1) Field of the Invention
The present invention relates to a technology for adjusting an angle of a liquid-crystal display (LCD) screen to improve operationality and safety by using a tilt-locking function of a ratchet mechanism and a anti-tilting function of an anti-tilting mechanism.
2) Description of the Related Art
Point-of-sales (POS) terminals are widely used in department stores and the restaurants as an information-display apparatus having an LCD screen. FIG. 8A and FIG. 8B are a perspective view and a side view of a conventional POS terminal 100, respectively. The POS terminal 100 includes an LCD screen 200, on which the operator performs the key-touch operation (for accounting operation or the like), a main body 100a, a printer 300, which prints a printing paper such as a receipt, and a controller 400. A receipt exit 500 is used to issue the receipts that the printer 300 prints.
A hinge 550 connects the LCD screen 200 and the main body 100a, and the ratchet mechanism (not shown), which includes a function for adjusting an angle of the LCD screen 200, is arranged in the hinge 550. In the operation of the LCD screen 200, the operator adjusts the angle of the LCD screen 200 to be a desirable position using the ratchet mechanism.
Japanese Patent Application Laid-Open No. 2000-300370 discloses an example of the display tilting apparatus that is used to connect a backrest and a seat of a legless chair, a sofa bed, or the like. This display tilting apparatus adjusts the angle of the backrest or the like to be a desirable position stepwise using the ratchet mechanism.
Another example of the display tilting apparatus that adjusts the angle of the LCD screen is a torque-hinge mechanism that uses a friction torque. The notebook computer has the torque-hinge mechanism, and the torque-hinge mechanism is arranged in a hinge that connects the LCD screen and a main body (keyboard). The LCD screen is tilted and fixed at any desirable position using the friction torque of the torque-hinge mechanism.
However, the conventional technologies have the following problems in adjusting the angle of the LCD screen. When the hinge has the ratchet mechanism, the LCD screen 200 can be fixed at any desirable position on the printer's side by engaging a ratchet gear with a locking pawl (to lock). On the other hand, the tilt-locking function of the ratchet mechanism does not work when the LCD screen 200 tilts to the operator's side, and the LCD screen 200 unexpectedly falls toward the operator. Therefore, there is a problem in safety when the ratchet mechanism is arranged in the hinge of the POS terminal.
When the hinge of the POS terminal has the torque-hinge mechanism, the LCD screen 200 can be tilted and supported at any desirable position using the friction torque (the friction drag) of the torque-hinge mechanism.
When the operator adjusts the angle of the LCD screen, preferably, the angle of the LCD screen can be adjusted with the comparatively weak force by configuring the strength of the friction torque similarly with the ratchet mechanism. On the other hand, when the operator performs the key-touch operation on the LCD screen and put some pressure on the LCD screen, it is required to have strength for retaining the angle of the LCD screen. Therefore, satisfying the contradict friction-torques is extremely difficult.