Patent Abstract:
A friction hinge assembly includes a spring that assists the opening of a first member relative to a second member by storing energy in the spring during the closing operation. The spring is of a unique multilayered torsion bar design.

Full Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority of U.S. Provisional Application for Patent Ser. No. 61/238,206, filed on Aug. 30, 2009, which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a hinge assembly for rotationally attaching a first member to a second member to allow rotational movement of the first member relative to the second member between a closed position and an open position. 
     2. Description of the Prior Art 
     Hinge assemblies for rotationally attaching a first member to a second member to allow rotational movement of the first member relative to the second member between a closed position and an open position are known in the prior art. In particular spring loaded hinge assemblies that assist the opening of the first member relative to the second member by storing energy in a spring during the closing operation are shown in U.S. Pat. No. 7,055,215 B1 to Ligtenberg at al., issued on Jun. 6, 2006. However, these hinges require special machined springs that are extremely costly and complex to manufacture. The multi-layer torsion bar of the present invention, which functions to assist the opening of the first member relative to the second member by storing energy during the closing operation, drastically reduces the cost and complexity of spring manufacture while maintaining the same performance. These and other advantages of the present invention will become apparent from the description and drawings that follow. None of the prior art hinge assemblies are seen to teach or suggest the unique features of the present invention or to achieve the advantages of the present invention. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a hinge assembly for rotationally attaching a first member to a second member to allow rotational movement of the first member relative to the second member between a closed position and an open position. The hinge assembly of the present invention includes a spring that assists the opening of the first member relative to the second member by storing energy in the spring during the closing operation. The spring is of a unique multilayered torsion bar design. The hinge assembly also includes a friction mechanism that exerts a sufficient frictional force on the hinge shaft such that the first member can be held in a range of desired angular positions on either side of the angular position corresponding to the relaxed state of the hinge spring and including the angular position corresponding to the relaxed state of the hinge spring. In addition, the multilayered torsion bar spring with its unique design and features is a significant invention in and of itself. Applying a torsion bar spring to a friction hinge is also another aspect of the invention. 
     Accordingly, it is an object of the invention to provide a multi-layer torsion bar spring. 
     It is another object of the invention to provide a spring assisted friction hinge that employs a multi-layer torsion bar spring. 
     It is yet another object of the invention to provide a spring assisted friction hinge that employs a torsion bar spring. 
     These and other objects of the present invention will become apparent from the attached description and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an environmental view of the hinge assembly of the present invention showing the hinge assembly applied to a laptop computer with the lid of the laptop computer in the closed position. 
         FIG. 2  is an environmental view of the hinge assembly of the present invention showing the hinge assembly applied to a laptop computer with the lid of the laptop computer in an angular position relative to the base of the laptop computer that corresponds to the relaxed state of the hinge spring. 
         FIG. 3  is an environmental view of the hinge assembly of the present invention showing the hinge assembly applied to a laptop computer with the lid of the laptop computer in an angular position relative to the base of the laptop computer that corresponds to the fully open state of the laptop computer lid. 
         FIG. 4  is a fragmentary environmental view showing the installation of the hinge assembly of the present invention to a laptop computer. 
         FIG. 5  is a fragmentary environmental view with a section taken through the laptop computer to show the installation of the hinge assembly of the present invention to the laptop computer. 
         FIGS. 6-13  are views of the hinge assembly of the present invention showing the hinge adaptor in an angular position relative to the base of the hinge assembly that corresponds to the relaxed state of the hinge spring. 
         FIG. 14  is an exploded view of the hinge assembly of the present invention. 
         FIG. 15  is an isometric view of the hinge assembly of the present invention showing the hinge adaptor in an angular position relative to the base of the hinge assembly that corresponds to the relaxed state of the hinge spring. 
         FIG. 16  is an isometric view of the hinge assembly of the present invention showing the hinge adaptor in an angular position relative to the base of the hinge assembly that corresponds to the relaxed state of the hinge spring with the spring cover removed to show the multilayered torsion bar spring in its relaxed state. 
         FIG. 17  is an isometric view of the hinge assembly of the present invention showing the hinge adaptor in an angular position relative to the base of the hinge assembly that corresponds to the relaxed state of the hinge spring. 
         FIG. 18  is an isometric view of the hinge assembly of the present invention showing the hinge adaptor in an angular position relative to the base of the hinge assembly that corresponds to the relaxed state of the hinge spring with the hinge assembly sectioned to reveal its internal details. 
         FIG. 19  is an isometric view of the hinge assembly of the present invention showing the hinge adaptor in an angular position relative to the base of the hinge assembly that corresponds to the fully twisted state of the hinge spring with the spring cover and cap removed and with the end piece of the hinge assembly sectioned to show the multilayered torsion bar spring in its fully twisted state. 
         FIG. 20  is an isometric view of the hinge assembly of the present invention showing the hinge adaptor in an angular position relative to the base of the hinge assembly that corresponds to the fully open position of the laptop computer lid. 
         FIG. 21  is an isometric view of the hinge assembly of the present invention showing the hinge adaptor in an angular position relative to the base of the hinge assembly that corresponds to the fully open position of the laptop computer lid with the spring cover removed to show the multilayered torsion bar spring in a twisted state corresponding to the fully open position of the laptop computer lid. 
         FIG. 22  is a cross-sectional view of the hinge assembly of the present invention taken along the line A-A in  FIG. 26  to reveal its internal details. 
         FIG. 23  is an isometric view of the hinge assembly of the present invention showing the hinge adaptor in an angular position relative to the base of the hinge assembly that corresponds to the fully twisted state of the hinge spring. 
         FIG. 24  is an isometric view of the hinge assembly of the present invention showing the hinge adaptor in an angular position relative to the base of the hinge assembly that corresponds to the fully twisted state of the hinge spring with the spring cover removed to show the multilayered torsion bar spring in its fully twisted state. 
         FIG. 25  is a fragmentary enlarged view showing the multilayered torsion bar spring in its fully twisted state. 
         FIGS. 26-27  are top and side views of the hinge assembly of the present invention to provide a guide to show the cut lines along which the cross-sectional views in FIGS.  22  and  28 - 35  are taken. 
         FIG. 28  is a cross-sectional view of the hinge assembly of the present invention taken along the line D-D in  FIG. 27  showing the hinge adaptor in an angular position relative to the base of the hinge assembly that corresponds to the fully open position of the laptop computer lid. 
         FIG. 29  is a cross-sectional view of the hinge assembly of the present invention taken along the line D-D in  FIG. 27  showing the hinge adaptor in an angular position relative to the base of the hinge assembly that corresponds to the relaxed state of the hinge spring. 
         FIG. 30  is a cross-sectional view of the hinge assembly of the present invention taken along the line D-D in  FIG. 27  showing the hinge adaptor in an angular position relative to the base of the hinge assembly that corresponds to the fully-twisted state of the hinge spring. 
         FIG. 31  is a cross-sectional view of the hinge assembly of the present invention taken along the line C-C in  FIG. 27  showing the hinge adaptor in an angular position relative to the base of the hinge assembly that corresponds to the fully open position of the laptop computer lid. 
         FIG. 32  is a cross-sectional view of the hinge assembly of the present invention taken along the line C-C in  FIG. 27  showing the hinge adaptor in an angular position relative to the base of the hinge assembly that corresponds to the relaxed state of the hinge spring. 
         FIG. 33  is a cross-sectional view of the hinge assembly of the present invention taken along the line C-C in  FIG. 27  showing the hinge adaptor in an angular position relative to the base of the hinge assembly that corresponds to the fully-twisted state of the hinge spring. 
         FIG. 34  is a cross-sectional view of the hinge assembly of the present invention taken along the line B-B in  FIG. 27  showing the hinge adaptor in an angular position relative to the base of the hinge assembly that corresponds to the relaxed state of the hinge spring. 
