Abstract:
An electronic device includes a movable unit having a top surface; a main body in which the movable unit is stowed and from which the movable unit is deployed by sliding the movable unit, the main body having a first surface opposed to the top surface when the movable unit is in a stowed state and in a deployed state; and a changing mechanism which changes a distance between the top surface and the first surface during a sliding operation of the movable unit so that the top surface and the first surface during the sliding operation are separated from each other by a distance greater than a distance between the top surface and the first surface in the stowed state and the deployed state of the movable unit.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     The present invention contains subject matter related to Japanese Patent Application JP 2004-306274 filed in the Japanese Patent Office on Oct. 21, 2004, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an electronic device that includes a main body and a movable unit, and that allows the movable unit to be stowed in the main body and deployed from the main body. 
     2. Description of the Related Art 
     In related art, electronic devices, such as mobile computers, including two separate elements, namely, a main body and a movable unit, are known. In such electronic devices, a shifting mechanism of the movable unit is achieved by providing grooves on two opposite inner side surfaces of the main body and protrusions extending outward from the top surface of the movable unit. The protrusions are engaged to the grooves so that the grooves guide the protrusions horizontally in a linear fashion. On the other hand, Japanese Unexamined Patent Application Publication No. 2003-169120 (Paragraph [0009], FIG. 1 etc.), for example, discloses a mobile phone which includes a main body having a key-operating portion, and a sliding unit provided with a liquid-crystal display portion. The main body and the sliding unit are provided with a sliding mechanism via which the sliding unit can be slid linearly when, for example, the liquid-crystal display portion is to be browsed. According to this structure, the key-operating portion and the liquid-crystal display portion can have large dimensions without increasing the dimension of the main body. 
     SUMMARY OF THE INVENTION 
     However, according to these structures mentioned above, in view of the fact that the device receives an operating load in a direction perpendicular to the moving direction of the movable unit or the sliding unit, a sufficient clearance is necessary in order to reduce the friction or interference between the main body and the movable unit or the sliding unit. For this reason, the structures mentioned above are problematic in that the overall thickness of the device is large. Moreover, constantly maintaining the clearance could lead to intrusion of, for example, foreign particles into the device through the clearance and thus induce malfunction of the device. 
     Accordingly, it is desirable to provide a dust-proof, high-durability electronic device with a reduced overall thickness. 
     According to an embodiment of the present invention, there is provided an electronic device which includes a movable unit having a top surface; a main body in which the movable unit is stowed and from which the movable unit is deployed by sliding the movable unit, the main body having a first surface opposed to the top surface when the movable unit is in a stowed state and in a deployed state; and a changing mechanism which changes a distance between the top surface and the first surface during a sliding operation of the movable unit so that the top surface and the first surface during the sliding operation are separated from each other by a distance greater than a distance between the top surface and the first surface in the stowed state and the deployed state of the movable unit. 
     The electronic device may be, for example, a PC (personal computer), a PDA (personal digital assistant), an electronic dictionary device, a mobile phone, or other electrical appliances. The movable unit may be, for example, a keyboard, an operating portion such as a touchscreen, or a display portion. The distance between the top surface and the first surface in the stowed state and the deployed state of the movable unit may be about 0 mm to 1 mm, and moreover, is preferably 0 mm. The distance between the top surface and the first surface during the sliding operation of the movable unit may be about 1.5 mm to 3 mm. However, the two distances are not limited to these values. 
     Accordingly, since the distance between the movable unit and the main body is increased during the sliding operation of the movable unit, the clearance between the movable unit and the main body can be reduced to the smallest possible dimension when the movable unit is in the stowed state and the deployed state. Consequently, this achieves reduced overall thickness of the electronic device as well as preventing malfunction of the electronic device caused by intrusion of, for example, foreign particles and dust. 
     Furthermore, in the electronic device, the top surface and the first surface may be in contact with each other when the movable unit is in the stowed state and in the deployed state. Accordingly, the distance between the movable unit and the main body is zero when the movable unit is in the stowed state and in the deployed state, whereby foreign particles and dust are prevented from entering the electronic device. Moreover, this implies that the final stopping positions of a stowing motion and a deploying motion (i.e. the sliding motion) of the movable unit are determined by surface contact between the top surface and the first surface, and that the movable unit is supported in a planar fashion. Consequently, in comparison with an example in which a movable unit is supported by guiding grooves after being slid via protrusions and the guiding grooves, the electronic device according to the embodiment of the present invention is capable of withstanding excessive operating load. 
