Abstract:
A low cost and long lasting hinge mechanism suitable for hinging a cover to a housing of a device is disclosed. The hinge mechanism has a pair of pins attached to the cover and a corresponding pair of apertures on the housing. The pins fit into the apertures to hinge the cover to the housing to allow the cover to be tilted from a closed position to an open position. The aperture has a first portion and a second constricted portion. A pivoting point is provided on a tab on the housing. A corresponding cam-profiled section is provided on the cover for interacting with the pivoting point to urge the pin into the corresponding constricted portion of the aperture for securing the cover in the open position.

Description:
FIELD OF INVENTION 
     This invention relates to a hinge mechanism. More particularly, this invention relates to a hinge mechanism for hinging a cover to a housing. The cover can be tilted between a closed and an open position in relation to the housing. In the open position, the cover is securely held in place. 
     BACKGROUND 
     In the prior art, a cover for a device such as a palm-sized personal computer (P/PC) or personal digital assistant (PDA) is generally attached to a housing of the device using a simple pin and socket hinge. In such a device, the cover has a panel for either partially or fully covering a surface of the housing to protect a display on the surface or to protect the device against inadvertent activation. The panel of the cover has two pins arranged along a pivoting axis. These pins are usually round in cross section. Corresponding to these pins on the cover are apertures on the housing. When assembled, the pins on the cover are fitted into these corresponding apertures in the housing. Such an assembly allows the cover to be hinged to and tilted about the housing. The cover tilts about the pivoting axis of the pins to an open and a closed position. 
     In the closed position, the panel is juxtaposed to a housing surface to cover the surface. In the open position, the cover is tilted away from the surface to allow access to control buttons and the display. The cover is normally held in the open position by a simple detent on the device. This detent includes a bump of the cover and a corresponding dimple on the housing. In the open position, the bump sits snugly in the dimple to prevent the cover from tilting back to the closed position. 
     Such a hinge mechanism including the bump and dimple works but is prone to wear. Through frequent use, the bump on the cover wears down and does not engage well with the dimple to hold the cover in place. Such poor engagement will result in the cover being easily dislodged when in the open position. The cover will then have the tendency to tilt back towards the closed position when the device is subjected to rough use. 
     From the foregoing, the prior art therefore has a need for a low-cost and longer lasting hinge mechanism that is able to continue to function after prolonged usage. This hinge should also allow the hinged parts to be held apart in an open position substantially securely to prevent the two parts from being easily dislodged from the open position. This hinge should also preferably provide a user with a tactile feel that the open position is reached when tilting one part about the other. 
     SUMMARY 
     In accordance with a preferred embodiment, a hinge mechanism suitable for hinging a first part of a device to a second part of the device has a pair of pins attached to the first part and a pair of guides on the second part. The pair of guides receives the pins to allow the first part to hinge to the second part. The first part can be tilted from a closed position to an open position in relation to the second part. Each guide defines a first guide portion and a second guide portion within the confines of the guide. A pivoting point is provided on either the first or the second part of the device. A corresponding cam-profiled section is provided on the other part for interacting with the pivoting point to urge the pin into the corresponding second guide portion for securing the first part in the open position when the first part is tilted from the closed position to the open position. 
     Preferably, the cam-profiled section includes a notch that latches onto the pivoting point to prevent the parts from being dislodged when in the open position. 
     Also, preferably each pin has a flattened cross-section that has a narrow and a wide dimension. The second guide portion is also constricted to receive the pin by the narrow dimension so that the pin is securely held in the second guide portion when the first part is in the open position. 
     Preferably, the hinge mechanism further includes at least one bump along the periphery within the confines of the guide between the first and the second portions of the guide. This bump restricts the movement of the pin between the first guide portion and the second guide portion. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     The invention will be better understood with reference to the following drawing, in which: 
     FIG. 1A is a side view of a palm-sized personal computer (P/PC) which has a hinge mechanism according to the present invention. The P/PC has a cover hinged to a housing using the hinge mechanism. The cover is shown in a closed position. 
     FIG. 1B is an enlarged side view of a pin and an aperture of the hinge mechanism of FIG.  1 A. 
