Patent Publication Number: US-2005136998-A1

Title: Spring biased hinge and methods therefor

Description:
FIELD OF THE DISCLOSURE  
      The present invention relates generally to electronics devices and, more particularly to portable wireless handsets having multiple housing portions that are hinged together and rotate between open and closes positions.  
     BACKGROUND  
      Wireless cellular communications devices having hinged flip portions are known generally. For example, a compression spring biased cam that engages a cam follower to pivot a housing member, such as a cover or flip portion, about an axis of rotation that is the same the axis of the compression spring is known.  
      U.S. Pat. No. 5,640,690 entitled “Hinged Assembly Having Cam Follower” discloses, for example, a compression spring biased cam that engages a cam follower to pivotal a body member cover or flip portion.  
      Wireless or portable communication devices continue to add features while maintaining or even reducing the device size to promote portability. The existing hinges of folding devices take up space within the housing, which reduce the amount of already limited space that is available for the incorporation of other desirable features. Control over the motion of the relative housing portions is also limited. Additionally, the incorporation of an open assistance feature is limited, takes up valuable space within the device or is not possible with the existing hinge assemblies.  
      Some hinges force a spring urged follower into a detent cam, positioning the two elements at various angles relative to one another, based on the position of the detent. U.S. Pat. No. 3,644,023 entitled “Hinged Spring-Loaded Spectacle Hinge” discloses, for example, a spring biased cam means that forces a follower into a detent to hold the side arms in a respective service position. These hinges, however, do not provide motion of one element relative to the other element.  
      The various aspects, features and advantages of the present invention will become more fully apparent to those having ordinary skill in the art upon careful consideration of the following Detailed Description of the Invention with the accompanying drawings described below. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is an exemplary electronics device having a hinge.  
       FIG. 2  is an exemplary wireless communications handset schematic block diagram.  
       FIG. 3  is an exemplary cross section of the electronics device having a hinged portion.  
       FIG. 4  is an exemplary electronic device in a first rotation position.  
       FIG. 5  is an exemplary cross sectional view of a hinge follower.  
       FIG. 6  is an exemplary cross sectional view of a cam and follower hinge.  
       FIG. 7  is an exemplary free body diagram illustrating exemplary forces of the cam follower assembly.  
       FIG. 8  is an exemplary sectional view of a cam and follower hinge.  
       FIG. 9  is an exemplary electronics device having a hinge.  
    
    
     DETAILED DESCRIPTION  
      While the present disclosure is achievable by various forms of embodiment, there is shown in the drawings and described hereinafter present exemplary embodiments with the understanding that the present disclosure is to be considered an exemplification and is not intended to limit the claims below to the specific embodiments contained herein.  
       FIG. 1  illustrates an exemplary closeable electronic device  100  in an open position. In the exemplary embodiment, the electronics device  100  is a radiotelephone. The radiotelephone  100  described herein is a representation of the type of wireless communication device that may benefit from the present invention. However, it is to be understood that the present invention may be applied to any type of hand-held or portable electronic device including, but not limited to, the following devices: radiotelephones, cordless phones, paging devices, personal digital assistants, portable computers, pen-based or keyboard-based handheld devices, remote control units, an audio player (such as an MP3 player), including handheld storage containers, for example, a pocket-sized cigarette container, and the like. Accordingly, any reference herein to the radiotelephone  100  should also be considered to apply equally to other hand-held or portable electronic devices.  
      The device  100  is shown having a first housing  110 , for example a radiotelephone handset housing, pivotally coupled to a second housing  120  or cover, for example a radiotelephone phone flip. A spring biased hinge, couples the first housing  110  to the second housing  120 , and affects the motion of the first housing  110  relative to the second housing  120 . However, the hinges and spring biasing mechanisms of the present invention may be used more generally in any application where it is desirable to provide a spring-biased hinge, in a collapsible device as will become more fully apparent from the discussion below.  