     Furthermore, in the electronic device, the movable unit may include a side surface. The main body may include a second surface facing the side surface. The changing mechanism may include a first protrusion provided on the side surface of the movable unit, and a first guiding groove provided in the second surface and engaged with the first protrusion so as to guide the first protrusion, the first guiding groove being sloped in an up-down direction in at least first and second end portions thereof. 
     The first guiding groove may have, for example, its first end portion sloped in the downward direction and its second end portion sloped in the upward direction, and may have its intermediate portion between the first and second end portions extending in the horizontal direction. Alternatively, the first guiding groove may have any shape that allows the top surface and the first surface to be separated by a first distance when the movable unit is in the stowed state and in the deployed state, allows the distance between the top surface and the first surface to be increased to a second distance during the sliding motion, and allows the distance between the top surface and the first surface to return to the first distance at the end of the sliding motion (i.e. when the movable unit is in the stowed state and in the deployed state). Furthermore, the first protrusion is preferably, for example, cylindrical, but may have other alternative shapes. As described above, the first guiding groove may be sloped in at least its first and second end portions, and moreover, the first guiding groove may guide the first protrusion of the movable unit. Therefore, the movable unit and the main body form a space therebetween only during the sliding motion of the movable unit. This contributes to the reduced overall thickness of the electronic device when the movable unit is in the stowed state and in the deployed state. 
     Furthermore, in the electronic device, the first guiding groove may be curved from the first end portion to the second end portion. Consequently, even in a case where the top surface of the movable unit and the first surface of the main body are curved, the first guiding groove can correspond to these curved surfaces, thereby contributing to the reduced overall thickness of the electronic device. 
     Furthermore, in the electronic device, the changing mechanism may further include a second protrusion provided on the second surface, and a second guiding groove provided in the side surface and engaged with the second protrusion so as to guide the second protrusion, the second guiding groove being sloped in the up-down direction in at least opposite end portions thereof. Consequently, in conjunction with the first protrusion and the first guiding groove, the second protrusion and the second guiding groove allow the movable unit to slide so that the movable unit can be switched between the stowed state and the deployed state. Accordingly, the movable unit is given better stability and load-withstanding properties. 
     Furthermore, in the electronic device, the main body may further include a first electric circuit. The movable unit may further include a second electric circuit exchanging an electrical signal with the first electric circuit. The electronic device may further include a conducting mechanism which slides in synchronization with the movable unit and electrically connects the first electric circuit and the second electric circuit on a constant basis in order to ground the first and second electric circuits. Accordingly, regardless of the positioning of the movable unit during the sliding operation, the stowed state, or the deployed state, the conducting mechanism can electrically connect the first electric circuit and the second electric circuit on a constant basis in order to ground the first and second electric circuits. 
     Furthermore, in the electronic device, the conducting mechanism may include a conducting member and an electrically conductive resilient member disposed between the conducting member and one of the first electric circuit and the second electric circuit, the resilient member pulling the main body and the movable unit towards each other. Since the resilient member constantly generates a pulling force that pulls the main body and the movable unit towards each other, the first protrusion is introduced into the corresponding sloped end portion of the first guiding groove when the movable unit reaches the stroke end position corresponding to the stowed state or the deployed state. Accordingly, the movable unit can be stably supported in position without requiring a designated locking mechanism at each stroke end position. Moreover, when the movable unit reaches the stroke end position corresponding to the stowed state or the deployed state, the first protrusion enters the corresponding sloped end portion such that a sense of retraction is applied to a user of the electronic device. This gives the user a good sense of haptic feedback. 
