Abstract:
In a hinge structure suitable for use in a foldable mobile phone, the initial unfolding action is effected by converting a pushing stroke of an operating member into a rotational movement of the hinge by using a cam/cam follower mechanism. Thereby, an unexpected reaction force resulting from the inertia force acting between the two parts that are to be unfolded relative to each other can be avoided, and a favorable unfolding action without a shock can be achieved. In particular, it may be arranged such that the hinge is normally urged in the unfolding direction while a clutch is kept engaged to retain the hinge in the fully folded state, and that the hinge is resiliently driven in the unfolding direction by pushing the operating member and thereby disengaging the clutch.

Description:
TECHNICAL FIELD  
         [0001]    The present invention relates to a hinge for joining two members so as to be angularly moveable relative to each other, and in particular to a hinge structure incorporated with a rotary actuator and a spring drive mechanism so as to fold and unfold one member relative to the other.  
         BACKGROUND OF THE INVENTION  
         [0002]    Many of the most current cellular phones are provided with a microphone unit and a speaker unit that are joined by a hinge so as to be unfolded in use and folded not in use. To increase the convenience of such a foldable telephone set, a hinge opening/closing device is disclosed in Japanese patent laid open publication 8-125725 that allows the two parts of the telephone set to be held in the closed or folded state in a stable manner and to be readily unfolded or opened using only one hand. In this hinge opening/closing device, a torsion coil spring is used for providing the rotational drive power to the hinge device.  
           [0003]    However, the torsion coil spring stores the maximum amount of rotational energy when the two parts are fully folded, and this energy is released rapidly when a pushbutton is pressed to unfold the two parts so that the resulting reaction could cause a springy motion to the telephone set. Also, the retaining force that keeps the telephone set folded is related to the force required to operate the pushbutton. Therefore, when the retaining force is increased, the force required to operate the pushbutton increases, and this impairs the handling of the telephone set.  
           [0004]    Such an inconvenience could be avoided by providing a suitable amount of frictional resistance by using a damper mechanism or weakening the spring force. However, in either case, it is difficult to achieve a suitable initial operating speed, an adequately small operating force and a smooth operation over the entire stroke of operation.  
         BRIEF SUMMARY OF THE INVENTION  
         [0005]    In view of such problems of the prior art, a primary object of the present invention is to provide a hinge structure that can be smoothly folded and unfolded by using a simple structure.  
           [0006]    A second object of the present invention is to provide a hinge structure that is favorable for use in a foldable cellular or other mobile phone.  
           [0007]    To achieve such objects, the present invention provides a hinge structure including a first part and a second part that are joined to each other so as to be angularly moveable relative to each other, comprising: an operating member axially slidably supported by the first part and having an axially projecting outer end; a first spring member urging the operating member in an outwardly projecting direction; a cam member connected to the operating member and supported by the first part in an axially slidable but rotationally fast manner; and a cam follower member fixedly attached to the second part and adapted to convert an axial movement of the operating member into a rotational movement of the second part relative to the first part.  
           [0008]    Thus, because the initial unfolding movement of the hinge structure is effected by a manual action, an unexpected reaction arising from the inertia force acting between the two parts can be avoided from being transmitted to the user, and a highly favorable unfolding action free from a shock can be achieved.  
           [0009]    By providing a second spring member that urges the second part in an unfolding direction relative to the first part, the unfolding action is improved even further. In particular, according to the present invention, the spring force of the second spring member may be set relatively weak so that the shock in unfolding the hinge can be reduced even further.  
           [0010]    According to a preferred embodiment of the present invention, the hinge structure further comprises a clutch that releases a rotationally fast engagement of the cam follower member relative to the first part via the cam member to place the cam follower member in a freely rotatable manner when the operating member is depressed beyond a prescribed stroke, and the clutch is adapted to retain the rotationally fast state of the cam follower member relative to the first part via the cam member when the first part and the second part are relatively folded one upon the other with the operating member left free. Thereby, an unfolding action relatively free from frictional resistance and a controlled folding action can be achieved so that both the folding and unfolding actions can be optimized.  
