  132   b  when the cap  166  is threaded onto the collar  136 . As cap  166  is tightened, the shoulder portion  170  urges the split ring halves  132   a ,  132   b  further into the tapered cup  140  (to the left in  FIG. 7 ) which, in turn, forces the split ring halves  132   a ,  132   b  inwardly against the shaft  126 . This causes an increase in frictional resistance on shaft  126 , further resisting extension or retraction of shaft  126 . Conversely, as cap  166  is loosened, the shoulder portion  170  moves away from the split ring halves  132   a ,  132   b  (to the right in  FIG. 7 ), which allows the split ring halves  132   a ,  132   b  to move outwardly with respect to the tapered cup  140  and exert less force against the shaft  126 . This causes a decrease in frictional resistance on shaft  126 , which reduces resistance to extension or retraction of shaft  126 . 
         [0034]    While the principles of the invention have been described above in connection with preferred embodiments, it is to be clearly understood that this description is made only by way of example and not as a limitation of the scope of the invention.