         FIG. 35  is a cross-sectional view of the hinge assembly of the present invention taken along the line B-B in  FIG. 27  showing the hinge adaptor in an angular position relative to the base of the hinge assembly that corresponds to the fully-twisted state of the hinge spring. 
         FIGS. 36-41  are views of the adaptor of the hinge assembly of the present invention for attaching the hinge assembly to a first member such as, for example, a laptop computer lid. 
         FIGS. 42-49  are views of the spring end cap of the hinge assembly of the present invention for axially constraining one end of the multi-layer torsion bar spring relative to the hinge shaft. 
         FIGS. 50-57  are views of the end piece of the hinge assembly of the present invention for rotationally constraining one end of the multi-layer torsion bar spring relative to a second member such as, for example, a laptop computer base. 
         FIGS. 58-62  are views of one leaf of the multi-layer torsion bar spring of the hinge assembly of the present invention. 
         FIGS. 63-70  are views of the hinge base of the hinge assembly of the present invention. 
         FIGS. 71-76  are views of the hinge shaft of the hinge assembly of the present invention. 
         FIGS. 77-82  are views of the friction element of the friction mechanism of the hinge assembly of the present invention. 
         FIGS. 83-89  are views of the friction mechanism cover of the hinge assembly of the present invention. 
         FIGS. 90-95  are views of the channel insert of the friction mechanism of the hinge assembly of the present invention. 
         FIGS. 96-102  are views of the torsion bar spring cover of the hinge assembly of the present invention. 
         FIG. 103  is an environmental view of a second embodiment of the hinge assembly of the present invention showing the hinge assembly applied to a laptop computer with the lid of the laptop computer in the closed position. 
         FIG. 104  is an environmental view of the second embodiment of the hinge assembly of the present invention showing the hinge assembly applied to a laptop computer with the lid of the laptop computer in an angular position relative to the base of the laptop computer that corresponds to the relaxed state of the hinge spring. 
         FIG. 105  is an environmental view of the second embodiment of the hinge assembly of the present invention showing the hinge assembly applied to a laptop computer with the lid of the laptop computer in an angular position relative to the base of the laptop computer that corresponds to the fully open state of the laptop computer lid. 
         FIGS. 106-107  are fragmentary environmental views showing the installation of the second embodiment of the hinge assembly of the present invention to a laptop computer. 
         FIG. 108  is a fragmentary environmental view with a section taken through the laptop computer to show the installation of the second embodiment of the hinge assembly of the present invention to the laptop computer. 
         FIGS. 109-112  are views of the second embodiment of the hinge assembly of the present invention showing the hinge adaptor in an angular position relative to the base of the hinge assembly that corresponds to the relaxed state of the hinge spring. 
         FIG. 113  is a view of the second embodiment of the hinge assembly of the present invention showing the hinge adaptor in an angular position relative to the base of the hinge assembly that corresponds to the relaxed state of the hinge spring and with the outer shell and inner sleeves removed to show the torsion bar spring. 
         FIGS. 114-115  are cross sectional views of the second embodiment of the hinge assembly of the present invention showing the hinge adaptor in an angular position relative to the base of the hinge assembly that corresponds to the relaxed state of the hinge spring. 
         FIGS. 116-117  are exploded views of the second embodiment of the hinge assembly of the present invention. 
         FIG. 118  is an isometric view of the second embodiment of the hinge assembly of the present invention showing the hinge adaptor in an angular position relative to the base of the hinge assembly that corresponds to the closed state of the hinge assembly and the fully twisted state of the hinge spring. 
         FIGS. 119-121  are views of the second embodiment of the hinge assembly of the present invention showing the hinge adaptor in an angular position relative to the base of the hinge assembly that corresponds to the closed state of the hinge assembly and the fully twisted state of the hinge spring and that are partially broken away to reveal internal details. 
         FIG. 122  is an isometric view of the second embodiment of the hinge assembly of the present invention showing the hinge adaptor in an angular position relative to the base of the hinge assembly that corresponds to the open position of the laptop computer lid. 
         FIG. 123  is a view of the second embodiment of the hinge assembly of the present invention showing the hinge adaptor in an angular position relative to the base of the hinge assembly that corresponds to the fully open position of the laptop computer lid and that is partially broken away to reveal internal details. 
         FIG. 124  is a cross-sectional view of the second embodiment of the hinge assembly of the present invention taken along the line B-B in  FIG. 109  showing the hinge adaptor in an angular position relative to the base of the hinge assembly that corresponds to the fully closed position of the laptop computer lid. 
         FIG. 125  is a cross-sectional view of the second embodiment of the hinge assembly of the present invention taken along the line B-B in  FIG. 109  showing the hinge adaptor in an angular position relative to the base of the hinge assembly that corresponds to the relaxed state of the hinge assembly. 
         FIG. 126  is a cross-sectional view of the second embodiment of the hinge assembly of the present invention taken along the line B-B in  FIG. 109  showing the hinge adaptor in an angular position relative to the base of the hinge assembly that corresponds to the fully open position of the laptop computer lid. 
         FIG. 127  is a cross-sectional view of the second embodiment of the hinge assembly of the present invention taken along the line C-C in  FIG. 109  showing the hinge adaptor in an angular position relative to the base of the hinge assembly that corresponds to the fully closed position of the laptop computer lid. 
         FIG. 128  is a cross-sectional view of the second embodiment of the hinge assembly of the present invention taken along the line C-C in  FIG. 109  showing the hinge adaptor in an angular position relative to the base of the hinge assembly that corresponds to the relaxed state of the hinge assembly. 
         FIG. 129  is a cross-sectional view of the second embodiment of the hinge assembly of the present invention taken along the line C-C in  FIG. 109  showing the hinge adaptor in an angular position relative to the base of the hinge assembly that corresponds to the fully open position of the laptop computer lid. 
         FIG. 130  is a cross-sectional view of the second embodiment of the hinge assembly of the present invention taken along the line D-D in  FIG. 109  showing the hinge adaptor in an angular position relative to the base of the hinge assembly that corresponds to the fully closed position of the laptop computer lid. 
         FIG. 131  is a cross-sectional view of the second embodiment of the hinge assembly of the present invention taken along the line D-D in  FIG. 109  showing the hinge adaptor in an angular position relative to the base of the hinge assembly that corresponds to the relaxed state of the hinge assembly. 
         FIG. 132  is a cross-sectional view of the second embodiment of the hinge assembly of the present invention taken along the line D-D in  FIG. 109  showing the hinge adaptor in an angular position relative to the base of the hinge assembly that corresponds to the fully open position of the laptop computer lid. 
         FIG. 133  is a cross-sectional view of the second embodiment of the hinge assembly of the present invention taken along the line E-E in  FIG. 109  showing the hinge adaptor in an angular position relative to the base of the hinge assembly that corresponds to the fully closed position of the laptop computer lid. 
         FIG. 134  is a cross-sectional view of the second embodiment of the hinge assembly of the present invention taken along the line E-E in  FIG. 109  showing the hinge adaptor in an angular position relative to the base of the hinge assembly that corresponds to the relaxed state of the hinge assembly. 
         FIG. 135  is a cross-sectional view of the second embodiment of the hinge assembly of the present invention taken along the line E-E in  FIG. 109  showing the hinge adaptor in an angular position relative to the base of the hinge assembly that corresponds to the fully open position of the laptop computer lid. 
         FIGS. 136-142  are views of the adaptor of the second embodiment of the hinge assembly of the present invention for attaching the hinge assembly to a first member such as, for example, a laptop computer lid. 
         FIGS. 143-150  are views of the first spring end cap or holder of the second embodiment of the hinge assembly of the present invention for axially constraining one end of the multi-layer torsion bar spring relative to the hinge base. 
         FIGS. 151-158  are views of the second spring end cap or holder of the second embodiment of the hinge assembly of the present invention for axially constraining one end of the multi-layer torsion bar spring relative to the hinge shaft. 
         FIGS. 159-162  are views of one leaf of the multi-layer torsion bar spring of the second embodiment of the hinge assembly of the present invention. 
