Abstract:
A hinge assembly rotationally connecting two components includes at least a shaft coupled to one of the components and a tubular member connected to the other component and a defining an annular space around said shaft. A viscous damping fluid is disposed in said space and provides a damping force resisting relative rotation between the two components. A second tubular member is also provided that is connected to the shaft and is arranged axially around the first tubular member. In this latter configuration, static and dynamic frictional forces are generated between the tubular members that resist rotation between the components as well.

Description:
RELATED APPLICATIONS  
       [0001]     The subject matter of this application is related to our commonly owned U.S. patent application Ser. No. ______ filed ______ based on U.S. Provisional application No. 60/687,483, file Jun. 4, 2005, entitled Friction Hinge with Angularly Dependent Torque; and U.S. Patent publication entitled Reinforcer For Wrapped Band Hinges, No. 20050028321, published Feb. 10, 2005, both incorporated herein by reference. 
     
    
     BACKGROUND TO THE INVENTION  
       [0002]     a. Field of Invention  
         [0003]     This invention pertains to a novel hinge in which two cylindrical surfaces are separated by a space that is filled with a viscous damping fluid to generate a frictional force between the two surfaces that is proportional to the relative rotational speed of the two surfaces. Other surfaces are provided in the hinge that generate static and dynamic frictional forces controlling the movement of various hinge elements.  
         [0004]     b. Description of the Prior Art  
         [0005]     Friction hinges are now found in many products. Often they are used to hold display screens in position in laptop computers, video displays in automobiles, medical equipment and the like. The friction hinges in these devices have improved greatly within the past few years and do an excellent job of holding their displays in position. However, their performance is less then ideal because the static coefficient of friction between any two contacting elements is always substantially larger then the dynamic coefficient despite efforts to make the difference as small as possible. The result of this is that the device being controlled by the friction hinge, once in motion, tends to keep moving. This can result in laptop lids that slam shut and video screen in cars that swing too freely from their overhead mounts. This can be merely annoying or it can cause damage to the video screen or to its mountings.  
       SUMMARY OF THE INVENTION  
       [0006]     Our invention provides a friction hinge with viscous, and therefore velocity dependent damping. When stationary, the inventive hinge has the well known characteristics of friction hinges. In rotation, the hinge displays the characteristics usually associated with viscous damping and, therefore, provides a damping torque that increases with angular velocity which tends to limit the speed with which the device moves. As the speed of motion decreases, for other reasons, the damping torque also decreases so that the position at which the device comes to rest is more or less independent of the damping torque. However, since the device provides conventional static friction together with viscous damping, and since static friction becomes effective before the relative velocity of moving parts quite reaches zero, the final position will be the angular position at which the velocity is low enough for the static friction to dominate.  
         [0007]     In one embodiment, by combining our present invention with a selective friction hinge (described in U.S. patent application Ser. No. ______ filed ______ based on U.S. Provisional application No. 60/687,483, file Jun. 4, 2005, entitled Friction Hinge with Angularly Dependent Torque and incorporated herein by reference), a hinge can be made with wonderful operating characteristics: friction where needed, and viscous damping throughout the range of motion. Furthermore, because these hinges are often employed where space is at a premium, our inventive hinge has the advantage of providing these benefits without requiring significantly greater space than is needed for conventional friction hinges.  
         [0008]     Briefly, our inventive viscously-damped friction hinge is constructed of three coaxially disposed elements. There is an annular element which may or may not have cylindrical symmetry according to the geometric requirements of the frictional torque. Of the other two elements, one is disposed inside the annular element, and the other outside it. These two elements are irrotatably connected to one another, effectively giving the device two pieces that can undergo relative rotation. In practice, where the hinge would be used to control the motion and positioning of a screen, either of these can be connected to the screen and the other to its mounting which is usually referred to as ground.  
         [0009]     In the preferred embodiment the innermost element is a round shaft. This shaft may be solid, but it could be hollow to form a passage of wires or some other purposes. For simplicity, in what follows, we will refer to the inner element as a solid shaft.  