           [0011]    In particular, it may be arranged such that the hinge is normally urged in the unfolding direction while the clutch is kept engaged to retain the hinge in the fully folded state, and that the hinge is resiliently driven in the unfolding direction by pushing the operating member and thereby disengaging the clutch. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    Now the present invention is described in the following with reference to the appended drawings, in which:  
         [0013]    [0013]FIG. 1 is an external perspective view of a mobile phone to which the present invention is applied;  
         [0014]    [0014]FIG. 2 is an exploded perspective view of the hinge of the mobile phone;  
         [0015]    [0015]FIG. 3 is a sectional view of the hinge when it is fully folded;  
         [0016]    [0016]FIG. 4 is a sectional view of the hinge when it is unfolded by pushing the pushbutton; and  
         [0017]    [0017]FIG. 5 is a schematic view showing the folding and unfolding action of the mobile phone.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0018]    [0018]FIG. 1 shows the external view of a mobile phone to which the present invention is applied. This mobile phone  1  comprises a microphone unit  2  provided with a keypad, a speaker unit  3  provided with a LCD panel, and a hinge  4  that joins these two units so as to be foldable relative to each other. The basic structure of the telephone set is per se known, and is omitted from the description given hereinafter.  
         [0019]    Referring to FIGS. 2 and 3, a cylindrical housing  12  made of metal such as stainless steel and having an inner diameter of approximately 7.4 mm is provided with an inwardly directed radial flange in a left open end thereof in the drawings. This flange is formed by drawing, and performs the function of retaining inner components in place. In the left end of the housing  12  is retained a cam follower member  15  that comprises a main part  16  having a relatively small diameter and projecting out of the open left end of the housing  12  and a flange portion  17  that engages the radial flange of the housing  12 . The cam follower member  15  is generally cup-shaped, and a pair of spiral cam grooves  18  are formed on the inner circumferential surface thereof in a mutually symmetric relationship with respect to a central axial line as will be described in more detail hereinafter.  
         [0020]    An annular retaining member  25  is received in the housing  12  and abuts the right end of the cam follower member  15 . A pair of projections  26  formed on the outer circumferential surface of the retaining member  25  engage corresponding openings  13  of the housing  12  so as to retain the cam follower member  12  in a rotatable but axially fast manner, and retain the retaining member  25  in both rotationally and axially fast manner. The right end of a cylindrical cam member  19  is passed into and retained in the inner bore of the retaining member  25 , and the left end of the cam member  19  fits slightly into the right end of the cam follower member  15 . Under this condition (the unfolded state of the hinge), a pair of cams  20  formed in the cam member  19  slightly engage the cam grooves  18 . As will be described hereinafter, as the cam member  19  moves leftward, the left end of the cam member  19  moves deeper into the cam follower member  15 , and the cam follower member  15  rotates relative to the cam member  19  by virtue of the cooperation between the cams  20  and cam grooves  18 . A pair of projections  27  are formed on the inner circumferential surface of the retaining member  25 , and engage axial grooves  21  formed in an intermediate part of the cam member  19 . Each axial groove  21  has a prescribed length so that the projections  27  of the retaining member  25  engage the axial grooves  21  of the cam member  19  so as to retain the cam member  19  in a rotationally fast manner when the depth by which the left end of the cam member  19  is received in the cam follower member  15  is less than a prescribed value. When the depth by which the left end of the cam member  19  is received in the cam follower member  15  becomes greater than the prescribed value, the projections  27  are disengaged from the cam member  19  so that the cam member  19  is allowed to rotate freely.  
         [0021]    The cam grooves  18  of the cam follower member  15  and the cams  20  of the cam member  19  engage with each other via cam slopes  22  and  24  having such a spiral angle that an axial movement of the cam member  19  into the cam follower member  15  by a prescribed stroke (1.6 mm, for instance) causes a rotation of the cam follower member  15  by a corresponding angle (10 degrees, for instance). The cam grooves  18  of the cam follower member  15  include linear sections  18   a  so that the axial movement of the cam member  19  would cease to be converted into a rotational movement of the cam follower member  11  once the cams  19  have advanced in the cam grooves  18  beyond a prescribed distance (1.6 mm, for instance). The total axial stroke of the cam member  19  is approximately 2.4 mm.  
         [0022]    The right end of the cam member  19  is passed into a hollow and cylindrical clutch member  30  that comprises a main part  31  disposed on the left end thereof and provided with a relatively small diameter and a flange portion  32  provided on the right end thereof. The right end of the cam member  19  is provided with a pair of projections  24  that engage corresponding axial grooves  31   a  provided in the inner bore of the clutch member  30  so that the cam member  19  and clutch member  30  are axially slidable relative to each other but rotationally fast with each other. The axial grooves  31   a  terminate near the left end of the clutch member  30 , and define inner engagement portions  31   b  so that when the cam member  19  is pushed inward in the clutch member  30  by more than a prescribed stroke, the clutch member  30  starts to be forced leftward by the cam member  19  by virtue of the engagement between the inner engagement portions  31   b  and projections  24 .  