     According to the embodiment of the present invention, a dust-proof, high-durability electronic device with a reduced overall thickness is provided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a PDA  1  according to an embodiment of the present invention; 
         FIG. 2  is a perspective view of the PDA  1  in a state where a movable unit  3  is deployed; 
         FIG. 3  is a perspective view illustrating a state where the PDA  1  is disassembled into a main body  2  and the movable unit  3 ; 
         FIGS. 4A and 4B  respectively illustrate a stowed state and a deployed state of the movable unit  3  as viewed from the right side of the PDA  1 ; 
         FIG. 5  is an exploded perspective view illustrating components installed in a main-body rear cabinet  14 ; 
         FIG. 6  is an exploded perspective view of a contact plate  16  and the main-body rear cabinet  14 ; 
         FIG. 7  is a detail view of a slide block assembly  19 ; 
         FIG. 8  is an exploded perspective view illustrating components installed in a movable-unit front cabinet  15 ; 
         FIG. 9  is an exploded perspective view illustrating components disposed below a secondary substrate  26  shown in  FIG. 8 ; 
         FIG. 10  is a cross-sectional view of an area in which the slide block assembly  19  is disposed; 
         FIG. 11  illustrates a conduction path of an electrical conducting mechanism for grounding; 
         FIG. 12  is a perspective view of the main-body rear cabinet  14  and the movable-unit front cabinet  15  in a state where the movable unit  3  is deployed, as viewed from the reverse side of the movable-unit front cabinet  15 ; 
         FIG. 13  is a perspective view illustrating only the main-body rear cabinet  14 , as viewed from its reverse side; 
         FIG. 14  illustrates a conduction path of a secondary conduction mechanism corresponding to stroke end positions of the movable unit  3 ; 
         FIG. 15  is a cross-sectional view of the PDA  1  in a state where the movable unit  3  is stowed; 
         FIG. 16  is a cross-sectional view of the PDA  1  in a state where the movable unit  3  is deployed; 
         FIGS. 17A to 17D  illustrate a sliding process of the movable unit  3  from the stowed state to the deployed state; 
         FIGS. 18A and 18B  illustrate the transition of a pulling spring  22  during a sliding motion of the movable unit  3 ; 
         FIG. 19  is a top view of the main-body rear cabinet  14  and the movable-unit front cabinet  15  in the deployed state of the movable unit  3 ; 
         FIG. 20  is a bottom view of the main-body rear cabinet  14  and the movable-unit front cabinet  15  in the deployed state of the movable unit  3 ; 
         FIG. 21  is a perspective view illustrating the positional relationship between a magnet  30  and a Hall element  31 ; 
         FIGS. 22A and 22B  illustrate the PDA  1  in a state where the displaying direction of a display portion  4  is switched from one direction to the other; and 
         FIGS. 23A to 23C  are perspective views of the PDA  1  and a stylus pen  32  when the movable unit  3  is in the deployed state and in the stowed state. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An embodiment according to the present invention will now be described with reference to the drawings. An electronic device according to the embodiment is directed to a PDA (personal digital assistant). 
       FIG. 1  is a perspective view of a PDA  1  according to the embodiment. The PDA  1  includes a main body  2  and a movable unit  3 . By sliding the movable unit  3 , the movable unit  3  can be stowed in the main body  2  or be deployed from the main body  2 .  FIG. 1  illustrates a state where the movable unit  3  is stowed inside the main body  2 . Although not shown in  FIG. 1 , the main body  2  and the movable unit  3  are formed by joining a front cabinet to a rear cabinet. 
     A top surface of the main body  2  is provided with a display portion  4 , such as an LCD (liquid crystal display). The display portion  4  is provided with a pressure-sensitive panel through which various operations of the PDA  1  can be performed with a finger or by using a stylus pen. Therefore, the display portion  4  not only functions as a viewing portion, but also as an input portion that allows for an easy operation with a small number of inputs. 
       FIG. 2  is a perspective view of the PDA  1  in a state where the movable unit  3  is deployed from the main body  2 . As shown in  FIG. 2 , the top surface of the movable unit  3  in the deployed state is provided with a keyboard  5  suitable for inputting characters for writing, for example, long sentences, such that the movable unit  3  in the deployed state functions as, for example, an operating portion. Since the PDA  1  is divided into two parts, that is, the main body  2  and the movable unit  3 , the PDA  1  is advantageous in that it can be made compact when it is being carried. Moreover, the sliding function of the movable unit  3  is advantageous in that the movable unit  3  can be switched between the stowed state and the deployed state single-handedly within a small amount of time. 
       FIG. 3  is a perspective view illustrating a state where the PDA  1  is disassembled into the main body  2  and the movable unit  3 . As shown in  FIG. 3 , the main body  2  includes a pair of side plates  6 , namely, a right side plate  6   a  and a left side plate  6   b  facing the right side plate  6   a . On the other hand, the movable unit  3  includes a top surface  12  and side surfaces  9 , namely, a right side surface  9   a  and a left side surface facing the right side surface  9   a . The left side surface is not shown. 
     The right side surface  9   a  and the left side surface of the movable unit  3  are respectively provided with a protrusion  11   a  and a protrusion  11   b . On the other hand, inner surfaces of the right side plate  6   a  and the left side plate  6   b  of the main body  2  that respectively face the right side surface  9   a  and the left side surface of the movable unit  3  are provided with a guiding groove  8   a  and a guiding groove  8   b  (not shown). The guiding groove  8   a  and the guiding groove  8   b  respectively guide the protrusion  11   a  and the protrusion  11   b  during a sliding motion of the movable unit  3 . 
