Abstract:
The present invention is a torque producing apparatus comprising a first member, a second member, and a retention means. The first member has first and second arms, each having first and second ends, and a connection portion adjacent the joined first ends of the first and second arms. The arms have an outer surface and define an axial aperture. The axial aperture defines at least a portion of an inner surface of the arms. The second ends of the arms define an opening between the touter and inner surfaces. At least one of the inner and outer surfaces have a predetermined diameter when the member is in a relaxed state. The second member has a surface arranged to engage in interference fit against at least one surface of the first member when the first member is in its relaxed state. The retention means engages the connection portion of the first member so that the second member rotates relative to the first member upon relative rotation of the second member and the retention means.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to torque-producing friction hinges. More specifically, the present invention relates to a clip or multiple clips radially compressed on a shaft to produce rotational friction or torque between the shaft and the clip(s). 
     Friction hinge devices are used to support objects at selected angular positions relative to a main body. For example, friction hinges are used in notebook computers to support a computer screen at various angular locations relative to a computer base. They are also used to support windshield visors in motor vehicles at various angles. 
     One type of friction hinge is a spring hinge which utilizes a helical spring wrapped around a shaft. In a relaxed state, the spring has an inner diameter less than the outer diameter of the shaft to frictionally engage the shaft so that the spring and shaft will tend to rotate together. In use, the shaft is connected to a rotatable body. As the body and the shaft are rotated, one of the spring ends or “toes” is oriented to contact a stop, which is typically part of a stationary support. The engagement of the spring toe with the step will cause the spring to slip relative to the shaft, rather than rotate with the shaft. This will generate torque. Such a spring hinge can be designed to provide a fairly constant torque or resistance to rotation throughout its range of motion. 
     Another type of a friction hinge device is an axial compression hinge. An axial compression hinge includes at least two friction discs compressed against each other on a shaft. The axial compression hinge utilizes a compression force along the axis parallel with its shaft. An arm is attached to one of the friction discs while the other friction disc is secured to the shaft. As the arm is rotated relative to the shaft, the friction between the surfaces of the discs creates torque. 
     Both the spring hinge and the axial compression hinge have limitations and difficulties. For example, with respect to the axial compression hinge, it is often difficult to attach the friction discs to the arms and also difficult to secure the discs to the shaft. The difficulty in attaching the arms to the discs greatly increases when additional discs are added to the shaft in an attempt to increase torque. More particularly, each disc that is added must have an additional arm attached to it. The space limitations of most applications make the connection of additional arms impractical. 
     The axial compression hinge also must have a mechanism which sufficiently delivers enough axial compression force to maintain friction between the discs. It is often difficult to maintain a relatively constant axial compression force on the discs. This causes non-constant torque which is a very undesirable characteristic. 
     Also, the particular connection between the friction discs and the arm can affect the overall torque produced by the axial compression hinge. The friction effect is not constant or predictable and may also cause non-constant torque. 
     Finally, the friction discs must be formed to very specific tolerances. Variations in the size of the discs will significantly affect the overall torque of the device. This presents problems in machining multiple components to exact tolerances. 
     With respect to the spring hinge, the overall size of the spring hinge is often too large for certain applications requiring relatively large torque. With the spring hinge design, the most effect way to substantially increase torque is to add additional springs to the shaft. This will substantially increase the size of the package required to contain the friction spring hinge. Space limitations of many applications make the addition of spring elements impractical. 
     In addition, spring hinges require that the spring toe be secured to, or otherwise engage, the support base so that the spring is held stable as the shaft is rotated relative to the support base. However, if the spring toe is extended to engage a stop portion on the support base, this engagement will only occur in one direction of rotation of the shaft. In the opposite direction the spring toe will rise off the stop portion of the support base allowing the spring to rotate with the shaft. Hence, the torque producing effect of the spring hinge is unidirectional. Bi-directional spring hinges exist, but these usually require engaging a spring toe to the support base at both ends of the spring so that the spring is held stable as the shaft is rotated in either direction. 
     Spring hinges also require very accurate machine tolerances. The spring toes must terminate precisely at the stop portion of the support structure. The precise location of the spring toes relative to the stop is critical to the performance of the spring hinges. If the space between the spring toe and the stop is too large, the hinge will have free play, that is, there will be no torque for a limited range until the spring toe engages the stop. On the other hand, if the radial tolerance between the spring toe and the stop is too small, the toes will make the spring hover over the shaft resulting in no or low torque. 
     Finally, the overall torque of the spring hinge is usually significantly affected by the antirotation elements of the device. More specifically, the overall torque of the spring hinge is significantly affected by the engagement of the spring toe with the stop on the support base. As the spring toe engages the support base stop, the spring tends to “wrap open”, that is, lift off the shaft. This decreases the friction between the spring and the shaft, which in turns decreases the torque produced by the spring hinge. 