         FIGS. 163-170  are views of the hinge base of the second embodiment of the hinge assembly of the present invention, which also constitutes the friction mechanism of the second embodiment of the hinge assembly of the present invention. 
         FIGS. 171-178  are views of the hinge shaft of the second embodiment of the hinge assembly of the present invention. 
         FIGS. 179-186  are views of the outer shell covering the torsion bar spring of the second embodiment of the hinge assembly of the present invention. 
         FIGS. 187-194  are views of the inner torsion bar spring covers or sleeves of the second embodiment of the hinge assembly of the present invention that fit between the outer shell and the torsion bar spring. 
     
    
    
     Similar reference characters denote corresponding features consistently throughout the attached drawings. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIGS. 1-102 , the present invention is directed to a hinge assembly  300 ,  500  for rotationally attaching a first member to a second member to allow rotational movement of the first member relative to the second member between a closed position and an open position. Referring to  FIGS. 1-5 , two hinge assemblies  300  and  500  made in accordance with the present invention are shown being used to rotationally attach the lid  204  of a laptop computer  200  to the base  202  of the laptop computer  200 . The laptop lid  204  typically houses the laptop screen  206  and its angular position relative to the laptop base  202  should be adjustable within a range of angular positions suitable for people of a variety of sizes to properly view the laptop screen  206 . 
     The hinge assembly  300  is a left hinge assembly and the hinge assembly  500  is a right hinge assembly. The right hinge assembly  500  is a mirror image of the hinge assembly  300  about a plane perpendicular to longitudinal axes of the shafts of each of the hinge assemblies and positioned halfway between the two hinge assemblies. Accordingly, only the hinge assembly  300  is described in detail. The laptop lid  204  typically is releasably secured in the closed position relative to the laptop base  202  by a latch (not shown) of some sort. The latch can be operated by a user to release or free the laptop lid  204  for rotational movement to the open position relative to the laptop base  202 . 
     The hinge assembly  300  can be used to rotationally attach a first member to a second member to allow rotational movement of the first member relative to the second member between a closed position and an open position. In the illustrated example, the first member is the laptop lid  204  and the second member is the laptop base  202 . The hinge assembly  300  includes an elongated shaft  320 , an adaptor  340 , a hinge base  302 , a friction mechanism  430 , an end piece  360 , a torsion bar spring  380 , a cap  400 , and a torsion bar cover  420 . 
     Referring to  FIGS. 1-35  and  71 - 76 , the elongated shaft  320  has at least a first end portion  326 , a second portion  324  and a head portion  322 . The first end portion  326  of the shaft  320  is provided with a plurality of elongated teeth  328  of triangular cross section evenly distributed about the circumference of the first end portion  326  of the shaft  320 . Each of the plurality of elongated teeth  328  extends for at least the majority of the length of the first end portion  326  of the shaft  320 . In the illustrated example, the second portion  324  of the shaft  320  is of larger diameter compared to the first end portion  326 . The head portion  322  of the shaft  320  is in the form of a cylindrical disk of a larger diameter as compared to the second portion  324 . The head portion  322  of the shaft  320  has a slot  330  that extends transversely, i.e. perpendicularly, to the longitudinal axis of the shaft  320 . The head portion  322  of the shaft  320  has a pair of prongs  332  projecting from the head portion  322  on either side of the slot  330 . The prongs  332  extend from the head portion  322  of the shaft  320  in a direction parallel to the longitudinal axis of the shaft  320  and away from the first end portion  326  and the second portion  324 . The prongs  332  have a plurality of ribs  334  provided on their outer surfaces. In the illustrated example, the ribs  334  are curved and have a saw tooth profile in cross section. 
     The adaptor  340  is attached to the shaft  320  at the first end portion  326  of the shaft  320 . The adaptor  340  is attached to the first end portion  326  of the shaft  320  such that the adaptor  340  is constrained to rotate with the shaft  320  as a unit. The adaptor  340  is adapted for fixed attachment to the first member, the laptop lid  204  in the illustrated example, so as to move with the first member as a unit. Referring to  FIGS. 1-35  and  36 - 41 , the adaptor  340  has a body portion  342  that is rectangular with two rounded corners in plan view. The body portion  342  of the adaptor  340  is provided with a plurality of holes  344  to allow the adapter  340  to be securely fastened to the first member, for example the laptop lid  204 , by screws  346 . 
     The adaptor  340  has a bore  348  provided on one side of the rectangular body portion  342 . The bore  348  of the adapter  340  is designed to receive the first end portion  326  of the shaft  320  in a press fit or interference fit such that the shaft  320  is securely fastened to the adaptor  340  and the shaft  320  and the adaptor  340  are rotationally coupled to rotate together as a unit. The teeth  328  on the shaft&#39;s end portion  326  assist in rotationally coupling the shaft  320  to the adaptor  340  by providing a stronger grip between the internal surface of the bore  348  of the adapter  340  and the exterior surface of the first end portion  326  of the shaft  320 . Thus, the bore  348  of the adapter  340  and the toothed exterior surface of the first end portion  326  of the shaft  320  form the means for securely fastening the shaft  320  to the adaptor  340  and rotationally coupling the shaft  320  and the adaptor  340  together in the illustrated embodiment. 
     Many other suitable means may also be employed for securely fastening the shaft  320  to the adaptor  340  and rotationally coupling the shaft  320  and the adaptor  340  together. The exterior surface of the first end portion  326  of the shaft  320  may be smooth and inserted into the bore  348  in an interference fit to secure and couple the shaft  320  and the adaptor  340  together. A key cooperating with slots in the shaft  320  and the bore  348  may be used to secure and couple the shaft  320  and the adaptor  340  together. Fasteners extending through the wall of the bore  348  either extending into corresponding holes in the shaft  320  or frictionally engaging the shaft  320  may be used to secure and couple the shaft  320  and the adaptor  340  together. Also, the adaptor  340  may be clamped to the shaft  320  using a clamping arrangement such as by providing a longitudinal slot that extends completely through the wall of the bore  348  and providing one or two flanges adjacent the longitudinal slot with screws that can be tightened to draw the edges of the longitudinal slot together to clamp the adaptor  340  to the shaft  320 . 
     The hinge base  302  is adapted for fixed attachment to the second member, the laptop base  202  in this example, so as to move with the second member as a unit. The hinge base  302  has at least one bearing surface  304 ,  306  that rotationally supports the shaft  320  such that, when the adaptor  340  is attached to the first member and the hinge base  302  is attached to the second member, the first member is rotationally attached to the second member such that the first member can rotationally move relative to the second member between a closed position and an open position. In the illustrated example, the first and second members are the laptop lid  204  and the laptop base  202 , respectively. The bearing surface of the hinge base  302  supports a portion of the second portion  324  of the shaft  320  to provide for rotational support of the shaft  320  by the hinge base  302 . 
     Referring to  FIGS. 1-35  and  63 - 70 , in the illustrated example, the hinge base  302  has two bearing surfaces  304  and  306 . The hinge base  302  has one side  308  that is closest to the adaptor  340  and one side  310  that is farthest from the adaptor  340 . The side  308  has an opening  312  that allows the shaft  320  to extend outward from the hinge base  302  to the adapter  340 . The side  310  has an opening  314  that allows the head portion  322  of the shaft  320  to be at least partially exposed and accessible from the side of the hinge base  302  farthest from the adapter  340 . A curved recess  316  is provided along a portion of the rim of the opening  314 . The recess  316  has end walls  318  and  319 . The hinge base  302  has a flange  301  that has a plurality of holes  303  to allow the hinge base  302  to be securely fastened to the second member, for example the laptop base  202 , by screws  305 . 