     Moreover, the inner surfaces of the right side plate  6   a  and the left side plate  6   b  of the main body  2  are also provided with a protrusion  7   a  and a protrusion  7   b , respectively. On the other hand, the right side surface  9   a  and the left side surface of the movable unit  3  are respectively provided with guiding grooves  10   a  and  10   b  for guiding the protrusions  7   a  and  7   b  during the sliding motion of the movable unit  3 . 
     The protrusions  7   a ,  7   b ,  11   a , and  11   b  are, for example, cylindrical. On the other hand, each of the guiding grooves  8   a ,  8   b ,  10   a , and  10   b  has its intermediate portion extending in the horizontal direction and its opposite end portions, for example, sloped in the up-down direction so as to move the main body  2  and the movable unit  3  away from each other. The guiding grooves  8   a  and  10   a  are symmetrical to each other in the vertical direction, and similarly, the guiding grooves  8   b  and  10   b  are symmetrical to each other in the vertical direction. 
       FIGS. 4A and 4B  illustrate the stowed state and the deployed state of the movable unit  3  as viewed from the right side. Specifically,  FIG. 4A  illustrates the stowed state of the movable unit  3 , whereas  FIG. 4B  illustrates the deployed state of the movable unit  3 . 
     As shown in  FIGS. 4A and 4B , when the guiding grooves  8   a  and  10   a  overlap each other, one end portion of the guiding groove  8   a  and one end portion of the guiding groove  10   a  are separated from each other by a distance a. The distance a is set such that the top surface  12  of the movable unit  3  and a bottom surface  13  of the main body  2  facing the top surface  12  come into contact with each other before the protrusions  11   a  and  7   a  abut on the edges of the corresponding end portions of the guiding grooves  8   a  and  10   a  when the movable unit  3  is being stowed or deployed. Thus, a small clearance is formed between each protrusion  7   a ,  11   a  and the edge of the corresponding end portion of the guiding groove  10   a ,  8   a . Accordingly, instead of being supported by the protrusions and the edges of the opposite end portions of the guiding grooves, the main body  2  and the movable unit  3  are supported in a surface contact fashion via the top surface  12  of the movable unit  3  and the bottom surface  13  of the main body  2 . Thus, the main body  2  and the movable unit  3  are capable of withstanding excessive operating load. 
     Furthermore, a height b of the sloped opposite end portions of the guiding grooves  8   a  and  10   a  is set in view that when the protrusions move along the intermediate horizontal portions of the guiding grooves during the sliding motion of the movable unit  3 , the main body  2  and the movable unit  3  do not interfere with each other even if an operating load acts on the main body  2  and the movable unit  3  in a direction perpendicular to the sliding direction. Specifically, the height b is set in a range between, for example, 1.5 mm to 3 mm so that a space is formed between the main body  2  and the movable unit  3  during the sliding motion of the movable unit  3 . 
     The internal mechanisms of the main body  2  and the movable unit  3  will now be described. 
       FIG. 5  is an exploded perspective view illustrating components installed in a main-body rear cabinet  14 . As shown in  FIG. 5 , a metallic contact plate  16  is fixed to the main-body rear cabinet  14  by welding, and a main substrate  25  is disposed over the contact plate  16 . The contact plate  16  includes cantilever segments  28  which are resiliently in contact with ground sections of the main substrate  25  on a constant basis. Thus, electrical conduction between the main body  2  and the movable unit  3  is achieved when the movable unit  3  in a stationary state and when the movable unit  3  is at each of stroke end positions of the sliding motion. Such electrical conduction allows the static electricity entering the PDA  1  from an external source to be conducted to the ground sections of the main substrate  25 , whereby a grounded state is achieved. 
       FIG. 6  is an exploded perspective view of the contact plate  16  and the main-body rear cabinet  14 . As shown in  FIG. 6 , a metallic thrust plate  17  is disposed below the contact plate  16  and is attached to the main-body rear cabinet  14  by, for example, welding. A sliding sheet  18  formed of a self-lubricating material, such as polysilicon, is fixed on the thrust plate  17  by, for example, bonding. The thrust plate  17  is provided with a slit  17   a . Moreover, a slide block assembly  19  is disposed on the thrust plate  17  in a manner such that the slide block assembly  19  is movable horizontally on the sliding sheet  18  while being guided by the slit  17   a  during the sliding motion of the movable unit  3 . The reason that the sliding sheet  18  is formed of a self-lubricating material is to prevent the sliding sheet  18  from being baked in response to the sliding friction of the slide block assembly  19 . 