     The present invention solves these and other problems associated with the prior art. 
     SUMMARY OF THE INVENTION 
     The present invention is a torque producing apparatus comprising first and second members and retention means. The first member has a first arm, a second arm, and a connection portion. The first and second arms have an inner and an outer surface and define an aperture. The first and second arms have an opening between the inner and outer surfaces. When the member is in a relaxed state, at least one of the inner or the outer surface has a predetermined diameter. The second member has a surface that engages one of the inner or outer surface of the first member. The retention means engages the connection portion of the first member so that the second member rotates relative to the first member upon relative rotation of the second member and the retention means. 
     In one embodiment of the present invention the second member is a rotatable shaft. The shaft has a surface with an outer diameter greater than a predetermined diameter of the inner surface of the first member when the first member is in a relaxed state. The surface of the shaft is engaged in interference fit to the inner surface of the first member. The retention means engages the connection portion of the first member so that the shaft rotates relative to the first member upon relative rotation of the shaft and the retention means. 
     In another embodiment of the present invention the second member is a sleeve. The sleeve has a surface with an inner diameter smaller than a predetermined diameter of the outer surface of the first member when the first member is in a relaxed state. The surface of the sleeve is engaged in interference fit to the outer surface of the first member. The retention means includes a shaft configured to engage the connection portion of the first member so that the sleeve rotates relative to the first member upon relative rotation of the sleeve and the shaft. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a friction hinge according to a preferred embodiment of the present invention. 
     FIG. 1A is an end view of a friction hinge according to a preferred embodiment of the present invention. 
     FIG. 2 is a perspective view of a partially assembled friction hinge according to a preferred embodiment of the present invention. 
     FIG. 3 is a perspective view of a clip for a friction hinge according to a preferred embodiment of the present invention. 
     FIG. 4 is a perspective view of a friction hinge according to a first modification of the present invention. 
     FIG. 5 is a perspective view of a friction hinge according to a second modification of the present invention. 
     FIG. 6 is a perspective view of a clip for the friction hinge according to the second modification of the present invention. 
     FIG. 7 is a perspective view a friction hinge according to a third modification of the present invention. 
     FIG. 8 is a perspective view of a clip for the friction hinge according to the third modification of the present invention. 
     FIG. 9 is a perspective view of a friction hinge according to a fourth modification of the present invention. 
     FIG. 10 is a perspective view of a clip for the friction hinge according to the fourth modification of the present invention. 
     FIG. 11 illustrates the formation of multiple clips from a single sheet of material. 
     FIG. 12 is a perspective view of a clip for a friction hinge according to a fifth modification of the present invention. 
     FIG. 13 is a perspective view of a clip for a friction hinge according to a sixth modification of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1-3 show a torque producing apparatus  20  inn accordance with the present invention. Torque producing apparatus  20  includes shaft  22  which has a shaft surface  24 , a plurality of clip members  26  and restraint  28 . Members  26  are frictionally engaged to the shaft surface  24  of shaft  22 . Restraint  28  has an inner restraint surface  29 . 
     Each member  26  has an outer member surface  27  and includes connection portion  30 , first arm  32 , and second arm  34 . First and second arms  32  and  34  are disjointed to define an opening or slit  36 . First and second arms  32  and  34  include inner member surface  39  which defines aperture  38 . (See FIG.  3 ). When member  26  is in a relaxed state, inner member surface  39  has a diameter smaller than the outer diameter of shaft surface  24 . Consequently, when shaft  22  is connected though aperture  38  to member  26 , inner member surface  39  frictionally engages shaft surface  24 . Arms  32  and  34  of member  26  exert radial compression on shaft  22 . 
     In a preferred embodiment of the present invention, outer member surface  27  of first and second arms  32  and  34  form a circular shape. Connection portion  30  comprises a rectangular-like projection with rounded protruding edges extending tangentially from the circular shape of first and second arms  32  and  34 . In this way, the profile of outer member surface  27  appears substantially circular, with one overhanging portion extending tangentially off the circle. The diameter of the profile of outer member surface  27  is such that the radial thickness of arms  32  and  34  is substantially larger than the axial thickness of member  26 . 
     Also in a preferred embodiment of the present invention, restraint  28  comprises a housing which contains members  26  and substantially contains shaft  22 . Restraint  28  has a cylindrical-like body, a cross-section of which substantially matches the profile of outer member surface  27 . Inner restraint surface  29  follows the shape of outer member surface  27 . In the substantially circular portion comprising first and second arms  32  and  34 , inner restraint surface  29  is spaced away from member  26  defining gap  35 . (See FIG.  1 A). The projection portion extending off the circular portion comprising connection portion  30  directly engages inner restraint surface  29 . 