       FIG. 2  is an exemplary wireless communications handset schematic block diagram  200  comprising generally a processor  210  coupled to memory  220 , for example RAM, ROM, EPROM, etc. The exemplary wireless handset also includes a radio transceiver  230 , a display  240 , optionally a touch screen display, optionally a second display, inputs  250 , for example a keypad, a microphone and video inputs, outputs  260 , for example a sound and tactile or haptic outputs, and other ports  280 , for example power, audio, etc., all of which are coupled to the processor.  
      The various elements of the exemplary radiotelephone  100 , for example the processor, memory, inputs, outputs are disposed generally in a housing. The display is often mounted on the housing whether it is a part of a one piece assembly, or a multiple piece assembly where the housing elements move relative to one another. The housings may also include a keypad or keypads. The location and arrangement of these exemplary wireless handset elements is only an exemplary application and is immaterial to the structure of the hinges and spring biasing mechanisms, which are discussed more fully below.  
      In reference again to  FIG. 1 , an exemplary radiotelephone  100  in an open position is provided having a first housing  110  and a second housing  120 . The first housing  110  has an elongated shape with at least a first face  104 . The second housing  120  has a similar elongated shape with a second face (not shown) In a closed position the second housing  120  substantially covers the first housing  110  wherein the first face  104  and the second face are substantially planarly adjacent. The second housing  120  rotates relative to the first housing  110  about a rotation axis  128  which is substantially perpendicular to at least the first face  104  of the first housing  110 . The first housing  110  includes a hollow portion  132  that carries a follower  102  and a yielding member  134 . The follower  102  and the yielding member  134  reciprocate within the hollow portion  132 , the exemplary combination of which may be considered to be a biasing member or assembly. In other embodiments, the biasing member does not require the hollow portion, for example, in applications where other structure provide support for the spring or in embodiments where the spring is sufficiently stiff not to require a carrier or support. The follower may be integral with the spring or it may be a discrete element. In the exemplary embodiment the spring is of the compression type, though in other embodiments it may be a torsion spring or a leaf-type spring or some other spring member.  
      The second housing  120  includes a retaining ring  106  carrying the cam  122 , the cam  122  having a contoured surface portion  138  adapted to engage the follower  102 . The first housing  110  rotates about rotation axis  128  relative to the second housing  120  such that the first face  104  and the second face maintain the same plane while rotating. A hinge pin  130  extends from the first housing  110  to the second housing  120  along the rotation axis  128 .  
      In reference to  FIG. 3 , a cross section of the exemplary embodiment shown in  FIG. 1  illustrates the first housing  110  and the second housing  120  in a closed position. The first housing  110  includes the hollow portion  132  including a void or notch  300  at a cam end  131  thereof. The notch  300  forms a fork  302  in the cam end  131  of the hollow portion  132  that straddles the cam  122  such that the cam  122  is partially enclosed between the two tines of the fork  302  of the hollow portion  132 . The hinge pin  130  extends though the fork  302  and the cam  122  allowing the cam  122  to rotate between the tines of the fork  302 . The follower  102  engages both the cam  122 , between the tines of the fork  302 , and the yielding element  134 , within the hollow portion  132 . The hinge pin  130  is coupled to the first housing at a first housing bushing  304  and is coupled to the second housing  120  at a second housing bushing  306 . While the exemplary embodiment include two tines, other embodiments may include only a single tine.  
      The cam  122  is carried on the retaining ring  106  extending from the ring inward to the center of the retaining ring  106 . The retaining ring  106  rotatably couples the first housing  110  to the second housing  120  preventing the second housing  120  from separating from the first housing  110 . A flange  308  on the retaining ring  106  supports the second housing  120  within the first housing  110  by mating with a support edge  310  of the first housing  110 . The retaining ring  106  is rigidly fixed to the cam  122  such that when the cam  122  rotates, the retaining ring  106  rotates as does the second housing  120 , which is attached thereto.  