       FIG. 7  is a detail view of the slide block assembly  19 . As shown in  FIG. 7 , the slide block assembly  19  includes a metallic slide plate  19   a , a metallic contact spring  19   b  disposed on the slide plate  19   a , and two metallic shafts  19   c  and  19   d  fastened to the slide plate  19   a  by, for example, caulking. The reason these components are metallic is to obtain the electrically conductive state for grounding during the sliding motion of the movable unit  3 . Specifically, the contact spring  19   b  is composed of phosphor bronze and has a cantilever structure so that the contact spring  19   b  is resiliently in contact with the contact plate  16  on a constant basis. 
       FIG. 8  is an exploded perspective view illustrating components installed in a movable-unit front cabinet  15  as viewed from a reverse side of the PDA  1 .  FIG. 9  is an exploded perspective view illustrating components disposed below a secondary substrate  26  shown in  FIG. 8 .  FIG. 10  is a cross-sectional view of an area in which the slide block assembly  19  is disposed. 
     The movable-unit front cabinet  15  is provided with the secondary substrate  26 . The secondary substrate  26  is disposed over an H-shaped metallic pulling-spring-holding plate  20 , which is attached to the movable-unit front cabinet  15  by, for example, welding. Furthermore, referring to  FIGS. 8 and 9 , a plate-like contact spring  21 , which is formed of a metallic material such as phosphor bronze and is in contact with the pulling-spring-holding plate  20 , is attached to the movable-unit front cabinet  15  by, for example, caulking. The secondary substrate  26  and the contact spring  21  are pressure-bonded to each other with secondary-substrate fastening screws  29 . Accordingly, this achieves the electrical conduction between the movable unit  3  and the main body  2  for grounding. 
     Referring to  FIGS. 9 and 10 , the pulling-spring-holding plate  20  is provided with two shaft holes  20   a  so that the movable unit  3  is capable of moving vertically along the two shafts  19   c  and  19   d  of the slide block assembly  19  in directions indicated by a double-headed arrow A. Furthermore, referring to  FIGS. 8 ,  9 , and  10 , a spring-connecting plate  23  is fastened to the shaft  19   c  and the shaft  19   d  of the slide block assembly  19  by caulking and also by using a spring fastening screw  24 . Consequently, the main-body rear cabinet  14  and the movable-unit front cabinet  15  are joined to each other via the spring-connecting plate  23  and the shafts  19   c  and  19   d  extending through the slit  17   a  of the thrust plate  17  in the main-body rear cabinet  14  and through the two shaft holes  20   a  in the pulling-spring-holding plate  20 . 
     A metallic pulling spring  22  is sandwiched between the pulling-spring-holding plate  20  and the spring-connecting plate  23  fastened to the two shafts  19   c  and  19   d . In the stationary state shown in  FIGS. 8 ,  9 , and  10 , the pulling spring  22  generates a compressive force that attracts the pulling-spring-holding plate  20  and the spring-connecting plate  23  towards each other. As described above, the slide plate  19   a  is disposed above the thrust plate  17  attached to the main-body rear cabinet  14 , and the pulling-spring-holding plate  20  is attached to the movable-unit front cabinet  15 . Accordingly, referring to  FIGS. 9 and 10 , due to the pulling spring  22 , a force that reduces the distance between the slide plate  19   a  and the pulling-spring-holding plate  20  is generated. In other words, the main body  2  and the movable unit  3  are constantly pulled towards each other due to the pulling spring  22 . 
     Since the slide plate  19   a  of the slide block assembly  19  slides on the sliding sheet  18  bonded on the thrust plate  17  during the sliding motion of the movable unit  3 , the main body  2  and the movable unit  3  are constantly pulled towards each other regardless of the movement of the movable unit  3  or the position of the movable unit  3 . As described above, the thrust plate  17  and the pulling-spring-holding plate  20  are both made of metal, and therefore, even if these plates  17  and  20  are given reduced thicknesses, they still have higher rigidity in comparison with plates composed of resin. For this reason, even though these plates  17  and  20  constantly receive a pulling force of the pulling spring  22 , these metallic plates  17  and  20  are prevented from creeping in response to the force of the pulling spring  22  (see  FIGS. 9 and 10 ). 