     In operation, torque producing apparatus  20  is used to produce torque. Restraint  28  is mounted to a stationary device, such as to the base of a notebook computer. Shaft  22  is attached to a rotatable body such as a computer screen in the notebook computer. Friction between member  26  and shaft  22  produces torque which may be utilized to support the screen at various angular locations relative to the base. 
     As shaft  22  is rotated, for example as the computer screen is lifted, friction caused by the interference fit between shaft surface  24  and inner member surface  39  causes member  26  to tend to rotate with shaft  22 . However, inner restraint surface  29  engages connection portion  30  of member  26  such that member  26  is not able to rotate relative to restraint  28  as shaft  22  is rotated. 
     In operation, the restraint of rotation of members  26  relative to the shaft  22  causes resistance to rotation, or torque, as the computer screen is lifted relative to the computer base. In the preferred embodiment described above, the resistance caused by torque producing apparatus  20  will be substantially the same in either direction of the rotation of shaft  22 . Unequal torque may be produced in opposite directions by forming arms  32  and  34  with unequal radial thickness, or unequal radial length from connection portion  30  (See FIG.  13 ). 
     The apparatus of the present invention allows smaller packages to produce larger torque than was possible with previous designs. By adding additional members  26  to shaft  22  of the apparatus of the present invention, torque will be increased. Unlike previous spring hinge designs where the addition of an entire spring was necessary to increase torque, the members of the present invention are relatively thin. Thus, torque is selectively increased with the present invention with no significant increase in overall size of the device. 
     Similarly, where previous axial compression hinges required additional connection arms and the like in order to increase torque, no such similar features are needed for the present invention. Thus, relative size for the device is less for the present invention than with previous designs. 
     In addition, the apparatus of the present invention can be utilized without the often complicating concerns of securing or stabilizing a spring toe. As previously discussed, the means of securing a spring toe can affect the torque produced. However, with the apparatus of the present invention the torque produced by the device is unaffected by antirotation elements. More particularly, the antirotation elements of the present invention, namely, the connection portion of the member, is separate from the friction elements, namely, the outer surface of the shaft and the inner surface of the member. 
     FIG. 4 shows alternative torque producing apparatus  40  in accordance with the present invention. Torque producing apparatus  40  includes shaft  22  which has a shaft surface  24 , a plurality of clip members  26  and restraint  42 . Members  26  are frictionally engaged with shaft surface  24  of shaft  22 . Restraint  42  has an inner restraint surface  44  which contacts outer member surface  27 . 
     Shaft  22  and members  26  interact essentially as described above with respect to torque producing apparatus  20 . However, restraint  42  only encompasses connection portion  30  of member  26 . Inner restraint surface  44  follows the contour of outer member surface  27  on connection portion  30 . 
     In operation, torque producing apparatus  40  is used to produce torque essentially as described above with respect to torque producing apparatus  20 . As shaft  22  is rotated, friction between shaft  22  and member  26  causes member  26  to tend to rotate with shaft  22 . Inner restraint surface  44  engages connection portion  30  of member  26  such that member  26  is not able to rotate relative to restraint  42  as shaft  22  is rotated, hence causing resistance to rotation, or torque. 
     FIGS. 5 and 6 show alternative torque producing apparatus  50  in accordance with the present invention. Torque producing apparatus  50  includes shaft  52  which has a shaft surface  54 , a plurality of clip members  56  and restraint  58 . Members  56  are frictionally engaged to shaft surface  54  of shaft  52  and each have a first connection portion  60  and a second connection portion  62 , defining a slot  64 . (See FIG.  6 ). Restraint  58  is oriented to fit into slot  64  and has an outer restraint surface  59 . Thus, at least a portion of outer restraint surface  59  contacts both first and second connection portions  60  and  62 . 
     In operation, torque producing apparatus  50  is used to produce torque essentially as described above with respect to torque producing apparatus  20 . AS shaft  52  is rotated, friction between shaft  52  and member  56  causes member  56  to tend to rotate with shaft  52 . However, outer restraint surface  59  of restraint  58  engages either the first or second connection portion  60  and  62  such that member  56  is not able to rotate relative to restraint  58  as shaft  52  is rotated. 
     For example, if shaft  52  is rotated in the direction of arrow  51  indicated in FIG. 5, member  56  will also tend to rotate in that same direction. However, as shaft  52  is rotated, first connection portion  60  contacts outer restraint surface  59  such that member  56  cannot rotate. Similarly, as shaft  52  is rotated in the direction opposite to arrow  51  in FIG. 5, member  56  will also tend to rotate in that direction and second connection portion  62  will contact outer restraint surface  59  such that member  56  cannot rotate. 