      The hinge pin  130  is a shaft that extends through a portion of the first and second housings ( 110 ,  120 ) and substantially perpendicular to at least the first face  104  of the first housing  110 . The hinge pin  130  also extends through the cam  122  and the hollow portion  132 . The retainer ring  106  is coupled between the cam  122  and the second housing  120 . In other embodiments, the cam  122  may be coupled to the second housing  120  and retained by the first housing portion  110  by alternative pivotal coupling mechanisms, for example by a ball bearing race or a Teflon surface. The hinge pin  130  aligns with the axis of rotation  128  of the cam  122  and hence the second housing  120  relative to the first housing  110 .  
      In reference to  FIG. 4  the first housing  110 , shown in the exemplary embodiment of the device  100  is in a first open position  400 . The first housing  110  having an elongated shape and at least a first face  402  which is substantially flat. The first face  402  carries a user interface  404  in this embodiment that is accessible to the user when the radiotelephone  100  is in the first open position  400 . The user interface  404  may be a display, a keypad, a touch screen or any combination thereof, or the like. The first housing  110  has long dimension  408  and a short dimension  410 , the long dimension  408  having a longitudinal axis  412  running the length of the long dimension  408 .  
      Also illustrated in  FIG. 4 , is the second housing  120  having an elongated shape, similar to that of the first housing  110 , and at least a second face  108 . The second face  108  may or may not have a user interface. If the second face  108  does carry a user interface, the user interface may be a display, a keypad, a touch screen, a camera or any combination thereof. In the exemplary embodiment shown in  FIG. 4 , the second face  108  has a display  430  and buttons  426 . The second housing  120  may also have third face  414 . A user interface, or user interfaces, may be carried on the third face  414 , which in the exemplary embodiment, is on an opposing side to the second face  108  of the second housing  120 . The second housing  120  has long dimension  420  and a short dimension  424 , the long dimension  420  having a longitudinal axis  422  running the length of the long dimension  420 . In the illustrated embodiment, the second housing  120  principally functions as a cover, which as noted above can also include some functional electronic components, such as selection buttons  426 , a speaker  428 , a display  430  or indicator lights. However, in the illustrated embodiment, a majority of the functional electronic components are included as part of the first housing  110 , which is also referred to as the body or lower housing. As a cover, the second housing  120  substantially covers the first housing  110  when in a closed position protecting the components on the first face  104 .  
      Referring to  FIG. 5 , a cross section of the hollow portion  132  is shown coupled to the cam  122 . The hollow portion  132  retains the yielding member  134  which is a compression spring  501  in the exemplary embodiment, and the follower  102  is a spheroid  502  in the exemplary embodiment, such as a ball bearing or the like. The hollow portion  132  aligns the follower  502  with the cam  122 . The hollow portion  132  has two portions, a hollow portion cam end  503  and a hollow portion yielding member end  504 . The fork  302  is located at the hollow portion cam end  503  and comprises a first tine  506  and a second tine  508 . The fork  302  allows the follower  102  to align with the cam  122  and at the same time, allows the cam  122  to rotate between the first tine  506  and the second tine  508  of the fork  302  of the hollow portion  132 . The tines ( 506 ,  508 ) of the fork  302  guide the follower  102  such that the follower  102  does not escape from the hollow portion  132  laterally during reciprocation in conjunction with the rotation of the cam  122 . The hollow portion  132  guides the follower  102  to reciprocate in a plane which is perpendicular to the axis of rotation  128  and within the same plane as the rotation of the second housing  120  relative to the first housing  110 .  
      The fork  302  is formed by the notch  500  and the two tines of the hollow portion cam end  503  of the hollow portion  132 . The tines ( 506 ,  508 ) of the fork  302  are extensions of the hollow portion  138  such that an inner surface  510  of the hollow portion yielding member end  504  continues to the tines. The continuous shape of the inner surface  510  allows the follower  102  and the yielding element  134  to seamlessly reciprocate in both portions of the hollow portion  132 .  