       FIG. 11  illustrates a conduction path of an electrical conducting mechanism for grounding, which is defined by the metallic components included in the main body  2  and the movable unit  3  described above. In the metallic components between the main substrate  25  and the secondary substrate  26  shown in  FIG. 11 , the metallic components closer to the main body  2  are in contact with the ground sections of the main substrate  25 , and the metallic components closer to the movable unit  3  are in contact with the ground sections of the secondary substrate  26 . Consequently, static electricity entering the PDA  1  from an external source is conducted to the ground sections of the main substrate  25  via the metallic components so that a grounded state is achieved. This prevents, for example, electronic components disposed on each substrate  25  or  26  from being damaged due to static electricity. 
     According to this embodiment, in order to ensure the electrical conduction for grounding, a secondary conduction path is provided for when the movable unit  3  is at each of the stroke end positions of the sliding motion. A secondary conduction mechanism corresponding to the stroke end positions of the movable unit  3  will be described below. 
       FIG. 12  is a perspective view of the main-body rear cabinet  14  and the movable-unit front cabinet  15  in a state where the movable unit  3  is deployed, as viewed from the reverse side of the movable-unit front cabinet  15 .  FIG. 13  is a perspective view illustrating only the main-body rear cabinet  14 , as viewed from its reverse side. As shown in  FIGS. 12 and 13 , segments of the contact plate  16  provided in the ground sections of the main-body rear cabinet  14  are exposed at four locations on the bottom surface of the main-body rear cabinet  14 . On the other hand, the contact spring  21  provided in the movable-unit front cabinet  15  is provided with two projections  21   a , which are exposed at two locations on the upper surface of the movable-unit front cabinet  15 . 
       FIG. 14  illustrates the conduction path of the secondary conduction mechanism corresponding to the stroke end positions of the movable unit  3 . As shown in  FIG. 14 , at each of the stroke end positions of the sliding motion of the movable unit  3  (i.e. a stowing motion or a deploying motion), the contact plate  16  and the projections  21   a  of the contact spring  21  are directly in contact with each other at two locations, whereby the main substrate  25  of the main body  2  and the secondary substrate  26  of the movable unit  3  are electrically connected to each other. In comparison with the conduction path shown in  FIG. 11 , the secondary conduction path has a less number of intermediate components between the main substrate  25  and the secondary substrate  26 , and therefore, the secondary conduction path achieves electrical conduction with higher reliability. This means that a grounded state can be achieved with higher reliability. 
     In this embodiment, the main substrate  25  of the main body  2  and the secondary substrate  26  of the movable unit  3  are connected to each other via a flexible substrate so that electric signals are exchanged between the two substrates  25  and  26 . Thus, an electrical operation of the PDA  1  can be performed, which may include, for example, commanding the display portion  4  to display data input to the keyboard  5  of the movable unit  3  when the movable unit  3  is in the deployed state.  FIG. 15  is a cross-sectional view of the PDA  1  in a state where the movable unit  3  is stowed.  FIG. 16  is a cross-sectional view of the PDA  1  in a state where the movable unit  3  is deployed. In  FIGS. 15 and 16 , components that are not relevant to the electrical conduction are not shown. 
     In the stowed state of the movable unit  3  shown in  FIG. 15 , the main substrate  25  and the secondary substrate  26  are connected to each other via an intermediate flexible substrate  27 , whereby the electrical conduction between the two substrates  25  and  26  is maintained. On the other hand, in the deployed state of the movable unit  3  shown in  FIG. 16 , the flexible substrate  27  is bent in response to the movement of the movable unit  3 , whereby the electrical conduction between the main substrate  25  and the secondary substrate  26  is constantly maintained. 
     An operation of the PDA  1  having the structure described above will now be described.  FIGS. 17A to 17D  illustrate the sliding process of the movable unit  3  from the stowed state to the deployed state. Each of  FIGS. 17A to 17D  includes a front view of the PDA  1  on the left side as viewed in the sliding direction of the movable unit  3 , and a right side view of the PDA  1  on the right side. 
     Referring to  FIGS. 17A to 17D , when an operating force is applied to the movable unit  3  in the stowed state in a direction indicated by an arrow, the protrusions  11   a  and  11   b  of the movable unit  3  slide along the guiding grooves  8   a  and  8   b  of the main body  2 , and the protrusions  7   a  and  7   b  of the main body  2  slide along the guiding grooves  10   a  and  10   b  of the movable unit  3 . Since the opposite end portions of each guiding groove are sloped, the movable unit  3  moves downward at an angle away from the main body  2 , as shown in  FIG. 17B . Subsequently, referring to  FIG. 17C , the movable unit  3  moves horizontally while maintaining the distance corresponding to the height b that is perpendicular to the sliding direction. Finally, referring to  FIG. 17D , the movable unit  3  moves at an angle towards the main body  2  so that the top surface  12  of the movable unit  3  becomes surface contact with the bottom surface  13  of the main body  2  facing the top surface  12 . As a result, the movable unit  3  is stopped. As described above, since the final stopping positions of the movable unit  3  are determined by surface contact, the main body  2  and the movable unit  3  are capable of withstanding excessive operating load. 