     FIG. 2A is an exploded view of an inlay of the cover of FIG. 1A and a frame of the housing in FIG.  1 A. 
     FIG. 2B is an enlarged view showing a portion of the inlay and the frame in FIG.  2 A. 
     FIG. 3A is a side view similar to FIG. 1A with the cover tilted to an intermediate position between the open and a closed position. 
     FIG. 3B is an enlarged side view similar to FIG. 1B showing the pin in a corresponding intermediate position when the cover is tilted to the intermediate position. 
     FIG. 4A is a side view similar to FIG. 1A with the cover tilted to an open position. 
     FIG. 4B is an enlarged side view similar to FIG. 1B showing the pin wedged in position in a portion of the aperture in FIG.  1 B. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Hereafter, a preferred embodiment of the present invention will be described in the context of a palm-sized personal computer (P/PC) that has a cover hinged to a housing using a hinge mechanim. However, it is to be understood that the invention is equally applicable to other types of devices, casings or parts wherein one part is to be tilted to and held substantially securely in an open position in relation to a second part. 
     The housing of the P/PC contains a printed circuit board assembly (PCBA), a touch-screen liquid crystal display (LCD) and buttons for activating the P/PC. The cover protects the display and prevents inadvertent activation of the P/PC. The hinge mechanism allows the cover to be tilted to an open position for a user to access the buttons and the touch-screen display. When in the open position, the cover is held substantially securely in this position 
     FIG. 1A is a side view of a P/PC  2  with a cover  4  shown in a closed position in relation to a housing  6  using a hinge mechanism  8  according to the present invention. FIG. 2A is an exploded view of an inlay  10  of the cover  4  and a frame  12  of the housing  6  on which the hinge mechanism  8  is implemented. FIG. 2B is an enlargement of a portion of FIG. 2A indicated by an arrow A. The frame  12  with two sidewalls  14 . Apertures  16  are built into these sidewalls  14  for attachment of the cover. The aperture walls have thicknesses of preferably about 1.4 mm. This frame  12  is preferably molded from plastic such as PC. 
     The apertures  16  on the housing  6  are formed in the frame  12  during molding of the housing  6 . A contoured portion  18  along the aperture wall separates each aperture  16  into two portions—a larger portion  20  and a constricted portion  21 . This contoured portion  18  introduces a bump in the aperture  16 . The frame  12  also has a tab  22  that has a thickness of about 1.5 mm. An edge or side of this tab  22  acts as a pivoting point  23 . 
     The cover  4  is formed by an outer cover  24  and the inlay  10 . Such a design of the cover  4  allows the inlay  10  to define a compartment  26  between the inlay  10  and the outer cover  24  to store a stylus (not shown). In this preferred embodiment of the invention, the inlay  10  has a panel  28  with two opposite facing sidewalls  30  depending therefrom. Attached to these sidewalls  30  are oppositely directed pins  32  aligned along a pivoting axis. The pins  32  are preferably of lengths of approximately 1.5 mm. The cover  4  is hinged to the housing  6  by inserting these pins  32  into the corresponding apertures  16  in the housing  6 . Such an arrangement allows the cover  4  to be tilted about the housing  6  between a closed and an open position. In the closed position of the cover  4 , the pin  32  is located in the larger portion  20  of the aperture  16  and the pin  32  can be rotated therein. In the open position of the cover  4 , the pin  32  is at least partially received in the constricted portion  21  of the aperture. In this position, the pin  32  is prevented from freely rotating. As a result, the cover  4  is substantially secured in the open position. 
     The width of the inlay  10  of the cover  4  is wider than the width of the frame  12  of the housing  6  so that the sidewalls  30  of the inlay  10  is preferably clear of the housing  6  to reduce friction therebetween during use. With such a design, the pins  32  do not protrude the apertures  16  into the area enclosed by the frame  12 . This area is then maximized for containing the PCBA and the LCD. 
