A space efficient and cost effective hinge clutch mechanism for facilitating the rotational positioning of a lid member of a portable electronic device relative to the housing the device. The clutch mechanism includes an elongated cam-shaft extending through a plurality of aligned components including a face cam member, a cam follower, and a compression spring and partially through a hollow retaining member. Rotation of the retaining member prevents the cam-shaft from being inadvertently with drawn. The clutch mechanism may be manually or automatically pre-assembled before insertion into the housing. An idler positioned adjacent to the retaining member serves as conduit for wires extending from the rotating lid member and the housing of the portable electronic device. The interaction of the cam and cam follower retains the lid in its fully open or fully closed positions until sufficient rotational force is exerted on the lid to overcome the tangential force of the spring.

BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This present invention relates to portable electronic devices. More specifically, the present invention relates to hinge clutches employed in portable electronic devices. 
     2. Description of the Related Art 
     Portable electronic devices have gained universal acceptance in a variety of applications including, but not limited to, wireless phones, laptop and palmtop computers, cameras as well as entertainment devices. Such applications usually demand durable, lightweight, space-efficient, and ultimately cost effective devices and associated components. 
     Many portable electronic devices, such as common flip-phones, employ a body member and a separate, foldable lid. The foldable lid is rotationally supported by and attached to the body of the device via at least one clutch hinge mechanism. The clutch hinge allows for manual rotation of the lid from a closed position adjacent the body of the phone to an angular position relative to the phone body to facilitate use of the phone. 
     Existing clutch hinges, such as face cam clutch mechanisms, typically allow for discreet positioning of the accompanying rotational lid member. One such clutch hinge includes a spring-loaded face cam and cam follower fitted within a cylindrical housing. Either the cam or the cam follower is rigidly connected to the rotational member, such as a flip portion of a wireless phone. During operation, a torque applied to the rotational lid, functions to apply a corresponding torque to the face cam, causing the face cam to rotate and lock into discreet positions with respect to the cam follower. The cam follower compresses or decompresses a spring as the cam rotates relative to the cam follower. 
     Unfortunately, such movement will often cause unacceptable wear on the hinge housing. Because the housing and components are often made of lightweight and non-durable materials such as ABS or ABS-PC plastic, they often fail well before operating the intended cycles. In addition, the difficulty of inserting the hinge mechanism within the body of the phone may require special tools and procedures. As a consequence, when one of the hinge components fails, the entire assembly is usually discarded and replaced. 
     Due to the possibility of premature failure, many conventional electronic devices require separate clutch housings for each point of attachment between the housing and the foldable lid. The additional clutch housings facilitate spring-loading of the face cam and cam follower, secure the face cam clutch to the device hinge housing and help to reduce the overall wear of the hinge assembly. 
     Unfortunately, the need for an additional clutch housing has many shortcomings. The additional clutch housing must be manufactured from durable, relatively expensive materials, which are often unsuitable for very thin-walled designs and are difficult to color. As a result, face cam clutches that employ an additional housing are often excessively bulky and relatively expensive. 
     Additional clutch housings also require relatively high-tolerance slots in which protrusions, i.e., keys on the cam follower must slide, thereby rotationally fixing the cam follower relative to the additional clutch housing and allowing the cam follower to unduly translate along a longitudinal axis of the clutch. The requisite tolerances represent addition design and manufacturing costs. 
     In many electronic devices such as flip phones, it is necessary to establish a wire connection between components in the lid and in the housing. Unfortunately, the hinge clutch mechanism when rotated may pinch and even cut such wires, causing failure of the lid-mounted component. 
     Hence, a need exists in the art for a space-efficient, durable, and cost-effective hinge clutch assembly that allows for discreet positioning of a rotational member relative to housing. Such mechanism should be readily assembled and disassembled without the need for special tools or the need to discard the entire assembly when a component must be replaced. Finally, operation of the mechanism should not interfere with any wire connections extending between the rotational member and the housing. 