         [0010]     A viscous damping fluid is contained in the space between the inner shaft and the annular element. This fluid can be any of a number of commercially available greases made for this purpose. It is also possible to produce a suitable damping fluid by adding fillers to a lubricating oil to obtain whatever damping characteristics are required for a particular application. Care must be taken to provide smooth surfaces to the shaft and the surfaces of the annular element as close tolerances are needed to achieve useful levels of damping torque. In our experience, it has been necessary to grind the shaft surface and do careful boring of the hole in the annular element.  
         [0011]     In the preferred embodiment the outermost element produces friction through its contact with the exterior of the annular element. This friction can be produced by a number of different means that will be well know to those skilled in the art of friction hinges. In our preferred embodiment, friction is produced by means of a question-mark shaped band.  
         [0012]     If uniform frictional torque is required throughout the arcuate range of the hinge&#39;s motion, then the exterior cylindrical surface of the annular element would be circular. But, according to the teachings of the above-identified U.S. patent application Ser. No. ______), the torque can have an angular dependence with detents as needed.  
         [0013]     The object of our invention is to provide a hinge that combines the holding characteristics of friction hinges and which also has the benefits of hydraulically damped motion control when rotating.  
         [0014]     Another object of our invention is to provide a hinge that combines friction for positioning and viscous damping for motion control in a small size.  
         [0015]     Yet another object of our invention is to provide the frictional and the damping characteristics in a hinge that is compact and yet is easily and firmly attached to each of the elements whose motion is to be controlled thereby.  
         [0016]     The inventive pop-up friction hinge system accordingly comprises the features of construction, combination of elements, and arrangement of parts which will be exemplified in the constructions described hereinafter, and the scope of the invention will be indicated in the claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]      FIG. 1  is a perspective view of the preferred embodiment of our invention shown with the shaft adapter on the left.  
         [0018]      FIG. 2  is a cross-sectional view of the hinge of  FIG. 1 , taken through the centerline of the hinge.  
         [0019]      FIG. 3  is an exploded view of the hinge of  FIGS. 1 and 2 .  
         [0020]      FIG. 4   a  is an exploded view of an alternative embodiment of our invention depicting another method for the irrotatable attachment of the shaft and the question-mark band, and with an annular element and question-mark shaped band configured to produce an angularly dependent torque.  
         [0021]      FIG. 4   b  shows a cross-sectional view through the hinge of  FIG. 4   a.    
         [0022]      FIGS. 5   a  and  5   b  show perspective views of yet another embodiment of the invention depicting a hinge with angularly dependent torque and having an arcuate range without viscous friction.  
         [0023]      FIG. 6  is a perspective view of another embodiment of the inventive hinge with the question-mark shaped band mounted to a plate, with the round portion of the band being split into two segments which act as bearings, and a cam segment made a part of the annular element. Friction is generated by the contact between the cam and the mounting plate.  
         [0024]      FIGS. 7 and 8  are cut-away views of the hinge of  FIG. 6  shown in different angular positions, the cut-away being made to show the interaction of the cam against the plate.  
         [0025]      FIG. 9  shows two of our inventive hinges used to mount a video display to an overhead plate.  
         [0026]      FIG. 10  shows a further embodiment of the invention with another technique for generating friction.  
         [0027]      FIG. 11  represents one possible set of friction elements in a hinge of the type shown in  FIG. 1   FIG. 12  depicts another type of friction hinge adapted for use in the hinge of  FIG. 10 .  
         [0028]      FIG. 13  is an exploded view of a version of the invention in which viscous damping occurs outside of the middle element, and friction is generated on its interior surface. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0029]     Referring now to  FIGS. 1, 2 , and  3 , the subject hinge includes a question-mark shaped band  1  with a mounting flange  3  (visible only in  FIGS. 1 and 3 ), a circular portion  5 , a sleeve or annual element  7  and a shaft  11 . The flange  3  is formed with a plurality of holes  3 A for mounting to one of the components to be connected by the hinge of our invention. Though shown as flat, the flange  3  can be formed to any other convenient shape. Similarly, the number, size and shape of the mounting holes  3 A can changed as needed. Moreover, instead of flange  3  other firm mounting means can be employed.  