     Accordingly, the top surface  12  of the movable unit  3  is in contact with the bottom surface  13  of the main body  2  in both the stowed state and the deployed state. On the other hand, during the sliding motion of the movable unit  3 , the movable unit  3  moves away from the main body  2  by the distance corresponding to the height b due to the shape of the guiding grooves  8   a ,  8   b ,  10   a , and  10   b . For this reason, the main body  2  and the movable unit  3  does not require a fixed clearance therebetween on a constant basis, thereby achieving a reduced overall thickness of the PDA  1  in the stationary state of the movable unit  3 . Moreover, omitting such a fixed clearance may reduce the chances of, for example, intrusion of foreign particles and dust in the PDA  1 , whereby the PDA  1  can be prevented from malfunctioning. 
     Furthermore, as described above, during the sliding motion of the movable unit  3 , the slide plate  19   a  fastened to the movable unit  3  via the pulling spring  22  and the shafts  19   c  and  19   d  slides on the sliding sheet  18  bonded to the thrust plate  17  of the main body  2 . On the other hand, the slide plate  19   a  is stopped at one of the ends of the slit  17   a  when the movable unit  3  is in the stowed state or the deployed state. 
       FIGS. 18A and 18B  illustrate the transition of the pulling spring  22  during the sliding motion of the movable unit  3 . Specifically,  FIG. 18A  illustrates the pulling spring  22  in the stationary state of the movable unit  3 , i.e. the stowed state or the deployed state, and  FIG. 18B  illustrates the pulling spring  22  during the sliding motion of the movable unit  3 . Referring to  FIG. 18A , in the stationary state of the movable unit  3 , such as the state shown in  FIG. 17A  or  17 D, the pulling spring  22  generates a force that attracts the pulling-spring-holding plate  20  and the spring-connecting plate  23  towards each other, such that the main body  2  and the movable unit  3  are pulled towards each other. On the other hand, referring to  FIG. 18B , during the sliding motion of the movable unit  3  as shown in  FIGS. 17B and 17C , the movable unit  3  is guided by the guiding groove  8   a  so as to be shifted downward at an angle, and then moves horizontally while maintaining the distance corresponding to the height b. During this horizontal movement of the movable unit  3 , the pulling-spring-holding plate  20  fastened to the movable-unit front cabinet  15  of the movable unit  3  is shifted downward, whereby the pulling spring  22  becomes compressed. In this compressed state, the pulling spring  22  still generates the force attracting the pulling-spring-holding plate  20  and the spring-connecting plate  23  towards each other, such that the main body  2  and the movable unit  3  are pulled towards each other. 
     Furthermore, the force pulling the main body  2  and the movable unit  3  towards each other allows the protrusions  7   a  and  11   a  to be engaged to the corresponding sloped end portions of the respective guiding grooves  10   a  and  8   a . Accordingly, the movable unit  3  can be supported without requiring a designated locking mechanism. At the same time, the force pulling the main body  2  and the movable unit  3  towards each other also generates a sense of retraction at the stroke end positions of the stowing and deploying operations of the movable unit  3  so as to give a user a good sense of haptic feedback. 
     In addition to generating the pulling force, because the pulling spring  22  is electrically conductive, as described above, the pulling spring  22  also functions as a conductor between the main body  2  and movable unit  3 . 
     According to this embodiment, the displaying direction of the display portion  4  can be switched automatically in synchronization with the sliding motion. The structure and the operation for switching the displaying direction of the display portion  4  will be described below. 
       FIG. 19  is a top view of the main-body rear cabinet  14  and the movable-unit front cabinet  15  in the deployed state of the movable unit  3 . As shown in  FIG. 19 , a magnet  30  is provided in the main-body rear cabinet  14  at a section near the right side plate  6   a  and the protrusion  7   a.    
       FIG. 20  is a bottom view of the main-body rear cabinet  14  and the movable-unit front cabinet  15  in the deployed state of the movable unit  3 . As shown in  FIG. 20 , the movable-unit front cabinet  15  is provided with a Hall element  31 . The Hall element  31  detects a change in the magnetic field when it approaches the magnet  30 , and determines the position of the movable unit  3  based on the change in the magnetic field. Moreover, based on the position of the movable unit  3 , the Hall element  31  commands the main substrate  25  to switch the displaying direction of the display portion  4  between lengthwise and crosswise directions. 