     Referring to  FIGS. 1-35 ,  63 - 70 , and  77 - 95 , the hinge assembly  300  is provided with a friction mechanism  430  for frictionally resisting rotational motion of the shaft  320  relative to the hinge base  302 . The friction mechanism  430  is supported by the hinge base  302 . The friction mechanism  430  is located between the bearing surfaces  304  and  306 . The friction mechanism  430  includes a plurality of friction elements  440 , a channel insert, and friction mechanism cover  460 . The hinge base  302  has a channel  307  that extends between the bearing surfaces  304  and  306  in a direction parallel to the longitudinal axis of the shaft  320 . The friction elements  440  are of the symmetrical friction clip type and have a C-shaped portion  442  and a stem  444 . The stem  444  projects outward from the outer surface of the C-shaped portion  442  at a location opposite the gap between the tips  446  and  448  of the C-shaped portion  442 . The friction elements  440  engage the portion of the second portion  324  of the shaft  320  that extends between the bearing surfaces  304  and  306 . The inner radius of the C-shaped portion  442  is smaller than the radius of the outer surface of the second portion  324  of the shaft  320  so that the C-shaped portion  442  expands when placed around the second portion  324  of the shaft  320 . The resilience of the C-shaped portion  442  of the friction elements  440  causes the C-shaped portions  442  of the friction elements  440  to exert a gripping force on the second portion  324  of the shaft  320 . 
     The channel insert  450  fits into the channel  307 . The channel insert  450  is U-shaped in cross section and extends for the length of the channel  307 . The stems  444  of the friction elements  440  are received in the channel insert  450  and consequently in the channel  307  to prevent the friction elements  440  from rotating with the shaft  320 . Thus, the friction elements  440  are prevented from rotating relative to the hinge base  302 . The gripping force exerted by the C-shaped portions  442  of the friction elements  440  on the shaft  320  generates a friction torque that resists rotational motion of the shaft  320  relative to the hinge base  302 . The friction torque generated by the friction elements  440  can be matched to any specified value for a particular application by adjusting the geometry, number and material of the friction elements  440 . The friction mechanism cover  460  is C-shaped in cross section and extends for the length of the gap between the bearing surfaces  304  and  306 . The edges of the friction mechanism cover  460  seal against the outer surfaces of the C-shaped portions  442  of the friction elements  440  and the portions of the hinge base  302  that form the bearing surfaces  304  and  306 . The friction mechanism cover  460  keeps dirt and abrasive particles out of the friction mechanism  430  and keeps lubricant, needed to ensure smooth hinge operation and prevent premature friction element failure, confined to the friction mechanism  430 . The channel insert  450  is made of a relatively harder material compared to the hinge base  302  and acts to distribute forces exerted by the stems of the friction elements  440  evenly on the walls of the channel  307  so that the stems of the friction elements  440  do not dig into and warp the channel  307 . 
     The end piece  360  is adapted for fixed attachment to the second member, in this example the laptop base  202 , so as to move with the second member as a unit. The end piece  360  has a flange  362  and a socket  364 . The socket  364  has a front opening  366 , a back wall  368 , side edges  370  and  372 , top edge  374  and bottom edge  376 . The front opening  366  is rectangular. The flange  362  of the end piece  360  has a plurality of holes  378  to allow the end piece  360  to be securely fastened to the second member, for example the laptop base  202 , by screws  379 .  FIGS. 1-5  show the end piece  360  fastened to the laptop base  202 . 
     Referring to  FIGS. 1-35  and  42 - 62 , the torsion bar spring  380  extends from the end piece  360  to the head portion  322  of the shaft  320 . The torsion bar spring  380  has a first end  382  and a second end  384 . The torsion bar spring  380  is resilient and has a longitudinal axis. The first end  382  of the torsion bar spring  380  is constrained to rotate with the shaft  320  as a unit. The second end  384  of the torsion bar spring  380  is constrained by the end piece  360  so there can be essentially no relative rotation between the end piece  360  and the second end  384  of the torsion bar spring  380  about the longitudinal axis of the torsion bar spring  380  such that rotation of the shaft  320  relative to the end piece  360  causes the torsion bar spring  380  to be twisted about its longitudinal axis when the shaft  320  is initially in a neutral position. The neutral position refers to the position of any part of the hinge assembly  300  that corresponds to the relaxed state of the torsion bar spring  380 . The torsion bar spring  380  stores energy as it is twisted and tends to exert a force to restore the shaft  320  and the adaptor  340  to their neutral positions due to the resilience of the torsion bar spring  380 . 
     The torsion bar spring  380  is made of a plurality of leaves  390  that are stacked together in superimposed fashion. Each spring leaf  390  is in the form of an elongated rectangular strip having lateral tabs  391  extending from either side at one end of the elongated rectangular strip to form a T-shaped head  392 . As the spring leaves  390  are stacked together they give the first end  382  of the torsion bar spring  380  a “T” shape. The first end  382  of the torsion bar spring  380  is constrained against rotation relative to the head portion  322  of the shaft  320  and the second end  384  of the torsion bar spring  380  is constrained against rotation relative to the end piece  360  such that rotation of the shaft  320  relative to the end piece  360  causes the torsion bar spring  380  to be twisted about its longitudinal axis when the shaft  320  is initially in a neutral position. 
     The first end  382  of the torsion bar spring  380  is constrained against rotation relative to the head portion  322  of the shaft  320  by a cap  400 . The cap  400  has a rectangular opening  401  with rounded lateral edges  402  and top and bottom edges  403  and  404 , respectively. The cap  400  has two cavities  405  that receive the prongs  332  of the head portion  322  of the shaft  320  to securely fasten the cap  400  to the head portion  322  of the shaft  320 . Each cavity  405  receives a respective one of the prongs  332 . The prongs  332  will be in an interference fit with the cavities  405 . The ribs  334  on the prongs&#39; outer surfaces assist in securely fastening the cap  400  to the head portion  322  of the shaft  320  by providing a stronger grip between the internal surface of the cavities  405  and the exterior surface of the prongs  332 . Thus, the cavities  405  and the prongs  332  form the means for securely fastening the cap  400  to the head portion  322  of the shaft  320  in the illustrated embodiment. 
     The cap  400  has a rib  406  and two axial lateral projections  407  and  408 . The axial lateral projections  407  and  408  extend in a direction parallel to the longitudinal axis of the shaft  320  from either side of the cap  400 . When the cap  400  is securely fastened to the head portion  322  of the shaft  320 , the axial lateral projections  407  and  408  fit at least in part into the slot  330  of the shaft head portion  322  and close off the ends of the slot  330 . When the cap  400  is securely fastened to the head portion  322  of the shaft  320 , the rib  406  extends at least in part into the recess  316  of the hinge base  302  to limit the rotation of the hinge shaft  320  relative to the hinge base  302 . The rib  406  engages the end wall  319  of the recess  316  to stop the rotation of the hinge shaft  320  and adaptor  340  at a position corresponding to the fully open position of the laptop lid  204 . The rib  406  engages the end wall  318  of the recess  316  to stop the rotation of the hinge shaft  320  and adaptor  340  at a position slightly passed the closed position of the laptop lid  204 . The rib  406  and the recess  316  constitute a safety means for preventing the over stressing of the torsion bar spring  380  that can lead to breakage of the torsion bar spring  380 . 
     The torsion bar spring  380  extends through the opening  401  of the cap  400 . The rounded lateral edges  402  of the cap  400  are in direct contact with the surfaces  393  of the outermost leaves  390  of the torsion bar spring  380 . The distance between the rounded lateral edges  402  of the opening  401  of the cap  400  is such that the fit of the torsion bar spring  380  between the rounded lateral edges  402  of the opening  401  is very tight or with minimal clearance. Thus, the rounded lateral edges  402  of the opening  401  are responsible for transferring torque between the shaft  320  and the torsion bar spring  380 . Using the rounded lateral edges  402  of the opening  401  for torque transfer between the shaft  320  and the torsion bar spring  380 , places the torque transfer edges  402  at a slight displacement from the T-shaped heads  392  of the spring leaves  390 . This avoids the problem of stress concentration at the joint between the T-shaped heads  392  and the remainder of the rectangular strip body portions of the spring leaves  390 , which can lead to the premature failure of the torsion bar spring  380 . Also, the rounding of the edges  402  of the opening  401  of the cap  400  prevents stress concentration at the edges of the outermost spring leaves  390 , which can also lead to failure of the spring leaves  390  and consequently of the torsion bar spring  380 . The distance between the top edge  407  and the bottom edge  408  of the opening  401  of the cap  400  is such that the T-shaped heads  392  of the leaves  390  cannot pass through the opening  401 , and the T-shaped heads  392  of the leaves  390  are captured between the cap  400  and the shaft head portion  322 . This arrangement constrains the axial movement, i.e. movement in a direction parallel to the longitudinal axis of the shaft  320 , of the T-shaped heads  392  of the leaves  390 . 