         [0030]     The circular portion  5  is formed to a slightly smaller size than the outside diameter of annular element  7 . The difference between the respective sizes of these two components determines the frictional torque generated therebetween. In assembly, band  1  is pressed over annular element  7 . Relative rotation of one of these with respect to the other will, according to the well know principles of friction hinges, require overcoming the frictional torque produced by the interference in their diameters. Relative rotation in the direction so as to tighten the band around annular element  7  produces a higher torque than rotation in the other direction.  
         [0031]     As seen in  FIG. 3 , annular element  7  is a hollow cylinder. One end  7 A is knurled to form an irrotatable press fit into adapter  9 . Adapter  9  is used as a means for mounting to the other hinged component. The adapter  9  shown is of a commonly used type and configuration, but many different mounting members could be used for securing the hinge between two components without departing from the scope of our invention. Also, the press fit attachment is only by example, and many other firm attachments may be used to couple annular element  7  to a component as well.  
         [0032]     Apart from the knurl, annular element  7  has a uniform circular exterior surface  7 B. In conjunction with question-mark band  1 , this surface  7 B produces a torque that is essentially uniform over the full relative rotation of the parts. As will be seen in alternative embodiments, and in accordance with the structures shown in the above-mentioned patent application, the annular element  7  can have an outer surface  7  with a non-uniform shape to produce variations in torque, and even detent positions according to the details of that shape.  
         [0033]     Annular element  7  is hollow and is formed with an interior surface  7 C to accept shaft  11 . Shaft  11  has an outer surface  11  A coated with the viscous damping fluid  12  before insertion into annular element  7  so as to fill the space between the respective surfaces  7 C,  11 A. The diametrical clearance between surface  11 A and the inside surface  7 C, together with the shear characteristics of the viscous damping fluid used, are selected to provide damping. We have found that the clearance between surfaces  7 C and  11 A should be in the range of 0.5 and 1.5 mills.  
         [0034]     It may be convenient to include a shoulder  13  on shaft  11  to limit the axial movement of annular element  7  in one direction as best seen in  FIG. 2 . In this embodiment, there is nothing to limit the excursion of annular element in the other direction. It is not difficult to include a feature to accomplish that. But, as these hinges are most often used in pairs, with both attached to the same lid and base, it is usually sufficient to limit the travel in one direction only, and depend upon the other hinge, which can be mounted in the opposite orientation, to limit travel in the second direction.  
         [0035]     The shoulder end  13  of shaft  1  has cross slot  15 . Extending from mounting flange  3  is anti-rotation arm  17  which fits into slot  15  to cause band  1  and shaft  11  to rotate together.  
         [0036]     In operation, annular element  7  rotates relative to and between band  1  and shaft  11 . Friction is produced between the circular portion  5  of question-mark band  1  and the exterior surface of annular element  7 . In other words, annular element  7  and band  5  cooperate to generate static and dynamic friction therebetween in the usual manner. However, while these two elements rotate with respect to each other, the annular element  7 , the shaft  11  and the damping fluid  12  cooperate to generate a velocity-dependent, viscous damping torque or force between the interior surface of annular element  7  and shaft  11  which tends to slow the relative rotation. Thus, three kinds of forces are generated within the novel hinge described herein, which limit the movement of the components interconnected by this hinge: a static force generated between the outer surface  7 B of annular element  7  and the inner surface  5 A of the circular portion  5  of band  1 , a dynamic friction generated between the same components, and a velocity-dependant damping force generated between the outer surface  11 A of shaft  11  and the inner surface  5 A of circular portion  5 .  