     SUMMARY OF THE INVENTION 
     The need in the art is addressed by the space-efficient and cost-effective hinge clutch assembly of the present invention. In the illustrative embodiment, the inventive hinge clutch assembly is adapted for use with a portable electronic device and facilitates rotational positioning of a lid member relative to the housing of the device. The hinge clutch assembly includes an elongated cam-shaft having one end adaptable for joint rotation with the lid. A cam follower is mounted on the cam-shaft for joint rotation as well as longitudinal movement along the cam-shaft. A separate cam member is restrained from rotation and a compression spring serves to continuously press the cam follower against the cam member. A cylindrically-shaped retaining member is mounted on an end of the cam-shaft and functions to compress the spring against the cam follower. 
     The retaining member not only maintains the spring in its compressed position, by sliding the retaining member towards the cam follower, it is possible to further compress the spring, thereby reducing the overall length of the hinge assembly. This, in turn, allows the hinge mechanism to be easily disassembled from the housing and later reassembled. 
     Another aspect of the present invention resides in the use of a separate idler positioned between the retaining member and an attachment arm of the lid. The spring member compresses the retaining member against the idler to maintain its position in the housing. The idler is formed with a non-symmetrical configuration, which fits with a compatible portion of the housing to prevent the idler from rotating relative to the housing. In addition to supporting the retaining member in its proper position, the idler provides the routing for a wire/flexible circuit between the body of the electronic device and the foldable lid. During assembly, the idler may be displaced along its longitudinal axis to allow the foldable lid to be attached to the body of the electronic device. 
     Another embodiment of the present invention resides in the simplified method of assembly/disassembly of the hinge mechanism within the housing of the electronic device. The hinge clutch mechanism can be manually or automatically pre-assembled by inserting the cam-shaft through the remaining, aligned components, with the retaining member locking the components against separation. Once pre-assembly is complete, the hinge clutch mechanism can be readily inserted as a unit into the electronic device without the need for any special tools. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is partial view of the housing of an electronic device utilizing a face cam clutch assembly formed in accordance with the present invention. 
     FIG. 2 is an assembled view of the face cam clutch assembly of FIG.  1 . 
     FIG. 3 is an exploded view of a face cam clutch assembly of FIG.  2 . 
     FIGS. 4 and 5 are perspective views of the cam-shaft employed in the cam clutch assembly of FIG.  3 . 
     FIGS. 6 and 7 are magnified views of the face cam member employed in the cam clutch assembly of FIG.  3 . 
     FIGS. 8 and 9 are magnified views of the cam follower employed in the cam clutch assembly of FIG.  3 . 
     FIGS. 10 and 11 are magnified views of the retaining member employed in the cam clutch assembly of FIG.  3 . 
     FIGS. 12,  13  and  14  are magnified views of the idler member employed with the cam clutch assembly of FIG.  1 . 
     FIG. 15 is a partial assembled view of the idler of FIG.  12 . 
     FIG. 16 is a view of the flip lid of the electronic device partially shown in FIG.  1 . 
    
    
     DESCRIPTION OF THE INVENTION 
     While the present invention is described herein with reference to illustrative embodiments for particular applications, it should be understood that the invention is not limited thereto. Those having ordinary skill in the art and access to the teachings provided herein will recognize additional modifications, applications, and embodiments within the scope thereof and additional fields in which the present invention would be of significant utility. 
     FIG. 1 is a partial view of the housing  10  of an electronic device, which may, for purposes of the following discussion, take the form of a body of a flip phone assembly. Housing  10  may be formed of molded plastic or formed/cast metal and include a hollow, sleeve-shaped portion  12  with an indentation  14  formed on the surface thereof. As will be explained below, a hinge clutch mechanism  16  formed in accordance with the present invention is shown in FIG.  2 . The mechanism is specifically designed to be inserted within housing  10  with a portion of the mechanism extending within hollow sleeve  12 . Sleeve  12  serves as partial cover for protecting and supporting hinge clutch mechanism  16 . 