      The hollow portion  132  may be a chamber carried in the second housing  120  or may be a chamber integrally formed into the first housing  110 . Whether the hollow portion  132  is carried as an independent component in the first housing  110  or an integral part thereof, the inner surface  510  has a dimension that accommodates the follower  102 , sphere  502  in the exemplary embodiment, and the compression spring  501 , allowing the sphere  502  and the compression spring  501  to reciprocate along the long dimension of the hollow portion  132  as the follower  102  interacts with the cam  122 .  
      The first tine  506  has a first void and the second tine  508  has a second void for receiving the hinge pin  130 . The hinge pin  130  extends through the first void, the cam  122  and through the second void. The cam  122 , the hollow portion  132  and the follower  102  make up the cam-follower assembly coupled together by the hinge pin  130 . The hollow portion  132  rotates about the hinge pin  130  that extends through the first and second voids.  
      The compression spring  501  yields to the follower  102  in a reciprocating motion in response to the rotation of the cam  122  as the first housing  110  pivots about the rotation axis  128 . The compression spring  501  is compressible along a compression axis  503  of the compression spring  134  along a center axis  136  of the hollow portion  132 . The compression axis  503  is substantially perpendicular to the first face  104  of the first housing  110 . The compression spring  501  is disposed such that it applies a force to the follower  102  wherein the follower  102  remains coupled to the contoured surface  138  at all points along the contoured surface  138 . The compression spring  501  has a magnitude of compression in response to changes in the contoured surface portion  138  as the second housing  120  pivots about the axis of rotation  128 . In the embodiment shown in  FIG. 5 , the compression spring  501 , is compressably disposed in the hollow portion  132 . The compression spring  501  is compressible along the compression axis  503  of the compression spring  134  disposed along a center axis  136  of the hollow portion  132 . In the exemplary embodiment shown in  FIG. 5 ., the compression spring  501  is oriented such that it applies a force to the follower  102  wherein the follower  102  remains in contact with the contoured surface portion  138  at all points along the contoured surface portion  138 .  
      The follower  502  has a curved surface, e.g., a spheroid, ellipsoid, or other friction reducing shape, in the exemplary embodiment illustrated  FIG. 5 . The follower is guided within the hollow portion  132  by at least a portion of the fork  302  at the hollow portion cam end  503 . The follower  132  may also traverse along the hollow portion beyond the fork  302  as the cam  122  rotates. More particularly, as the distance from the rotation axis  128  to the contoured surface portion  138  in contact with the follower increase, the follower moves farther away from the rotation axis into the hollow portion  132 . Consequently, the compression spring  501  is compressed further exerting a greater rotational force on the first and second housings  110 ,  120 . The follower  502  either rolls along or slides along the contoured surface portion  138  of the cam  122  or a combination thereof. The follower  502  seats in the follower end  520  of the compression spring  503 . As the follower  502  moves, rolling or sliding or a combination thereof, along the contoured surface portion  138  it may rotate within the follower end  520  of the compression spring  501 .  
      The fork  302  captures and guides the follower  102  such that it aligns with the cam  122  and the compression spring  501  and at the same time, allows the cam  122  to rotate between the first tine  506  and the second tine  508  of the fork  302  of the hollow portion  132 .  
      The cam  122  is positioned inside of the first housing  110  by the retaining ring  106  and is coupled to the hollow portion by the hinge pin  130  and the follower  502 . The cam  122  is centered about the rotation axis  128 . In the exemplary embodiment, the rotation axis  128  of the cam is centered about the long axis  412  of the first housing  110  and the long axis  422  of the second housing  120 . The cam  122 , and hence the second housing  120 , rotate about the rotation axis  128  relative to the first housing  110 . In the exemplary embodiment, the contour surface portion  138  of the cam  122  is designed to achieve the motion of the second housing  120  relative to the first housing  110 . The change in diameter of the cam, at positions along the contour surface portion  138  cause the cam  122  to rotate about the rotation axis  128  as a result of the force exerted on the cam by the follower  502  and the compression spring  501  as described below. In other embodiment, the the proportions may be changed and/or the biasing member located to provide a different leveraging action on the cam.  