       FIG. 21  is a perspective view illustrating the positional relationship between the magnet  30  and the Hall element  31 . As shown in  FIG. 21 , the magnet  30  is disposed directly above the Hall element  31  in the vertical direction when the movable unit  3  is in the deployed state. 
       FIGS. 22A and 22B  illustrate the PDA  1  in a state where the displaying direction of the display portion  4  is switched from one direction to the other. Specifically,  FIG. 22A  illustrates the PDA  1  when the movable unit  3  is in the stowed state, whereas  FIG. 22B  illustrates the PDA  1  when the movable unit  3  is in the deployed state. Referring to  FIG. 22A , since the Hall element  31  and the magnet  30  are distant from each other when the movable unit  3  is in the stowed state, the Hall element  31  detects that the movable unit  3  is at the stowed position and commands the display portion  4  to display a screen in the lengthwise direction of the PDA  1 . In this case, the display portion  4  allows for a relatively simple input operation using, for example, a finger or a stylus pen. On the other hand, since the Hall element  31  and the magnet  30  are disposed close to each other in the vertical direction when the movable unit  3  is in the deployed state as shown in  FIG. 21 , the Hall element  31  detects that the movable unit  3  is at the deployed position and commands the display portion  4  to display the screen in the crosswise direction of the PDA  1 . In this case, the display portion  4 , for example, allows for a character input operation for relatively long sentences via the keyboard  5  on the movable unit  3 . According to the PDA  1  in this embodiment, the displaying direction of the display portion  4  can be switched in response to the positional detection of the movable unit  3  by the Hall element  31  without requesting the user for a switching operation, thereby contributing to better user-friendliness. 
     Furthermore, the PDA  1  according to this embodiment has a structure in which the stylus pen used for performing various input operations via the display portion  4  is prevented from falling out when the movable unit  3  is in the stowed state. Such a structure for storing the stylus pen will be described below in detail. 
       FIGS. 23A to 23C  are perspective views of the PDA  1  and a stylus pen  32  when the movable unit  3  is in the deployed state and in the stowed state. Specifically,  FIG. 23A  illustrates a state where the stylus pen  32  is taken out from the movable unit  3  in the deployed state. In the deployed state of the movable unit  3  shown in  FIG. 23A , if an input operation is to be performed via the display portion  4 , the stylus pen  32  is pulled out from an insertion opening  33  extending perpendicular to the lateral side surfaces of the movable unit  3 . 
     On the other hand,  FIG. 23B  illustrates a state where the stylus pen  32  is inserted in the insertion opening  33  of the movable unit  3  in the deployed state. The insertion opening  33  is designed such that the top end of the stylus pen  32  is prevented from protruding from the insertion opening  33 , i.e. the right side surface  9   a  of the movable unit  3 , when the stylus pen  32  is disposed inside insertion opening  33 . 
       FIG. 23C  illustrates a state where the stylus pen  32  is inserted in the insertion opening  33 , and the movable unit  3  is stowed in the main body  2 . When the movable unit  3  is in the stowed state as shown in  FIG. 23C , the right side plate  6   a  of the main body  2  retains the stylus pen  32  so that the stylus pen  32  is prevented from accidentally falling out when the PDA  1 , for example, is being carried. 
     The technical scope of the present invention is not limited to the above embodiment, and modifications are permissible within the scope and spirit of the present invention. 
     For example, although the electronic device is directed to a PDA in the above embodiment, the present invention may be applied to other types of electronic devices that include a main body and a movable unit, such as a personal computer, a mobile phone, and an electronic dictionary device. 
     Furthermore, although the opposite end portions of each of the guiding grooves  8   a ,  8   b ,  10   a , and lob are sloped and the intermediate portion between the opposite end portions of each guiding groove is linear in the above embodiment, the guiding grooves  8   a ,  8   b ,  10   a , and  10   b  may have other alternative shapes. For example, each guiding groove may be curved from one end portion to the other end portion. In other words, any shape is permissible as long as it allows the movable unit  3  to move away from the main body  2  during the sliding motion of the movable unit  3 . 
     Furthermore, although the movable unit  3  functions as an operating portion having, for example, the keyboard  5  in the above embodiment, the movable unit  3  does not necessarily have to function as an operating portion and may alternatively function as, for example, a display portion. In that case, the top surface of the main body  2  may also be provided with a display portion so that a total of two display portions are provided, or the display portion on the main body  2  may be omitted. 
     It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.