         [0037]      FIGS. 4   a  and  4   b  depict a hinge of our invention with the same general construction as the hinge shown in  FIGS. 1-3 . But this hinge has additional features previously disclosed. First, the attachment of the band to the shaft is done using means disclosed in US Patent publication entitled Reinforcer for Wrapped Band Hinges, No. 20050028321, published Feb. 10, 2005, and incorporated herein by reference. And second, the annular element and the question-mark shaped band are constructed as described in the aforementioned US Patent application entitled Friction Hinge with Angularly Dependent Torque. Anti-rotation arm  19  has a shaped hole  20  made to fit closely over generally oval shaped end  21  of shaft  23 . Slots  25  are shaped to receive tabs  27  of band  29  and to lock in place. Annular element  31  has cylindrical surface  33  formed with several zones  30 ,  32 ,  33  disposed at different radii from the axis provide angularly dependent torque as described in the latter patent application when combined with shaped portion  35  of band  29 . The annular member  31  receives shaft  23  and the space between the member  31  and the shaft  23  is filled with a dampening gel  23 A as described above.  
         [0038]     In operation, this hinge has the same characteristics as the hinge of the preferred embedment but also in combination with the benefits provided by the other two referenced applications.  
         [0039]      FIGS. 5   a  and  5   b  show a hinge of the same general construction as the hinge of  FIGS. 4   a  and  4   b.  The hinge is shown in two different angular positions. End  37  of the shaft has a key extending from the shaft center. Hole  39  in the anti-rotation arm is shaped to accept end  37  but with clearance for some desired angular displacement that is to take place without viscous damping.  FIG. 5   a  shows the hinge in the center of that angular range, and  FIG. 5   b  shows the hinge at one end of the angular range.  
         [0040]     In operation, the hinge has the same characteristics as the hinge of  FIGS. 4   a  and  4   b  except that each time the direction of rotation is reversed, and there is a range of motion without viscous damping. Thereafter, the viscous damping is resumed, and continues until the next reversal of direction.  
         [0041]     The alternative embodiment of our invention shown in  FIGS. 6, 7 , and  8  has hinge  41  mounted to plate  43  as might be used to mount a display as shown in  FIG. 9 . The two curved, bearing portions  45  of the band are shaped to fit snugly, but without interference, over the ends of shaft  47  to form bearings within which the shaft can rotate. Between the two bearing portions  45 , shaft  47  has a surface formed into cam  49 . Attached to shaft  47 , is output adapter  48 . The cross-sectional view shown in  FIG. 7  makes this clearer. As output adapter  48  and shaft  47  rotate, as shown in  FIG. 8 , also a cross-sectional view, cam  49  contacts plate  43 , causing shaft  47  to move away from plate  43 . This is possible because the band is made of spring material and bearing portions  45  of the band are at the ends of extensions  51  that connect the curved portions to the body of the band. These extensions form the spring against which the cam forces shaft  47  away from plate  43 , producing the desired friction.  
         [0042]     All of the embodiments shown have the desired compact structure combining viscous damping with friction in a package that is only slightly larger, if at all, then a state-of-the-art friction hinge.  FIGS. 10, 11 , and  12  show a hinge employing another method for achieving friction with viscous damping in a small package. Hinge  53  is comprised of annular element  55 , friction clamp  57 , and housing  59 . Also present, as in the previously shown embodiments, but not shown are a shaft and means providing an irrotational connection between the shaft and housing  59 . Friction clamp  57  and be a single piece as shown in  FIG. 11 , or a stack of shorter plates as shown in  FIG. 12 . In either case, friction clamp  57  moves with housing  59  because of a dovetail  61 or other similar mechanism. As in the previously shown embodiments, viscous damping is due to the shear in the fluid between the shaft and the annular element.  
         [0043]     A still further embodiment is represented in  FIG. 13 . In this case the fluid shear that produces viscous damping takes place between the outer surface of annular element  63  and the interior surface of housing  65 . Friction is achieved by the well known technique of a hairpin-like, split shaft  67  that is inserted into the co-axial hole in the center of annular element  63 . As before, the inner and outer elements must be irrotationally connected. This is accomplished by shaped end  69  of shaft  67  which fits closely into shaped hole  71  in housing  65 .  
         [0044]     It will thus be seen that the objects set forth above among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in the construction of the inventive friction hinge without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.  
         [0045]     It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.