      Depending on the relative location of the follower  102  on the contour surface portion  138  of the cam  122 , the second housing  120  is either stationary or rotating relative to the housing portion  120 . The location and motion of the second housing  120  is a consequence, of the follower  102  interaction with the contoured surface portion  138  as the cam  122  rotates about the axis of rotation  128 . The cam follower assembly is one source of force acting on the second housing  120 . The rotation of the second housing  120  is a result of the force of the follower  336  on the cam  122  as the follower  102  moves across the contoured surface portion  138 . The motion of the follower  102  across the contoured surface portion  138  is at least a function of the yielding element force and the slope of the contoured surface portion  138  relative to the second housing  120 . The force of the yielding element, or compression spring  501 , and the angle of the slope of the contoured surface portion  138  relative to the direction of the yielding element force, determines the magnitude of the force acting on the second housing  120  by the yielding element via the follower  502 .  
      As the yielding element force urges the follower  102  toward the contoured surface portion  138 , the contact between the follower  102  and the contoured surface portion  138  creates two component forces. These two components are perpendicular to one another, and are reactive to the yielding element force. When the angle or slope of the contoured surface portion  138  is not perpendicular to the yielding element force, a first component of the reactive force is created and acts parallel to the contoured surface portion  138  thereby urging the follower  102  to traverse the contoured surface portion  138 . Consequently the cam  122  and the retaining ring  106  in turn applies a force against the second housing  120 . A second component force reacts in a direction which is 180 degrees, or substantially opposite to the yielding element force.  
      The opposing end of the compression spring  134 , is held fixed at a position along the hollow portion  132  by an end of the hollow portion  132  or a fixturing element within the hollow portion  132  such as a wall or screw or bracket or combination thereof, within the hollow portion  132 . The outside dimensions of the hollow portion  132  does not have to resemble a tube like structure, as long as the yielding member  134  in the hollow portion  132  is free to travel in a direction along the compression axis  302  and in response to the urging force of the cam follower action assembly. In the exemplary embodiment, the inside diameter of the hollow portion  132  is large enough to accept and allow the compression spring  501  to move freely therein. This cam follower assembly is completely internal to the first housing  110  leaving the outer surfaces of the first and second housing portions free of hinge components creating an esthetically pleasing look.  
      The force diagram, shown in  FIG. 7  illustrates the yielding element force and the resulting or reactive force  726  on the follower  502  as a result of both the yielding element force and the slope of the contoured surface portion  138 .  FIG. 4  shows the follower  502  in a first position  702 . The yielding element force  706  acts along the compression axis  704  urging the follower  502  toward the contoured surface portion  138 . The follower  502  contacts the contoured surface portion  138  at a first contact point  708  where the slope has a first angle  710  relative to the compression axis  704 . The application of the yielding element force  706  to the follower  502 , which is in contact with the first angle  710 , results in a first parallel force  711  parallel to the contour surface portion  138 , at the point of contact for the first position  708 . The first parallel force  711  causes the follower to traverse across the contoured surface portion in a first direction  713  of the first parallel force  711 .  
      Also shown in  FIG. 7  is the follower  502  in a second position  712 . At the second position  712 , the angle of the slope is a second angle  714  relative to the compression spring axis  704 . In this configuration, the second parallel force  716  acts on the follower  502 , and because of the second angle  714  the follower  502  traverses in a second direction  718 , substantially opposite to the first direction  713 . The magnitude of the compression spring force  706  in the first position  702 , may or may not be the same as the compression spring force  720  in the second position  712 . The direction of the traveler is dependent upon the angle of the contoured surface portion slope. A force substantially perpendicular to the to the contoured surface, a first perpendicular force  722  at the first position  702  and a second perpendicular force  724  at the second position  712 , urges the follower to maintain contact with the contoured surface portion  138 .  