     The ends  394  of the leaves  390  that are farthest from the T-shaped heads  392  are stacked together in superimposed fashion when the torsion bar spring  380  is in a relaxed state, and the ends  394  form the second end  384  of the torsion bar spring  380 . The torsion bar spring  380  extends through the opening  366  of the socket  364 . The lateral edges  370  and  372  of the socket opening  366  are rounded. The rounded lateral edges  370  and  372  of the socket opening  366  are in direct contact with the surfaces  393  of the outermost leaves  390  of the torsion bar spring  380 . The distance between the rounded lateral edges  370  and  372  of the opening  366  of the socket  364  is such that the fit of the torsion bar spring  380  between the rounded lateral edges  370  and  372  of the opening  366  is very tight or with minimal clearance. Thus, the rounded lateral edges  370  and  372  of the opening  366  are responsible for transferring torque between the end piece  360  and the torsion bar spring  380 . Using the rounded lateral edges  370  and  372  of the opening  366  for torque transfer between the end piece  360  and the torsion bar spring  380 , provides for uniform stress distribution over the width of the spring leaves  390  and prevents stress concentration at the edges of the outermost spring leaves  390 . Both of these results enhance the life span of the spring leaves  390  and reduce the chance of the failure of the spring leaves  390  and consequently of the torsion bar spring  380 . The distance between the top edge  374  and the bottom edge  376  of the opening  366  of the socket  364  is such that the top edge  374  and the bottom edge  376  of the opening  366  will not interfere with the movements of the ends  394  of the leaves  390  within the socket  364 . 
     As the torsion bar spring  380  is twisted about its longitudinal axis to any given amount, the length per degree of twist of the helical path followed by the spring leaves  390  is longer for each leaf  390  the farther away it is from the center of the stack of leaves  390 . Accordingly, the ends  394  of the hinge leaves  390  begin to pull away from the back wall  368  of the socket  364  such that the farther a hinge leaf  390  is from the middle of the stack of leaves the more its end  394  will be pulled away from the back wall  368 . This result is illustrated in  FIGS. 19 and 25 . Constraining this axial movement of the ends  394  of the hinge leaves  390  would result in spring leaf breakage. Accordingly, at least one end of each of the plurality of leaves  390  must be free to move axially as the torsion bar spring  380  is twisted. The end  394  of each of the spring leaves  390  must be far enough into the socket opening  366  such that there is no possibility of it being pulled completely out of the socket opening  366  over the entire range of rotation of the shaft  320 . 
     It is possible to provide a mirror image of the socket  364  in the shaft head portion  322  in place of the cap  400 . In such an arrangement there would be no need for the spring leaves to have T-shaped heads; the spring leaves would simply be in the form of rectangular strips. No axial constraint would be applied to either end of the torsion bar spring, except that in the relaxed state all the spring leaves would be captive between the back walls of the socket in the end piece  360  and the socket in the shaft head portion  322 . 
     As the torsion bar spring  380  is twisted, the leaf ends  394  on one side of the middle of the stack tend to move up or down toward either the top edge  374  or the bottom edge  376  depending upon and in the direction of rotation of the shaft  320 , and the leaf ends  394  on the other side of the middle of the stack tend to move in the opposite direction but still in the same direction as the direction of rotation of the shaft  320 . These movements must also be accommodated to avoid overstressing the spring leaves  390 , which again could lead to spring leaf failure. Therefore, as was previously mentioned, the distance between the top edge  374  and the bottom edge  376  of the opening  366  of the socket  364  is such that the top edge  374  and the bottom edge  376  of the opening  366  will not interfere with the movements of the ends  394  of the leaves  390  within the socket  364 . 
     The torsion bar cover  420  fits over the exposed portion of the torsion bar spring  380  between the end piece  360  and the hinge base  302 . The torsion bar cover  420  is tubular with openings at both ends. The torsion bar cover  420  acts as a grease or lubricant container and does not restrict any of the movements and deflections of the spring leaves  390 , but provides for lubrication of the individual spring leaves. The openings  422  and  424  at the ends of the torsion bar cover  420  seal against the hinge base  302  and the end piece  360 , respectively. The torsion bar cover  420  provides continuous lubrication between the spring leaves  390  to ensure that the spring leaves can slide against one another as necessary to prevent overstressing and damage to the spring leaves. The torsion bar cover  420  has alignment feature on one side in the form of a rectangular or square opening  424  to assist in the assembly process of the torsion bar spring  380 . It is possible for both openings  422  and  424  to be circular or any other shape large enough not to interfere with the twisting of the torsion bar spring  380 . 
     With the hinge assembly  300  and its mirror image hinge assembly  500  installed in a laptop as shown, the neutral position of the adaptor  340  and of the laptop lid  204 , which correspond to the relaxed state of the torsion bar spring  380 , is between the fully open position of the laptop lid and the fully closed position of the laptop lid. In the illustrated example, the neutral position of the laptop lid is 32° from the fully open position and 85° from the closed position. The operation of the hinge assembly  300  will be described with the laptop lid initially in the neutral position. To close the laptop lid  204 , enough force must initially be applied to overcome the friction torque due to the friction mechanism  430 . As the laptop lid  204  rotates toward the closed position, the hinge shaft  320  is rotated causing the torsion bar spring  380  to be twisted. As the torsion bar spring  380  is twisted the force needed to continue the closing of the laptop lid  204  increases due to the resilience of the torsion bar spring  380 , however, because it is mechanically advantageous for a user to push down than to pull up, due to the action of gravity on the lid and by bringing his or her body weight into play if necessary, this is not a disadvantage. Also, as the torsion bar spring  380  is twisted energy is stored in the deformation of the torsion bar spring  380 . When the laptop lid  204  is in the closed position, a latch (not shown) releasably secures the laptop lid  204  in the closed position. To open the laptop lid a user operates the latch to release the laptop lid  204  for rotation to the open position. The laptop lid  204  automatically moves away from the closed position, without any effort from the user, as the torque exerted by the torsion bar spring  380  overcomes the frictional resistance or torque of the friction mechanism  430  until a point is reached, which is intermediate the neutral position and the closed position, where the torque exerted by the torsion bar spring  380  has dropped to equal the friction torque of the friction mechanism  430 . At that point the laptop lid  204  stops moving, and the user can comfortably move the laptop lid  204  manually to any desired position between that point and the fully open position of the laptop lid  204  to suit his or her needs. Even though there will be some deformation of the torsion bar spring  380  at any position away from the neutral position, within the range of positions corresponding to the normal usage range of the laptop screen  206  the friction torque of the friction mechanism  430  will hold the laptop screen in the desired position. 
     The material used for the spring leaves  390  is steel such as stainless steel or spring steel or any steel with a spring steel temper. The shaft  320  is also made of steel. The end piece  360 , the adapter  340 , and the hinge base  302  can be made of a die cast metal such as aluminum or zinc or of a high impact plastic. For lower torque applications the spring leaves  390  can be made of a composite or a polymer material as long as it has the requisite elasticity. 