     In either direction of rotation the interference fit between outer restraint surface  59  of restraint  58  and first or second connection portion  60  and  62  causes resistance to rotation, or torque. The torque generated by torque producing apparatus  50  will be substantially the same in either direction of the rotation of shaft  52 . 
     FIGS. 7 and 8 show alternative torque producing apparatus  70  in accordance with the present invention. Torque producing apparatus  70  includes shaft  72  which has a shaft surface  74 , a plurality of clip members  76  and restraint  78 . Members  76  are frictionally engaged with shaft surface  74  of shaft  72 . Restraint  78  has an inner restraint surface  79  which contacts outer member surface  77 . 
     Shaft  72  and members  76  interact essentially as described above with respect to torque producing apparatus  20 . However, member  76  includes connection portion  80 , first arm  82 , and second arm  84  which form a rectangular outer shape. Thus, the profile of outer member surface  77  appears substantially as a rectangle. (See FIG.  8 ). 
     Restraint  78  only engages connection portion  80  of member  76 . Inner restraint surface  79  follows the contour of outer member surface  77  on connecting portion  80 . 
     In operation, torque producing apparatus  70  is used to produce torque essentially as described above with respect to torque producing apparatus  20 . As shaft  72  is rotated, friction between shaft  72  and member  76  causes member  76  to tend to rotate with shaft  72 . However, inner restraint surface  79  contacts connection portion  80  of member  76  such that member  78  is not able to rotate relative to restraint  78 . This produces torque. 
     FIGS. 9 and 10 show alternative torque producing apparatus  90  in accordance with the present invention. Torque producing apparatus  90  includes a non-circular shaft  92 , a plurality of clip members  96  each of which have an outer member surface  97 , and sleeve  98 , which has an inner sleeve surface  99 . Outer member surface  97  is frictionally engaged with inner sleeve surface  99 . 
     Each member  96  has an outer member surface  97  and includes first arm  102  and second arm  104 . First and second arms  102  and  104  are disjointed to define slit  106  and oriented to define connection portion  100 . First and second arms  102  and  104  include inner member surface  109  which defines aperture  108 . (See FIG.  10 ). When member  106  is in a relaxed state, outer member surface  97  has a diameter larger than that of inner sleeve surface  99 . Consequently, when member  96  is oriented in sleeve  98 , inner sleeve surface  99  frictionally engages outer member surface  97 . 
     Shaft  92  has a shaft surface  94  and includes engagement portion  110  which interlocks with connection portion  100 . Connection portion  100  is shaped to fit into engagement portion  110  so that shaft  92  may be inserted into members  96  as they are oriented inside sleeve  98 . 
     In operation, torque producing apparatus  90  is used to produce torque. Sleeve  98  is mounted to a stationary device. Shaft  92  is attached to a rotatable body. The friction between member  96  and sleeve  98  produces torque which may be utilized in supporting the rotatable body at various angular locations relative to the stationary device. 
     As shaft  92  is rotated, the engagement of engagement portion  110  with connection portion  100 , as well as the friction caused by the interference fit between outer member surface  97  and inner sleeve surface  99 , causes sleeve  98  to tend to rotate with shaft  92 . However, because sleeve  98  is mounted to the stationary device, member  96  will slip relative to sleeve  98  producing friction, or torque. The torque generated by torque producing apparatus  90  will be substantially the same in either direction of the rotation of shaft  92 . 
     As shown in FIG. 11, a plurality of members  26  may be stamped out of a flat sheet of material  120 . Processes such as stamping, fine blanking and EDM may be used to produce highly repeatable members  26  at relatively low cost. In this way, members  26  can be manufactured at very strict tolerances in order to be used in the apparatus of the present invention to produce highly repeatable torque. 
     Previous hinge designs, such as spring hinges, rely upon very difficult forming procedures to produces rounded and shaped metals from a flat material. This leads to inconsistent part tolerances and inconsistent torque. By avoiding all forming-type processing, the present invention generates very consistent torque. 
     Using the stamping process, varying shapes may easily be implemented for member  26 . For example, member  56  (See FIG.  6 ), member  76  (See FIG.  8 ), and member  96  (See FIG. 10) can be manufactured using a stamping process. Further, member  26  can have connection portions  30  of varying configurations. FIGS. 12-13 show members  130  and  140  with corresponding connection portions  132  and  142 . 
     A torque producing apparatus in accordance with the present invention that includes member  130  with connection portion  132  would include a restraint that was shaped to accept connection portion  132  in order to prevent relative rotation of member  130  with rotation of a shaft extending through member  130 . 
     Member  140  includes connection portion  142  and slit  144 . Connection portion  142  is located adjacent slit  144  rather than directly across from it. Thus, a torque producing apparatus in accordance with the present invention that includes member  140  with connection portion  142  would produce different torque dependant upon which direction a shaft extending through member  140  is rotated. 
     Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.