     Referring now to FIG. 3, an exploded view of the hinge clutch mechanism  16  includes, from top to bottom, an elongated cam-shaft  18 , a face cam member  20 , a separate cam follower  22 , a compression spring  24  and a retaining member  26 . 
     As shown in FIGS. 4 and 5, cam-shaft  18  is substantially of rectangular configuration and includes an end portion  28  having a generally “Y” shaped configuration. The rotational lid portion  30  of the portable electronic has a compatible, generally “Y” shaped opening  32  as shown in FIG.  16 . It is to be understood that the end portion  28  and the lid opening  32  could be formed of any conventional, compatible shapes that would allow for transmission of torque. When the hinge clutch mechanism  16  is assembled within housing  10 , the “Y” shaped end  28  of cam-shaft  18  extends within the “Y” shaped opening  32  of the lid  30 . As lid  30  is rotated relative to housing  10 , interaction of the end portion  28  with the lid opening  32  causes cam-shaft  18  to rotate in a similar manner. The importance of this rotation will soon become clear. 
     Cam-shaft  18  includes a first pair of oppositely disposed, substantially-rectangular lands  34  extending generally less than one half the length of cam-shaft  18  starting from end  28 . Cam-shaft  18  also includes a second pair of oppositely disposed, substantially rectangular lands  36 , wherein each land  36  is positioned approximately 90° from each land  34 . The second pair of lands  36  also extends from end  28  a distance greater than the length of the first pair of lands  34 . As will be discussed, the lands  34  and  36  serve to lock cam follower  22  for joint rotation with cam-shaft  18  while allowing cam follower  22  to move along the longitudinal axis of cam-shaft  18 . 
     Cam-shaft  18  includes a further end  38  oppositely disposed from end  28  and formed with a pair of rectangular protrusions  40 . The protrusions  40  extend outwardly on opposite sides of cam-shaft  18  and are aligned with lands  34 . The protrusions  40  prevent the retaining member  26  from inadvertently separating from cam-shaft  18  in a manner that will become clear. 
     Face cam member  20  is shown in FIGS. 6 and 7 to be of generally cylindrical configuration with a cylindrically shaped through opening  42 . Through opening  42  is of sufficient diameter to allow the elongated cam-shaft  18 , including lands  34  and  36  to freely extend through cam member  20  a distance until cam member  20  abuts cam-shaft end portion  28 . As shown in FIGS. 2 and 6, a curved lip  44  extends both outwardly from the cylindrical surface of cam  20  and beyond the flat end face  46  of cam member  20 . When the hinge clutch mechanism  16  is assembled as shown in FIG. 2, lip  44  overhangs cam shaft end portion  28 . When cam member  20  is disposed within housing  10  as part of hinge clutch mechanism  16 , the lip  44  rests in and engages a compatible opening formed in housing  10 , not shown, preventing cam  20  from rotating about its longitudinal axis. 
     As best shown in FIG. 7, cam member  14  further includes a specially designed, undulating ridge end face  48  confronting cam follower  22 . Ridge face  48  is contoured to mate with a confronting ridge end face  50  of cam follower  22  as will be discussed. 
     As shown in FIGS. 8 and 9, respectively, cam follower  22  is of generally cylindrical configuration with a centrally disposed through opening  52 . Opening  52  has a generally cross-shaped configuration compatible in size to the lands  34  and  36  extending from cam-shaft  18 . When assembled, the lands  34  and  36  of cam-shaft  18  pass through opening  52  of cam follower  22 . Cam follower  22  can be moved along cam-shaft  18  until its ridge end face  50  is adjacent the confronting ridge end face  48  of cam member  20 . Because opening  52  is similar in shape to lands  34  and  36 , rotation of cam-shaft  18  causes a similar rotation of cam follower  22 . 
     As shown in FIG. 9, cam follower  22  further includes a flat end face  54  oppositely disposed from ridge end face  50 . When hinge clutch mechanism  16  is assembled, a forward end of compression spring  24  abuts end face  54 , pressing confronting ridge faces of cam follower  22  cam member  20  against each other. Spring  24  also functions to press cam member  20  against cam-shaft end  28 . 