     Referring to  FIGS. 103-194 , a second illustrative embodiment of the hinge assembly  600 ,  800  in accordance with the present invention can be seen. Each of the hinge assemblies  600 ,  800  provides for rotationally attaching a first member to a second member to allow rotational movement of the first member relative to the second member between a closed position and an open position. Referring to  FIGS. 103-105 , two hinge assemblies  600  and  800  made in accordance with the present invention are shown being used to rotationally attach the lid  204   a  of a laptop computer  200   a  to the base  202   a  of the laptop computer  200   a . The laptop lid  204   a  typically houses the laptop screen  206   a  and its angular position relative to the laptop base  202   a  should be adjustable within a range of angular positions suitable for people of a variety of sizes to properly view the laptop screen  206   a.    
     The hinge assembly  600  is a left hinge assembly and the hinge assembly  800  is a right hinge assembly. The right hinge assembly  800  is a mirror image of the hinge assembly  600  about a plane perpendicular to longitudinal axes of the shafts of each of the hinge assemblies and positioned halfway between the two hinge assemblies. Accordingly, only the hinge assembly  600  is described in detail. The laptop lid  204   a  typically is releasably secured in the closed position relative to the laptop base  202   a  by a latch (not shown) of some sort. The latch can be operated by a user to release or free the laptop lid  204   a  for rotational movement to the open position relative to the laptop base  202   a.    
     The hinge assembly  600  can be used to rotationally attach a first member to a second member to allow rotational movement of the first member relative to the second member between a closed position and an open position. In the illustrated example, the first member is the laptop base  202   a  and the second member is the laptop lid  204   a . The hinge assembly  600  includes an elongated shaft  620 , an adaptor  640 , a hinge base  602 , a friction mechanism  730 , an end piece  660 , a torsion bar spring  680 , a first cap  700 , and a shell  677 . 
     Referring to  FIGS. 103-132  and  171 - 178 , the elongated shaft  620  has at least a first end portion  626 , a second or intermediate portion  624  and a second end portion  622 . The first end portion  626  of the shaft  620  is provided with a plurality of elongated teeth  628  of triangular cross section evenly distributed about the circumference of the first end portion  626  of the shaft  620 . Each of the plurality of elongated teeth  628  extends for at least the majority of the length of the first end portion  626  of the shaft  620 . The teeth  628  are also known in the art as splines. In the illustrated example, the second or intermediate portion  624  of the shaft  620  is of larger diameter compared to the first end portion  626 . The second end portion  622  of the shaft  620  is also provided with a plurality of teeth or splines  623  that are similar in configuration to the teeth  628 . The intermediate portion  624  of the shaft  620  is of a larger diameter as compared to the second end portion  622 . The second end portion  622  of the shaft  620  is inserted into a bore  625  of the first cap  700  to fix the first cap  700  to the second end portion  622  of the shaft  620  such that there can be no relative movement between the second end portion  622  of the shaft  620  and the first cap  700 . The teeth  623  on the shaft&#39;s second end portion  622  assist in rotationally coupling the shaft  620  to the first cap  700  by providing a stronger grip between the internal surface of the bore  625  of the first cap  700  and the exterior surface of the second end portion  622  of the shaft  620 . This is due to the teeth  623  providing a more positive grip between the internal surface of the bore  625  of the first cap  700  and the exterior surface of the second end portion  622  of the shaft  620  when the second end portion  622  of the shaft  620  is press fitted to the bore  625  of the first cap  700 . Thus, the bore  625  of the first cap  700  and the toothed exterior surface of the second end portion  622  of the shaft  620  form the means for securely fastening the shaft  620  to the first cap  700  and rotationally coupling the shaft  620  and the first cap  700  together in the illustrated embodiment. (See also  FIGS. 143-150 ) 
     The first cap  700  also has a front opening  630  that has side edges  632  and  634 , top edge  633  and bottom edge  635 . The front opening  630  is rectangular. 
     The adaptor  640  is attached to the shaft  620  at the first end portion  626  of the shaft  620 . The adaptor  640  is attached to the first end portion  626  of the shaft  620  such that the adaptor  640  is constrained to rotate with the shaft  620  as a unit. The adaptor  640  is adapted for fixed attachment to the first member, the laptop base  202   a  in the illustrated example, so as to move with the first member as a unit. Referring to  FIGS. 103-135  and  136 - 142 , the adaptor  640  has a body portion  642  that is provided with a plurality of holes  644  to allow the adapter  640  to be securely fastened to the first member, for example the laptop base  202   a , by screws  646 . 
     The adaptor  640  has a bore  648  provided on one side of the body portion  642 . The bore  648  of the adapter  640  is designed to receive the first end portion  626  of the shaft  620  in a press fit or interference fit such that the shaft  620  is securely fastened to the adaptor  640  and the shaft  620  and the adaptor  640  are rotationally coupled to rotate together as a unit. The teeth  628  on the shaft&#39;s first end portion  626  assist in rotationally coupling the shaft  620  to the adaptor  640  by providing a stronger grip between the internal surface of the bore  648  of the adapter  640  and the exterior surface of the first end portion  626  of the shaft  620 . Thus, the bore  648  of the adapter  640  and the toothed exterior surface of the first end portion  626  of the shaft  620  form the means for securely fastening the shaft  620  to the adaptor  640  and rotationally coupling the shaft  620  and the adaptor  640  together in the illustrated embodiment. 
     Many other suitable means may also be employed for securely fastening the shaft  620  to the adaptor  640  and the first cap  700  and rotationally coupling the shaft  620  to the adaptor  640  and to the first cap  700 . These include the same means enumerated for the attachment of the shaft  320  to the adaptor  340 . Of course, means where the bores  648 ,  625 , and  348  have teeth that mate with the teeth  628 ,  623 , and  328 , respectively, is part of this list. 
     The hinge base  602  is adapted for fixed attachment to the second member, the laptop lid  204   a  in this example, so as to move with the second member as a unit. The hinge base  602  has at least one bearing surface  604 ,  606  that rotationally supports the shaft  620  such that, when the adaptor  640  is attached to the first member and the hinge base  602  is attached to the second member, the first member is rotationally attached to the second member such that the first member can rotationally move relative to the second member between a closed position and an open position. In the illustrated example, the first and second members are the laptop base  202   a  and the laptop lid  204   a , respectively. The bearing surface of the hinge base  602  supports a portion of the second or intermediate portion  624  of the shaft  620  to provide for rotational support of the shaft  620  by the hinge base  602 . 
     Referring to  FIGS. 103-135  and  163 - 170 , in the illustrated example, the hinge base  602  has two bearing surfaces  604  and  606 . The hinge base  602  has one side  608  that is closest to the adaptor  640  and one side  610  that is farthest from the adaptor  640 . The side  608  has an opening  612  that allows the shaft  620  to extend outward from the hinge base  602  to the adapter  640 . The side  610  has an opening  614  that allows the shaft  620  to extend outward from the hinge base  602  toward the torsion bar spring  680  where it can engage the first cap  700 . A stop projection  616  is provided along a portion of the rim of the opening  612 . The stop projection  616  has end walls  618  and  619 . The hinge base  602  has a flange  601  that has a plurality of holes  603  to allow the hinge base  602  to be securely fastened to the second member, for example the laptop lid  204   a , by screws  605 . 
     Referring to  FIGS. 103-135  and  163 - 170 , the hinge assembly  600  is provided with a friction mechanism  730  for frictionally resisting rotational motion of the shaft  620  relative to the hinge base  602 . In this example, the friction mechanism  730  is integrated into the material of the hinge base  602 . The friction mechanism  730  is formed by at least one band  740 ,  742  that is attached at one end to the flange  601 . The band  740 ,  742  wraps around at least part of the intermediate portion  624  of the shaft  620  and the band  740 ,  742  terminates in a free end that is spaced apart from the band&#39;s attachment to the flange  601  to define a C-shaped profile for the band  740 ,  742 . In the illustrated example, two bands  740  and  742  are provided that wrap around the intermediate portion  624  of the shaft  620  in opposite directions. The bands  740  and  742  define the bearing surfaces  604  and  606 , respectively. The bands  740  and  742  also define the friction elements of the friction mechanism  730  by frictionally gripping the intermediate portion  624  of the shaft  620  to provide a friction torque that acts as a resistance to relative rotation between the shaft  620  and the hinge base  602 . The inner radius of the C-shaped bands  740  and  742  is originally smaller than the radius of the outer surface of the second portion  624  of the shaft  620  so that each of the C-shaped bands  740  and  742  expands when placed around the second portion  624  of the shaft  620 . The resilience of the C-shaped bands  740  and  742  causes the C-shaped bands  740  and  742  to exert a gripping force on the second portion  624  of the shaft  620 . 