         [0023]    The right end of the clutch member  30  is engaged by a lid member  35  that is in turn engaged by the axial end of the housing  12  via an annular shoulder formed along the outer periphery of the lid member  35 . By crimping tabs  14  formed at the axial end of the housing  12  onto corresponding recesses  38  formed around the outer periphery of the lid member  35 , the lid member  35  is integrally secured to the housing  12 .  
         [0024]    A torsion coil spring  29  is interposed between the retaining member  25  and the flange portion  32  of the clutch member  30  to rotationally urge the clutch member  30  and axially urge the clutch member  30  toward the lid member  35 . The axial ends of the coil wire of the torsion coil spring  29  extend axially and fit into axial holes  28  and  34  provided in the retaining member  25  and the flange portion  32  of the clutch member  30 , respectively. A pair of axially projecting engagement projections  36  are provided in the inner end of the lid member  35  facing the housing at diametrically opposing positions, and normally (when the hinge is fully folded or unfolded) fit into corresponding recesses  33  of the flange portion  32  of the clutch member  30  to prevent the rotation of the clutch member  30 .  
         [0025]    A cylindrical connecting member  39  is passed into the central holes of the lid member  35  and clutch member  30 , and the free end or left end of the connecting member  39  snap fits into the central hole of the cam member  19  formed on the right end thereof so that the cam member  19  and connecting member  39  are axially joined to each other for integral axial movement.  
         [0026]    A compression coil spring  41  is resiliently interposed between an annular shoulder surface formed on the inner periphery of the outer end surface of the lid member  35  and pushbutton  42 . A metallic rod  44  is passed into the central bore of the connecting member  39  to transmit the force that pushes the pushbutton  42  inward to the cam member  19  in a reliable manner and with an adequate mechanical strength.  
         [0027]    The mode of operation of the hinge incorporated with a rotary actuator according to the present invention is described in the following additionally with reference to FIG. 4.  
         [0028]    When the speaker unit  3  is folded onto the microphone unit  2 , the clutch member  30  is pushed rightward by the axial force of the torsion coil spring  29 . Under this condition, the projections  36  of the lid member  35  are in engagement with the recesses  32  of the clutch member  30  (the engaged state of the clutch) so that the clutch member  30  is kept rotationally immobile with respect to the housing  12  even though the torsion coil spring  29  applies a rotational force to the clutch member  30 . A clutch is thus formed by the projections  36  of the lid member  35 , recesses  32  of the clutch member  30  and torsion coil spring  29 .  
         [0029]    The cam member  19  which is connected to the clutch member  30  so as to be rotationally fast but axially slidable within a prescribed range relative to the clutch member  30  is displaced fully rightward under the axial force of the compression coil spring  41  acting on the pushbutton  42 . Furthermore, in this state, the cam member  19  is rotationally fast with the retaining member  25  by virtue of the engagement between the axial grooves  21  and projections  27 . Therefore, the cam follower member  15  which is in engagement with the cams  20  on the left end of the cam member  19  is rotationally immobile. Thereby, the speaker unit  3  and microphone unit  2  are kept folded one upon the other.  
         [0030]    When the pushbutton  42  is pushed leftward by a small stroke (1.6 mm) under this condition, the connecting member  39  integrally joined to the pushbutton  42  moves leftward, and the cam member  19  connected to the inner end of the connecting member  39  moves leftward. Because the cam member  19  is kept rotationally fast relative to the retaining member  25  by virtue of the engagement between the axial grooves  21  and projections  27 , the cams  20  on the left end of the cam member  19  move axially leftward without rotating. Therefore, by the action of the cam slopes  22  and  23  defined by the cam grooves  18  and cams  20 , the cam follower member  15  rotates. This rotation causes the speaker unit  3  that is integrally connected to the cam follower member  15  to open or unfold by an angle of approximately 10 degrees (angle Pr in FIG. 5).  