      As illustrated in  FIG. 8 , one embodiment of the present invention comprises the hollow portion  132  and the second housing  120 , which pivots or rotates about the axis of rotation  128 .  FIG. 8  illustrates the interaction between the hollow portion  132 , the follower  502 , the cam surface  138  and the compression spring  501  as the second housing  120  rotates relative to the first housing  110  about the axis of rotation  128 . The cam  122  and consequently second housing  120  attached thereto, pivot from a first position  802  to a second position  804 , for example about the axis of rotation  128 . As the second housing  120  pivots about the axis of rotation  128 , the follower  502  in the illustrated embodiment, rolls or slides along a cam surface  138  of the cam  122  while being urged against the cam surface  138  by the compression spring  134 . The angle of the cam surface  138  relative to the hollow portion  132  and the compression spring axis  503  changes as the contour of the cam surface  138  changes.  
      When the angle of the cam surface  138 , at the point of contact with the follower  501 , is perpendicular to the compression spring axis  302 , such as at position  804 , a reactive force  822  of the cam surface  138  on the follower  502  is substantially opposite and parallel to the force of the compression spring  501 . As the angle of the cam surface  138  changes relative to the compression spring axis  503 , such as at position  802 , a lateral component reactive force  824  results. This lateral component reactive force  824  is parallel to the contour surface portion  138  at the point of intersection of the cam  122  surface and the follower  502 . The lateral component reactive force  824  urges the follower  502  to move along the contour surface portion  138  in the direction illustrated by the first arrow  826  of the lateral component reactive force  824 . As the follower  502  is urged in the direction of the lateral component reactive force  824 , the follower  502  exerts a follower force  828  on the hollow portion, causing second housing  120  to rotate about the axis of rotation  128 .  
      As the second housing rotates about the axis of rotation  128 , the compression spring  501  compresses or decompresses in response to the shape of the contoured surface portion  138  maintaining the force on the follower  502 . As the cam  122  rotates from the first position  802  on the contoured surface  138  to second position  804  on the contoured surface portion  138 , the distance between the contoured surface portion  138  and the axis of rotation  128  of rotation changes, resulting from a varying contour of the contoured surface portion  138 . This change in distance, or contour, causes the compression spring  134  to compress and decompress a varying amount as the follower  592  moves along the cam surface  138  and moves longitudinally within the hollow portion  132  in the direction of the compression spring axis  503 . The follower force  828 , exerted by the follower  502  on the hollow portion  132 , causes the second housing  120  to rotate about the axis  128 . The follower force  828  is applied against the side of the hollow portion  132  a distance away from the first axis  128  resulting in a torque that rotationally biases the arms of the cover  110 . The magnitude of the torque is a function of the lateral component reactive force  824 , which is a function of the angle or slope of the cam surface  142  relative to the arm and the force due to the compression spring  134 .  
      The contoured surface portion  138  dictates the amount of compression and correspondingly the force the compression spring  134  applies against the cam follower assembly at the various positions along the contoured surface portion  138 . The variation in force creates the torque profile. The contoured surface portion  138  can be shaped to achieve a desired torque profile having specific desired values at particular points along the contoured surface portion  138  and hence at different points of rotation of the second housing  120  relative to the first housing  110 . This allows the designer to vary the torque profile, via the contoured surface portion  138  that ultimately affects the force applied to the second housing  120  at the different points of rotation. For example in one exemplary embodiment, the contoured surface portion  138  is shaped similar to a triangle  508  having a rounded tip portion  810 . The rounded tip portion  810  allows the follower to traverse more easily over the cam surface  142 . At the first position  802  in  FIG. 8 , the compression spring begins to exert a force  812 . This can be a nominal force where the compression spring  134  is in a resting or at a near equilibrium position, or a force less than the maximum force achieved when the compression spring  134  is compressed all the way. However, the spring force  812  at the first position  802  cannot be the maximum spring force, in this embodiment as this would prevent the compression spring  134  from compressing further, and consequently preventing the cam  122  from rotating. In the preferred embodiment the compression spring  501  exerts a different force  814 , at the point along the contoured surface portion  138  that forms the rounded tip  810  of the contoured surface portion  138 . In-between the first position  802  and the second position  804 , the compression spring  501  compresses further and correspondingly generates an increasing amount of force until it reaches the second position  804 . It should be noted that other forces are associated with other rotational positions other than the ones specifically exemplified in  FIG. 8 . One skilled in the art will appreciate the correlation between the position of the arm and the resulting force due to the relative amount of spring compression with in the cam follower assembly.  