     Because the friction elements  740 ,  742  are attached at one end to the flange  601 , the friction elements  740 ,  742  are prevented from rotating relative to the hinge base  602 . The gripping force exerted by the C-shaped bands or friction elements  740 ,  742  on the shaft  620  generates a friction torque that resists rotational motion of the shaft  620  relative to the hinge base  602 . The friction torque generated by the friction elements  740 ,  742  can be matched to any specified value for a particular application by changing the geometry, number and material of the friction elements  740 ,  742 . 
     The end piece  660 , also referred to as the second cap, must be held in a fixed relationship relative to the second member, in this example the laptop lid  204   a , in order for the torsion bar spring  680  to generate the spring torque for the proper operation of the hinge assembly  600 . In hinge assembly  600  the end piece  660  is fixed relative to the second member by being fixed to the hinge base  602 , which is then mounted to the second member, rather than being directly mounted to the second member as in the case of the end piece  360  of the hinge assembly  300 . Accordingly, once the hinge base  602  is mounted to the second member, the end piece  660  becomes fixed relative to the second member such that the end piece  660  moves with the second member as a unit. The end piece  660  has two lateral projections  662  and a socket  664 . The socket  664  has a front opening  667 , a back wall  668 , side edges  670  and  672 , top edge  674  and bottom edge  676 . The front opening  667  is rectangular. The projections  662  of the end piece  660  engage and fit into respective notches  675  provided in one end of the outer shell  677  in order to prevent relative rotation between the end piece  660  and the shell  677 . The shell  677  is in turn fixed to the hinge base  602  in order to rotationally fix the end piece  660  to the hinge base  602 . The shell  677  is cylindrical and encases the torsion bar spring  680 . The end piece  660  is axially held in place at the end of the shell  677  distal from the hinge base  602  by friction fit to the bore of the shell  677 , by adhesives, by pins or other fasteners, or by any other suitable means. The shell  677  has one or more flanges  673  that register with a portion of the hinge base flange  601 . Two flanges  673  are provided in the illustrated example that straddle a portion of the hinge base flange  601 . Each flange  673  is provided with one or more holes  678  that register with one or more corresponding holes  681  in the hinge base flange  601  to allow the shell  677 , and in turn the end piece  660 , to be securely fastened to the hinge base  602  by, for example, the rivets  679 . 
     Referring to  FIGS. 103-135  and  159 - 162 , the torsion bar spring  680  extends from the end piece  660  to the first end cap  700  on the shaft  620 . The torsion bar spring  680  has a first end  682  and a second end  684 . The torsion bar spring  680  is resilient and has a longitudinal axis. The first end  682  of the torsion bar spring  680  is constrained to rotate with the shaft  620  so there can be essentially no relative rotation between the shaft  620  and the first end  682  of the torsion bar spring  680  about the longitudinal axis of the torsion bar spring  680 . The second end  684  of the torsion bar spring  680  is constrained by the end piece  660  so there can be essentially no relative rotation between the end piece  660  and the second end  684  of the torsion bar spring  680  about the longitudinal axis of the torsion bar spring  680  such that rotation of the shaft  620  relative to the end piece  660  causes the torsion bar spring  680  to be twisted about its longitudinal axis when the shaft  620  is initially in a neutral position. The neutral position refers to the position of any part of the hinge assembly  600  that corresponds to the relaxed state of the torsion bar spring  680 . The torsion bar spring  680  stores energy as it is twisted and tends to exert a force to restore the shaft  620  and the adaptor  640  to their neutral positions due to the resilience of the torsion bar spring  680 . 
     The torsion bar spring  680  is made of a plurality of leaves  690  that are stacked together in superimposed fashion. Each spring leaf  690  is in the form of an elongated rectangular strip. The first end  682  of the torsion bar spring  680  is constrained against rotation relative to the second end portion  622  of the shaft  620  and the second end  684  of the torsion bar spring  680  is constrained against rotation relative to the end piece  660  such that rotation of the shaft  620  relative to the end piece  660  causes the torsion bar spring  680  to be twisted about its longitudinal axis when the shaft  620  is initially in a neutral position. 
     A lug  706  is provided on the shaft  620 . When the hinge assembly  600  is fully assembled, the lug  706  is positioned to contact the stop projection  616  of the hinge base  602  to limit the rotation of the hinge shaft  620  relative to the hinge base  602 . The lug  706  engages the end wall  619  of the stop projection  616  to stop the rotation of the hinge shaft  620  and adaptor  640  at a position corresponding to the fully open position of the laptop lid  204   a . The lug  706  engages the end wall  618  of the stop projection  616  to stop the rotation of the hinge shaft  620  and adaptor  640  at a position slightly passed the closed position of the laptop lid  204   a . The lug  706  and the stop projection  616  constitute a safety means for preventing the over stressing of the torsion bar spring  680  that can lead to breakage of the torsion bar spring  680 . 
     The first ends  692  of the leaves  690  that are farthest from the end piece  660  are stacked together in superimposed fashion when the torsion bar spring  680  is in a relaxed state. The first ends  692  of the leaves  690  form the first end  682  of the torsion bar spring  680 . The ends  694  of the leaves  690  that are farthest from the first cap  700  are stacked together in superimposed fashion when the torsion bar spring  680  is in a relaxed state, and the second ends  694  form the second end  684  of the torsion bar spring  680 . The torsion bar spring  680  extends through the opening  667  of the socket  664  of the end piece  660 . The lateral edges  670  and  672  of the socket opening  667  are rounded. The rounded lateral edges  370  and  372  of the socket opening  667  are in direct contact with the surfaces  693  of the outermost leaves  690  of the torsion bar spring  680 . The distance between the rounded lateral edges  670  and  672  of the opening  667  of the socket of the end piece  660  is such that the fit of the torsion bar spring  680  between the rounded lateral edges  670  and  672  of the opening  667  is very tight or with minimal clearance. Thus, the rounded lateral edges  670  and  672  of the opening  667  are responsible for transferring torque between the end piece  660  and the torsion bar spring  680 . Using the rounded lateral edges  670  and  672  of the opening  667  for torque transfer between the end piece  660  and the torsion bar spring  680 , provides for uniform stress distribution over the width of the spring leaves  690  and prevents stress concentration at the edges of the outermost spring leaves  690 . Both of these results enhance the life span of the spring leaves  690  and reduce the chance of failure of the spring leaves  690  and consequently of the torsion bar spring  680 . The distance between the top edge  674  and the bottom edge  676  of the opening  667  of the socket of the end piece  660  is such that the top edge  674  and the bottom edge  676  of the opening  667  will not interfere with the movements of the ends  694  of the leaves  690  within the socket  664 . 
     As the torsion bar spring  680  is twisted about its longitudinal axis to any given amount, the length per degree of twist of the helical path followed by the spring leaves  690  is longer for each leaf  690  the farther away it is from the center of the stack of leaves  690 . Accordingly, the ends  694  of the hinge leaves  690  begin to pull away from the back wall  668  of the socket  664  such that the farther a hinge leaf  690  is from the middle of the stack of leaves the more its end  694  will be pulled away from the back wall  668 . This result is illustrated in  FIGS. 119-121 . Constraining this axial movement of the ends  694  of the hinge leaves  690  would result in spring leaf breakage. Accordingly, at least one end of each of the plurality of leaves  690  must be free to move axially as the torsion bar spring  680  is twisted. The end  694  of each of the spring leaves  690  must be far enough into the socket opening  667  such that there is no possibility of it being pulled completely out of the socket opening  667  over the entire range of rotation of the shaft  620 . 