         [0031]    As the pushbutton  42  is pushed further, the cams  20  of the cam member  19  eventually reach the linear sections  18   a  of the cam grooves  18  of the cam follower member  15 , and the cam follower member  15  ceases to rotate any further. On account of the engagement between the inner engagement portions  31   b  and projections  24 , the continued axially inward movement of the cam member  19  causes the clutch member  30  to move leftward. When the pushbutton  42  has been fully depressed, the projections  36  of the flange  28  of the clutch member  30  disengage from the recesses  33  of the lid member  35  (the disengaged state of the clutch), and the rotationally fast engagement between the retaining member  25  and cam member  19  owing to the engagement between the projections  27  of the retaining member  25  and the axial grooves  21  of the cam member is released at the same time.  
         [0032]    As a result, the rotational biasing force of the torsion coil spring  29  normally acting upon the clutch member  30  is released. Because the cam grooves  18  of the cam follower member  15  and cams  20  of the cam member  19  are in a rotationally fast engagement with each other, and cam member  19  and the clutch member  30  are also in a rotationally fast engagement with each other, the clutch member  30 , cam member  19  and cam follower member  15  all rotate in a single body. In other words, the microphone unit  2  and speaker unit  3  automatically unfold relative to each other. The maximum unfolding angle (indicated by MAX in FIG. 5) is determined by the mechanically defined unfolding angle of the hinge  4 .  
         [0033]    Under this condition, because the projections  36  ride over the end surface of the flange  32 , the clutch member  30  is prevented from moving rightward in spite of the axial biasing force of the torsion coil spring  29 . Similarly, because a rotation preventing means  24  provided between the cam member  19  and the retaining member  25  is at a mismatched phase relationship, the cam member  19  is prevented from moving rightward in spite of the axial biasing force of the compression coil spring  36 . As a result, the unfolded state of the hinge is maintained as long as no external force is applied thereto. Under this condition, the pushbutton  42  remains in the fully depressed state.  
         [0034]    When the microphone unit  2  and speaker unit  3  are manually folded one over the other against the rotational biasing force of the torsion coil spring  29 , the cam follower member  15  and cam member  19  initially rotate together, but once the phase relationship between the projections  27  of the retaining member  25  and axial grooves  21  of the cam member  19  matches up, the axial force of the compression coil spring  36  forces the projections  27  and axial grooves  21  into alignment, and the cam member  19  is forced rightward. At this time, because the cams  20  are engaged by the linear sections  18   a  of the cam grooves  18 , no rotational force is applied to the cam member  19 .  
         [0035]    Because the rightward axial biasing force of the torsion coil spring  29  normally acts upon the clutch member  30 , once the projections  36  of the lid member  35  and recesses  33  of the flange  32  come into alignment with each other, and the clutch becomes engaged. As a result, the rotational biasing force of the coil spring  29  is kept in check. The axial biasing force of the compression coil spring  36  forces only the cam member  19  further rightward, and the cam follower member  15  rotates under the action of the cam slopes  22  and  23  until the microphone unit  2  and speaker unit  3  are completely folded one over the other. Under this condition, the axial biasing force of the compression coil spring  36  keeps the two units in the fully folded state, and the pushbutton  42  is brought back to the fully projecting state.  
         [0036]    According to the embodiment described above, a high level of convenience can be achieved for a device that can be folded because the two parts that are mutually folded one over the other are partly unfolded by slightly depressing the pushbutton, and are fully unfolded automatically under the biasing force of a torsion spring by further depressing the pushbutton. The two parts can be folded in the same manner as the conventional device. In particular, the unfolding action takes place in two stages, first by the manual force applied to the pushbutton and transmitted to the cam, and second by the force of the spring. Therefore, the shock when initially unfolding the hinge can be minimized as compared with the convention hinge that relies on the spring force for the initial unfolding action, and the necessary spring force can be reduced because the spring force is not relied upon for the initial unfolding torque. Furthermore, because the hinge is incorporated with a rotary actuator as an independent unit, the same actuator can be used for a number of different devices, and a significant advantage can be gained in simplifying the manufacturing process and components management.  
         [0037]    Industrial Applicability  
         [0038]    The foregoing description was directed to an application to a mobile telephone set, but the present invention can also be applied to a hinge device for connecting a keyboard unit and a display unit in a laptop computer, and a hinge device for connecting a lid to a main body of a container. The folded state was the normal state in the foregoing embodiment, but the unfolded state may also be the normal state and the hinge may be adapted to automatically fold by suitably selecting the position for engaging the clutch and direction of the torsional biasing force. Additionally, by combining a per se known rotary damper using viscous fluid, an even more smooth action can be achieved.