      The resulting torque produced by the force applied to the second housing  120  by the cam follower assembly is such that just prior to the arm reaching the second position  804  (i.e. before the follower  502  meets the rounded tip  810  of the contoured surface portion  138  the force of the compression spring  501  urges the ball bearing  502  to travel along the contoured surface portion  138  in a direction away from the rounded tip  810  of the contoured surface portion  138 , and back toward the first position  802 . As a consequence, this force biases the cam  122  in a direction that will rotate the second housing  120  toward the first position  802 . In one embodiment, a first physical stop  821  prevents the cam  122  from rotating beyond a third position  806 . Similarly a second physical stop  820 , holds the cam  122  in the fourth position (not Shown). Coincidentally, the contour of the contoured surface portion  138  at the first position  802  is such that the second housing  120  is biased towards the closed position with enough force to maintain contact or closure of the second housing  120  relative to the housing portion  120  until a force is exerted by the user. This can also be independent of or in conjunction with the first physical stop if present.  
      Similarly, once the second housing  120  is rotated past the second position  804  (i.e. the follower  502  moves beyond the rounded tip  810  of the contoured surface portion  138  at the second position  804 , the force  813  produced by the spring  501  urges the follower  502  to move away from the second position  804  toward the third position  806  which coincides with the open position of the first housing  110  relative to the second housing  120 . This is but one example of topology of the cam surface  138  that creates one possible desired motion of the cover  110 . Other exemplary contoured surfaces will be discussed below.  
      For example, referring back to  FIG. 1 , the topology of the contoured surface portion  138  urges the second housing  120  to automatically open to the 90 degree angle position  900 . A 90 degree detent  140  in the cam  122  holds the second housing  120  at the 90 degree angle until the second housing  120  is either rotated back to the closed position or to a full open position  FIG. 9  where the second housing is 180 degrees relative to the first housing  110 . When moving from a position where the follower is positioned in a detent on the cam  122 , the second housing  120  will move automatically once the follower  502  is manually moved along the cam  122  to a point that overcomes the cam  122  as discussed above in reference to  FIG. 8 .  
      The cam follower assembly assists the user in opening and positioning the device for use. The contoured surface portion of the cam  122  causes the first housing  110  to rotate relative to the second housing  120  and position as the user desires. A detent in the cam  122  may keep the device in the closed position. When the user exerts a force great enough to displace the follower  102 ,  502  from the detent in the contoured surface portion  138  of the cam  122 , the cam follower interaction automatically causes the second housing to rotate to the next desired position defined by a stop on the cam  122  or a detent in the contoured surface portion  138 . The next detent at the  90  degree position ( FIG. 1 ) may be used for a camera position or to rotate the display to a landscape orientation. Rotating the device to a 180 degree open position  FIG. 9 , may be a radiotelephone or gaming mode. The are examples and as one skilled in the art realize there are multiple functions which may be associated with the relative positions of the housing portions.  
      While the present inventions and what is considered presently to be the best modes thereof have been described in a manner that establishes possession thereof by the inventors and that enables those of ordinary skill in the art to make and use the inventions, it will be understood and appreciated that there are many equivalents to the exemplary embodiments disclosed herein and that myriad modifications and variations may be made thereto without departing from the scope and spirit of the inventions, which are to be limited not by the exemplary embodiments but by the appended claims.