     The opening  630  in the end cap  700  is a mirror image of the socket opening  667 . The torsion bar spring  680  extends through the opening  630  of the first cap  700 . The lateral edges  632  and  634  of the opening  630  are rounded. The rounded lateral edges  632  and  634  of the opening  630  are in direct contact with the surfaces  693  of the outermost leaves  690  of the torsion bar spring  680 . The distance between the rounded lateral edges  632  and  634  of the opening  630  of the end cap  700  is such that the fit of the torsion bar spring  680  between the rounded lateral edges  632  and  634  of the opening  630  is very tight or with minimal clearance. Thus, the rounded lateral edges  632  and  634  of the opening  630  are responsible for transferring torque between the end cap  700  and the torsion bar spring  680 . Using the rounded lateral edges  632  and  634  of the opening  630  for torque transfer between the end cap  700  and the torsion bar spring  680 , provides for uniform stress distribution over the width of the spring leaves  690  and prevents stress concentration at the edges of the outermost spring leaves  690 . Both of these results enhance the life span of the spring leaves  690  and reduce the chance of failure of the spring leaves  690  and consequently of the torsion bar spring  680 . The distance between the top edge  633  and the bottom edge  635  of the opening  630  of the end cap  700  is such that the top edge  633  and the bottom edge  635  of the opening  630  will not interfere with the movements of the ends  692  of the leaves  690  within the socket formed by the first cap  700  and the shaft&#39;s second end portion  622 . 
     As the torsion bar spring  680  is twisted about its longitudinal axis to any given amount, the length per degree of twist of the helical path followed by the spring leaves  690  is longer for each leaf  690  the farther away it is from the center of the stack of leaves  690 . Accordingly, the ends  692  of the hinge leaves  690  begin to pull away from the shaft&#39;s second end portion  622  such that the farther a hinge leaf  690  is from the middle of the stack of leaves the more its end  692  will be pulled away from the shaft&#39;s second end portion  622 . This result is illustrated in  FIGS. 119-121 . Thus, in the embodiment  600 , both ends of each of the plurality of leaves  690  are free to move axially as the torsion bar spring  680  is twisted. The end  692  of each of the spring leaves  690  must be far enough into the opening  630  such that there is no possibility of it being pulled completely out of the opening  630  over the entire range of rotation of the shaft  620 . All the spring leaves  690  are captivated between the back wall of the socket in the end piece  660  and the socket formed by the first cap  700  and the shaft&#39;s second end portion  622 . 
     As the torsion bar spring  680  is twisted, the leaf ends  694  on one side of the middle of the stack tend to move up or down toward either the top edge  674  or the bottom edge  676  depending upon and in the direction of rotation of the shaft  620 , and the leaf ends  694  on the other side of the middle of the stack tend to move in the opposite direction but still in the same direction as the direction of rotation of the shaft  620 . These movements must also be accommodated to avoid overstressing the spring leaves  690 , which again could lead to premature spring leaf failure. Therefore, as was previously mentioned, the distance between the top edge  674  and the bottom edge  676  of the opening  667  of the socket  664  is such that the top edge  674  and the bottom edge  676  of the opening  667  will not interfere with the movements of the ends  694  of the leaves  690  within the socket  664 . The situation is the same for the ends  692  of the spring leaves  690 . 
     The two inner sleeves  720 ,  721  fit over the portion of the torsion bar spring  680  between the end piece  660  and the first cap  700  inside the shell  677 . The two inner sleeves  720 ,  721  are tubular with openings at both ends. The two inner sleeves  720 ,  721  act as grease or lubricant containers and do not restrict any of the movements and deflections of the spring leaves  690 , but provide for lubrication of the individual spring leaves. The openings  722  at one end of each of the inner sleeves  720 ,  721  seal against the first cap  700  and the end piece  660 , respectively. The openings  724  of the inner sleeves  720 ,  721  seal against one another. The inner sleeves  720 ,  721  provide continuous lubrication between the spring leaves  690  to ensure that the spring leaves can slide against one another as necessary to prevent overstressing and damage to the spring leaves. The openings  722  at one end of each of the inner sleeves  720 ,  721  are in the form of rectangular openings to serve as alignment feature on one side to assist in the assembly process of the torsion bar spring  680 . The two inner sleeves  720  and  721  also provide bearing support to the outer shell  677 . 
     With the hinge assembly  600  and its mirror image hinge assembly  800  installed in a laptop as shown, the neutral position of the hinge base  602  and of the laptop lid  204   a , which correspond to the relaxed state of the torsion bar spring  680 , is between the fully open position of the laptop lid and the fully closed position of the laptop lid. In the illustrated example, the neutral position of the laptop lid is 32° from the fully open position and 85° from the closed position. The operation of the hinge assembly  600  will be described with the laptop lid initially in the neutral position. To close the laptop lid  204   a , enough force must initially be applied to overcome the friction torque due to the friction mechanism  730 . As the laptop lid  204   a  rotates toward the closed position, the end piece  660  is rotated causing the torsion bar spring  680  to be twisted. As the torsion bar spring  680  is twisted the force needed to continue the closing of the laptop lid  204   a  increases due to the resilience of the torsion bar spring  680 , however, because it is mechanically advantageous for a user to push down than to pull up, due to the action of gravity on the lid and by bringing his or her body weight into play if necessary, this is not a disadvantage. Also, as the torsion bar spring  680  is twisted energy is stored in the deformation of the torsion bar spring  680 . When the laptop lid  204   a  is in the closed position, a latch (not shown) releasably secures the laptop lid  204   a  in the closed position. To open the laptop lid a user operates the latch to release the laptop lid  204   a  for rotation to the open position. The laptop lid  204   a  automatically moves away from the closed position, without any effort from the user, as the torque exerted by the torsion bar spring  680  overcomes the frictional resistance or torque of the friction mechanism  730  until a point is reached, which is intermediate the neutral position and the closed position, where the torque exerted by the torsion bar spring  680  has dropped to equal the friction torque of the friction mechanism  730 . At that point the laptop lid  204   a  stops moving, and the user can comfortably move the laptop lid  204   a  manually to any desired position between that point and the fully open position of the laptop lid  204   a  to suit his or her needs. Even though there will be some deformation of the torsion bar spring  380  at any position away from the neutral position, within the range of positions corresponding to the normal usage range of the laptop screen  206   a  the friction torque of the friction mechanism  730  will hold the laptop screen in the desired position. 
     It is possible to interchange the friction mechanisms  730  and  430  and to interchange the structures for rotationally coupling the torsion bar springs  680 ,  380  to the hinge shafts  620 ,  320  between the two disclosed embodiments  300  and  600 . Such permutations of the disclosed embodiments are within the scope of the invention. 
     The preferred material used for the spring leaves  690  is steel such as stainless steel or spring steel or any steel with a spring steel temper. The hinge base  602  is preferably also made of a resilient steel. The shaft  620  is also made of steel. The end piece or second cap  660  and the adapter  640  can be made of a die cast metal such as aluminum or zinc or of a high impact plastic. For lower torque applications the spring leaves  690  can be made of a composite or a polymer material as long as it has the requisite elasticity. 
     Although the hinge assemblies  300  and  600  have been illustrated in the context of a laptop computer, the counterbalancing function provided by the torsion bar springs  380 ,  680  can be used to allow friction hinges to be used in heavier applications, where friction torque alone would cause the operating efforts to be objectionably high, or beyond the limits of normal human factors. The laminated design of the torsion bar spring allows the counterbalancing function to be achieved in a compact space, and with relatively low cost. The hinge assemblies  300 ,  600  or a similar hinge assembly employing the laminated torsion bar design could be used in other applications where gas springs are typically used, such as toolbox lids, storage bins, baggage doors, deck hatches, and vehicle lift gates. 
     It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.

Technology Classification (CPC): 8