     Preferably, each sidewall  30  of the cover  4  has a cam-profiled section  34 . This cam-profiled section  34  should preferably have a thickness of about 1.5 mm. Also, a notch  36  is preferably built into the sidewall at one end of this cam-profiled section  34 . The pin  32  preferably has a generally flattened cross section that has a wide and a narror dimension. The sidewalls  30  and pins  32  are integrally molded with the inlay  10 , using plastics such as Velox, nylon and PC/ABS. 
     The operation of the hinge mechanism  8  is next described in detail. In the closed position of the cover  4  as shown in FIG. 1B, the pin  32  is located in the larger aperture portion  20  of the housing. As the cover is tilted away from this closed position towards the open position, the pin  32  rotates within the confines of the larger aperture portion  20  to allow the cover  4  to swing away from the housing  6 . As the cover  4  swings open, it will come into an intermediate position where the cam-profiled section  34  of the sidewall comes into contact with the pivoting point  23  of the tab  22  on the housing  6 . If the cover  4  is tilted beyond this intermediate position, the cam-profiled section  34  will interact with the pivoting point  23  to urge the pin  32  towards the constricted aperture portion  21 . FIG. 3A is a side view showing the cover tilted to this intermediate position where the angle between the cover  4  and the housing  6  is about 60 degrees. FIG. 3B is an enlarged side view that shows the pin  32  position in the aperture  16  when the cover  4  is in the intermediate position. When in this position, the pivot point  23  impedes the further tilting of the cover  4  towards the open position. A slightly larger force is required to overcome the inertia of the pivoting point  23  on the cam-profiled section  34  to tilt the cover  4  further towards the open position. 
     Also when in the intermediate position, the pin  32  on the cover  4  comes into contact with the aperture wall that defines the contoured aperture portion  18  to further impede the tilting of the cover  4 . The larger force that is required to tilt the cover beyond the intermediate position will also need to overcome the inertia of the pin  32  against the contoured aperture portion. When a user applies such a force, the cover will tilt beyond the intermediate position to allow the pin  32  to move towards the constricted aperture portion  21 . This movement of the pin  32  is along a horizontal axis and covers a distance of approximately 2 mm. Such a small movement in the horizontal direction is hardly noticeable by the user. When the pin  32  clears the contoured aperture portion, the user is however able to get a tactile feel that the open position is reached. FIG. 4A is a side view that shows the cover tilted to the open position where the angle between the cover  4  and the housing  6  is about 115 degrees. FIG. 4B is an enlarged side view which shows the pin held or wedged in the constricted aperture portion  21 . Further tilting of the cover will result in the pin  32  being pushed against the constricted aperture portion  21  as shown in FIG.  4 B. In this position, the notch  36  on the cover sidewall  30  also latches onto the pivoting point  23  on the tab  22 . This wedging action of the pin  32  in the constricted aperture portion  21  and the latching of the notch  36  on the pivoting point  23  are sufficient to hold the cover  4  in place. Another smaller contoured portion  38  in the aperture  16  positioned across from the first contoured portion  18  can be provided to further secure the pin  32  in the constricted aperture portion  21 . 
     Although there are larger areas of contact between moving parts in the hinge mechanism  8 , wear caused by abrasion between these moving parts is reduced by the design of the cam-profiled surface  34 , tab  22 , pin  32  and aperture  16  wall. The length of the pins and the thickness of the aperture walls are designed to be sufficiently large to withstand wear. The dimensions of the cam-profiled section  34  and the tab  22  can be similarly designed to withstand wear. Overall, this design results in a hinge mechanism that is more resistant to wear and is therefore able to last longer. 
     While the present invention has been shown and described with reference to the foregoing operational principles and preferred embodiment, it will be apparent to those skilled in the art that other changes in form and detail may be made. For example, some of the features of the preferred embodiment can be removed without adversely affecting the operation of the hinge mechanism. An example of which is the notch  36 . The notch can be removed and the hinge mechanism  8  will still work albeit not as ideally. Likewise, the two contoured portions  18 ,  38  in the aperture  16  can also be removed. 
     In the preferred embodiment, the aperture  16  is built into the housing  6  and the pin  32  attached to the cover  4 . An embodiment with the aperture built into the cover and the pin attached to the housing would also work. The apertures can also be replaced by appropriately contoured and raised tabs to guide the movement of the pins.