     The cylindrically-shaped retaining member  26 , are shown in FIGS. 10 and 11 to include an end wall  55  having an opening  56  of substantially rectangular configuration. Opening  56  is compatible in size to the size of overall size of cam-shaft end  38  including protrusions  40 . During assembly of hinge clutch mechanism  16 , cam-shaft end  38  is inserted through opening  56  of retaining member  26 , after which retaining member  26  is then rotated approximately 90°. Such rotation brings protrusions  40  out of alignment with the rectangular shape of opening  56 . A rearward end of spring  24  presses against wall  55  of retaining member  26  to maintain wall  55  in contact with protrusions  40 , preventing separation of cam-shaft  18  and retaining member  26 . 
     In the present specific embodiment, the undulating cam ridge end face  48  and the confronting, undulating cam follower ridge end face  50  each have two oppositely disposed peaks and two oppositely disposed valleys. Specifically, ridge face  48  has opposite peaks  48   a  and  48   b  and opposite valleys  48   c  and  48   d , respectively. Likewise, ridge face  50  has opposite peaks  50   a  and  50   b  and opposite valleys  50   c  and  50   d  respectively. When a first peak  48   a  rests in a first valley  50   c , cam member  20  assumes a first potential energy state or potential well corresponding to a first stable orientation of the lid portion  30  relative to housing  10  of the electronic device. At the same time the first peak  50   a  rests in the first valley  48   c , the second peak  50   b  will rest in valley  48   d.    
     When the first peak  48   a  rests in the second valley  50   d , the cam member  20  is in a second potential energy state or potential energy well corresponding to second stable orientation of the lid portion  30  relative to the housing  10  of the electronic device. The potential energies of cam member  20  in the first potential energy state and the second potential energy state are approximately equivalent. 
     The relative positions of the valleys  48   c ,  48   d  and peaks  48   a ,  48   b  on the ridge  48  of cam member  20  and on the valleys  50   c ,  50   d  and peaks  50   a ,  50   b  on the ridge  50  of cam follower  22  are substantially 180° apart; however, open and closed states are only 150-155° apart. The difference, substantially 25-30°, facilitates the stabilization of the first and second stable orientations, corresponding to open and closed states, respectively, of the lid  30  relative to the housing  10  of the electronic device. 
     When the hinge clutch mechanism  16  is in the first or second potential energy states, the compression spring  24  is in a more decompressed state but remains slightly compressed to maintain a spring-loaded state of the hinge clutch mechanism  16 . 
     The hinge clutch mechanism  16  assumes a third potential energy state when a first peak  48   a  rides on a first peak  50   a  and a second peak  48   b  rides on a second peak  50   b.  In the third potential energy state, the position of the lid  30  relative to housing  10  of the electronic device is relatively unstable. 
     Similarly, the hinge clutch mechanism  16  is in a fourth potential energy state when a first peak  48   a  rides on a second peak  50   b.  In the fourth potential energy state, the lid  30  and the housing  10  of the electronic device are relatively unstable. 
     The potential energies of the hinge clutch mechanism  16  in the third and fourth potential energy states are approximately equivalent. When the hinge clutch mechanism  16  is in either the third or fourth potential energy states, the spring  24  is in a more compressed state than when the hinge clutch mechanism  16  is in the first or second potential energy states. 
     When cam-shaft  18  is caused to rotate by rotation of attached lid  30 , the lands  34 ,  36  on cam-shaft  18  cause cam follower  22  to rotate in a similar direction. While cam follower  22  may rotate, cam member  20  is restrained from rotation by the engagement of curved lip  44  with the compatible cavity, not shown, in housing  10 . As cam follower  22  starts to rotate, the ridge end face  50  of cam follower  22  rides on ridge end face  48  of fixed position cam member  20 . The only way the undulating ridges  48  and  50  can rotate relative to one another is for cam follower  22  to move away from cam  20  along the longitudinal axis of cam-shaft  18 . This axial movement of cam follower  22  causes spring  24  to first compress as the peaks  48   a  and  50   a  come into contact with one another and then decompress as the peaks  48   a ,  48   b  and  50   a ,  50   b  each move into the valleys  48   c ,  48   d  and  50   c ,  50   d , respectively. When peaks on the ridge  50  of cam follower  22  ride on corresponding peaks of ridge  48  of cam  20 , the spring  24  is maximally compressed and the hinge clutch mechanism  16  assumes its relatively unstable state. In this relatively unstable state, the tangential resistance about the longitudinal axis of cam-shaft  18  is relatively small. When the valleys  48   c  and  48   d  on the ridge  48  of cam  20  ride on the corresponding peaks  50   a  and  50   b  of the ridge  50  of cam follower  22 , the hinge clutch mechanism  16  is in a relatively stable state and the spring  24  is minimally compressed. The tangential resistance about the longitudinal axis of cam-shaft  18  is relatively large. 
     When the lid  30  of the electronic device is in its fully closed or fully open position, the peaks of either the cam follower  22  or the cam member  20  are adjacent the valleys of the other component. In order to rotate the lid  30  from its closed to its open or from its open to its closed position, it will be necessary to apply sufficient force to over come the resistance exerted by spring  24 . Sufficient force will be needed to move the peaks of cam follower  22  past the peaks of cam member  20 . Once facing peaks are passed, the action of the spring  24  actually assists in completing the rotation of the lid  30  to its fully open or closed position, respectively. 
     As shown in FIG. 10, retaining member  26  is formed with a pair of indentations  60  of sufficient size to insert a small screwdriver or similar tool. During assembly or disassembly of hinge clutch mechanism  16 , retaining member  26  can be moved along the axis of cam-shaft  18  by inserting such a tool into one of the indentations  60  and pressing in the direction of cam follower  22 . This action serves to collapse the hinge clutch mechanism  16  by compressing spring  24 . Once the mechanism is sufficiently compressed, it may be easily removed from the housing  10  of the electronic device. To assist in the removal, a buttress  64  may be molded or otherwise mounted in housing  10 , see FIG. 1, and disposed such that a small pair of pliers may have one end applied to buttress  64  and the remaining end inserted into one of the indentations  60 . By squeezing the pliers, spring  24  is compressed, allowing retaining member  26  to slide towards cam follower  22 . 
     As shown in FIGS.  1  and  12 - 14 , a separate idler  70  is positioned in housing  10  adjacent to retaining member  26 . Idler  70  is preferably formed of plastic or similar cost effective material. Spring  24  presses retaining member  26  into frictional contact with idler  70 . Idler  70  includes a substantially “C” shaped end portion  72  which extends through a portion of housing  10 , see FIG.  15 . Because of the non-symmetrical shape of idler  70 , it will not rotate relative to housing  10 . 
     Idler  70  includes a dove-tailed opening  80  extending from a central passageway  78  through a side wall to the external surface. When assembled, wire or flexible cable joining housing  10  to lid  30  may pass through slit  76 , passageway  78  and dove-tailed opening  80 . Because of the continuous passageway through idler  70  and the fact that idler  70  is fixed against rotation, the wire  70   a  will not be pinched or torn when lid  30  is rotated between its fully open and fully closed positions. The dove-tailed opening  80  further serves to prevent any connecting wire  70   a  from slipping out of proper alignment during repeated opening and closing of lid  30 . 
     During disassembly, after retaining member  26  is pressed toward cam follower  22 , compressing spring  24 , cam-shaft  18  may be removed from housing  10 . At this point, idler  70  may be separated from housing  10 . 
     All parts of the hinge clutch mechanism  16  of the present invention may be molded or formed or machined by processes well known to one of ordinary skill in the art. 
     Thus the present invention has been described herein with reference to a particular embodiment for a particular application. Those having ordinary skill in the art and access to the present teachings will recognize additional modifications, applications and embodiments within the scope thereof. 
     It is therefore intended by the appended claims to cover any and all such applications, modifications and embodiments within the scope of the present invention.